bluuebunny/crossref_metadata_2025_split huggingface dataset:
Development and organization of glial cells in the peripheral nervous system of Drosophila melanogaster
Authors: Giangrande Angela , Murray Marjorie A. , Palka John 
Published: April 2021

ABSTRACT
We have used enhancer trap lines as markers to recognize glial cells in the wing peripheral nervous system of Drosophila melanogaster. Their characterization has enabled us to define certain features of glial differentiation and organization. In order to ask whether glial cells originate within the disc or whether they migrate to the wing nerves from the central nervous system, we used two approaches. In cultured wing discs from glialspecific lines, peripheral glial precursors are already present within the imaginal tissue during the third larval stage. Glial cells differentiate on a wing nerve even in mutants in which that nerve does not connect to the central nervous system. To assess whether peripheral glial cells originate from ectoderm or from mesoderm, we cultured discs from which the mesodermally derived adepithelial cells had been removed. Our findings indicate that peripheral glial cells originate from ectodermally derived cells. As has already been shown for the embryonic central nervous system, gliogenesis in the periphery is an early event during adult development: glial cells, or their precursors, are already present at stages when neurons are still differentiating. Finally, our results also suggest that peripheral glial cells may not display a stereotyped arrangement.
Two enhancer regions in the mouse En-2 locus direct expression to the mid/hindbrain region and mandibular myoblasts
Authors: Logan C. , Khoo W. K. , Cado D. , Joyner A. L. 
Published: April 2021

ABSTRACT
An En-2/lacZ gene fusion containing 9.5 kb of En-2 genomic DNA was capable of directing lacZ expression in an En-2-specific manner both temporally and spatially during embryogenesis and in the adult. lacZ expression was confined in the embryo to cells within the mid/hindbrain and mandibular arch regions and in the adult to cells of the molecular and granular layers of the cerebellum, and within the pons and colliculi regions. Interestingly, in the adult, transgene expression patterns within the cerebellum in two lines appeared to mark distinct anterior-posterior compartments. Analysis of the expression pattern of this transgene, in fetal and adult mice lacking a functional En-2 protein, provided evidence that the En-2 gene in mouse is not autoregulated. Deletion analysis of the En-2 genomic region and the use of a heterologous promoter identified two enhancer-containing regions of 1.5 and 1.0 kb in length, 5 of the transcribed sequences, which independently directed expression in the embryo to either the mid/hindbrain region or mandibular myoblasts, respectively. The 1.5 kb fragment contains the most anterior neural enhancer and the 1.0 kb fragment, the earliest myogenic enhancer thus far characterized. These En-2-specific regulatory regions can now be used in a biochemical analysis to identify proteins important in anterior-posterior patterning of the vertebrate CNS and in the specification of muscle identity as well as in a mutational analysis to direct expression of other developmentally important genes to these regions.
Expression of β1 integrin complexes on the surface of unfertilized mouse oocyte
Authors: Tarone Guido , Russo Mario A. , Hirsch Emilio , Odorisio Teresa , Altruda Fiorella , Silengo Lorenzo , Siracusa Gregorio 
Published: April 2021

Abstract
Integrins are a family of cell surface receptors that mediate cell-cell and cell-matrix interactions in a variety of different cellular systems. Here we show that unfertilized mouse oocytes express β1 class integrins both at mRNA and protein levels. Using the reverse transcription polymerase chain reaction and oligonucleotide primers based on the DNA sequence of mouse integrins, the RNA transcripts for the β1, α5 and α6 subunits were detected in unfertilized oocytes. The expression of the mRNAs is paralleled by the expression of the corresponding proteins, in fact, theα 5/ β1 and the α6/ β1 complexes can be immunoprecipitated with specific antibodies from 125I-surface-labeled oocytes. Using subunit-specific antibodies we also demonstrate the presence of the α3/ β1 at the oocyte surface but α1, α2, α4 or αV subunits were not detectable. Since the mouse 3 DNA sequence is not available, we have not tested for the corresponding transcript. Integrin subunits α6 and β1 were differently distributed on the oocyte surface, as visualized by immunofluorescence staining and by immunoelectron microscopy. α6 antigen was mainly confined to the microvillous area of the oocyte surface, while β1 was more homogeneously distributed over the whole oolemma. These data demonstrate for the first time the expression of three β1 integrin complexes in unfertilized mouse oocytes. Such proteins may have a role in sperm-egg interaction or during very early steps of embryogenesis.
A paternally imprinted X chromosome retards the development of the early mouse embryo
Authors: Thornhill Alan R. , Burgoyne Paul S. 
Published: April 2021

