pinecone/core-2020-05-10-deduplication huggingface dataset:
Regulation and Function of SF/HGF during Migration of Limb Muscle Precursor Cells in Chicken

AbstractLimb muscles of vertebrates are derived from migratory dermomyotomal cells which emanate from a limited number of somites located adjacent to the developing limb buds. We have generated additional limb buds in chicken embryos by implantation of FGF-beads into the interlimb region in order to analyze whether these somites can be programmed to supply ectopic limbs with myogenic precursor cells. We show that migrating myogenic precursor cells are released from somites at the level of the newly formed limb, even when cell migration into the natural limb has been completed. The implantation of FGF beads in the lateral plate mesoderm rapidly induces SF/HGF expression. FGF beads implanted between HH stages 10 and 12 inhibit limb bud formation or shift the normal limb position. When an additional FGF bead was implanted at the original limb position at HH stage 15, SF/HGF expression was transiently induced to low levels without inducing a new limb. This demonstrates that the initial induction of SF/HGF by FGF does not require limb formation. Expression of SF/HGF during early limb bud stages was found in the entire developing bud and the adjacent lateral plate mesoderm with direct contacts to the lateral edge of the dermomyotome. Later, the SF/HGF expression domain retracts to a distal region below the apical ectodermal ridge. To investigate the role of SF/HGF in the migratory process, we implanted beads soaked in SF/HGF-alone or together with FGF into different locations of the developing chick embryo. In the experiments SF/HGF caused delamination of migratory cells from the dermomyotomal epithelium but no chemotactic attraction of migrating cells toward the SF/HGF source
Platelet-Activating Factor Acetylhydrolase Expression and Activity Suggest a Link between Neuronal Migration and Platelet-Activating Factor

AbstractA hemizygous deletion ofLIS1,the gene encoding αLis1protein, causes Miller–Dieker syndrome (MDS). MDS is a developmental disorder characterized by neuronal migration defects resulting in a disorganization of the cerebral and cerebellar cortices. αLis1binds to two other proteins (β and γ) to form a heterotrimeric cytosolic enzyme which hydrolyzes platelet-activating factor (PAF). The existence of heterotrimers is implicated from copurification and crosslinking studies carried outin vitro.To determine whether such a heterotrimeric complex could be present in tissues, we have investigated whether the αLis1, β, and γ genes are coexpressed in the developing and adult brain. We have isolated murine cDNAs and show byin situhybridization that in developing brain tissues αLis1, β, and γ genes are coexpressed. This suggests that αLis1, β, and γ gene products form heterotrimers in developing neuronal tissues. In the adult brain, αLis1and β mRNAs continue to be coexpressed at high levels while γ gene expression is greatly diminished. This reduction in γ transcript levels is likely to result in a decline of the cellular concentration of αLis1, β, and γ heterotrimers. The developmental expression pattern of αLis1, β, and γ genes is consistent with the neuronal migration defects seen in MDS; regions containing migrating neurons such as the developing cerebral and cerebellar cortices express these genes at a particularly high level. Furthermore, we uncovered a correlation between γ gene expression, granule cell migration, and PAF hydrolytic activity in the cerebellum. In this tissue γ gene expression and PAF hydrolysis peaked at Postnatal Days P5 and P15, a period during which neuronal migration in the cerebellum is most extensive. Mechanisms by which PAF could affect neuronal migration are discussed
Effects of Calcium-BAPTA Buffers and the Calmodulin Antagonist W-7 on Mouse Egg Activation

