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JP2007506439A - Method for synthesizing a small amount of nucleic acid - Google Patents
Method for synthesizing a small amount of nucleic acid Download PDF
JP2007506439A
JP2007506439A JP2006528313A JP2006528313A JP2007506439A JP 2007506439 A JP2007506439 A JP 2007506439A JP 2006528313 A JP2006528313 A JP 2006528313A JP 2006528313 A JP2006528313 A JP 2006528313A JP 2007506439 A JP2007506439 A JP 2007506439A
JP2006528313A
カドゥシン，ジェームズ・エム
データスコープ・インベストメント・コーポレイション
2003-09-26 Priority to US50624703P priority Critical
2004-09-27 Application filed by データスコープ・インベストメント・コーポレイション filed Critical データスコープ・インベストメント・コーポレイション
2004-09-27 Priority to PCT/US2004/031804 priority patent/WO2005030984A2/en
2007-03-22 Publication of JP2007506439A publication Critical patent/JP2007506439A/en
A method for synthesizing nucleic acids, which has a specific use in the synthesis of cDNA. The method allows the cDNA to be applied to a microarray after cDNA synthesis without having to concentrate or purify the cDNA.
RELATED APPLICATION This application claims priority from US Provisional Application No. 60 / 506,247, filed Sep. 26, 2003.
This application also claims US priority provisional application 60 / 261,231 filed on January 13, 2001, US non-provisional application 10/14, filed January 14, 2002. It is also a continuation-in-part of U.S. Non-Provisional Application No. 10 / 825,776 (pending), filed April 16, 2004, which is a continuation application of 050,088 (abandoned).
This application also claims US Provisional Application No. 10/316, filed on September 3, 2002, which claims priority from US Provisional Application No. 60 / 316,116, filed on August 31, 2001. It is also a continuation-in-part of 234,069 (pending).
This application also claims PCT Application No. PCT / US03 / filed on March 25, 2003, claiming priority of US Provisional Application No. 60 / 367,438, filed March 25, 2002. It is also a partial continuation application of 09232 (pending) (“'232 application”).
Priority is claimed for all of these applications, all of which are hereby incorporated by reference in their entirety.
TECHNICAL FIELD OF THE INVENTION The present invention relates to an improved method for nucleic acid synthesis.
Background of the Invention Nucleic acid synthesis methods are one of the foundations of modern molecular biology and are used in a wide variety of experimental and diagnostic techniques. Of the various forms of nucleic acids currently known, cDNA or “complementary DNA” is a copy of DNA made from a template of messenger RNA (mRNA) or other type of RNA molecule.
Synthesis of cDNA molecules from the original mRNA is accomplished using an enzyme known as reverse transcriptase (RT), ie, an RNA-dependent DNA polymerase. Reverse transcriptase was originally discovered in connection with retroviruses, from viruses such as avian myeloblastosis virus (AMV) or Moloney murine leukemia virus (M-MuLV), or from cells containing the cloned gene. It can be obtained by purification.
Using mRNA isolated from any cell source, a library of cDNA molecules complementary to the cell mRNA can be generated. This cDNA library can be used for various experimental purposes. For example, a cDNA library created from a specific tissue type can be used for gene expression analysis, that is, provide information regarding the expression of nucleic acids in an initial sample. Gene expression analysis includes, for example, identification of new gene expression, correlation of gene expression to a specific phenotype, disease predisposition screening, and cellular genes of specific agents in toxicity testing and screening for new drug compounds It can be useful for a variety of applications such as identifying effects on expression.
To perform the analysis, total (or messenger) RNA is extracted from the desired cell sample. Reverse transcription produces a copy of complementary DNA (cDNA) from the RNA. This cDNA copy is labeled with a marker or label, such as a fluorescent marker, and broken down into short fragments.
As discussed in the inventor's prior patent application, analysis of cDNA sequences in any sample can be accomplished using high-speed techniques for nucleic acid analysis such as DNA microarrays (eg, US provisional application filed on August 31, 2001). US Non-Provisional Application No. 10 / 234,069 filed on September 3, 2002, claiming priority of 60 / 316,116, and International Application No. PCT filed on September 3, 2002 / US02 / 027799, International Publication No. WO 03/020902 A2, “Methods for Blocking Nonspecific Hybridizations of Nucleic Acids”, all of which are incorporated herein by reference. Built in) It is particularly effective in cases. All microarrays function on a similar principle. That is, a substantially flat substrate, such as a glass slide or silicon chip or nylon film, is coated in a grid with fine spots having a diameter of about 20 to 100 microns. Each spot (or feature) contains millions of copies of short sequences of DNA or nucleotides, and the computer keeps track of the position of each sequence on the substrate, allowing the user to make thousands of small scale Allows test tube-like reactions to occur simultaneously.
After labeling the cDNA copy, the labeled fragment is washed off on the microarray and left overnight to allow the labeled fragment to hybridize to the DNA attached to the microarray. Once hybridized, features on the microarray paired with fluorescent cDNA emit a fluorescent signal that is observable under a microscope or detectable by a computer. In this way, it is possible to know which sequence on the microarray matches the cDNA of the test sample. Even if mismatches occur, the use of millions of probes for each spot or feature ensures that fluorescence is detected only in the presence of complementary cDNA. The stronger the fluorescent signal (ie, the brighter the spot), the more matched cDNA was present in the cell.
Unfortunately, however, in conventional methods known in the art, the cDNA is prepared in a hybridization mixture that is applied to the microarray unless the cDNA is concentrated after reverse transcription. Cannot be used with. In addition, when the cDNA is labeled with a dye, purification must often be performed. These enrichment and / or purification steps add extra time and expense to the test analysis.
For example, one typical method for concentrating nucleic acids is the ethanol precipitation method. The specific protocol of the ethanol precipitation method that enables cDNA enrichment is as follows.
1. Ethanol precipitation method of synthesized cDNA Adjust the volume of synthesized cDNA to 130 μL with 1 × TE buffer.
2. Add 3 μl of linear acrylamide (5.0 mg / mL) to the synthetic cDNA mixture.
3. Add 6 μl of 5M NaCl or 250 μl of 3M ammonium acetate and mix.
4). Add 540 μl of 100% ethanol when using NaCl, or 875 μl of 100% ethanol when using 3M ammonium acetate. Mix by moderate vortexing.
5). Incubate at -20 ° C for 30 minutes.
6). Samples are centrifuged for 15 minutes at greater than 10,000 g.
7). Carefully aspirate the supernatant so that the cDNA pellet is not lost. Do not decant because decanting can cause the pellets to slip off and be lost.
8). Add 300 μl of 70% ethanol to the cDNA pellet. Gently tap the side of the tube to mix gently. Overmixing will destroy the cDNA pellet and should not be overmixed.
9. Centrifuge for 5 minutes at greater than 10,000 g and remove the supernatant. Do not decant.
10. Heat at 65 ° C. for 10-30 minutes to completely dry the cDNA pellet. If the cDNA pellet is not completely dry, it can be difficult to resuspend and incomplete resuspension can result in a spotty background and / or unclear results on the microarray.
11. Proceed to hybridization of the cDNA to the array.
The ethanol precipitation method is a conventionally accepted nucleic acid enrichment method, but unfortunately the pelleted cDNA is either partially or completely lost or the resolubilization of the precipitated cDNA is incomplete. Can lead to inconsistent results. For example, as described above, reverse transcription of a small amount of RNA produces a very small amount of a cDNA pellet that is easily lost during processing or by attaching to the inside of a pipette tip. If the ethanol precipitation process is not performed carefully, problems may occur.
Another method of concentrating the cDNA pellet is a concentration method using a registered Microcon microconcentrator. The sample protocol of the registered trademark Microcon concentration method is as follows.
Concentration of cDNA using Millipore (registered trademark) Microcon YM-30 centrifugal filter device The cDNA sample was obtained from Millipore (registered trademark) Microcon YM-30 centrifugal filter device (30,000 molecular weight cutoff, Millipore catalog number 42409). And can be concentrated. The following protocol is an example of a method provided to reduce the volume of a cDNA synthesis reaction from 130 μl to 3-10 μl for hybridization to an array. (Note: The sample protocol below is similar to the protocol provided by the manufacturer, but includes some modifications for use with the 3DNA Array 350 kit. In addition, those using the registered Microcon YM-30. Should evaluate their centrifuge settings to determine the optimal time and speed settings to achieve a final volume of 3-10 μl.)
1. Place the microcon YM-30 sample container into a 1.5 ml collection tube.
2. 100 μl of TE, pH 8.0 is added to the microcon YM-30 sample container, and the container membrane is pre-washed.
3. Place the tube / sample container assembly into a fixed angle rotor tabletop centrifuge capable of 10 to 14,000 g.
4). Spin at 10-14,000g for 3 minutes.
5). Add all 130 μl of the cDNA reaction to the sample container Microcon YM-30. Do not touch the membrane with the tip of the pipette.
6). Place the tube / sample container assembly into a fixed angle rotor tabletop centrifuge capable of 10 to 14,000 g.
7). Centrifuge at 10-14,000g for 8-10 minutes.
8). Remove the tube / sample container assembly. Carefully separate the collection tube from the sample container so as not to spill liquid in the sample container.
9. Add 5 μl of 1 × TE buffer (10 mM Tris-HCl, pH 8.0 / 1 mM EDTA) to the sample container membrane without touching the membrane. Tap the side of the concentrator to facilitate mixing of the concentrate with 1 × TE buffer.
10. Carefully place the sample container upside down on a new collection tube. Centrifuge for 2 minutes at maximum speed in the same centrifuge.
11. Separate the sample container from the collection tube and discard the container. Record the volume collected at the bottom of the tube (total volume 3-10 μl). The cDNA sample can be stored in a collection tube for later use.
12 Proceed to hybridization of the cDNA to the array.
As can be seen from the above example, the sample enrichment protocol previously used before applying cDNA to the microarray requires an extra sequence of time-consuming steps after cDNA synthesis. In some cases, these additional steps can reduce efficiency and the results obtained in the assay.
Accordingly, it is an object of the present invention to provide an improved method for synthesizing cDNA that eliminates the post-synthesis sample concentration described above.
SUMMARY OF THE INVENTION An object of the present invention is to provide an improved method for synthesizing nucleic acids.
A further object of the present invention is to provide an improved method for synthesizing cDNA.
It is a further object of the present invention to provide a method that eliminates the need for enrichment of cDNA after it has been synthesized.
It is a further object of the present invention to provide a method that eliminates the need for a purification step that removes unwanted molecules from a cDNA sample after synthesis of the cDNA.
A further object of the present invention is to provide a method for synthesizing cDNA using a very small amount of sample material.
It is a further object of the present invention to provide a method for synthesizing cDNA that provides high sensitivity.
It is a further object of the present invention to provide an improved method for synthesizing cDNA for use in a microarray.
A further object of the present invention is to provide a method for synthesizing cDNA, which makes it possible to apply the cDNA to a microarray without the need for enrichment of the cDNA after synthesis of the cDNA. .
A further object of the present invention is a method for synthesizing cDNA, which makes it possible to apply cDNA to a microarray without the need for removal of unwanted molecules from the cDNA sample after synthesis of the cDNA. Is to provide.