ABSTRACT
It has previously been shown that XO mouse fetuses with a paternally derived X chromosome (Xp) are developmentally retarded and consequently smaller than their XX sibs, and that XX fetuses are retarded when compared with their XY sibs. The genetic basis for these early XO-XX and XX-XY differences has not been determined. Here we show that 10.5 day post coitum XO mouse fetuses with a maternal X chromosome, rather than being smaller than their XX sibs, are significantly larger and equivalent in size to their XY sibs. Thus the retardation of XpO fetuses must be due to an effect of their paternally derived X chromosome. The finding that XmO fetuses are larger than XX fetuses and equivalent in size to XY fetuses suggests that the XX-XY difference present at 10.5 days post coitum is largely due to the difference in X chromosome constitution rather than to a Y chromosome effect.
Clonal heterogeneity in the germinal zone of the developing rat telencephalon
Authors: Acklin Susan E. , Kooy Derek van der 
Published: April 2021

ABSTRACT
A double-labeling technique, combining retroviral tagging of individual cell lines (one clone per brain hemisphere) with the simultaneous [3H]thymidine-labeling of dividing cells in S phase, was used to study proliferation characteristics of individual precursor cell lines in the germinal zone of the developing rat forebrain. The cortical germinal zone was found to be segregated into three spatially distinct horizontal populations of precursor cell lineages, which differed in cell cycle kinetics, amount of cell death, and synchronous versus asynchronous mode of proliferation. The striatal germinal zone demonstrated a similar heterogeneity in the cell cycle characteristics of proliferating clones, but did not show nearly as distinct a spatial segregation of these different populations. The results demonstrate the clonal heterogeneity among precursor populations in the telencephalon and the differential spatial organization of the cortical and the striatal germinal zones. This germinal zone heterogeneity may predict some of the differences found among cellular phenotypes in the adult forebrain.
A Xenopus homeobox gene defines dorsal-ventral domains in the developing brain
Authors: Saha Margaret S. , Michel Rosana B. , Gulding Kathryn M. , Grainger Robert M. 
Published: April 2021

ABSTRACT
One of the distinguishing features of vertebrate development is the elaboration of the anterior neural plate into forebrain and midbrain, yet little is known about the early tissue interactions that regulate pattern formation in this region or the genes that mediate these interactions. As an initial step toward analyzing the process of regionalization in the anterior-most region of the brain, we have screened an anterior neural cDNA library for homeobox clones and have identified one which we have called XeNK-2 (Xenopus NK-2) because of its homology to the NK-2 family of homeobox genes. From neurula stages, when XeNK-2 is first detectable, through hatching stages, XeNK-2 mRNA is expressed primarily in the anterior region of the brain. By swimming tadpole stages, XeNK-2 expression resolves into a set of bands positioned at the forebrain-midbrain and the midbrain-hindbrain boundaries, after which XeNK2 transcripts are no longer detectable. In addition to localized expression along the anterior-posterior axis, XeNK-2 may also play a role in the process of regionalization along the dorsal-ventral axis of the developing brain. At all stages examined, XeNK-2 mRNA is restricted to a pair of stripes that are bilaterally symmetrical in the ventral-lateral region of the brain. To begin to identify the tissue interactions that are required for the proper spatial and temporal localization of XeNK-2, we have performed a series of explant experiments. Consistent with earlier work showing that the A/P axis is not fixed at mid-gastrula stages, we show that XeNK-2 expression is activated when assayed in gastrula stage explants taken from any region along the entire A/P axis and that the tissue interactions necessary to localize XeNK-2 along the A/P axis are not completed until later neurula stages.
The development of indirect flight muscle innervation in Drosophila melanogaster
Authors: Fernandes Joyce , VijayRaghavan K. 
Published: April 2021