AbstractResults of numerous experiments indicate that the transient rise in intracellular Ca2+following sperm–egg fusion is essential for the subsequent events that constitute egg activation. Some events of egg activation, e.g., cortical granule exocytosis, however, appear more sensitive to intracellular Ca2+than other events, e.g., cell cycle resumption. To examine if specific events of egg activation have different thresholds for Ca2+, we manipulated buffered intracellular Ca2+concentrations by microinjecting Ca2+-BAPTA buffers and then examined the effect on the cortical granule exocytosis, recruitment of maternal mRNAs, and cell cycle resumption. We find that whereas cortical granule exocytosis occurs over a narrow threshold range of injected free Ca2+concentrations between 0.5 and 1.0 μM,recruitment of maternal mRNAs is only partially stimulated at injected free Ca2+concentrations of 2.5 μM,and no evidence for cell cycle resumption was observed (up to 2.5 μMCa2+). Although the Ca2+- and phospholipid-dependent protein kinase, protein kinase C, is implicated in aspects of egg activation, calmodulin is also a potential target for the transient increase in Ca2+that occurs following fertilization. Whereas incubation of eggs in the presence of the calmodulin antagonist W-7 followed by insemination does not block cortical granule exocytosis, cell cycle resumption, as assessed by the metaphase-to-anaphase transition, a decrease in histone H1 kinase activity and the time course for the emission of the second polar body are significantly delayed/inhibited
Lineage-Specific Regulation of the Neural Differentiation GeneMASH1

AbstractMash1 is a transcription factor required during embryogenesis for the development of multiple neural lineages. It is expressed in restricted domains at specific stages in the developing central and peripheral nervous systems and in the developing olfactory epithelium. We have investigated the regulation ofMash1expression during embryogenesis using transgenic mice containingMash1/lacZreporter constructs.Cis-acting regulatory elements controllingMash1expression in the central nervous system are located within an 8-kb sequence upstream of theMash1coding region. This 8-kb sequence does not contain elements directing expression to the peripheral nervous system, olfactory epithelium, or retina. Sequences outside this 8 kb but within 36 kb of theMash1locus contain elements responsible for expression in the autonomic division of the peripheral nervous system. However, transgene expression in embryos containing the 36-kb sequence was never detected in the olfactory epithelium and retina. Thus, regulatory elements driving expression in these lineages may be at even greater distances from theMash1coding region. These data provide evidence for complex regulation ofMash1expression in which multiple lineage-specificcis-acting regulatory regions span greater than 36 kb of theMash1locus. Further characterization of these regions will facilitate the study of factors that regulate the temporal and spatial expression ofMash1during development. In addition, the regulatory sequences identified here can direct expression of heterologous genes to developing neural lineages that normally expressMash1,thus providing an important tool for examining the function of candidate regulatory genes in mammalian nervous system development
X-Inactivation and Histone H4 Acetylation in Embryonic Stem Cells

AbstractIn female mammalian cells, dosage compensation for X-linked genes is achieved by the transcriptional silencing, early in development, of many genes on just one of the two X chromosomes. Several properties distinguish the inactive X (Xi) from its active counterpart (Xa). These include expression ofXist,a gene located in the X-inactivation center (Xic), late replication, differential methylation of selected CpG islands and underacetylation of histone H4. The relationship between these properties and transcriptional silencing remains unclear. Female mouse embryonic stem (ES) cells have two active X chromosomes, one of which is inactivated as cells differentiate in culture. We describe here the use of these cells in studying the sequence of events leading to X-inactivation. By immunofluorescent labeling of metaphase chromosome spreads from ES cells with antibodies to acetylated H4, we show that an underacetylated X chromosome appears only after 4 days of differentiation, and only in female cells. The frequency of cells with an underacetylated X reaches a maximum by Day 6. In undifferentiated cells, H4 in centric heterochromatin is acetylated to the same extent as that in euchromatin but has become relatively underacetylated, as in adult cells, by Day 4 of differentiation (i.e., when deacetylation of Xi is first seen). The overall deacetylation of Xi followsXistexpression and the first appearance of a single, late-replicating X, both of which occur on Day 2. It also follows the silencing of X-linked genes. Levels of mRNA from four such genes,Hprt, G6pd, Rps4,andPgk-1,had all fallen by approximately 50% (relative to the autosomal geneAprt) by Days 2–4. The results show that properties that characterize Xi are put in place in a set order over several days. H4 deacetylation occupies a defined place within this sequence, suggesting that it is an intrinsic part of the X-inactivation process. The stage at which a completely deacetylated Xi is first seen suggests that deacetylation may be necessary for the maintenance of silencing but is not required for its initiation. Nor is it required for, or an immediate consequence of, late replication. However, we note that selective deacetylation of H4 on specific genes would not be detected by the microscopical approach we have used and that such selective deacetylation may still be part of the silencing process
The Development of Vision in the Zebrafish (Danio rerio)