It is a further object of the present invention to provide a method for synthesizing cDNA for application to a microarray in a manner that can be easily automated.
In addition to the above objects, improved nucleic acid synthesis methods are disclosed in accordance with the present invention. This method provides more sensitive results from very small sample materials than provided by conventional methods in the art by eliminating the sample enrichment protocol after nucleic acid synthesis.
In a preferred embodiment, the present invention is used to synthesize cDNA (complementary DNA) from an initial sample of RNA, such as mRNA from a sample source of interest. In a further preferred embodiment, the method is used for nucleic acids intended for application to a microarray and for assaying these nucleic acids using hybridization of synthetic nucleic acids to known molecules immobilized on the array. Used for. In a further preferred embodiment, the assay is performed using a dendritic nucleic acid reagent. More preferably, the capture sequence is used to label synthetic nucleic acids and / or nucleic acids on the array.
In further embodiments of the invention, kits for performing the methods disclosed herein can be provided. In addition, the process can be used on other types of sample preparations for other applications.
The elimination of the post-synthesis sample concentration protocol is an important advantage of the method of the present invention, in particular because such a protocol can cause excessive loss of sample. The method is particularly useful for small amounts of preparation from less than 1 microgram (1000 nanograms) of total RNA or equivalent nucleic acid sample.
A further important advantage of the present invention is that the time and number of manipulations required to perform a complete synthesis of cDNA can be reduced. This advantage is particularly important for a variety of situations and applications, such as laboratories, diagnostic kits, and medical site needs.
However, a further important advantage of the present invention is that it provides a more consistent reproducibility of the final cDNA yield with the same input material, resulting in better reproducibility of the results.
Further objects and advantages of the present invention should become apparent with the detailed disclosure contained herein.
DETAILED DESCRIPTION OF THE INVENTION AND PREFERRED EMBODIMENTS In further describing the present invention, the present invention is not limited to the specific embodiments of the invention described herein, and modifications may be made to the specific embodiments. It should be understood that they are still within the scope of the present invention or the appended claims.
It is also to be understood that the terminology used is for the purpose of describing particular embodiments and is not intended to be limiting.
The present invention relates generally to methods of nucleic acid synthesis that eliminate the need for sample concentration after synthesis. Because it is a cost-effective and effective way to prepare nucleic acid sequence samples and perform the methods of the invention using conventional laboratory techniques, equipment and reagents, they are used in research and clinical applications. And particularly suitable for automation.
The present invention is particularly suitable for nucleic acid synthesis such as cDNA synthesis performed in connection with assays on microarrays. In such methods, an array of DNA or gene probes that are immobilized or stably bound to a substantially planar surface of the substrate (“microarray”) is used for the complementary probe / target complex. Contact with the target nucleic acid sample under hybridization conditions sufficient to generate a hybridization pattern. A variety of microarrays that can be used are known in the art. The hybridized nucleic acid sample then becomes the target of the labeled probe and hybridizes to generate a detectable signal corresponding to a specific hybridization pattern. Each labeled probe hybridized to the target nucleic acid can all produce the same signal with a known intensity. Thus, each positive signal in the microarray can be “measured” to obtain quantitative information about the gene profile of the target nucleic acid sample.
A microarray DNA or gene probe that can hybridize sequence-specifically with a target nucleic acid can be a polynucleotide, or its analogs or mimetics, such as phosphorothioate, methylimino, methylphosphonic acid, Phosphoramidate, guanidine, etc., nucleic acids in which the phosphodiester bond is substituted with a substituent linkage group, nucleic acids in which the ribose subunit is substituted, such as hexose phosphate diester, peptide nucleic acid, etc. It is not limited to these. The length of the probe is usually in the range of 10 to 1000 nucleotides, but the present invention is not limited to such a length of probe. In some embodiments of the invention, for example, the probe will be an oligonucleotide of 15-150 nucleotides, more commonly 15-100 nucleotides. In another embodiment, the probe is longer, typically 150-1000 nucleotides in length, where the polypeptide probe may be single stranded or double stranded, usually single stranded. Yes, it may be a PCR fragment amplified from cDNA. The DNA or gene probe on the surface of the substrate preferably corresponds to a known gene from the physiological source being analyzed and is placed at a known location on the microarray so that positive hybridization occurs. Can be correlated with the expression of a specific gene in a physiological source that is the source of the target nucleic acid sample. As described below, because of the method of generating a target nucleic acid sample, gene probe microarrays typically have sequences complementary to the non-template strands of the genes to which they correspond.
The substrate to which the gene probe is stably bound can be manufactured from various materials such as plastic, ceramic, metal, gel, film, and glass. The microarray can be prepared according to a simple and usual method such as pre-forming gene probes and then stably binding them to the surface of the support, or directly growing the gene probes on the support. Numerous different microarray configurations and fabrication methods are known to those skilled in the art, one of which is described in Science, 283, 83, 1999, the contents of which are hereby incorporated by reference.
In accordance with the methods of the present invention, a desired microarray having probe nucleic acid sequences that are stably immobilized is provided. In addition, a sample having a target molecule to be studied is provided. Although the target molecule is labeled for detection, the term “label” as used herein refers to detection either directly or through interaction with one or more additional members of a signal generating system. An agent that can provide a possible signal. The label preferably does not provide a variable signal, but instead provides a constant and reproducible signal over a given time. The target molecule can be labeled before or after the target is applied to the array, but it is usually preferred to label it before applying it. Preferably, a dendrimer or another such as, for example, a relative light scatter detection method using a nanogold label, such as a Genicon. Inc./Invitrogen label. A method for generating a very sensitive signal such as a method for generating a relatively high sensitivity signal is used.
In the context of the present invention, dendritic nucleic acid molecules are particularly suitable for detection ability (although any type of labeled molecule with suitable sensitivity can be utilized with the invention disclosed herein). . Dendritic nucleic acid molecules or dendrimers are complex, highly branched molecules consisting of multiple monomeric subunits of natural or synthetic double-stranded DNA linked together. Dendrimers are described in Nilsen et al., Dendritic Nucleic Acid Structures, J. MoI. Theor. Biol. , 187, 273-284 (1997), Steers et al., A novel high-sensitivity detection system for high-density microarrays using dendrimer technology (A Novel, Sensitive Detection System High-Density Microarrays Usage Dendrimer.). Genomics, 3: 93-99 (2000); and US Pat. Nos. 5,175,270, 5,484,904, 5,487,973, 6,072,043, 6,110. , 687 and 6,117,631 are described in great detail in various US patents. All of which are also incorporated herein by reference in their entirety. Similarly, for various inventions related to dendrimers and their use on microarrays, see PCT Application No. PCT / US03 / 09232 filed March 25, 2003, US Provisional Application filed March 25, 2002. No. 60 / 367,438, U.S. non-provisional application No. 10 / 825,776 filed on Apr. 16, 2004, U.S. non-provisional application No. 10 / 050,088 filed on Jan. 14, 2002. No., US Provisional Application No. 60 / 261,231, filed on January 13, 2001, US Non-Provisional Application No. 10 / 730,823, filed on December 8, 2003, March 20, 2003 US non-provisional application 10 / 393,519 filed on the same day, PCT application PCT / US01 / 29589 filed on September 20, 2001, 200 US Provisional Application No. 60 / 234,060 filed on September 20, 2001, US Non-Provisional Application No. 09 / 908,950 filed on July 19, 2001, filed on July 19, 2000 US Provisional Application No. 60 / 219,397, US Provisional Application No. 60 / 187,681 filed on March 8, 2000, US Non-Provisional Application No. 09 filed on March 8, 2001 / 802,162, and US Provisional Application No. 60 / 187,681, filed March 8, 2000, PCT Application No. PCT / US2003 / 009232, and PCT Application No. PCT / US2003 / 025865. All of which are incorporated herein by reference in their entirety.
Dendrimers contain two types of single-stranded hybridization “arms” on the surface that are used to join two major functional groups. A single dendrimer molecule can have 100 or more arms of each type on the surface. One type of arm is used to attach a specific target molecule to establish target specificity, and the other type is used to attach a label or marker. Molecules that determine the specificity of the dendrimer target and label are attached as oligonucleotides or as oligonucleotide conjugates. Using simple DNA labels, hybridization and ligation reactions, dendrimer molecules can be set up to act as highly labeled target-specific probes.
Formulating the prepared mixture in the presence of an appropriate buffer to form a dendrimer having a fluorescent label attached to one type of “arm” and an oligonucleotide attached to the other type of “arm”, wherein RT A dendrimer hybridization mixture is obtained comprising a dendrimer having an oligonucleotide complementary to the capture sequence of the cDNA fragment bound to the primer. CD for nucleic acids spotted on the surface of the array
Oligonucleotides designed to block non-specific interactions of NA or dendrimers can also be added at this point, and blocking oligonucleotides containing multiple identical nucleobases can be added to cDNA and microarrays derived from RNA samples. It can block long strands of identical complementary bases found in nucleic acid probes on the surface.
To prepare fluorescently labeled dendrimers, the sequence complementary to the capture sequence above the registered Cy3 RT primer and registered Cy5 RT primer was separately added to the purified dendritic core material prepared by the method described above. (See Nilson et al., Supra, and U.S. Patents' 270, '904, and' 973, supra). Next, a 30 nucleotide long oligonucleotide is synthesized that is complementary to the outer arm of a four-layer dendrimer having registered Cy3 or registered Cy5 on the 5 'side (Oligoseth, Inc., Wilsonville, OR). (Oligos etc., Inc.)). The registered Cy3 and registered Cy5 oligonucleotides are then hybridized to the outer surface of the corresponding dendrimer and covalently crosslinked. Excess capture labeled and fluorescently labeled oligonucleotides are then removed by techniques such as size exclusion chromatography and density gradient ultracentrifugation.
The dendrimer concentration is determined by measuring the optical density of the purified material at 260 nm with a UV / visible spectrometer. Fluorescence at the optimal signal / noise wavelength is measured using a fluorimeter (FluoroMax, SPEX Industries). Since Cy3 can be excited at 542 nm, the emission is measured at 570 nm. Since Cy5 can be excited at 641 nm, the emission is measured at 676 nm.
In a preferred embodiment of the present invention, a dendrimer having about 850 fluorescent dyes on each molecule is used, such as a dendrimer that can be used with the Genisphere 3DNA Array 900 labeling kit. Alternatively, conventional dendrimers having about 300 dyes or dendrimers having more than 500 fluorescent dyes can be used.
When such a dendrimer probe is used, the increase in sensitivity is remarkably increased due to the excellent signal amplification ability of the dendrimer. Increased sensitivity reduces the amount of RNA required for the assay and requires the use of a smaller initial sample. In particular, the present invention uses 0.25 to 1 microgram total RNA, or only 100 nanograms (0.1 microgram) total RNA, or 1 to 1000 nanograms poly A RNA (mRNA). It can be easily implemented. Accordingly, these improved results are preferably obtained using dendrimers having about 850 or more fluorescent dyes. Increased detection sensitivity in the art (e.g., using improved dendrimers, or other improved labeling or signal molecules) allows the invention to be used to assay smaller amounts of RNA samples.
