bluuebunny/crossref_metadata_2025_split huggingface dataset:
N-cadherin expression in developing, adult and denervated chicken neuromuscular system: accumulations at both the neuromuscular junction and the node of Ranvier
Authors: Cifuentes-Diaz Carmen , Nicolet Marc , Goudou Danièle , Rieger François , Mege René Marc 
Published: April 2021

ABSTRACT
N-cadherin, a member of the Ca2+-dependent cell adhesion molecule family plays essential roles in morphogenesis and histogenesis. N-cadherin has been shown in vitro to promote myoblast fusion and neurite outgrowth. We report here the cellular localization of N-cadherin during development and regeneration of the chick neuromuscular system. N-cadherin was uniformly expressed along the surface of myoblasts and myotubes of E6 limb muscles. Later, as synaptogenesis and secondary myogenesis proceeded, N-cadherin expression was down-regulated and restricted to some large-diameter fibres, then to the areas of contact between few myofibres and subsequently disappeared by embryonic day 17, suggesting that this cadherin may be implicated predominantly in fusion of primary myoblasts and, at lower degree, of secondary myoblasts. The presence of N-cadherin in muscle during the period of nerve trunk ingrowth and its down-regulation after synaptogenesis suggests that this molecule might be implicated in both processes. N-cadherin became accumulated at the neuromuscular junction only a few days after the first synaptic contacts were established and remained at the adult neuromuscular junction, suggesting a role of this molecule in the stabilization of the mature neuromuscular junction. In sciatic nerve, the level of N-cadherin expression remained unchanged from hatching to adult life. N-cadherin was widely distributed on the surface of myelinated fibres and on myelinating Schwann cells: in addition, it was concentrated at the node of Ranvier. At the ultrastructural level, the molecule was detected inside, at the surface and in the basal lamina of Schwann cells and also associated with endoneurial collagen. These observations suggest a role of N-cadherin in the structuring and stabilization of the myelin sheaths. After nerve injury, N-cadherin continued to be expressed by proliferating Schwann cells in the distal stump providing a substratum for regenerating axons. N-cadherin reappeared at the surface of denervated muscle fibres without disappearing from the former synaptic sites. It was detected not only in the sarcoplasm and on sarcolemma of denervated muscle fibres, but also in the basal lamina and in the extracellular matrix. The reexpression of N-cadherin at the surface of denervated muscle fibres suggests a role for this molecule in muscle reinnervation. The presence of N-cadherin in basal lamina and its association with collagen fibres raise questions about the release of N-cadherin in the extracellular space and the existence of a putative heterophilic ligand for N-cadherin.
Developmental regulation of the orphan receptor COUP-TF II gene in spinal motor neurons
Authors: Lutz Beat , Kuratani Shigeru , Cooney Austin J. , Wawersik Stefan , Tsai Sophia Y. , Eichele Gregor , Tsai Ming-Jer 
Published: April 2021

ABSTRACT
Members of the steroid/thyroid hormone receptor super- family are involved in the control of cell identity and of pattern formation during embryonic development. Chicken ovalbumin upstream promoter-transcription factors (COUP-TFs) can act as regulators of various steroid/thyroid hormone receptor pathways. To begin to study the role of COUP-TFs during embryogenesis, we cloned a chicken COUP-TF (cCOUP-TF II) which is highly homologous to human COUP-TF II. Northern analysis revealed high levels of cCOUP-TF II transcripts during organogenesis. Nuclear extracts from whole embryos and from embryonic spinal cords were used in electrophoretic mobility shift assays. These assays showed that COUP-TF protein is present in these tissues and is capable of binding to a COUP element (a direct repeat of AGGTCA with one base pair spacing). Analysis of cCOUP-TF expression by in situ hybridization revealed high levels of cCOUP-TF II mRNA in the developing spinal motor neurons. Since the ventral properties of the spinal cord, including the development of motor neurons, is in part established by inductive signals from the notochord, we transplanted an additional notochord next to the dorsal region of the neural tube in order to induce ectopic motor neurons. We observed that an ectopic notochord induced cCOUP-TF II gene expression in the dorsal spinal cord in a region coextensive with ectopic domains of SC1 and Islet-1, two pre-viously identified motor neuron markers. Collectively, our studies raise the possibility that cCOUP-TF II is involved in motor neuron development.
Function of Drosophila ovo+ in germ-line sex determination depends on X-chromosome number
Authors: Oliver Brian , Singer Jason , Laget Valérie , Pennetta Giuseppa , Pauli Daniel 
Published: April 2021