ABSTRACT
We have examined the development of innervation to the indirect flight muscles of Drosophila. During metamorphosis, the larval intersegmental nerve of the mesothorax is remodelled to innervate the dorsal longitudinal muscles and two of the dorsoventral muscles. Another modified larval nerve innervates the remaining dorsoventral muscle. The dorsal longitudinal muscles develop using modified larval muscles as templates while dorsoventral muscles develop without the use of such templates. The development of innervation to the two groups of indirect flight muscles differs in spatial and temporal patterns, which may reflect the different ways in which these muscles develop. The identification of myoblasts associated with thoracic nerves during larval life and the association of migrating myoblasts with nerves during metamorphosis indicate the existence of nerve-muscle interactions during indirect flight muscle development. In addition, the developing pattern of axonal branching suggests a role for the target muscles in respecifying neuromuscular junctions during metamorphosis.
Retinoic acid receptors and cellular retinoid binding proteins III. Their differential transcript distribution during mouse nervous system development
Authors: Ruberte Esther , Friederich Valérie , Chambon Pierre , Morriss-Kay Gillian 
Published: April 2021

ABSTRACT
We have studied the transcript distribution of the retinoic acid receptors (RARs) and the cytoplasmic retinoid binding proteins during embryonic development of the mouse nervous system. Of the three retinoic acid receptors, only RAR-γ was not expressed in developing neural structures. RAR-β and RAR-α both showed rostral limits of expression in the medulla oblongata equivalent to their patterns of expression in the neuroepithelium of the early hindbrain neural tube. Within their expression domains in the spinal cord and brain, RAR-α was ubiquitously expressed, whereas RAR-β transcripts showed very specific patterns of expression, suggesting that this receptor is involved in mediating retinoic acid-induced gene expression in relation to the development of specific neural structures or pathways.
The cytoplasmic binding proteins, cellular retinoic acid binding proteins type I and II (CRABP I and CRABP II) and cellular retinol binding protein type I (CRBP I), were widely distributed in developing neural structures. Their differential spatiotemporal patterns of expression suggest that fine regional control of availability of retinoic acid (RA) to the nuclear receptors plays an important role in organization and differentiation of the nervous system. For instance, expression of CRABP I in the migrating cells that give rise to the olivary and pontine nuclei, which develop abnormally in conditions of retinoid excess, is consistent with observations from a variety of other systems indicating that CRABP I limits the access of RA to the nuclear receptors in normal physiological conditions. Similarly, expression of CRBP I in the choroid plexuses, which develop abnormally in conditions of vitamin A deficiency, is consistent with observations indicating that this binding protein mediates the synthesis of RA in tissues requiring high levels of RA for their normal developmental programme. RAR-β and CRABP II, which are both RA-inducible, were coexpressed with CRBP I in the choroid plexus and in many other sites, perhaps reflecting the fact that all three genes are RAinducible. The function of CRABP II is not well understood; its domains of expression showed overlaps with both CRABP I and CRBP I.
Epithelial cell proliferation and islet neogenesis in IFN-g transgenic mice
Authors: Gu Danling , Sarvetnick Nora 
Published: April 2021