With respect to the assay method itself, it is preferably a technique that uses a continuous hybridization step (“two-step method”) where the reverse transcribed cDNA is applied to the array for a time sufficient to hybridize to the array. A technique is used in which the cDNA molecule is hybridized to a target fixed probe, and then a washing treatment is performed to remove unbound cDNA and excess RT primer from the array. The cDNA preferably has a capture sequence incorporated into it for binding to a dendritic nucleic acid having a label capable of producing a detectable signal, as disclosed below. The fluorescently labeled dendrimer molecule (or another molecule that can bind to the capture sequence incorporated into the cDNA) is then applied to the washed array, and in the course of this second hybridization, the capture sequence associated with the cDNA. Hybridize to. Excess dendrimers are washed away during the secondary washing process, and the array is scanned to detect the signal generated by the labeled molecules.
If desired, in a further preferred embodiment, temperature cycling can be used to selectively control hybridization between the target nucleic acid and the microarray and between the capture reagent and the microarray (preferably, CDNA-microarray hybridization and cDNA-dendrimer hybridization, respectively). By using such cycling, it is possible to carefully control the hybridization such that the cDNA first hybridizes only to the microarray and then the cDNA hybridizes to the dendrimer. This treatment can be used to improve the hybridization reaction rate of each of the two components, ie, the target nucleic acid for the probe and the capture reagent for the target nucleic acid. Further details regarding the use of such temperature cycling can be found in US Non-Provisional Application No. 10 / 050,088, filed Jan. 14, 2001, US Provisional Application No. 60/0, filed Jan. 13, 2001. 261, 231 and the protocol published by the inventors and Genisphere Inc., Montvale, New Jersey, all of which are fully incorporated by reference. Reference is incorporated herein.
In a preferred embodiment of the invention, the synthesized nucleic acid is usually DNA reverse transcribed from RNA obtained from a natural source, where the RNA is total RNA, poly (A) + It can be selected from the group consisting of RNA, amplified RNA and the like. The initial RNA-derived source can be present in a variety of different samples, where the sample is generally obtained from a physiological source. Physiological sources can be obtained from a variety of sources, but the physiological sources of interest include unicellular organisms such as yeast or bacteria, and multicellular organisms such as plants and animals, particularly mammals. Where the physiological source from the multicellular organism can be obtained from a particular organ or tissue of the multicellular organism or can be obtained from an isolated cell derived therefrom. it can. When the sample RNA to be analyzed is obtained from the physiological source from which it is derived, the physiological source can be subjected to a number of processing steps, where such known processing steps include tissue Homogenization, cell isolation and cytoplasm extraction, nucleic acid extraction, poly A tailing, and the like. Methods for isolating RNA from cells, tissues, organs or whole organisms are well known to those skilled in the art, for example, Maniatis et al., Cold Spring Harbor Laboratory Press, 1989 (Cold Spring Harbor Laboratory Press, 1989), molecules Cloning: Experimental Manual, Second Edition (Molecular Cloning: A Laboratory Manual., 2nd ed.), And John Wiley & Sons, Inc., 1998 Ausubel et al., Molecular Biology Latest protocol (Current Protocols
in Molecular Biology), both of which are hereby incorporated by reference in their entirety.
The sample mRNA is preferably a target in cDNA form by hybridizing an oligo (dT) primer or RT primer to the mRNA under conditions sufficient to enzymatically extend the hybridized primer. Reverse transcribe to nucleic acid. The primer is long enough to efficiently hybridize to the mRNA tail, where this region is typically 10-25 nucleotides, usually 10-20 nucleotides, more usually 12 It is ˜18 nucleotides in length.
Given the need to use sequence-specific primers in general in application situations, standard primers as used in the present invention further include a nucleotide portion of a “capture sequence”. Suitable capture sequences referred to herein are registered trademark Cy3 RT primer capture, as disclosed, for example, in International Application No. PCT / US02 / 027799 filed September 3,2002. The sequence (Oligosetose, Inc., Wilsonville, Oreg.) Or the registered Cy5 RT primer capture sequence (Oligosetose, Inc., Wilsonville, Oregon), which is incorporated herein by reference in its entirety.
For custom primers, a capture sequence should be attached to the 5 'end of the custom-made oligonucleotide primer. In this way, the custom primer replaces the standard RT primer. Since the present invention is designed for standard RT primers, some changes may be required if a custom primer is substituted. Such changes are well known to those skilled in the art and may include adjusting the amount and formulation of the primer based on the amount and type of RNA sample used. As described above, the primer has a capture sequence consisting of a specific nucleotide sequence. The capture sequence is complementary to an oligonucleotide that is further bound to an arm of a dendrimer probe having at least one label. Such complementary nucleotides can be obtained from external vendors, or can be obtained as labeling moieties. As is well known in the art, the label can be attached directly or via a linking group to one or more oligonucleotides attached to the arm of the dendrimer probe. In a preferred embodiment, the dendrimer probe is labeled by hybridizing and cross-linking oligonucleotides labeled with registered Cy3 or registered Cy5 to the arms of the dendrimer. The oligonucleotides labeled with the registered trademark Cy3 or registered trademark Cy5 are complementary to the RT primer capture sequence of the registered trademark Cy3 or registered trademark Cy5, respectively.
When creating a target nucleic acid sample, contact the primer with RNA in the presence of reverse transcriptase and other reagents necessary to extend the primer under conditions sufficient to induce first strand cDNA synthesis. Let Although usually a DNA polymerase, various enzymes having reverse transcriptase activity can be used in the first strand cDNA synthesis step. Examples of suitable DNA polymerases include DNA polymerases derived from organisms selected from the group consisting of thermophilic and archaebacteria, retroviruses, yeasts, Neurosporas, Drosophila, primates and rodents. Suitable DNA polymerases with reverse transcriptase activity are either commercially available or isolated from organisms obtained from cells expressing high levels of the cloned gene encoding the polymerase by methods known to those skilled in the art. Here, the specific method of obtaining the polymerase is selected mainly based on factors such as convenience, cost, availability and the like. The order of mixing the reagents can be changed as desired.
In one preferred embodiment of the present invention, the cDNA synthesis protocol comprises total RNA or poly (A) + RNA (mRNA) mixed with RT primer and RNase free water to form an RNA-RT primer mixture. Including getting. As described below, very small amounts of initial RNA can be used in accordance with the present invention.
Next, the RNA-RT primer mixture is mixed and microcentrifuged, and the contents are collected at the bottom of the microcentrifuge tube. Then, the RNA-RT primer mixture is heated at an appropriate temperature (for example, 80 ° C.) for 10 minutes and immediately transferred onto ice. In a separate microcentrifuge tube placed on ice, RT buffer, DTT (dithiothreitol), RNase inhibitor, dNTP mix, and reverse transcriptase are mixed with RNase-free water (reaction) Main liquid mixture). The mixture is slowly mixed (not vortexed), briefly microcentrifuged and the contents collected at the bottom of the microcentrifuge tube to recover the reaction mixture. Next, the RNA-RT primer mixture is mixed with the main reaction mixture and incubated at an appropriate temperature (eg, about 42 ° C.) for a time sufficient to form the first strand cDNA primer extension product. Usually takes about 2 hours. The reaction is stopped with 1.0 M NaOH / 100 mM EDTA and then incubated at an appropriate temperature (eg, 65 ° C.) to denature the DNA / RNA hybrid and degrade the RNA. Next, neutralize with 2M Tris-HCl (pH 7.5).
Once this is complete, the cDNA is applied directly to the array and hybridized to it without concentrating the cDNA after synthesis. (In one additional embodiment, no purification of cDNA is performed after synthesis.) Otherwise, the mixture obtained above is added directly to the microarray, and at the second hybridization temperature, the cDNA is transferred to the microarray. Incubate for a sufficient time to bind to. Suitable hybridization conditions are well known to those skilled in the art and are outlined in Maniatis et al., Supra, where the conditions can be adjusted to obtain the desired hybridization specificity. If desired, use blocking LNA oligonucleotides as discussed in International Application No. PCT / US02 / 027799 and International Publication No. WO 03/020902 A2 filed on September 3, 2002. Thus, nonspecific binding between the cDNA and the array can be reduced. These are then referenced and incorporated herein. The array is then washed to reduce background on the array (eg, caused by free RT primers that are not incorporated into cDNA molecules).
A label molecule (preferably a dendrimer with the desired label) is then applied to the array to hybridize the label to the capture sequence of the cDNA to provide a detectable signal. After the hybridization step, a washing step is used to remove unhybridized complexes from the microarray, thereby leaving a visible discontinuous pattern of hybridized cDNA-dendrimer probes bound to the microarray. Various washing solutions and protocols for these applications are known and available to those skilled in the art. The specific wash conditions utilized will necessarily depend on the specific nature of the signal generation system used and are known to those skilled in the art who are familiar with the specific signal generation system used.
The resulting hybridization pattern of the labeled cDNA fragment can be visualized or detected by various methods, and the specific detection method is selected based on the specific label of the cDNA. Here, typical detection means include scintillation measurement, autoradiography, fluorescence measurement, calorimetry, and luminescence measurement.
Following the hybridization step and any washing steps and / or subsequent processing as described above, the resulting hybridization pattern is detected. When the hybridization pattern is detected and visualized, not only the intensity or signal value of the label is detected but also quantified, which means that the signal from each hybridization spot is measured.
After detection or visualization, the hybridization pattern can be used to determine quantitative and qualitative information about the initial RNA sample. For example, it is possible to obtain information on the gene characteristics of a labeled target nucleic acid sample that has contacted the microarray to generate a hybridization pattern. From this data, information about the physiological source from which the target nucleic acid sample originated, such as the type of gene expressed in the tissue or cell that is the physiological source and the expression level of each gene, in particular quantitative representations. Obtainable. When using the methods of the invention to compare target nucleic acids from two or more physiological sources, hybridization patterns can be compared to identify pattern differences. When using a microarray where each of the different probes corresponds to a known gene, any discrepancy can be correlated to differences in the expression of a particular gene in the physiological source being compared. Thus, for example, the methods of the present invention have applications in assaying for differences in gene expression, eg, diseased and normal tissues such as neoplastic and normal tissues, or different tissue or subtype types. The method of the present invention can be used to analyze expression differences such as
Many other variations of the above processing operations can be used consistently with the present invention. For example, instead of using RNA extracted from a sample that has been converted to cDNA prior to hybridization, the present invention can be used directly with RNA samples. In one such embodiment, an appropriate capture sequence can be ligated to the RNA using known methods of splicing RNA, such as through enzymatic means. Alternatively, if the RNA contains a specific oligonucleotide useful as a capture sequence, a complementary oligonucleotide can be attached to the dendrimer to label the RNA molecule. Further details regarding methods of using RNA directly without the need for reverse transcription are described in International Application No. PCT / US01 / 22818, filed July 19, 2001, which is hereby incorporated herein by reference. Embedded in the book.
