bluuebunny/crossref_metadata_2025_split huggingface dataset:
X-chromosome activity of the mouse primordial germ cells revealed by the expression of an X-linked lacZ transgene
Authors: Tam Patrick P. L. , Zhou Sheila X. , Tan Seong-Seng 
Published: April 2021

ABSTRACT
We have determined the timing of the inactivation and reactivation of the X chromosome in the mouse primordial germ cells (PGCs) by monitoring the expression of an X-linked HMG-lacZ reporter gene. PGCs were identified by their distinct alkaline phosphatase activity and they were first localised in the primitive streak and allantoic bud of the 7.5-day gastrulating embryo. Although inactivation of the transgene was found in some PGCs at these sites, at least 85% of the population were still expressing the lacZ gene. This suggests that, although X-inactivation has commenced during gastrulation, the majority of PGCs still possess two active X chromosomes. Transgene activity remained unchanged during the relocation of PGCs to the hindgut endoderm, but decreased abruptly when PGCs left the hindgut and migrated through the mesentery. X-inactivation was completed during the migration of PGCs, but not simultaneously for the whole population. The first wave of PGCs entering the genital ridge at 9.5 days did not immediately re-activate the silent transgene until about 24 hours later. Re-activation of the transgene took place in over 80% of PGCs entering the genital ridge at 10.5 –13.5 days p.c., preceding the entry into meiosis. About 90% of the meiotic germ cells in the 14.5 –15.5 day fetal ovary expressed the transgene. Similar profiles of transgene activity were observed in PGCs of embryos that have inherited the lacZ transgene from different parents, showing unequivocally that X-inactivation in the germ cell lineage is not related to parental legacy. In contrast to those germ cells in the genital ridges, a small population of PGCs that was left outside the genital ridges at 13.5 –15.5 days did not re-activate the silent X. This strongly suggests that reactivation of the silent X chromosome in the female germ cells is a response to local signals in the genital ridge.
Developmental expression of the mouse c-rel proto-oncogene in hematopoietic organs
Authors: Carrasco Daniel , Weih Falk , Bravo Rodrigo 
Published: April 2021

ABSTRACT
We have studied the expression of the c-rel proto-oncogene during mouse embryonic development and adult animals using in situ hybridization and immunocytochemical analysis. c-rel transcripts were detected late in development with an expression pattern that parallels the emergence and diversification of hematopoietic cells. In the embryo, c-rel is expressed first in the mesoderm-derived hematopoi-etic cells of the liver and later also in other hematopoietic tissues such as thymus and spleen. This correlation between c-rel expression and places of hematopoietic infiltration is conserved in the postnatal period, with expression of c-rel mRNA in the medullary region of the thymus and in splenic B cell areas, including the marginal zone and the outer region of the periarterial sheath. High levels of c-rel transcripts were also detected in the splenic germinal centers, lymph nodes and Peyer’s patches. Using double immuno-fluorescence and cell preparations from different embryonic and adult hematopoietic organs, we have defined the pattern and cell types of c-rel expression in different hematopoietic cell lineages and in the stromal cell content of the thymus. By using electrophoretic mobility shift assays, we have also correlated c-Rel expression in spleen with κB-binding activity in the form of c-Rel/p50 and c-Rel/p52 heterodimers. The timing and pattern of expression of the c-rel proto-oncogene in the different cell lineages suggest that temporally regulated changes in c-Rel expression may be required for vertebrate hematopoiesis.
Autonomous concentration-dependent activation and repression of Krüppel by hunchback in the Drosophila embryo
Authors: Schulz Cordula , Tautz Diethard 
Published: April 2021