AbstractWe studied the development and maturation of the visual system by determining when zebrafish begin to see and to move their eyes. This information was correlated with the time courses of the development of the retina, the retinofugal projection, the retinal image, and the extraocular muscles, to obtain an integrated picture of early visual development. Two visual behaviors were monitored over 48–96 hr postfertilization (hpf). The startle response (body twitch) was evoked by an abrupt decrease in light intensity. The optokinetic response (tracking eye movements) was evoked by rotation of a striped drum. Visually evoked startle developed over 68–79 hpf, more than 20 hr after the onset of a touch-evoked startle. It was not seen in eyeless fish, excluding a role for nonretinal light senses. Tracking eye movements developed over 73–80 hpf. They were always in the direction of drum rotation, even when the fish had been light deprived from blastula stage, ruling out a “trial and error” period of learning to track the drum. The image formed by the ocular lens was examined in intact fish made transparent by suppressing the formation of melanin. The eye was initially far sighted and gradually improved, so that by 72 hpf the image plane coincided with the photoreceptor layer. The extraocular muscles assumed their adult configuration between 66 and 72 hpf. Thus, the retinal image and functional extraocular muscles appeared nearly simultaneously with the onset of tracking eye movements and probably represent the last events in the construction of this behavior
Loss of Occludin and Functional Tight Junctions, but Not ZO-1, during Neural Tube Closure—Remodeling of the Neuroepithelium Prior to Neurogenesis

AbstractNeuroepithelial cells can generate nonepithelial cells, the neurons. Here we have investigated, for chick and mouse embryos, the epithelial character of neuroepithelial cells in the context of neurogenesis by examining the presence of molecular components of tight junctions during the transition from the neural plate to the neural tube. Immunoreactivity for occludin, a transmembrane protein specific to tight junctions, was detected at the apical end of the lateral membrane of neuroepithelial cells throughout the chick neural plate. During neural tube closure, occludin disappeared from all neuroepithelial cells. Correspondingly, the addition of horseradish peroxidase to the apical side of the neuroepithelium by injection into the amniotic cavity of mouse embryos revealed the presence of functional tight junctions in the neural plate (Embryonic Day 8), but not the neural tube (Embryonic Day 9). In contrast to occludin, expression of ZO-1, a peripheral membrane protein of tight junctions, increased from the neural plate to the neural tube stage, also being confined to the apical end of the lateral neuroepithelial cell membrane. This localization coincided with that of N-cadherin, whose expression increased concomitantly with the disappearance of occludin. We propose that the loss of tight junctions from neuroepithelial cells reflects an overall decrease in their epithelial nature, which precedes the generation of neurons
altFGF-2, A Novel ER-Associated FGF-2 Protein Isoform: Its Embryonic Distribution and Functional Analysis during Neural Tube Development

AbstractA novel fibroblast growth factor-2 (FGF-2) protein isoform, calledaltFGF-2, is expressed abundantly during chicken embryogenesis. The amino-terminal domain of the 21.5-kDaaltFGF-2 protein diverges completely from the other three FGF-2 proteins due to alternative splicing of their first coding exons. Furthermore, thealtFGF-2 protein, in contrast to FGF-2 proteins, is targeted predominantly to the endoplasmic reticulum. In chicken embryos,altFGF-2 and FGF-2 proteins are differentially distributed in several mesodermal structures including developing limbs and kidneys. All four FGF-2 protein isoforms are also expressed in the developing neural tube from early neural plate stages onward. In contrast to FGF-2 proteins, thealtFGF-2 isoform is distributed in a dynamic, spatially restricted pattern in notochord and ventral neural tube (floor plate and motor neurons) during specification of neuronal populations. To study the possible shared or differential signaling functions of chickenaltFGF-2 and FGF-2 gene products, they were ectopically expressed in the dorsal neural tube aspect of transgenic mouse embryos. Dorsal expression ofaltFGF-2, but not FGF-2 gene products, induced alteration of neural tube morphology in a significant fraction of mouse embryos (25%). However, no alterations of dorsoventral (d/v) neural tube polarity were detected, indicating thataltFGF-2 and FGF-2 gene products either function as permissive cofactors or regulate neural tube growth without affecting establishment of its primary d/v polarity
The Plant OncogenerolDStimulates Flowering in Transgenic Tobacco Plants