The present invention is particularly suitable for improved cDNA synthesis and measurement methods that use very small amounts of initial starting material because it has made it possible to use smaller amounts of initial RNA samples than conventional methods. For example, in combination with 3DNA dendrimer technology (or other very sensitive signal generation techniques such as relative light scattering detection using nanogold labels such as Genicon / Invitrogen), this cDNA method can be This is particularly beneficial because the total RNA sample can be reduced to 250 nanograms or less without the need for any amplification. The present invention can easily be used with 0.25 to 1 microgram samples, or 100 nanogram (0.1 microgram) initial total RNA sample if desired, or 1 to 1000 nanograms of poly A RNA (mRNA). Can be used. This is about two orders of magnitude more than the direct uptake method that requires 20-50 micrograms of total RNA, or 1-2.5 micrograms of poly A RNA (mRNA) to achieve the same sensitivity level. Are better.
Thus, the method allows the use of very small starting samples that would otherwise be lost in post-synthesis enrichment or purification steps using other methods. As detection sensitivity increases in the art (eg, using improved dendrimers, or dendrimers with additional fluorescent dyes, or other signal generation methods), smaller amounts of RNA samples can be used in the present invention. become. Similarly, such a sample can be applied to a microarray without performing concentration after cDNA synthesis.
While the present invention can scale up the reaction, it can still eliminate the need for concentration of the final cDNA synthesis purification. A further benefit of the present invention, although avoided with the present invention, is to reduce the non-specific background on the microarray that occurs due to the presence of large amounts of cDNA, either directly or indirectly. That is. Similarly, the method results in improved data quality (especially the range of differences in gene expression studies), as a result of using very small amounts of cDNA in the on-array hybridization assay. There is a high possibility. This is due to the fact that the present invention does not concentrate cDNA after synthesis, in contrast to conventional methods. Conventional methods generally require a larger amount of sample than is required for non-3DNA methods, and hybridization on a microarray requires a smaller amount of sample, so most types of arrays In order to use the cDNA in the above, it is necessary to concentrate the cDNA.
Similarly, a further improvement provided herein is that the cDNA synthesis method, which directly incorporates the dye, purifies the cDNA synthesis product normally performed to remove excess dye and enzyme that was not incorporated into the cDNA. Is not necessary.
Furthermore, the present invention is further used in this context in that it can be easily automated as opposed to the concentration and purification steps that are currently difficult to perform automatically or robotically. Provide benefits.
Further advantages, features and aspects of the present invention will become apparent in connection with the following examples.
CDNA synthesis from total RNA Mix the following in a microtube:
1-5 μl total RNA (0.25-1.0 μg mammalian total RNA or 0.5-2.5 μg plant total RNA)
1 μl RT primer (5 pmole / μl).
Add nuclease-free water to a final volume of 6 μl.
This is the RNA-RT primer mixture.
Note: Using 5 pmoles / μl of RT primer may produce a non-specific background signal in some types of arrays (ie slides coated with poly-L-lysine). This type of background can be reduced by diluting the RT primer up to 2.5-fold with nuclease-free water before adding it to the RNA sample (Note: primer below 2 pmole / μl) If this happens, the efficiency of cDNA synthesis will deteriorate, so do not dilute lower than this.)
2. Mix and microcentrifuge briefly to collect contents at the bottom of the tube.
Heat to 80 ° C. for 3.5 minutes and immediately transfer to ice for 2-3 minutes.
4). When provided as part of a kit, the reverse transcriptase and the reaction buffer for the enzyme can be included in the kit or purchased separately. It is recommended to use SuperScript II reverse transcriptase (Gibco, catalog number 18064-014-10,000 units @ 200 U / μl).
The main mix solution for the reaction must be formulated to the final volume depending on the number of cDNA synthesis initiated simultaneously. Each cDNA synthesis requires 4.5 μl of the main reaction solution. In order to reduce pipetting errors, the main reaction mixture must be at least 9 μL (a sufficient amount for two rounds of cDNA synthesis).
Mix in separate microtubes according to the table below on ice.
This is the main reaction mixture (the main reaction mixture should be kept on ice until use).
5). Mix gently (do not vortex) and briefly microcentrifuge to collect the contents of the reaction mixture at the bottom of the tube.
6). Add 4.5 μl of the reaction solution from step 5 to 6 μl of the RNA-RT primer mixture from step 1 (to a final volume of 10.5 μl).
7). Mix gently (do not vortex) and incubate at 42 ° C. for 2 hours. 8. Stop the reaction by adding 1.0 μl of 1.0 M NaOH / 100 mM EDTA.
9. Incubate at 65 ° C for 10 minutes to denature the DNA / RNA hybrid and degrade the RNA.
10. The reaction is neutralized with 1.2 μl of 2M Tris-HCl, pH 7.5. Here, the preparation solution for cDNA synthesis can be used for experiments (microarray, blot, FISH, etc.) without requiring concentration after synthesis. If desired, this cDNA preparation can be used after some purification after synthesis.
CDNA synthesis method for use in a microarray without sample concentration after synthesis The following method is an example of a method for synthesizing cDNA for use in a microarray, according to the present invention, Eliminates the need for sample concentration after synthesis. In a preferred embodiment disclosed herein, the method is designed for Genisphere reagents, particularly to provide high sensitivity on microarrays when using very small amounts of RNA. Designed for use with the Genisphere® 3 DNA Array 900 kit (available from Genisphere Inc. of Montvale, New Jersey and Hatfield Pennsylvania). (All kit instructions provided with the Array 900 kit are incorporated herein by reference.) Alternatively, the method can be performed in a separate kit or system using the low volume synthesis method disclosed below. It is also possible to use it.
In a preferred method, better sensitivity is obtained by using the modified cDNA synthesis protocol of the present invention, which eliminates sample concentration after synthesis and thus avoids sample loss during the concentration process. In addition, by using a registered Genisphere 3 DNA capture reagent that has been modified to provide a more efficient hybridization reaction rate in the form of a dendrimer containing about 850 fluorescent dyes, it also has superior hybridization efficiency. Genisphere® 2-fold enhanced cD designed to obtain
The sensitivity can be further improved by using a buffer for NA hybridization (2X Enhanced cDNA Hybridization Buffer).
The Genisphere® 3 DNA Array 900 Kit is easy to use and is designed for arrays that print oligonucleotides or PCR products (cDNA). First, either total RNA or poly (A) + RNA is reverse transcribed using a deoxynucleotide triphosphate mixture and specific RT dT primers. Then, the cDNA and the fluorescent 3DNA reagent are successively hybridized to the microarray. The fluorescent 3 DNA reagent contains a “capture sequence” complementary to the sequence on the 5 ′ end of the RT primer, and thus hybridizes to the cDNA.
The 3DNA array 900 labeling system provides a more predictable and consistent signal than direct or indirect dye uptake for two reasons. The first is that since the fluorescent dye is part of the 3DNA reagent, it is not necessary to incorporate it during the cDNA preparation process. This avoids inefficient hybridization of cDNA to the array caused by incorporation of a fluorescent dye and nucleotide conjugate into the reverse transcript. Second, since each 3DNA molecule contains an average of about 850 fluorescent dyes, and each bound cDNA can be detected by one 3DNA molecule, the signal resulting from each message is largely independent of the base composition and length of the transcript. . In contrast, the signal resulting from each message labeled by dye incorporation varies with the base composition and length of the message.
It should be noted that when using a total RNA sample, the pattern of the array produced by the kit may be slightly different from the pattern produced by the labeling method with direct or indirect dye incorporation. The reason is that reverse transcriptase is known to label not only RNA but also genomic DNA (without the need for primers). Thus, dye uptake labeling methods may also produce labeled genomic DNA. When labeled genomic DNA binds to the microarray, the amount of fluorescence is inappropriate and misleading for false positive results for genes that do not exist and / or array elements that also bind cDNA produced by reverse transcription of RNA. Bring. In contrast, the 3DNA reverse transcription method uses unlabeled nucleotides that cannot incorporate any fluorescence into the genomic DNA, thus eliminating the possibility of involvement of signals from the genomic DNA. Thus, since the 3DNA label is different from the dye incorporation labeling method, the array pattern produced can vary depending on which labeling method is used. However, in various expression experiments, if genomic DNA is removed from the sample, the expression pattern between the two RNA samples should be the same regardless of the labeling method.
Kit Contents (Some components of the Genisphere® Array 900 kit, in particular vials 1, 2 and 11, may not be compatible with other microarray labeling kits.)
Vial 1 Cy3 / Alexa Fluor 546 (red cap) or Cy5 / Alexa Fluor 647 (blue cap) 3DNA array 900 capture reagent. (The dendrimer probe reagent described herein, labeled with about 850 fluorescent dyes per molecule. A dendrimer labeled with Cy3 (or Alexa Fluor 546) is a 5 ′ complementary to the dendrimer bound to the capture sequence. Only cDNA synthesized with primers containing terminal sequences contain the same unique capture sequence that allows dendrimers to be targeted, dendrimers labeled with Cy5 (or Alexa Fluor 647) have different capture sequences. Including, dendrimers labeled with Cy3 and Cy5 are capable of differentially binding to cDNA.)
Vial 2 Cy3 / Alexa Fluor 546 (red cap) or Cy5
/1.0 pmole / μl RT primer for Alexa Fluor 647 (blue cap). (RT primer (48-mer) containing 3'-end dT (17) and 5'-end 31-mer capture sequence).
Vial 3 Deoxynucleotide triphosphate mixture (10 mM dATP, dCTP, dGTP, and dTTP each in water).
Vial 4 Superase-In ™ RNase inhibitor (Ambion).
Vial 5 buffer for 2x-enhanced cDNA hybridization (Genisphere in Montvale, NJ and Hatfield, PA)
Inc. Available from).
Vial 6 Hybridization buffer based on 2xSDS (0.50M NaPO4; 1% SDS; 2mM EDTA: 2xSSC; 4x Denhardt's solution)
Vial 7 Hybridization buffer based on 2x formamide (50% formamide; 8x SSC; 1% SDS; 4x Denhardt's solution)
Vial 8 Anti-fading reagent (0.1M DTT)
Vial 9 LNA ™ dT blocker (for PCR product (cDNA) microarray) (13 out of 36 nucleotides are LNA (locked nucleic acid, Exiqon)
AG) dT blocker containing nucleotides that are residues. For example, US Non-Provisional Application No. 10 / 234,069, filed September 3, 2002, claiming priority of US Provisional Application No. 60 / 316,116, filed August 31, 2001. And “Methods for Blocking Nonspecific Hybridization of Nucleic Acids”, International Application No. PCT / US02 / 027799, filed Sep. 3, 2002, International Publication No. WO03. / 020902 See A2. All of which are incorporated herein by reference).
Vial 10 Nuclease-free water (available from Ambion)
Capture 5.0 pmole / μl RT primer (3 ′ end dT (17), and 5 ′ end 31-mer to vial 11 Cy3 / Alexa Fluor 546 (red cap) or Cy5 / Alexa Fluor 647 (blue cap) RT primer containing the sequence (48-mer)).
Vials 1-11 must be stored in the dark at -20 ° C. Vial 1 can also be stored at 4 ° C. for a short period (about 1 week).
Other required materials Additional materials required to utilize the method include the following.
• Microarray: commercial or in-house prepared from either oligonucleotides or PCR / cDNA products.