ABSTRACT
Germ-line sex determination in Drosophila melanogaster requires an assessment of the number of X chromosomes as measured against autosomal standards (XX =; female, X =; male) and signaling from the soma. Both of these sex determination cues are required for female-specific Sex-lethal+ function in germ cells. The ovo+ locus encodes zinc finger protein(s) required for female-specific splicing of Sex-lethal+ pre-mRNA, making ovo+ a candidate function acting between the two principal cues and Sex-lethal+. We have made ovo reporter genes and find that they show high activity in the germ line of females and low activity in the germ line of males. XY flies transformed into somatic females do not show high levels of reporter activity, while XX flies transformed into somatic males do. This shows that high level ovo+ expression depends on the number of X chromosomes, not the somatic sexual signals. The requirement for ovo+ function is restricted to XX flies. Mutations in ovo have no effect on XY males, X0 males or XY females, but have pronounced effects on germ cell viability in XX females, XX females with sex transformed germ lines, and XX males indicating that ovo+ gene products are required for events occurring only in flies with two X chromosomes.
GP330 is specifically expressed in outer cells during epithelial differentiation in the preimplantation mouse embryo
Authors: Gueth-Hallonet Catherine , Santa-Maria Angelica , Verroust Pierre , Maro Bernard 
Published: April 2021

ABSTRACT
During preimplantation development of the mouse embryo, a layer of outer cells differentiates into a perfect epithelium, the trophectoderm. The divergence between the trophectoderm and the inner cell mass takes place from the 8-cell stage to the 64-cell stage and precedes their commitment at the blastocyst stage. In this work, we have investigated the expression of gp330, a 330×103Mr glycoprotein found in clathrin-coated areas of the plasma membrane of some epithelial cells characterized by a high level of endocytic activity. Our results show that gp330 is first synthesized in 16-cell stage embryos and that its appearance is restricted to outer cells until the blastocyst stage. Furthermore, its expression is repressed in inner cells at a post-transcriptional level, probably through the development of extensive cell-cell contacts.
Apoptosis during macrophage-dependent ocular tissue remodelling
Authors: Lang Richard , Lustig Marc , Francois Fritz , Sellinger Meredith , Plesken Heide 
Published: April 2021

ABSTRACT
We have characterized the nature and pattern of cell death during regression of the pupillary membrane, a developmentally transient capillary network found in the anterior chamber of the eye. This analysis has revealed that the cellular components of the pupillary membrane include vascular endothelial cells in an intricate network of fine capillaries as well as attendant macrophages. The capillaries are situated on the anterior surface of the lens and held in relative position by a cobweb-like meshwork of extracellular matrix fibres that regress along with the cellular components of this structure. Cell death during regression of the pupillary membrane is characteristic of apoptosis. Specifically, apoptotic bodies containing condensed chromatin can be observed in vascular endothelial cells and genomic DNA isolated from the pupillary membrane shows the nucleosomal fragmentation pattern typical of apoptotic cells. Using a method for labelling fragmented DNA in tissue preparations (TUNEL), we have assessed the overall pattern of apoptotic cell death during pupillary membrane regression. We find that apoptosis occurs either in single cells in healthy vessels or synchronously along the entire length of a capillary segment. Both morphological and TUNEL analysis indicate that capillary regression occurs from junction to junction one segment at a time. We propose a model to explain the pattern of capillary regression observed and conclude from these and previous experiments (Lang and Bishop (1993)Cell 74, 453-462), that during regression of the pupillary membrane, the macrophage elicits target cell death by inducing apoptosis.
Strain-specific differences in mouse oocytes and their contributions to epigenetic inheritance
Authors: Latham Keith E. 
Published: April 2021