AbstractTheAgrobacterium rhizogenesT-DNA oncogenerolDunder the control of its own 5′ regulatory region was transferred to day-neutral tobacco plants. The main trait induced byrolDin transgenic plants is a striking precocity in flower setting and a strong enhancement of the flowering potential. InrolDplants, early flowering is followed by the very rapid growth of numerous lateral inflorescences. The analysis of several morphological and histological parameters suggests that some characteristic morphological abnormalities observed inrolDplants can be accounted for by their early reproductive phase transition and points to the involvement in the transition of a greater portion of the plant body than is the case for untransformed tobacco. Thein vitromorphogenic potential of tissues fromrolDplants was also tested. Superficial thin cell layer explants fromrolDplants show an earlier and much enhanced flower organogenesis, compared to controls, both on flowering and on hormone-free medium
In VitroDifferentiation Potential of the Periosteal Cells from a Membrane Bone, the Quadratojugal of the Embryonic Chick

AbstractThe quadratojugal (QJ) is a neural crest-derived membrane bone in the maxillary region of the avian head.In vivoits periosteum undergoes both osteogenesis to form membrane bone and chondrogenesis to form secondary cartilage. This bipotential property, which also exists in some other membrane bones, is poorly understood. The present study used cell culture to investigate the differentiation potential of QJ periosteal cells. Three cell populations were enzymatically released from QJ periostea and plated at different densities. Cell density greatly affected phenotypic expression and differentiation pathways. We found two culture conditions that favored osteogenesis and chondrogenesis, respectively. In micromass culture, the periosteal cells produced a layer of osteogenic cells that expressed alkaline phosphatase (APase) and secreted bony extracellular matrix (ECM). In contrast, low-density monolayer culture elicited chondrogenesis. Cells with pericellular refractile ECM and round shape appeared at 7 to 8 days and formed colonies later. The chondrogenic phenotype of these cells was confirmed by immunolocalization of type II collagen and Alcian blue staining of ECM. This result demonstrated that a fully expressed chondrogenic phenotype can be achieved from membrane bone periosteal cells in primary monolayer culture. Chondrogenesis requires a cell density lower than confluence and cannot be initiated in confluent cultures. Among the three cell populations, those cells from the outer layer have the highest growth rate and require the lowest initial plating density (below 5 × 103cells/ml) to achieve chondrogenesis. Cells from the inner layer have the slowest growth rate and chondrify at the highest initial density (below 5 × 104cells/ml). Chondrocytes from all populations express distinct phenotypic markers—APase and type I collagen—from initial chondrogenesis, but are not hypertrophic morphologically. Furthermore, the fact that chondrocytes arise within the same colony as APase-positive polygonal cells suggests that chondrocytes may differentiate from precursors related to the osteogenic cell lineage. This cell culture approach mimics secondary cartilage and membrane bone formationin vivo
The Establishment of Embryonic Axial Properties in the Nemertean,Cerebratulus lacteus

AbstractExperiments were performed to determine whether the first cleavage division plays a role in setting up the dorsoventral axis in embryos of the equal-cleaving nemerteanCerebratulus lacteus.Fertilized eggs were compressed to change the orientation of the first cleavage spindle, and thus the plane of the first cleavage division. One cell of the resulting two-celled embryos was then injected with lineage tracer to determine whether the first cleavage plane always maintains its normal relationships to the median and frontal planes or whether new relationships (and thus, novel cell lineages) could be created. Many of these compressed embryos gave rise to normal-appearing pilidium larvae in which the first cleavage plane had taken on various oblique angular relationships relative to the plane of bilateral symmetry and the dorsoventral axis of the larva. These findings indicate that the first cleavage plane can be dissociated from its normal relationships to these axial properties. Thus, the first cleavage division is not causally involved in the establishment of the dorsoventral and bilateral axes. We argue that the dorsoventral axis is specified prior to the first cleavage division
A Newtinman-Related Gene,nkx2.7,Anticipates the Expression ofnkx2.5andnkx2.3in Zebrafish Heart and Pharyngeal Endoderm