A microarray reader equipped to read Cy3 / Alexa Fluor 546 fluorescent color and / or Cy5 / Alexa Fluor 647 fluorescent dye. Total RNA sample (100 ng / μl or more) or poly (A) + RNA sample (50 ng / μl or more)
Reverse transcriptase SuperScript II (Invitrogen catalog number 18064-014-10,000 units, @ 200 U / μl)
Genisphere RT enzyme (Genisphere catalog number RT300320)
Or other equivalent reverse transcriptase (such as Promega).
Cot-1 DNA (selective, species specific, available from Invitrogen)
・ Reagent grade deionized water (recommended: VWR catalog number RC9150-5)
Note: As described in the Internet List Server, the registered trade name MilliQ water has been shown to damage Cy5 (http://groups.yahoo.com/group/microarray/messages). / 2867).
・ 1.0 M NaOH, 100 mM EDTA (solution for stopping cDNA synthesis)
10 mM Tris-HCl, pH 8.0 / 1 mM EDTA (1 × TE buffer) Glass coverslip (Corning brand distributed by Fisher or VWR) or LifeSlipsO (Erie) Scientific).
・ 2 × SSC, 0.2% SDS buffer ・ 2 × SSC buffer ・ 0.2 × SSC buffer ・ Glass coplinger (or equivalent)
0.5M NaOH / 50mM EDTA (optional: for use with Appendix A or B)
1M Tris-HCl, pH 7.5 (optional: for use with Appendix A or B)
-Millipore Microcon YM-30 Centrifugal Filter (30,000 molecular weight cut-off, Millipore catalog number 42409) (optional: for use with Appendix C--Millipore Microcon treatment)
・ Isopropanol (optional: for use with Appendix D)
0.2% SDS buffer (optional: for use with Appendix D)
95% ethanol (optional: for use with Appendix D)
・ Dye Saver (Genisphere catalog number Q100200) (optional: to store fluorescent signals and prevent photobleaching)
The preparation and use of high quality RNA determines the success of microarray experiments.
Using degraded RNA, the RT reaction with dT primer only produces a short poly dT tail as opposed to the full-length cDNA. Little or no. If a degraded RNA sample has to be used, good results may be obtained if the sample is labeled with a 3DNA array 350RP (version 2) kit from Genisphere.
It is strongly recommended to use RNase inhibitor (Superase-In, vial 4). The RNase inhibitor should be added to a stock RNA sample suspected of being contaminated with RNase. In addition, an inhibitor should be added in order to prevent RNA from being degraded during cDNA synthesis during the reverse transcriptase reaction. For more information on RNA degradation by RNases, see the following references (all of which are incorporated herein by reference). Sambrook, J. et al. Fritsch, E .; F. , And Maniatis, T .; “Molecular Cloning: Experimental Manual (Molecular Cloning, A Laboratory)
(Second Edition) Cold Spring Harbor Laboratory Press, 1989; Ausubel, F.M. M.M. Brent, R.M. , Kingston, R .; E. , Moore, D .; D. Seidman, J .; G. Smith, J .; A. , And Struhl, K .; “Current Protocols in Molecular Biology” John Wiley & Sons, Inc. 1998.
The 3DNA array 900 labeling system does not label genomic DNA. Therefore, it is not essential to remove genomic DNA contamination. However, if the genomic DNA is decomposed away, the amount and quality of RNA present can be measured more accurately. Further, if the genomic DNA is left in the sample, it may bind to a part of the RT enzyme and the enzyme cannot be used for reverse transcription. DNase free from RNase is recommended for degrading contaminating genomic DNA.
When DNase is used, it is important to completely inactivate this DNase before proceeding to the cDNA synthesis process. Methods for inactivating DNase include phenol-chloroform extraction and the use of Qiagen's registered RNeasy kit. Inactivation of DNase by high temperature cannot completely inactivate the enzyme.
High quality RNA has the following characteristics.
1. The ratio of OD 260/280 is 1.9 to 2.1.
2. On agarose gels, plant and mammalian total RNA appear as two distinct bright bands. In mammalian RNA, the bands are at about 4.5 kb and about 1.9 kb, representing the 28S and 18S ribosomal subunits, respectively.
(As such, any suitable protocol known in the art for RNA purification methods for producing high quality RNA can be used, such as that of the registered trademark Genisphere).
Microarray selection and preparation:
Pre-spot cDNA arrays produced by Genomic Solutions, Agilent, and Takara do not require special processing prior to use. Pre-spot oligo arrays manufactured by MWG Biotech require pre-cleaning as described in Appendix E for optimal results. For other purchased arrays, the microarray is prepared or pretreated as described by the manufacturer. For arrays created “in-house”, it is recommended that one of the protocols in Appendix D be used to pre-process the array. These protocols do not require succinic anhydride treatment, resulting in stronger signals and lower background on many types of arrays (this protocol is not compatible with Agilent arrays) Please keep in mind.)
Genissphere uses a certain amino-silane coated slide, specifically Clonetech DNA-Ready, for spotting PCR products (cDNA).
The use of Type II, Corning GAPS II and UltraGAPS, and Telechem SuperAmine slides is recommended. It has been demonstrated that good DNA binding can be obtained when these slides are used with a 3DNA array 900 kit.
Arrays prepared on poly-L-lysine, aldehyde or amino-silane (eg Corning GAPS) surfaces are either pre-washed or pre-hybridized to reduce the background seen after hybridization. It will be necessary. See Appendix E or F for treatments that help reduce background on the microarray, respectively.
As the array ages, the specific signal may decrease and the amount of background noise increases. In some cases, as the array ages, the spotted probe will show background in the “green” (Cy3) channel. This occurs with arrays on all substrate surfaces, both commercially available and “in-house”. Both commercial and “in-house” arrays are subjected to quality control testing immediately after spotting (or receipt of the array) and periodically thereafter to provide a characteristic non-specific back when the array and other materials are out of date Ground noise should be confirmed. Also, all solutions used for array processing after spotting should be tested to ensure that they are consistent and have minimal contribution to non-specific array background.
Hybridization conditions :
Because microarrays are diverse, it is important to determine optimal hybridization conditions for each array type, including optimal buffer selection. For example, the Genisphere Array 900 kit includes the following hybridization buffers:
1. Double-enhanced cDNA hybridization buffer (vial 5) —used only for cDNA hybridization steps when additional sensitivity is desired. This buffer can be used in arrays that withstand relatively high temperatures (up to 65 ° C.).
2. Hybridization buffer based on 2 × SDS (vial 6) —for both cDNA and 3DNA hybridization steps, this buffer can be used for arrays that withstand relatively high temperatures (up to 65 ° C.) .
3. Hybridization buffer based on 2 × formamide (vial 7) —for both cDNA and 3DNA hybridization steps, this buffer is a high stringency formulation and should be used at relatively low temperatures Designed to.
It is recommended to test the hybridization buffer to determine which is best suited for the type of array being utilized. Note that a relatively large amount of hybridization volume is required under the coverslip because the 2x enhanced cDNA hybridization buffer (vial 5) is viscous and loses volume upon pipetting. Furthermore, the hybridization temperature range included in this product manual is provided as a guide. Genisphere recommends that the optimal hybridization temperature be experimentally determined for each microarray lot. For example, the poly-L-lysine surface of the array may come off at the hybridization temperature required to use the vial 5 and 6 buffers. If you have experienced this problem, use vial 7 according to the instructions.
Since most PCR products contain poly (dA / dT) sequences, it is recommended to use an LNA dT blocker (vial 9) on the cDNA array. LNA dT blocker is a highly efficient poly-T blocking reagent designed by Genisphere (patent pending, International Application No. PCT / US02 / 027799, filed September 3, 2002, International Publication No. See WO 03/020902 A2, which is incorporated herein by reference in its entirety). It is designed to completely block all poly A sequences present in the array features, including control spots that contain only poly dA sequences. This novel blocking reagent contains locked nucleic acid (LNA) nucleotides (patented Exiqon technology) at key positions in the synthetic strand of poly dT. The presence of these modified nucleotides stabilizes the hybridization between the complementary strands of the nucleic acid, thereby improving the blocking ability of the poly dT reagent. See reference 3 below for more information on LNA chemistry. The average array signal intensity for a blocked array may be lower compared to an unblocked array, but does not deleteriously affect the specific signal resulting from reverse transcribed cDNA bound to complementary array elements It should be. A 2 μl volume of LNA dT blocker (vial 9) is recommended for each hybridization, but depending on the array, better efficiency can be obtained by using an increased amount of LNA dT blocker (3-4 μl) It may be.
Furthermore, a competing nucleic acid (for example, species-specific Cot-1 DNA from Invitrogen) is added as necessary. Use competing nucleic acids at one-tenth the mass of total RNA input (ie, use 100 ng Cot-1 DNA for 1 mg total RNA). If there are too many competitors, the signal may be reduced because excess competitors interact non-specifically with the finite cDNA during hybridization. It is recommended to denature Cot-1 DNA and other competing nucleic acids (95-10 ° C. for 5-10 minutes) prior to addition to the hybridization mixture.
Procedure of use The steps necessary to synthesize cDNA from total RNA are summarized below. If poly (A) + RNA is used, follow the procedure for cDNA described in Appendix B. Because the amount of microarray and RNA preparation varies, the exact amount of RNA required for a given experiment is typically 0.25 to 1.0 μg of total animal RNA and total plant RNA. It is in the range of 0.5 to 2.5 μg. When used for the first time, it is recommended to synthesize cDNA starting from 1 μg of animal total RNA and 2 μg of plant total RNA. Depending on the quality of the RNA sample and array, greater or lesser amounts of RNA may be required to obtain optimal results.
Larger amounts of RNA (> 2 μg) can be used for large-scale cDNA synthesis. Appendix A details a simple method for synthesizing cDNA from 2-50 μg of total RNA. Alternatively, the method outlined on page 11 can be scaled up to accommodate larger amounts of total RNA. However, since a large reaction volume is possible, it is necessary to concentrate the target cDNA sample (see Appendix C). In addition, cDNA prepared by using a procedure with other Genisphere kits can also be used with the Array 900 kit. The following Genisphere kit includes components for cDNA synthesis that produce cDNA compatible with Array 900 3DNA Capture Reagent (vial 1).
Array 350 (catalog numbers: W300100, W300110, W300130, W300140, W300180 and W300184)
Array 350HS (catalog numbers: H300100, H300110, H300130, H300140, H300180, and H300184)
Array 50 (version 2) (catalog numbers: B100121, B100122, B100171, B100172, B100187 and B100189)
Low-volume synthesis method without post-synthesis concentration Notes: This treatment method requires pipetting of very small samples and reagents. It is recommended to use a pipetter designed for accurate pipetting from 0.5 μl to 10 μl.
1. Prepare RNA-RT primer mix in 0.5 mL “non-stick” microtube.
Total RNA 1-5 μl (0.25-1.0 μg mammalian total RNA or 0.5-2.5 μg plant total RNA)
RT primer 1μl (vial 2, 1 pmole/μl)
Add nuclease free water (vial 10) to a final volume of 6 μl.
2. Mix the RNA-RT primer mix and microcentrifuge briefly to collect the contents at the bottom of the tube.
Heat to 80 ° C for 3.5 minutes, then immediately transfer to ice for 2-3 minutes. Centrifuge briefly to collect the contents at the bottom of the tube and return to ice.