ABSTRACT
Previous experiments revealed a strain-dependent effect of egg cytoplasm on the developmental potential of androgenetic (two paternal genomes) mouse embryos. Eggs obtained from C57BL/6 mice supported androgenone development to the blastocyst stage at a much higher frequency than eggs from DBA/2 mice. Transient exposure of paternal pronuclei to DBA/2 egg cytoplasm also compromised development, indicating that the DBA/2 egg cytoplasm negatively affected the ability of paternal pronuclei to support blastocyst formation. An essential first step toward understanding the molecular mechanism by which egg modifier factors influence gene expression is to determine the number of loci that are responsible for the strain difference. To do this, (B6D2)F1 hybrid females were backcrossed to DBA/2 males and the eggs from individual female progeny assayed for their ability to support androgenetic development. Approximately one fourth of the backcross females produced eggs that failed to support androgenone development, indicating that two independently segregating genetic loci are most likely responsible for the difference between DBA/2 and C57BL/6 egg phenotypes. Comparison of DBA/2 and C57BL/6 oocytes by two-dimensional protein gel electrophoresis revealed at least 17 proteins that exhibited significant, reproducible, quantitative differences in rates of synthesis. All of these proteins were synthesized in (B6D2)F1 oocytes. These data, combined with the previous observation that the C57BL/6 egg phenotype is dominant, are consistent with a model in which a C57BL/6 allele at either locus provides a protective function, either by antagonizing the actions of the DBA/2 alleles or by providing, through partial or complete redundancy, a function not provided by the DBA/2 alleles.
TGF-β1 influences the relative development of the exocrine and endocrine pancreas in vitro
Authors: Sanvito F. , Herrera P.-L. , Huarte J. , Nichols A. , Montesano R. , Orci L. , Vassalli J.-D. 
Published: April 2021

ABSTRACT
Pancreatic rudiments from E12.5 mouse embryos undergo extensive development and differentiation when cultured in three-dimensional gels of extracellular matrix proteins for up to 12 days. Whereas collagen gels promote the formation of numerous exocrine acini and relatively small clusters of endocrine cells, in basement membrane (EHS) matrices the development of endocrine cells is dramatically favoured over that of acinar tissue. Buds embedded in a collagen gel contiguous to an EHS gel also fail to develop acini, suggesting the involvement of diffusible factor(s). Addition of cytokines to cultures of pancreatic buds in collagen gels modifies the relative proportions of the epithe-lial components of the gland. In the presence of EGF the proportion of the tissue occupied by ducts overrides that of acinar structures, whereas the endocrine portion of the tissue is not significantly modified. TGF-β1 partially mimicks the effect of EHS matrix in inhibiting the devel-opment of acinar tissue without decreasing the amount of ducts and mesenchyme; TGF-β1 also promotes the devel-opment of endocrine cells, in particular of insulin-contain-ing β cells and of cells expressing genes of the PP-fold family. These results show that cytokines can modulate the development of the pancreas and suggest a role for TGF-β1 in regulating the balance between the acinar and endocrine portions of the gland in vivo. More generally, they are compatible with the notion that, during organo-genesis, cytokines act as paracrine factors responsible for the development and maintenance of appropriate proportions of different tissue constituents.
Regulatory role of the Gα1 subunit in controlling cellular morphogenesis in Dictyostelium
Authors: Dharmawardhane Suranganie , Cubitt Andrew B. , Clark Alexandra M. , Firtel Richard A. 
Published: April 2021