ABSTRACT
The subdivision of the anterior-posterior axis in Drosophila is achieved by a cascade of spatially regulated transcription factors which form short-range gradients at the syncytial blastoderm stage. These factors are assumed to have concentration-dependent regulatory effects on their target genes. However, there is so far little direct in vivo evidence that a single factor can autonomously activate and repress a given target gene. We have analysed here the regulatory capabilities of the gap gene hunchback by creating an artificial gradient of hunchback in the early embryo. This was achieved by providing the maternally expressed mRNA of hunchback with the anterior localization signal of the bicoid RNA. The effects of this artificial hunchback gradient were then studied in different types of mutant background. We show that under these conditions hb is autonomously capable of activating the target gene Krüppel at low concentrations and repressing it at high concentrations. In addition, we show that the artificially created hunchback gradient can organize a large part of the segment pattern, although it is expressed at a different position and in a different shape than the wild-type gradient of hunchback.
Mouse embryonic germ (EG) cell lines: transmission through the germline and differences in the methylation imprint of insulin-like growth factor 2 receptor (Igf2r) gene compared with embryonic stem (ES) cell lines
Authors: Labosky Patricia A. , Barlow Denise P. , Hogan Brigid L. M. 
Published: April 2021

ABSTRACT
Primordial germ cells of the mouse cultured on feeder layers with leukemia inhibitory factor, Steel factor and basic fibroblast growth factor give rise to cells that resemble undifferentiated blastocyst-derived embryonic stem cells. These primordial germ cell-derived embryonic germ cells can be induced to differentiate extensively in culture, form teratocarcinomas when injected into nude mice and contribute to chimeras when injected into host blastocysts. Here, we report the derivation of multiple embryonic germ cell lines from 8.5 days post coitum embryos of C57BL/6 inbred mice. Four independent embryonic germ cell lines with normal male karyotypes have formed chimeras when injected into BALB/c host blastocysts and two of these lines have transmitted coat color markers through the germline. We also show that pluripotent cell lines capable of forming teratocarcinomas and coat color chimeras can be established from primordial germ cells of 8.0 days p.c. embryos and 12.5 days p.c. genital ridges. We have examined the methylation status of the putative imprinting box of the insulin-like growth factor type 2 receptor gene (Igf2r) in these embryonic germ cell lines. No correlation was found between methylation pattern and germline competence. A significant difference was observed between embryonic stem cell and embryonic germ cell lines in their ability to maintain the methylation imprint of the Igf2r gene in culture. This may illustrate a fundamental difference between these two cell types.
Glia in the fly wing are clonally related to epithelial cells and use the nerve as a pathway for migration
Authors: Giangrande Angela 
Published: April 2021

ABSTRACT
The Drosophila major wing nerve collects axons from the anterior margin sensory organs. Using the flp recombinase to make clones, I show that all glia present on this nerve are clonally related to wing epithelial cells. Glial cells arise only from regions that also give rise to sensory organs and migrate along the nerve following the direction taken by axons. As in vertebrates, wing glial cells start migrating at a stage at which axons are growing. The migration of wing glial cells is affected by two mutations altering axonogenesis, fused and Notch, which suggests that the two processes are tightly associated.
The sevenless signalling cassette mediates Drosophila EGF receptor function during epidermal development
Authors: Diaz-Benjumea Fernando J. , Hafen Ernst 
Published: April 2021

ABSTRACT
In Drosophila, Drk, an SH2 adaptor protein, Sos, a putative activator of Ras1, Ras1, raf and rolled/MAP kinase have been shown to be required for signalling from the sevenless and the torso receptor tyrosine kinase. From these studies, it was unclear whether these components act in a single linear pathway as suggested by the genetic analysis or whether different components serve to integrate different signals. We have analyzed the effects of removing each of these components during the development of the adult epidermal structures by generating clones of homozygous mutant cells in a heterozygous background. Mutations in each of these signalling components produce a very similar set of phenotypes. These phenotypes resemble those caused by loss-of-function mutations in the Drosophila EGF receptor homolog (DER). It appears that these components form a signalling cassette, which mediates all aspects of DER signalling but that is not required for other signalling processes during epidermal development.
Sex-determining genes in the homosporous fern Ceratopteris
Authors: Banks Jo Ann 
Published: April 2021