4). Prepare the main reaction mixture in a microtube placed on ice (see table below). The main reaction solution for the reaction must be formulated to a final volume depending on the number of cDNA synthesis started simultaneously. Each cDNA synthesis requires 4.5 μl of the main reaction solution. In order to reduce pipetting errors, the main reaction solution must be at least 9 μL.
Mix gently (do not vortex) and briefly microcentrifuge to collect the contents of the main reaction mixture at the bottom of the tube. Keep on ice until use.
5). Add 4.5 [mu] l of the main reaction solution in step 4 to 6 [mu] l of the RNA-RT primer mixture in step 3 (final volume 10.5 [mu] l).
6). Mix gently (do not vortex) and incubate at 42 ° C. for 2 hours.
7. Stop the reaction by adding 1.0 μl of 1.0 M NaOH / 100 mM EDTA.
8. Incubate at 65 ° C for 10 minutes to denature the DNA / RNA hybrid and degrade the RNA.
9. Neutralize reaction with 1.2 μl 2M Tris-HCl, pH 7.5.
10. Proceed to “Sequential Hybridization of cDNA and 3DNA to Microarray” below.
Sequential hybridization of cDNA and 3DNA to microarray (Note: The following protocol is not compatible with Agilent arrays)
cDNA hybridization 1.2x hybridization buffer (vial 5, vial 6, or vial 7) is thawed and reheated by heating to 65-70 ° C for at least 10 minutes or until completely resuspended. Suspend. Vortex to ensure that the ingredients are resuspended evenly. If necessary, repeat heating and vortexing until all material is resuspended. Microcentrifuge for 1 minute.
2. For each array, prepare the following cDNA hybridization mix for use with 24 x 50 glass coverslips.
No.1 for cDNA synthesis 12.7μl
No. 2 for cDNA synthesis or nuclease free water for one channel experiment (vial 10) 12.7 μl
2 × Hybridization Buffer (Vial 5, Vial 6, or Vial 7) (50% of the final cDNA hybridization mixture) 27.4 μl
LNA dT blocker (vial 9) (may not be required for oligo array) 2 μl
Total volume 54.8μl
Optional: If desired, 1.0 μl of COT-1 DNA can be added (need to be denatured at 95-100 ° C. for 10 minutes before use).
* Alternatively, if a smaller cover slip and hybridization volume are desired, simply prepare a larger amount of cDNA than is used on one array and load a lower cDNA volume per array. For example, starting with 1000 ng of total RNA in cDNA synthesis and using half the volume of the final cDNA reverse transcription reaction to give a hybridization volume of 30 μl containing 500 ng of cDNA from total RNA per channel. Can do. The final hybridization mixture will contain:
No.1 for cDNA synthesis 6.5μl
No.2 for cDNA synthesis 6.5μl
2 × Hybridization buffer 15 μl
LNA blocker 2.0μl
Total volume 30.0μl
If a larger coverslip or lifter slip is required, add an equal volume of 2x hybridization buffer (vial 5, 6 or 7) and nuclease-free water (vial 10) to mix for cDNA hybridization The volume of the liquid can be increased.
Note: The 2x enhanced cDNA hybridization buffer (vial 5) is viscous and loses volume when pipetting, requiring a relatively large volume of hybridization. To address this, add an equal volume of nuclease-free water (vial 10) and 2 × enhanced cDNA hybridization buffer (vial 5) to increase the total volume of the cDNA hybridization mixture.
(Note: It has not been confirmed that this product can be used in a hybridization station.)
3. After all components are added, gently vortex the cDNA hybridization mixture and briefly microcentrifuge. This cDNA hybridization mixture is first incubated at 75-80 ° C. for 10 minutes and then at the hybridization temperature until loaded into the array (see the table below step 5 for recommended hybridization temperatures). . Preheat the microarray to the hybridization temperature.
4). Gently vortex the cDNA hybridization mix and briefly centrifuge. Add the cDNA hybridization mixture to the preheated microarray, taking care to leave a precipitate at the bottom of the tube.
5). Place an appropriate glass cover slip on the array. The array is incubated overnight at a suitable hybridization temperature in a dark humidified chamber.
The recommended hybridization temperature in this protocol is given as a starting point and should be used as a guide. It may be necessary to adjust the temperature to meet stringency requirements that depend on the nature of the nucleic acids spotted on the array as well as the chemical nature of the slide surface. In particular, when the hybridization temperature is increased by 5 ° C., non-specific signals can be removed.
Washing after cDNA hybridization :
Preheat wash buffer with 1.2x SSC, 0.2% SDS.
PCR product (cDNA) array is 55-65 ° C
Oligonucleotide spotted array at 42 ° C
2. Remove the coverslip by washing the array in preheated 2 × SSC, 0.2% SDS for 2-5 minutes or until the coverslip is lifted *. If a 2-fold enhanced cDNA hybridization buffer (vial 5) is used, it may take longer to remove the coverslip.
3. Wash for 10-15 minutes in preheated 2X SSC, 0.2% SDS.
4). Wash for 10-15 minutes in 2 × SSC at room temperature.
5). Wash for 10-15 minutes in 0.2 × SSC at room temperature.
6). Transfer the array to a dry 50 mL centrifuge tube and orient the slide so that all label is down in the tube. Without capping the tube, immediately centrifuge at 800-1000 RPM for 2 minutes to dry the slide (this process results in high background even a slight delay). Do not touch the surface of the array.
7). To achieve optimal array efficiency, it may be necessary to further optimize the wash conditions. If it is necessary to reduce the background on the array, it is recommended to increase some or all wash times to 15-20 minutes. Shaking during washing may also help reduce background due to non-specific binding to the surface of the array.
* Note: If it is difficult to remove the coverslip, it may be because it has dried. To prevent this problem from recurring in future experiments, add equal volumes of nuclease-free water (vial 10) and 2x hybridization buffer (vial 5, 6 or 7) to make the total volume of the cDNA hybridization mixture. Increase. In addition, make sure that the hybridization chamber is properly humidified and sealed.
3DNA hybridization 1.3 DNA array 900 capture reagent (vial 1) is prepared. There is a need to break up aggregates that may result from the freezing process.
a. Thaw 3DNA array 900 capture reagent (vial 1) in the dark at room temperature for 20 minutes.
b. Vortex set to maximum, stir for 3 seconds, and microcentrifuge briefly.
c. Incubate at 50-55 ° C for 10 minutes.
d. Vortex set to maximum and stir for 3-5 seconds.
e. Microcentrifuge the tube briefly and collect the contents at the bottom.
Samples are checked for aggregates prior to use and, if necessary, vortex mixing is repeated. Aggregates appear as small bubbles or flakes on the side of the tube below the solution surface. If necessary, repeat steps ae.
Thaw and resuspend 2.2 × hybridization buffer (vial 6 or vial 7) by heating to 70 ° C. for at least 10 minutes or until completely resuspended. Vortex to ensure that the ingredients are resuspended evenly. If necessary, repeat heating and vortexing until all material is resuspended. Microcentrifuge for 1 minute.
Precautions: Do not use 2x enhanced cDNA hybridization buffer (vial 5) in the 3DNA hybridization step.
3. The anti-fading reagent (vial 8) suppresses the fluorescent dye from fading after hybridization. A stock solution is prepared by adding 1 μl of antifade reagent to 100 μl of 2 × hybridization buffer (vial 6 or vial 7). Store unused hybridization buffer at -20 ° C and use within 2 weeks. However, if the array is printed on an aldehyde-coated slide, the background will be blurred and this antifade reagent should not be used. The anti-fading reagent is frozen again after use.
4). For each array, prepare the following 3DNA hybridization mix for use with 24x50 glass coverslips *.
Cy3 / Alexa Fluor 546 3DNA array 900 capture reagent (vial 1) 2.5 μl
Cy5 / Alexa Fluor 647 3DNA array 900 capture reagent (vial 1) 2.5 μl
2 × Hybridization buffer (vial 6 or 7) (50% of 3DNA hybridization mixture) 27.5 μl
Nuclease-free water (vial 10) 22.5 μl
Total volume 55.0μl
Note: For single channel expression analysis, use 2.5 μl of nuclease free water (vial 10) instead of the second 3DNA array 900 capture reagent.
* Alternatively, if a smaller cover slip and hybridization volume are desired, a volume of 2x hybridization buffer (vial 6 or 7) and nuclease-free water (vial 10) is appropriate for the desired cover slip. Adjust to capacity. For example, a final 3 DNA hybridization mixture with a volume of 30 μl includes:
2 × Hybridization buffer (vial 6 or 7) (50% of 3DNA hybridization mixture) 15.0 μl
Nuclease-free water (vial 10) 10.0 μl
5.3 Gently vortex the DNA hybridization mixture and briefly centrifuge. This 3DNA hybridization mixture is first incubated at 75-80 ° C. for 10 minutes and then at the hybridization temperature until loaded into the array (see table below step 7 for recommended hybridization temperatures) .
6.3 Gently vortex the DNA hybridization mixture and briefly centrifuge. Add the 3DNA hybridization mixture to the preheated microarray, taking care to leave a precipitate at the bottom of the tube. (Preheating the microarray to the hybridization temperature can reduce the background.)
7. Place a 24 × 50 glass coverslip on the array. If a larger cover slip or lifter slip is required, add an equal volume of 2 × hybridization buffer (vial 6 or 7) and nuclease-free water (vial 10) to add 3 mL hybridization mixture. The capacity can be increased. The array is placed in a dark humidified chamber and incubated at the appropriate hybridization temperature for 4-5 hours.
Washing after 3DNA hybridization After hybridization, the slide is washed several times to remove unbound 3DNA molecules. These washings are done in the dark to prevent photobleaching and fading of the fluorescent dye. In order to suppress Cy5 fading after hybridization, it may be beneficial to include DTT at a final concentration of 0.5 to 1 mM in the buffer for the first two washes. Be sure to work with fresh DTT, as old or low quality DTTs can increase the background that appears “haze” in the Cy3 channel. See Appendix G for recommendations on inhibiting Cy5 degradation when performing microarray experiments.
Precautions: When preparing the washing buffer, avoid the use of water that can cause damage to Cy5 / Alexa 647. As described in the Internet List Server, the registered trade name MilliQ water has been found to compromise Cy5 (http://groups.yahoo.com/group/microarray/messages/2867). ). Also, the DEPC-treated solution must make sure that all DEPC is completely removed (DEPC is a strong oxidant). Alternatively, the use of non-DEPC treated nuclease free solutions is recommended. Solutions (water, buffers, etc.) commercially available from Ambion have been found to work well with Cy5 labeled microarrays. In addition to Ambion water, DI water from VWR (catalog number RC91505) can also be recommended. The water from Ambion and VWR has been confirmed to be usable for microarrays and does not contain components that oxidize Cy5.
Pre-warm the 1.2 × SSC, 0.2% SDS wash buffer as follows.
1. PCR product (cDNA) arrays and oligonucleotide arrays longer than 50 nucleotides in length at 65 ° C,
2. Oligonucleotide arrays shorter than 50 nucleotides are 42 ° C
8). Remove the coverslip by washing the array in preheated 2 × SSC, 0.2% SDS for 2-5 minutes or until the coverslip is lifted *.