ABSTRACT
To determine the function of the Dictyostelium Gα1 subunit during aggregation and multicellular development, we analyzed the phenotypes of gα1 null cells and strains overexpressing either wild-type Gα1 or two putative constitutively active mutations of Gα1. Strains overexpressing the wild-type or mutant Gα1 proteins showed very abnormal culmination with an aberrant stalk differentiation. The similarity of the phenotypes between Gα1 overexpression and expression of a putative constitutively active Gα1 subunit suggests that these phenotypes are due to increased Gα1 activity rather than resulting from a non-specific interference of other pathways. In contrast, gα1 null strains showed normal morphogenesis except that the stalks were thinner and longer than those of wild-type culminants. Analysis of cell-type-specific gene expression using lacZ reporter constructs indicated that strains overexpressing Gα1 show a loss of ecmB expression in the central core of anterior prestalk AB cells. However, expression of ecmB in anterior-like cells and the expression of prestalk A-specific gene ecmA and the prespore-specific gene SP60/cotC appeared normal. Using a Gα1/lacZ reporter construct, we show that Gα1 expression is cell-type-specific during the multicellular stages, with a pattern of expression similar to ecmB, being preferentially expressed in the anterior prestalk AB cells and anterior-like cells. The developmental and molecular phenotypes of Gα1 overexpression and the cell-type-specific expression of Gα1 suggest that Gα1-mediated signaling pathways play an essential role in regulating multicellular development by controlling prestalk morphogenesis, possibly by acting as a negative regulator of prestalk AB cell differentiation.
During the aggregation phase of development, gα1 null cells display a delayed peak in cAMP-stimulated accumulation of cGMP compared to wild-type cells, while Gα1 overexpressors and dominant activating mutants show parallel kinetics of activation but decreased levels of cGMP accumulation compared to that seen in wild-type cells. These data suggest that Gα1 plays a role in the regulation of the activation and/or adaptation of the guanylyl cyclase pathway. In contrast, the activation of adenylyl cyclase, another pathway activated by cAMP stimulation, was unaf fected in gα1 null cells and cell lines overexpressing wild-type Gα1 or the Gα1(Q206L) putative dominant activating mutation. However, the Gα1(G45V) putative constitutively active mutation showed significantly reduced adenylyl cyclase activity in response to cAMP. All Gα1 mutant cell lines aggregated normally; however, aggregates of cells expressing Gα1(G45V) developed ring-like structures that then developed a polarity and a small mound-like structure before forming a slug. Immunoprecipitation results suggest that the G45V phenotypes may be due to altered properties of this subunit and its association with the βg subunit.
XASH genes promote neurogenesis in Xenopus embryos
Authors: Ferreiro Beatriz , Kintner Chris , Zimmerman Kathy , Anderson David , Harris William A. 
Published: April 2021

ABSTRACT
Neural development in Drosophila is promoted by a family of basic helix-loop-helix (bHLH) transcription factors encoded within the Achaete Scute-Complex (AS-C). XASH-3, a Xenopus homolog of the Drosophila AS-C genes, is expressed during neural induction within a portion of the dorsal ectoderm that gives rise to the neural plate and tube. Here, we show that XASH-3, when expressed with the promiscuous binding partner XE12, specifically activates the expression of neural genes in naive ectoderm, suggesting that XASH-3 promotes neural development. Moreover, XASH-3/XE12 RNA injections into embryos lead to hypertrophy of the neural tube. Interestingly, XASH-3 misexpression does not lead to the formation of ectopic neural tissue in ventral regions, suggesting that the domain of XASH proneural function is restricted in the embryo. In contrast to the neural inducer noggin, which permanently activates the NCAM gene, the activation of neural genes by XASH-3/XE12 is not stable in naive ectoderm, yet XASH-3/XE12 powerfully and stably activates NCAM, Neurofilament and type III β-tubulin gene expression in noggin-treated ectoderm. These results show that the XASH-3 promotes neural development, and suggest that its activity depends on additional factors which are induced in ectoderm by factors such as noggin.
β-catenin localization during Xenopus embryogenesis: accumulation at tissue and somite boundaries
Authors: Fagotto François , Gumbiner Barry M. 
Published: April 2021