ABSTRACT
Haploid Ceratopteris gametophytes are either hermaphroditic or male. The determinate of sex type is the pheromone antheridiogen (ACE) which is secreted by the meristic hermaphrodite and promotes ameristic male development of sexually undetermined gametophytes. Several mutations effecting the sex of the haploid gametophyte have been isolated and are described. The hermaphroditic (her) mutants are insensitive to ACE and develop as meristic hermaphrodites. These mutations effect ameristic male development in the presence of ACE but have no effect on hermaphroditic development. While most her mutations also have no effect on diploid sporophyte development, some partially ACE-insensitive her mutations have profound effects on sporophyte development. The transformer (tra) mutation effects both meristem and archegonia formation and causes the gametophyte to be an ameristic male under conditions that promote hermaphroditic development. The feminization (fem) mutation effects antheridia development in both male and hermaphroditic gametophytes and causes the gametophyte to develop as a meristic female in the absence or presence of the pheromone. The her1 tra1 double mutant is male in the absence or presence of ACE, indicating that tra1 is epistatic to her1. The phenotypes of her1, tra1 and fem1 single gene mutant phenotypes and the her1 tra1 double mutant phenotype are used to deduce a model suggesting how the products of these genes might interact in a regulatory pathway to control sex determination.
Stage-specific requirement for myosin II during Dictyostelium development
Authors: Springer M. L. , Patterson B. , Spudich J. A. 
Published: April 2021

ABSTRACT
Dictyostelium cells that lack a functional myosin II heavy chain are motile and are capable of aggregation, but fail to undergo further multicellular development. We have used a Dictyostelium mutant expressing a cold-sensitive myosin heavy chain to examine the requirement for myosin throughout the course of development. The loss of myosin function upon cooling is rapid and reversible. Tempera-ture-shift experiments reveal that myosin is essential during two different stages of development. During aggregation, myosin function appears to be necessary for cells to sort correctly in a way that allows further development to occur. During the final stage of development, it is required for the formation of a complete stalk and the raising of the spore head. Development between those stages, however, proceeds normally in the absence of myosin function. Aggregates at non-permissive temperature undergo an aberrant form of development resulting in a ball of cells. Calcofluor staining and reporter gene fusions reveal that these structures contain defective spores and a miniature stalk.
Promoter-specific IGF2 imprinting status and its plasticity during human liver development
Authors: Ekström Tomas J. , Cui Hengmi , Li Xuri , Ohlsson Rolf 
Published: April 2021

ABSTRACT
IGF2 has been shown to be expressed preferentially from the paternally derived allele, although the maternal allele can be found active during both prenatal and postnatal development as well as in neoplastic tumours in humans. We addressed here whether or not the biallelic expression patterns that can be seen during postnatal human liver development reflected a coordinated change in the activities of the four promoters of human IGF2. We show here that the P2, P3 and P4 promoters, but not the P1 promoter, display monoallelic activity in embryonic, neonatal and younger infant liver specimens. The P2, P3 and P4 promoters can, however, be found active either monoallelically or biallelically or even monoallelically on opposite parental alleles in older infant and adult liver specimens. In contrast, H19, which is closely linked to IGF2, is monoallelically expressed in all postnatal liver samples analysed. We conclude that the functional imprinting status of IGF2 during postnatal liver development appears to be promoter/enhancer-specific and either partly or completely independent of H19.
Invagination centers within the Drosophila stomatogastric nervous system anlage are positioned by Notch-mediated signaling which is spatially controlled through wingless
Authors: González-Gaitán Marcos , Jäckle Herbert 
Published: April 2021

ABSTRACT
The gut-innervating stomatogastric nervous system of Drosophila, unlike the central and the peripheral nervous system, derives from a compact, single layered epithelial anlage. Here we report how this anlage is initially defined during embryogenesis by the expression of proneural genes of the achaete-scute complex in response to the maternal terminal pattern forming system. Within the stomatogastric nervous system anlage, the wingless-dependent inter-cellular communication system adjusts the cellular range of Notch-dependent lateral inhibition to single-out three achaete-expressing cells. Those cells define distinct invagination centers which orchestrate the behavior of neighboring cells to form epithelial infoldings, each headed by an achaete-expressing tip cell. Our results suggest that the wingless pathway acts not as an instructive signal, but as a permissive factor which coordinates the spatial activity of morphoregulatory signals within the stomatogastric nervous system anlage.
The existence of inositol 1,4,5-trisphosphate and ryanodine receptors in mature bovine oocytes
Authors: Yue Caiping , White Kenneth L. , Reed William A. , Bunch Thomas D. 
Published: April 2021