9. Wash for 10-15 minutes in preheated 2X SSC, 0.2% SDS.
10. Wash for 10-15 minutes in 2 × SSC at room temperature.
11. Wash for 10-15 minutes in 0.2 × SSC at room temperature.
12 Transfer the array to a dry 50 mL centrifuge tube and orient the slide so that all label is down in the tube. Without capping the tube, immediately centrifuge at 800-1000 RPM for 2 minutes to dry the slide (this process will result in high background even a slight delay). Do not touch the surface of the array.
To achieve optimal array efficiency, it may be necessary to further optimize the wash conditions. If it is necessary to reduce the background on the array, some or all of the wash time is increased to 15-20 minutes. Shaking during washing may also help reduce background due to non-specific binding to the surface of the array.
Proceed to “Signal detection” or first apply DyeServer coating (Genisphere catalog number Q100200) to store the fluorescent signal.
* Note: If it is difficult to remove the coverslip, it may be because it has dried. To prevent this problem from recurring in future experiments, add equal volumes of nuclease-free water (vial 10) and 2X hybridization buffer (vial 6 or 7) to increase the total volume of the 3DNA hybridization mixture. Let In addition, make sure that the hybridization chamber is properly humidified and sealed.
Signal detection Important: Store the array in the dark until scanning. The fluorescence of 3DNA reagents, especially Cy5 and Alexa Fluor 647, can be rapidly attenuated by oxidation even under steady light. Cy5 / Alexa Fluor when performing microarray experiments
See Appendix F for recommendations on suppressing 647 degradation.
The microarray is scanned according to the scanner manufacturer's instructions. Excessive multiple scans are avoided because dyes can photobleach when exposed to the light source of the scanner.
When using a Packard scanner, it is recommended that you start with the laser set to 80% power and use the “Auto Balance” feature or the table below to Set initial scanning parameters to balance the channels. In order to balance the various fluorophore channels, it may be necessary to adjust the laser output of the scanner and the voltage on the photomultiplier tube (PMT). If the PMT setting is too high, the observed background may be unacceptable. In such cases, the PMT setting should be lowered to increase the laser power and optimize the signal to noise ratio. However, after one scan, the laser setting should not be too high (> 90-95%) to prevent photobleaching of fluorescent dyes, especially Cy5 / Alexa Fluor 647.
Note: Offsetting the laser or PMT to balance the image can result in a non-linear distribution of data in each channel. In such cases, statistical standardization will be required. Refer to the instrument's instruction manual for further instructions.
When using an Axon 4000 series scanner, the recommended PMT settings are as follows:
The following references have additional background descriptions as techniques discussed herein, and are incorporated herein by reference in their entirety.
1. Nilsen, T .; W. Grayzel, J .; , And Prensky, W.M. “Dendric Nucleic Acid Structures”. J. et al. Theor. Biol. (1997) 187:
2. Steers, R.D. L. , Getts, R .; C. , Gullans, S .; R. "A novel, sensitive detection system for high-density microarray using dendrimer technology (A novel, sensitive detection system for
high-density microarrays using dendrimer technology). Physiol Genomics 3: 93-9
9, 900.
3. Singh, S.H. K. Nielsen, P .; , Kohskin. A. A. , And Wengel, J.A. LNA (Locked Nucleic Acids): Synthesis and high-affinity nucleic acid recognition. Chem Commun. 455-456, 1998.
Note: Cy is a trademark of Amersham Bioscience, Alexa Fluor is a trademark of Molecular Probes, RNeasy and Qiagen are trademarks of Qiagen, and Superase- In is a trademarked product of Ambion, Exiqon and LNA are trademarks of Exiqon A / S, Millipore, MilliQ and Microcon are trademarks of Millipore, and LiftSlip is Trademark of Erie Scientific Co., and also 3DNA, Genisphere, Array 350RP, Array 350, rray 50, Array 900 and DyeSaver is, New Jersey Montvale (Montvale, New
Is a trademark of Datascope Corp. of Jersey.
Scale-up cDNA Preparation Method A scale-up reverse transcription reaction can be performed from 2-50 μg of total RNA to provide extra cDNA for repeated experiments, cDNA quantification, or other parallel analysis.
1. Prepare the RNA-RT primer mix in a microcentrifuge tube without 0.5 or 1.5 mL RNase.
1-10 μl total RNA (2-50 μg mammalian total RNA or 25-125 μg plant total RNA)
1 μl RT primer (vial 11, 5 pmole / μl).
Add RNase-free water to a final volume of 11 μl.
2. The RNA-RT primer mixture is mixed and microcentrifuged briefly to collect the contents at the bottom of the tube.
3. Heat to 80 ° C. for 10 minutes and immediately transfer to ice for 2-3 minutes.
4). In a separate microtube, mix the following (on ice):
4 μl of 5 × Superscript II first strand buffer or equivalent reaction buffer (supplied with the enzyme)
2 μl of 0.1 M dithiothreitol (DTT) (supplied with the enzyme)
1 μl Superase-In (vial 4)
1 μl of dNTP mixture (vial 3)
1 μl SuperScript II enzyme, 200 units This is the reaction solution. The final volume should be 9 μl. Mix gently (do not vortex) and microcentrifuge briefly to collect contents at the bottom of the tube. Keep on ice until use.
5). Add 9 μl of the reaction solution from step 4 to 11 μl of the RNA-RT primer mixture from step 3 (final volume 20 μl).
7. Stop the reaction by adding 3.5 μl of 0.5 M NaOH / 50 mM EDTA.
8. Incubate at 65 ° C. for 10 minutes to denature the DNA / RNA hybrid and degrade the RNA.
Neutralize the reaction with 9.5 μl of 1 M Tris-HCl, pH 7.5. The obtained solution is the target cDNA.
10. Dilute the cDNA to a concentration suitable for the desired hybridization volume.
Proceed to “Sequential Hybridization of cDNA and 3DNA to Microarray”.
Preparation of cDNA from poly (A) + RNA The following procedure summarizes the steps required to synthesize cDNA from poly (A) + RNA. Because microarrays and RNA preparations vary in quality, the exact amount of RNA required for a given experiment will range from 12.5 to 50 ng poly (A) + RNA. For first-time users, 50 ng of poly (A) + RNA is recommended as a starting point for cDNA synthesis.
1. In a microcentrifuge tube without 1.5 mL RNase, mix:
1-10 μl of poly (A) + RNA (25-100 ng)
1 μl Superscript II enzyme, 200 units This is the reaction solution. The final volume should be 9 μl. Mix gently (do not use vortex) and briefly centrifuge briefly to collect contents at the bottom of the tube. Keep on ice until use.
5. Add 11 μl of the RNA-RT primer mixture of step 3 to 9 μl of the reaction mixture of step 4 (final volume 20 μl).
Concentration of cDNA A cDNA sample can be concentrated using a Microcon YM-30 centrifugal filtration device (molecular weight cut-off 30,000, Millipore catalog number 42409) manufactured by Millipore. These devices can reduce the volume of the cDNA synthesis reaction to 3-10 μl in about 8-10 minutes. The following procedure repeats the manufacturer's instructions with minor modifications to the 3DNA array 900 kit.
Usage notes: The use of a Millipore Microcon YM-30 centrifugal filtration device can result in significant loss of small amounts (<1.0 μg) of cDNA samples.
Important: Microcon YM-30 users must evaluate their centrifugation settings to determine the optimal time and speed settings to achieve a final volume of 3-10 μl.
2. Add 100 μl of 1 × TE buffer to the Microcon YM-30 sample container and pre-clean the container membrane.
4. Rotate at 10-14,000g for 3 minutes.
5). Bring the volume of the cDNA reaction to 100 μl with 1 × TE buffer. Add all of the cDNA reaction to the Microcon YM-30 sample container. Do not touch the membrane with the tip of the pipette.
6. Place the tube / sample container assembly into a fixed angle rotor tabletop centrifuge capable of 10 to 14,000 g.
7. Centrifuge for 8-10 minutes at 10-14,000 g.
9. Add 5 μl of 1 × TE buffer to the sample vessel membrane without touching the membrane. Tap the side of the concentrator to facilitate mixing of the concentrate with 1 × TE buffer.
11. Separate the sample container from the collection tube and discard the container. Write down the volume collected at the bottom of the tube (total volume 3-10 μl). The cDNA sample can be stored in a collection tube for later use.
12 Add water to the desired cDNA volume.
Array processing procedure (without succinic anhydride)
Option 1 (recommended) (crosslink, isopropanol wash and boil)
1. Preheat (boiling) 2 liters of reagent grade deionized distilled water (the highest quality water available) to 95-100 ° C. in a 4 liter beaker on a hot plate. 2. Transfer 250 mL of isopropanol to a glass rectangular staining dish and place a small stir bar in the dish. Place the dish on a magnetic stir plate and allow the bar to stir slowly and at a steady rate.
3. Harvest the raw array. Carefully pick up a slide at the corner and hold it over boiling water (from step 1) for 5 seconds. Make sure the array is facing up. The slide is shaken in the air for 3 seconds and then placed on a non-fibrous laboratory cloth with the array side up. Repeat until 8 slides are hydrated and dry.
4. Transfer 8 slides to the crosslinker set at 50-220 mJ with the array side up.
5). After cross-linking, the 8 arrays are transferred into grooved glass / metal Wheaton staining slide holders (the slides should not be placed in the grooves on both ends). The holder with the slide is placed in isopropanol (from step 2) and incubated for 15 minutes with agitation.
6). Transfer the slide holder into boiling water (from step 1) and incubate for 8-10 minutes. Make sure the slide is under water.
7). Remove the slide holder from boiling water and place it on a laboratory cloth to remove excess moisture. The array is now ready for hybridization.
Option 2 (crosslink, SDS wash, boil, and cold ethanol rinse)
1. Prepare 2 liters of 0.2% SDS solution in reagent grade deionized distilled water (highest quality water). For example, 40 mL of 10% SDS and 1960 mL of water are mixed in a 2 liter autoclaved glass bottle. The solution is filtered to remove any precipitated SDS. Transfer this 0.2% SDS solution to a 250 mL rectangular glass staining dish and place a small stir bar in the dish. Place the dish on a magnetic stir plate and allow the bar to stir at a slow and steady rate.
2. Preheat (boiling) 2 liters of reagent grade deionized distilled water (the highest quality water available) to 95-100 ° C. in a 4 liter beaker on a hot plate. 3. Transfer 2 liters of reagent grade deionized distilled water into a 4 liter beaker and place at room temperature.
4. Transfer 250 mL of ethanol to a rectangular glass staining dish. Place this dish in an ice bucket and set an ice-cooled ethanol bath.
5). Harvest the raw array. Carefully pick up a slide at the corner and hold it over boiling water (from step 2) for 5 seconds. Make sure the array is facing up. The slide is shaken in the air for 3 seconds and then placed on a non-fibrous laboratory cloth with the array side up. Repeat until 8 slides are hydrated and dry.
6.8 Slides are transferred to the crosslinker set at 50-220 mJ with the array side up.
7). After cross-linking, the 8 arrays are transferred into grooved glass / metal Wheaton staining slide holders (the slides should not be placed in the grooves on both ends). The holder with the slide is placed in 0.2% SDS (from step 1) and incubated for 10 minutes with agitation.