AbstractTheDrosophilahomeobox genetinmanand its vertebrate homologsNkx-2.5andNkx-2.3are critical determinants of cardiac development. We report here the identification of a newtinman-related gene,nkx2.7,as well as orthologs ofNkx-2.5andNkx-2.3in the zebrafish. Analysis of their expression in the developing zebrafish embryo reveals thatnkx2.7transcripts are the first to appear in cardiac mesodermal and pharyngeal endodermal precursors of the anterior hypoblast, anticipating both temporally and spatially the later expression ofnkx2.5andnkx2.3in these lineages. The preeminence ofnkx2.7in these embryonic lineages is consistent with a key role in cell fate determination, perhaps in part through the induction ofnkx2.5andnkx2.3.The findings provide the first molecular clues as to the spatial organization of endodermal and cardiac mesodermal precursors in the zebrafish hypoblast immediately following gastrulation. They suggest a coordinate role for these threetinman-related genes in the development of the heart and pharyngeal arches, and reinforce the paradigm of gene duplication and subspecialization betweenDrosophilaand vertebrate species. The results provide a framework in which to analyze potential changes intinman-related gene expression during abnormal zebrafish development
Troponin T Gene Switching Is Developmentally Regulated by Plasma-Borne Factors in Parabiotic Chicks

AbstractMyogenesis involves a conserved program of muscle gene isoform switching requiring the synchronized induction and repression of numerous muscle-specific gene family members. Central to understanding the regulation of this process are questions related to the origin and transmission of regulatory signals to the myofiber. We show here that troponin T gene switching can be precociously initiated by extrinsic blood-borne components but also requires other mechanisms that are regulated locally, intrinsically, or posttranscriptionally. We established a chimeric blood circulation by parabiosis between fetal chicks and quails to determine whether signals inducing earlier troponin T mRNA isoform switching in quails could be transduced to chick partners through the serum. While quail fetuses were unaffected by parabiosis, quail serum caused premature troponin T iso-mRNA switching in chick muscle, although initiation remained later than in quails. The onset of repression of a known innervation-dependent acetylcholine receptor mRNA did not coincide with the initiation of troponin T iso-mRNA switching and was not affected by parabiosis. These results support serum-borne factor regulation of isoform switching as an important and distinct mechanism relevant to understanding how extrinsic and intrinsic cues are integrated during muscle differentiation and development
TheDrosophila Broad-ComplexEarly Gene Directly Regulates Late Gene Transcription during the Ecdysone-Induced Puffing Cascade

AbstractThe ensemble of tissue-specific changes that drivesDrosophilametamorphosis is initiated by the steroid hormone ecdysone and proceeds through a transcriptional cascade comprised of primary response transcriptional regulators and secondary response structural genes. TheBroad-Complex(BR-C) primary response early gene is composed of several distinct genetic functions and encodes a family of related transcription factor isoforms. Our objective in this study was to determine whether individual BR-C isoforms directly regulate secondary response target genes. A cluster of 10 salivary gland-specific secondary responseL71late genes are dependent on theBR-C rbp+genetic function. Transgenic animals expressing individual BR-C isoforms were tested for their ability to provide theBR-C rbp+genetic function by monitoring the transcriptional activation of theL71genes. We found that the BR-C Z1 isoforms could complement the transcriptional defects seen inrbpmutants but the Z2, Z3, and Z4 isoforms could not. We conclude that theBR-C rbp+function is provided by the BR-C Z1 isoform in prepupal salivary glands.L71gene rescue was restricted to the prepupal salivary gland, suggesting the involvement of additional factors inL71gene regulation. Interestingly, we found that the overexpression of Z3 or Z4 isoforms inBR-C+salivary glands repressedL71expression, indicating that BR-C proteins might also function as transcriptional repressors. Molecular mapping and characterization of the regulatory sequences that controlL71-6expression revealed several Z1 isoform binding sites. Mutagenesis of these Z1 binding sites resulted in the failure to activate late gene expressionin vivowhen measured by transgenic reporter genes. We conclude that theBR-Cearly gene directly activates late gene transcription by interacting with late genecis-acting regulatory elements and that this interaction is responsible for the temporal linkage of early and late ecdysone-induced gene expression