ABSTRACT
We have identified a model system for the study of pancreatic islet development and regeneration in transgenic mice bearing the interferon-gamma (IFN-g) gene expressed in the pancreatic islets. Previous studies showed that the locally produced IFN-g causes lymphocyte infiltration and islet cell destruction. Here we demonstrate that new islet cells are formed continuously from duct cells as evidenced by (1) the dramatic proliferation of duct cells, (2) the appearance of primitive cells and (3) their subsequent differentiation to endocrine cells. The IFN-g induced islet neogenesis is similar to embryonic islet morphogenesis and offers a model system for studying factors modulating islet development. Additionally, the duct cells occasionally transdifferentiate to gastrointestinal-like cell types and hepatocytes. These results underscore the lymphokine’s ability to initiate a complex ‘transdifferentiation’ pathway, providing a window for understanding lineage interrelationships within a terminally differentiated structure.
Differential expression of multiple fork head related genes during gastrulation and axial pattern formation in the mouse embryo
Authors: Sasaki Hiroshi , Hogan Brigid L. M. 
Published: April 2021

ABSTRACT
Four genes encoding fork-head-domain-containing proteins (FD genes) have been isolated from a mouse 8.5 days post coitum (p.c.) embryo cDNA library. Two are mouse homologues of rat HNF-3β and HNF-3α. The other two are novel and have been named MF-1 and MF-2 (for mesoderm/mesenchyme fork head). Wholemount in situ hybridization of embryos between 6.5 and 9.5 days p. c. shows that each gene has a unique expression pattern. HNF-3β is expressed in the node, notochord, floor plate and gut, while HNF-3α is mainly in the definitive endoderm and gut, but also in the floor plate of the midbrain. These results suggest that HNF3β and HNF-3α, in addition to their known functions as transcriptional activators in adult liver, play a role in body axis formation, neural tube patterning and definitive endoderm formation during gastrulation. MF-1 RNA is present in non-notochordal mesoderm, and in neural-crest-derived head mesenchyme, while MF-2 transcripts are found in the sclerotomes of the somites and in head mesenchyme, including that from neural crest. Studies on gastrulation stage embryos suggest that the early temporal and spatial patterns of HNF-3β? MF1 and HNF-3α correlate with populations of cells undergoing commitment to different developmental fates. A model is proposed linking FD gene expression with gastrulation events in the mouse.
Vital dye labelling of Xenopus laevis trunk neural crest reveals multipotency and novel pathways of migration
Authors: Collazo Andres , Bronner-Fraser Marianne , Fraser Scott E. 
Published: April 2021

ABSTRACT
Although the Xenopus embryo has served as an important model system for both molecular and cellular studies of vertebrate development, comparatively little is known about its neural crest. Here, we take advantage of the ease of manipulation and relative transparency of Xenopus laevis embryos to follow neural crest cell migration and differentiation in living embryos. We use two techniques to study the lineage and migratory patterns of frog neural crest cells: (1) injections of DiI or lysinated rhodamine dextran (LRD) into small populations of neural crest cells to follow movement and (2) injections of LRD into single cells to follow cell lineage. By using non-invasive approaches that allow observations in living embryos and control of the time and position of labelling, we have been able to expand upon the results of previous grafting experiments. Migration and differentiation of the labelled cells were observed over time in individual living embryos, and later in sections to determine precise position and morphology. Derivatives populated by the neural crest are the fins, pigment stripes, spinal ganglia, adrenal medulla, pronephric duct, enteric nuclei and the posterior portion of the dorsal aorta. In the rostral to mid-trunk levels, most neural crest cells migrate along two paths: a dorsal pathway into the fin, followed by presumptive fin cells, and a ventral pathway along the neural tube and notochord, followed by presumptive pigment, sensory ganglion, sympathetic ganglion and adrenal medullary cells. In the caudal trunk, two additional paths were noted. One group of cells moves circumferentially within the fin, in an arc from dorsal to ventral; another progresses ventrally to the anus and subsequently populates the ventral fin. By labelling individual precursor cells, we find that neural tube and neural crest cells often share a common precursor. The majority of clones contain labelled progeny cells in the dorsal fin. The remainder have progeny in multiple derivatives including spinal ganglion cells, pigment cells, enteric cells, fin cells and/or neural tube cells in all combinations, suggesting that many premigratory Xenopus neural crest precursors are multipotent.
wingless expression mediates determination of peripheral nervous system elements in late stages of Drosophila wing disc development
Authors: Phillips R. G. , Whittle J. R. S. 
Published: April 2021