ABSTRACT
Intracellular Ca2+ (Ca2+i) transients during fertilization are critical to the activation of eggs in all species studied. Activation of both the inositol 1,4,5-trisphosphate (IP3) receptor (IP3R) and ryanodine receptor (RYR) are responsible for the calcium oscillations during fertilization in sea urchin eggs. Using in vitro matured bovine oocytes loaded with Fura-2 AM ester as Ca2+i indicator, we addressed whether IP3Rs and RYRs coexist in mammalian eggs. Our results indicate that microinjection of 50-250 nM IP3 or 10-20 mM caffeine, 100-200 μM ryanodine and 4-8 μM cyclic ADP-ribose all induced Ca2+i release. The Ca2+i release induced by 250 nM IP3 could only be inhibited by prior injection of 1 mg/ml heparin which was overcome by continuous injection of IP3 to 1 μM. Prior injection of either 50 μM ruthenium red, 50 μM procaine or 1 % vehicle medium (VM) did not affect the Ca2+i release induced by IP3. Prior injection of heparin or VM did not affect the Ca2+i release induced by 10-20 mM caffeine or 200 μM ryanodine, but prior injection of 50 μM ruthenium red or procaine completely inhibited the effect of 10-20 mM caffeine. In addition, continuous injection of caffeine up to 40 mM overcame the inhibitory effect of ruthenium red or procaine. The same 50 μM concentration of ruthenium red or procaine only partially blocked the effect of 200 μM ryanodine, but 200 μM ruthenium red or procaine completely blocked the effect of 200 μM ryanodine. Oocytes were refractory for 15 minutes to further injections of IP3 after the initiation of Ca2+i release induced by 200 nM IP3; a 10 minute refractory period was observed for 10-20 mM caffeine and 200 μM ryanodine; either caffeine or ryanodine can desensitize RYRs to the other. However, the desensitization of IP3Rs by 200 nM IP3 does not abolish the effect of 200 μM ryanodine, as effectively as the reciprocal treatment. Prior injection of a subthreshold concentration of ryanodine itself only induced a slight increase in Ca2+i level, but it sensitized the RYR to a subsequent injection of a subthreshold concentration of caffeine. Similar results were obtained when ryanodine was first injected followed by injection of caffeine Based on these results, we conclude that independent IP3Rs and RYRs exist in mature bovine oocytes.
Localization of oskar RNA regulates oskar translation and requires Oskar protein
Authors: Rongo Christopher , Gavis Elizabeth R. , Lehmann Ruth 
Published: April 2021

ABSTRACT
The site of oskar RNA and protein localization within the oocyte determines where in the embryo primordial germ cells form and where the abdomen develops. Initiation of oskar RNA localization requires the activity of several genes. We show that ovaries mutant for any of these genes lack Oskar protein. Using various transgenic constructs we have determined that sequences required for oskar RNA localization and translational repression map to the oskar 3′UTR, while sequences involved in the correct temporal activation of translation reside outside the oskar 3′UTR. Upon localization of oskar RNA and protein at the posterior pole, Oskar protein is required to maintain local- ization of oskar RNA throughout oogenesis. Stable anchoring of a transgenic reporter RNA at the posterior pole is disrupted by oskar nonsense mutations. We propose that initially localization of oskar RNA permits translation into Oskar protein and that subsequently Oskar protein regulates its own RNA localization through a positive feedback mechanism.
four-jointed is required for intermediate growth in the proximal-distal axis in Drosophila
Authors: Villano J. Lee , Katz Flora N. 
Published: April 2021