8). Remove the slide holder and place it on a laboratory cloth to remove excess moisture. The holder is then immersed 5 times in 2 liters of room temperature water (from step 3).
9. Transfer slide holder into boiling water (from step 2) and incubate for 8-10 minutes. Make sure the slide is under water.
10. Remove the slide holder from boiling water and place it on a laboratory cloth to remove excess moisture. Transfer the slide holder into ice-cold ethanol (from step 4) and incubate for 5 minutes. Make sure the slide is below the ethanol surface.
11. Remove the slide holder and place it on a laboratory cloth to remove excess moisture. Transfer each slide into a 50 mL centrifuge tube. Centrifuge at 1000 rpm for 3 minutes to dry the slides. The array is now ready for hybridization.
1. Pre-cleaning the array to reduce background Wash the microarray under the following conditions:
a. 2 × SSC / 0.2% SDS at 55 ° C. for 20 minutes b. 0.2 × SSC at room temperature for 5 minutes c. 1. 3 minutes at room temperature with deionized distilled water Immediately transfer the array to a dry 50 mL centrifuge tube. This is done promptly so that there is no uneven background on the slide. Place the slide so that the sign descends down in the tube. Without capping the tube, centrifuge at 800-1000 RPM for 2 minutes to dry the slide. Do not touch the surface of the array. Transfer the array of microarrays into a dish or Coplin jar with 0.2 × SSC for 5 minutes at room temperature.
Here, the array is ready for pre-hybridization or hybridization with cDNA.
Array prehybridization to reduce background:
Non-specific binding to the array surface is a problem common to many types of arrays. The prehybridization protocols described below are recommended to suppress some types of non-specific binding and reduce the background seen after hybridization.
1. Preheat the microarray to 50 ° C. for 10 minutes.
Thaw and resuspend 2.2x hybridization buffer (vial 7) by heating to 70 ° C for at least 10 minutes or until completely resuspended. Vortex to ensure that the ingredients are resuspended evenly. If necessary, repeat heating and vortexing until all material is resuspended. Microcentrifuge for 1 minute.
3. Prepare the following prehybridization mixture.
25 μl of 2 × formamide based hybridization buffer (vial 7)
1 μl of human Cot-1 DNA
24 μl of nuclease free water 4. Heat the prehybridization mixture to 80 ° C. for 10 minutes The prehybridization mixture is applied to the preheated microarray and covered with a 24 × 60 mm coverslip.
6. Incubate at 50 ° C for 1-2 hours.
7). Wash the array under the following conditions:
a. 15 min at 60-65 ° C. with 2 × SSC, 0.2% SDS b. 10 minutes at room temperature with 2 × SSC c. 7. 0.2 × SSC for 10 minutes at room temperature Immediately transfer the array to a dry 50 mL centrifuge tube. This is done promptly so that there is no uneven background on the slide. Place the slide so that the sign descends down in the tube. Without capping the tube, centrifuge at 800-1000 RPM for 2 minutes to dry the slide. Do not touch the surface of the array.
The array is ready for hybridization with cDNA.
Recommendations for Suppressing Cy5 or Alexa Fluor 647 Degradation When Performing Microarray Experiments The performance of Cy5 / Alexa Fluor 647 dye is affected by a variety of factors that are particularly common in the summer. Exposure of arrays hybridized with Cy5 / Alexa Fluor 647 dye solution to light and oxidizing environment can lead to rapid fading of Cy5 / Alexa Fluor 647 dye, regardless of what labeling system was utilized. Limiting or controlling exposure of the array to these environments has been shown to significantly suppress Cy5 / Alexa Fluor 647 fading.
The following are recommendations for suppressing Cy5 / Alexa Fluor 647 degradation when performing microarray experiments.
1. Always keep solutions and arrays containing Cy5 / Alexa Fluor 647 out of light, especially sunlight. Cy5 / Alexa Fluor 647 is photobleached when exposed to light from an ordinary fluorescent lamp or the like.
2. Hybridized and dry arrays protect against exposure to air, especially on hot summer days. Atmospheric ozone levels resulting from summer air pollution may cause oxidative degradation of Cy5 / Alexa Fluor 647. An array containing Cy5 / Alexa Fluor 647 placed in an inert atmosphere (nitrogen) in a small container (50 mL tube) can significantly delay the fading of Cy5 / Alexa Fluor 647. Some researchers also add a small amount of DTT or β-mercaptoethanol (BME) to the bottom of the tube to further promote the reducing microenvironment (confirm that the array does not come into contact with these chemicals. To do).
3. Use antifade reagent (provided in 3DNA kit) in hybridization solution containing Cy5 / Alexa Fluor 647 capture reagent. The anti-fading reagent has antioxidant properties that delay the oxidation process.
4). When preparing the wash buffer, avoid using water that will damage the Cy5 / Alexa Fluor 647. As described in the Internet List Server, the registered trade name MilliQ water has been found to compromise Cy5 (http://groups.yahoo.com/group/microarray/messages/2867). ). Also, the DEPC-treated solution must make sure that all DEPC is completely removed (DEPC is a strong oxidant). Alternatively, the use of non-DEPC treated nuclease free solutions is recommended. Solutions (water, buffers, etc.) commercially available from Ambion have been found to work well with Cy5 labeled microarrays. In addition to Ambion water, DI water from VWR (catalog number RC91505) can also be recommended. The water from Ambion and VWR has been confirmed to be usable for microarrays and does not contain components that oxidize Cy5.
5). A small amount of dithiothreitol (DTT) is added to the post-hybridization wash solution to a final concentration of 0.1 mM. This powerful reducing agent protects Cy5 / Alexa Fluor 647 on the array from attack by oxidizing agents in the wash buffer.
6). Always mix the desired 3DNA Cy3 / Alexa Fluor 546 and Cy5 / Alexa Fluor 647 capture reagents (vial 1) to break up any aggregates that occur during storage.
a. Thaw 3DNA capture reagent (vial 1) at room temperature in the dark for 20 minutes.
b. Vortex set to maximum, stir for 3 seconds, and microcentrifuge briefly (1 second).
Always check for aggregates before use and, if necessary, repeat the vortex mixing process. Aggregates appear as small bubbles or flakes on the side of the tube below the surface liquid level. Repeat steps ae if necessary.
7). If the above recommendations do not solve the problem of Cy5 decomposition, a likely cause is exposure to air pollutants. To address this issue, Genisphere developed a reagent called DyeSaver (Genisphere catalog number Q100200) that was applied to the array after final washing and centrifugation. DyeSaver is easy to use, compatible with most array surface chemistry methods, and protects Cy5 from atmospheric oxidation for up to 3 weeks. DyeSave has also been shown to suppress Cy5 damage due to photobleaching.
While this invention has been described with reference to specific embodiments, this description is not intended to be limiting, since further embodiments, modifications and variations will be apparent or suggested to those skilled in the art. Should be understood. This application is intended to cover such embodiments, modifications, and variations.
FIG. 2 is a schematic diagram of a preferred method according to the present invention.
Obtaining an initial sample of RNA;
Reverse transcription of the RNA sample to synthesize a cDNA sample, and applying the cDNA sample to a microarray,
A method of applying a cDNA sample to a microarray without concentrating the cDNA sample after cDNA synthesis and before applying the cDNA sample to the microarray.
The method of claim 1, wherein the cDNA sample is applied to the microarray after purification of the cDNA sample and before the cDNA sample is applied to the microarray without purifying the cDNA sample.
The method of claim 1, wherein the initial sample of RNA comprises total RNA.
The method of claim 1, wherein the initial sample of RNA comprises messenger RNA.
The method of claim 1, wherein the initial sample of RNA comprises about 0.1 to 1 microgram of total RNA.
The method of claim 1, wherein the initial sample of RNA comprises about 1 to 1000 nanograms of mRNA.
The method according to any one of claims 1 to 6, further comprising a step of hybridizing a dendrimer to cDNA in a cDNA sample.
The method according to any one of claims 1 to 6, further comprising the step of hybridizing a dendrimer to cDNA in a cDNA sample, wherein the dendrimer is labeled so as to generate a detectable signal.
The method according to any one of claims 1 to 6, further comprising the step of hybridizing a dendrimer to cDNA in a cDNA sample, wherein the dendrimer is labeled to generate a detectable signal, and the dendrimer Wherein each dendrimer molecule is labeled with more than 500 fluorescent dyes.
Reverse transcription of the RNA sample to synthesize a cDNA sample;
Applying the cDNA sample to a microarray, the microarray having a nucleic acid sample immobilized thereon,
Hybridizing the cDNA in the cDNA sample to a nucleic acid sample on a microarray; and
Hybridizing a dendrimer to cDNA in the cDNA sample, comprising:
11. The method of claim 10, wherein the cDNA sample is applied to the microarray after purification of the cDNA sample and before the cDNA sample is applied to the microarray without purifying the cDNA sample.
12. The method of claim 10, wherein the initial sample of RNA comprises total RNA.
12. The method of claim 10, wherein the initial sample of RNA comprises messenger RNA.
12. The method of claim 10, wherein the initial sample of RNA comprises about 0.1 to 1 microgram of total RNA.
11. The method of claim 10, wherein the initial sample of RNA comprises about 1 to 1000 nanograms of mRNA.
16. The method of any of claims 10-15, further comprising the step of hybridizing the dendrimer to cDNA in a cDNA sample, wherein the dendrimer is labeled to generate a detectable signal.
16. The method of any of claims 10-15, further comprising the step of hybridizing a dendrimer to cDNA in a cDNA sample, wherein the dendrimer is labeled to produce a detectable signal, and the dendrimer Wherein each dendrimer molecule is labeled with more than 500 fluorescent dyes.
JP2006528313A 2003-09-26 2004-09-27 Method for synthesizing a small amount of nucleic acid Withdrawn JP2007506439A (en)
US50624703P true 2003-09-26 2003-09-26
PCT/US2004/031804 WO2005030984A2 (en) 2003-09-26 2004-09-27 Method for small volume nucleic acid synthesis
JP2007506439A true JP2007506439A (en) 2007-03-22
JP2006528313A Withdrawn JP2007506439A (en) 2003-09-26 2004-09-27 Method for synthesizing a small amount of nucleic acid
IL (1) IL174486D0 (en)
WO (1) WO2005030984A2 (en)
2004-09-27 EP EP04789156A patent/EP1664350A4/en not_active Withdrawn
2004-09-27 JP JP2006528313A patent/JP2007506439A/en not_active Withdrawn
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EP1803823B1 (en) 2016-01-20 Probe set, probe immobilized carrier and gene examination method
JP4291143B2 (en) 2009-07-08 Affinity-shifted probe for quantification of analyte polynucleotide
US20050244885A1 (en) 2005-11-03 Array based methods for synthesizing nucleic acid mixtures
DE60133111T2 (en) 2009-03-12 Method for detecting and assaying nucleic acid sequences
JP2004533204A (en) 2004-11-04 Method for controlling microbiological quality of aqueous medium and kit therefor
CA2574832A1 (en) 2006-02-02 Method for determining the abundance of sequences in a sample
EP1438416A2 (en) 2004-07-21 Assays for dna methylation changes
JP2002504812A (en) 2002-02-12 Nucleic acid array