ABSTRACT
We have used conditional wingless genotypes to dissect the role of this gene in late stages of wing disc development. One of these genotypes (wgIL/wg-lacZ) is simultaneously a reporter of wingless transcription and temperature-sensitive for wingless function, and has allowed us to define its pattern of transcription in the absence of wingless activity. The primordia of a subset of the bristles of the notum, which develop in or immediately adjacent to wingless-expressing cells, depend upon wing less activity. The time-course of this contribution and the effect on proneural gene expression together suggest that wingless may regulate the activity of products of the achaete-scute complex in proneural clusters. wing less activity is also required at the presumptive wing margin and is a necessary precondition for the change in proliferation pattern in this region. The involvement of wingless in transducing or mediating positional signals for spatial patterning in imaginal disc development is discussed.
FGF signalling in the early specification of mesoderm in Xenopus
Authors: Amaya Enrique , Stein Pascal A. , Musci Thomas J. , Kirschner Marc W. 
Published: April 2021

ABSTRACT
We have examined the role of FGF signalling in the development of muscle and notochord and in the expression of early mesodermal markers in Xenopus embryos. Disruption of the FGF signalling pathway by expression of a dominant negative construct of the FGF receptor (XFD) generally results in gastrulation defects that are later evident in the formation of the trunk and tail, though head structures are formed nearly normally. These defects are reflected in the loss of notochord and muscle. Even in embryos that show mild defects and gastrulate properly, muscle formation is impaired, suggesting that morphogenesis and tissue differentiation each depend on FGF. The XFD protein inhibits the expression of the immediate early gene brachyury throughout the marginal zone, including the dorsal side; it does not, however, inhibit the dorsal lip marker goosecoid, which is expressed in the first involuting mesoderm at the dorsal side that will underlie the head. The XFD protein also inhibits Xpo expression, an immediate early marker of ventral and lateral mesoderm. These results suggest that FGF is involved in the earliest events of most mesoderm induction that occur before gastrulation and that the early dorsal mesoderm is already composed of two cell populations that differ in their requirements for FGF.
flk-1, an flt-related receptor tyrosine kinase is an early marker for endothelial cell precursors
Authors: Yamaguchi Terry P. , Dumont Daniel J. , Conlon Ronald A. , Breitman Martin L. , Rossant Janet 
Published: April 2021

ABSTRACT
We have used RT-PCR to screen pluripotent murine embryonic stem cells to identify receptor tyrosine kinases (RTKs) potentially involved in the determination or differentiation of cell lineages during early mouse development. Fourteen different tyrosine kinase sequences were identified. The expression patterns of four RTKs have been examined and all are expressed in the mouse embryo during, or shortly after, gastrulation. We report here the detailed expression pattern of one such RTK, the flt-related gene flk-1. In situ hybridization analysis of the late primitive streak stage embryo revealed that flk-1 was expressed in the proximallateral embryonic mesoderm; tissue fated to become heart. By headfold stages, staining was confined to the endocardial cells of the heart primordia as well as to the blood islands of the visceral yolk sac and the developing allantois. Patchy, speckled staining was detected in the endothelium of all the major embryonic and extraembryonic blood vessels as they formed. During early organogenesis, expression was detected in the blood vessels of highly vascularized tissues such as the brain, liver, lungs and placenta. Since flk-1 was expressed in early mesodermal cells prior to any morphological evidence for endothelial cell differentiation (vasculogenesis), as well as in cells that form blood vessels from preexisting ones (angiogenesis), it appears to be a very early marker of endothelial cell precursors. We have previously reported that another novel RTK, designated tek, was expressed in differentiating endothelial cells. We show here that flk-1 transcripts are expressed one full embryonic day earlier than the first tek transcripts. The expression of these two RTKs appear to correlate with the specification and early differentiation of the endothelial cell lineage respectively, and therefore may play important roles in the establishment of this lineage.