ABSTRACT
β-catenin is a cytoplasmic protein associated with cadherin adhesion molecules and has been implicated in axis formation in Xenopus (McCrea, P. D., Brieher, W. M. and Gumbiner, B. M. (1993) J. Cell Biol. 127, 477-484). We have studied its distribution in Xenopus embryos by immuno-fluorescence on frozen sections. Consistent with its function in cell-cell adhesion, β-catenin is present in every cell. However, high levels are expressed in certain regions and different tissues of the embryo. No simple correlation appears to exist between the levels of β-catenin with the expected strength of adhesion. High levels of β-catenin were found in regions undergoing active morphogenetic movements, such as the marginal zone of blastulae and gastrulae. This suggests that high expression of β-catenin could be involved in dynamic adhesion events. Surprisingly, β-catenin also accumulates on plasma membranes that probably do not establish direct or strong contacts with other cells. In particular, high amounts of β-catenin are found transiently at boundaries between tissue anlagen and at the intersomitic boundaries. This unexpected pattern of β-catenin expression raises the possibility that this molecule participates in developmental processes, perhaps independently of its classical role in cell-cell adhesion.
dishevelled is required during wingless signaling to establish both cell polarity and cell identity
Authors: Theisen Heidi , Purcell Judith , Bennett Mary , Kansagara Dipul , Syed Adeela , Marsh J. Lawrence 
Published: April 2021

ABSTRACT
The dishevelled gene of Drosophila is required to establish coherent arrays of polarized cells and is also required to establish segments in the embryo. Here, we show that loss of dishevelled function in clones, in double heterozygotes with wingless mutants and in flies bearing a weak dishevelled transgene leads to patterning defects which phenocopy defects observed in wingless mutants alone. Further, polarized cells in all body segments require dishevelled function to establish planar cell polarity, and some wingless alleles and dishevelled; wingless double heterozygotes exhibit bristle polarity defects identical to those seen in dishevelled alone. The requirement for dishevelled in establishing polarity is cell autonomous. The dishevelled gene encodes a novel intracellular protein that shares an amino acid motif with several other proteins that are found associated with cell junctions. Clonal analysis of dishevelled in leg discs provides a unique opportunity to test the hypothesis that the wingless dishevelled interaction specifies at least one of the circumferential positional values predicted by the polar coordinate model. We propose that dishevelled encodes an intracellular protein required to respond to a wingless signal and that this interaction is essential for establishing both cell polarity and cell identity.
p75-deficient embryonic dorsal root sensory and neonatal sympathetic neurons display a decreased sensitivity to NGF
Authors: Lee Kuo-Fen , Davies Alun M. , Jaenisch Rudolf 
Published: April 2021

ABSTRACT
To understand the role of low-affinity neurotrophin receptor p75 in neural development, we previously generated mice carrying a null mutation in the p75 locus (Lee, K. F., Li, E., Huber, L. J., Landis, S. C., Sharpe, A. H., Chao, M. V. and Jaenisch, R. (1992) Cell 69, 737 –749). To elucidate the mechanisms leading to deficits in the peripheral nervous system in p75 mutant mice, we have employed dissociated cultures to examine the responses of p75-deficient dorsal root ganglion (DRG) and superior cervical ganglion (SCG) neurons to different neurotrophins. We found that p75-deficient DRG and SCG neurons displayed a 2- to 3-fold decreased sensitivity to NGF at embryonic day 15 (E15) and postnatal day 3 (P3), respectively, ages that coincide with the peak of naturally occurring cell death. Furthermore, while p75-deficient E15 DRG neurons did not change their response specificity to BDNF, NT-3, and NT-4/5, P3 SCG neurons became more responsive to NT-3 at higher concentrations (nanomolar ranges). These results may help explain the deficits in the peripheral nervous system in p75 mutant mice and provide evidence that p75 can modulate neurotrophin sensitivity in some neurons.