ABSTRACT
Genes capable of translating positional information into regulated growth lie at the heart of morphogenesis, yet few genes with this function have been identified. Mutants in the Drosophila four-jointed (fj) gene show reduced growth and altered differentiation only within restricted sectors of the proximal-distal (PD) axis in the leg and wing, thus fj is a candidate for a gene with this coordination function. Consistent with a position-sensitive role, we show that fj is expressed in a regional pattern in the developing leg, wing, eye and optic lobe. The fj gene encodes a novel type II membrane glycoprotein. When the cDNA is translated in an in vitro translation system in the presence of exogenous microsomal membranes, the intralumenal portion of some of the molecules is cleaved, yielding a secreted C-terminal fragment. We propose that fj encodes a secreted signal that functions as a positive regulator of regional growth and differentiation along the PD axis of the imaginal discs.
Mutations affecting development of the zebrafish inner ear and lateral line
Authors: Whitfield Tanya T. , Granato Michael , Eeden Fredericus J. M. van , Schach Ursula , Brand Michael , Furutani-Seiki Makoto , Haffter Pascal , Hammerschmidt Matthias , Heisenberg Carl-Philipp , Jiang Yun-Jin , Kane Donald A. , Kelsh Robert N. , Mullins Mary C. , Odenthal Jörg , Nüsslein-Volhard Christiane 
Published: April 2021

ABSTRACT
Mutations giving rise to anatomical defects in the inner ear have been isolated in a large scale screen for mutations causing visible abnormalities in the zebrafish embryo (Haffter, P., Granato, M., Brand, M. et al. (1996)Development 123, 1-36). 58 mutants have been classified as having a primary ear phenotype; these fall into several phenotypic classes, affecting presence or size of the otoliths, size and shape of the otic vesicle and formation of the semicircular canals, and define at least 20 complementation groups. Mutations in seven genes cause loss of one or both otoliths, but do not appear to affect development of other structures within the ear. Mutations in seven genes affect morphology and patterning of the inner ear epithelium, including formation of the semicircular canals and, in some, development of sensory patches (maculae and cristae). Within this class, dog-eared mutants show abnormal development of semicircular canals and lack cristae within the ear, while in van gogh, semicircular canals fail to form altogether, resulting in a tiny otic vesicle containing a single sensory patch. Both these mutants show defects in the expression of homeobox genes within the otic vesicle. In a further class of mutants, ear size is affected while patterning appears to be relatively normal; mutations in three genes cause expansion of the otic vesicle, while in little ears and microtic, the ear is abnormally small, but still contains all five sensory patches, as in the wild type. Many of the ear and otolith mutants show an expected behavioural phenotype: embryos fail to balance correctly, and may swim on their sides, upside down, or in circles. Several mutants with similar balance defects have also been isolated that have no obvious structural ear defect, but that may include mutants with vestibular dysfunction of the inner ear (Granato, M., van Eeden, F. J. M., Schach, U. et al. (1996)Development, 123, 399-413,). Mutations in 19 genes causing primary defects in other structures also show an ear defect. In particular, ear phenotypes are often found in conjunction with defects of neural crest derivatives (pigment cells and/or cartilaginous elements of the jaw). At least one mutant, dog-eared, shows defects in both the ear and another placodally derived sensory system, the lateral line, while hypersensitive mutants have additional trunk lateral line organs.
Left-right pattern of cardiac BMP4 may drive asymmetry of the heart in zebrafish
Authors: Chen Jau-Nian , Eeden Fredericus J. M. van , Warren Kerri S. , Chin Alvin , Nüsslein-Volhard Christiane , Haffter Pascal , Fishman Mark C. 
Published: April 2021

ABSTRACT
The first evident break in left-right symmetry of the primitive zebrafish heart tube is the shift in pattern of BMP4 expression from radially symmetric to left-predominant. The midline heart tube then ‘jogs’ to the left and subsequently loops to the right. We examined 279 mutations, affecting more than 200 genes, and found 21 mutations that perturb this process. Some cause BMP4 to remain radially symmetric. Others randomize the asymmetric BMP4 pattern. Retention of BMP4 symmetry is associated with failure to jog: right-predominance of the BMP4 pattern is associated with reversal of the direction of jogging and looping. Raising BMP4 diffusely throughout the heart, via sonic hedgehog injection, or the blocking of its action by injection of a dominant negative BMP4 receptor, prevent directional jogging or looping. The genes crucial to directing cardiac asymmetry include a subset of those needed for patterning the dorsoventral axis and for notochord and ventral spinal cord development. Thus, the pattern of cardiac BMP4 appears to be in the pathway by which the heart interprets lateralizing signals from the midline.