pinecone/core-2020-05-10-deduplication huggingface dataset:
Ectopic c-kit Expression Affects the Fate of Melanocyte Precursors inPatchMutant Embryos

AbstractThePatch(Ph) mutation in the mouse, a deletion that includes the gene for PDGFRα, is a recessive lethal that exhibits a dominant pigment phenotype in heterozygotes. To assess whether thePhmutation acts cell-autonomously or non-autonomously on melanocyte development, we have examined the melanogenic potential of neural crest populations from normal and mutant crest cellsin vitroand the pattern of dispersal and survival of melanocyte precursors (MPs)in vivo.We report that trunk neural crest cells from homozygousPhembryos give rise to pigmented melanocytesin vitroin response to Steel factor (SlF).In vivo,homozygousPhembryos contain a subpopulation of crest-derived cells that express c-kit and tyrosinase-related protein-2 characteristic of MPs. These cells begin to migrate normally on the lateral crest migration pathway, but then fail to disperse in the dermal mesenchyme and subsequently disappear. Although dermal mesenchyme is adversely affected inPhhomozygotes, SlF mRNA expression by the cells of the dermatome is normal inPhembryos when neural crest-derived MPs start to migrate on the lateral pathway. In contrast, mRNA for the SlF receptor, c-kit, was observed to be ectopically expressed in somites and lateral mesenchyme in embryos carrying thePhmutation. Based on this ectopic expression of c-kit inPhmutant embryos, and the observed distribution of SlF protein in normal and mutant embryos, we suggest that competition for limited amounts of SlF localized on the lateral neural crest migration pathway alters melanocyte dispersal and survival
Molecular, Phenotypic, and Expression Analysis ofvein,a Gene Required for Growth of theDrosophilaWing Disc

Abstractvein1(vn1) mutants lack portions of longitudinal wing vein 4 and the anterior crossvein. Stronger alleles, originally calleddefective dorsal discs,showvnis also required for the growth of the wing and haltere discs, as mutants for these alleles have tiny dorsal discs.vnfunctions nonautonomously and encodes a secreted EGF-like protein. Here we characterize the role ofvnin the imaginal wing disc by describing the expression pattern and correlating this pattern withvnmutant phenotypes and the requirement forvn. vnis expressed in wing discs in a complex and dynamic pattern. In larval wing discsvnis first expressed in the presumptive notum and later in the wing-pouch and hinge regions. There is a striking localization ofvntranscripts to intervein regions which begins with a stripe of expression straddling the AP boundary in late larval discs and develops in all intervein regions after puparium formation. We isolated newvnmutations including nulls and hypomorphs. Hypomorphicvnalleles revealed region-specific requirements forvnwithin the wing disc. We mapped lesions caused by 10vnmutations and defined a minimum size of 48 kb for the gene. The phenotype and expression analyses showvnhas an early role in global proliferation of the wing disc and specific roles in the development of the notum, hinge, longitudinal vein 4, and all intervein regions. The role ofvnin the EGF receptor signaling pathway is discussed
Regulated Demethylation of themyoDDistal Enhancer during Skeletal Myogenesis

AbstractmyoDis one of a family of four related basic helix-loop-helix transcription factors involved in the specification and differentiation of skeletal muscle. We previously identified a 258-bp distal enhancer that is sufficient for embryonic activation ofmyoDand is highly conserved between humans and mice. In this paper, we show using a modified bisulfite deamination/PCR amplification method that the distalmyoDenhancer is completely unmethylated at all the CpG sites tested in myogenic cells and a subpopulation of somite cells. Conversely, the distal enhancer in nonmuscle cells and tissues is methylated to an average level of >50% and we find no chromosomes in these tissues with a completely unmethylated enhancer. We present evidence that demethylation of the distal enhancer in somites of mouse embryos precedesmyoDtranscription, suggesting that demethylation of the distal enhancer is an active, regulated process that is essential formyoDactivation. We also show by analysis of transgenic mice carrying a human distal enhancer/reporter construct in which the three enhancer CpG sites have been mutated that methylation of the distal enhancer is not required to prevent precocious or ectopic embryonicmyoDexpression. We propose that a subset of somite cells demethylate the distal enhancer in response to specific developmental signals, thus making the enhancer accessible and able to respond to subsequent signals to activate themyoDgene
Mouse Mutants Lacking the Type 2 IGF Receptor (IGF2R) Are Rescued from Perinatal Lethality inIgf2andIgf1rNull Backgrounds

AbstractThe cation-dependent and cation-independent mannose 6-phosphate receptors (CD- and CI-MPRs) bind the phosphomannosyl recognition marker of lysosomal hydrolases, but in mammals the latter also interacts with insulin-like growth factor II (IGF-II). While IGF signaling is mediated by the type 1 IGF receptor (IGF1R), the type 2 receptor (IGF2R/CI-MPR) serves IGF-II turnover. Mouse mutants inheriting maternally a targeted disruption of the imprintedIgf2rgene, which is normally expressed only from the maternal allele, have increased serum and tissue levels of IGF-II and exhibit overgrowth (135% of normal birthweight) and generalized organomegaly, kinky tail, postaxial polydactyly, heart abnormalities, and edema. These mutants usually die perinatally, but a small minority can survive depending on genetic background and can occasionally reproduce, except for some females characterized by an imperforate vagina and hydrometrocolpos. Consistent with the hypothesis that lethality in the absence of IGF2R-mediated turnover is caused by excess of IGF-II overstimulating IGF1R,Igf2rmutants are completely rescued when they carry a second mutation eliminating either IGF-II or IGF1R. Normal embryonic development of theIgf1r/Igf2rdouble mutants, which differ from wild-type siblings only in the pattern of postnatal growth, appears to occur by signaling of IGF-II, being in excess, through a genetically identified unknown receptor, since triple mutants lacking IGF1R, IGF2R, and IGF-II are nonviable dwarfs (30% of normal size). In contrast with theIgf2r/Igf2double mutants, mice lacking IGF2R/CI-MPR and CD-MPR survive in an IGF-II null background at a very low frequency and only for a few postnatal weeks, indicating that the mannose 6-phosphate-mediated lysosomal enzyme trafficking is essential for viability
Developmental- and Eye-Specific Transcriptional Control Elements in an Intronic Region of a Ca2+-Activated K+Channel Gene

AbstractThe range of electrical properties that a neuron or muscle cell can manifest is determined by which ion channel genes it expresses and in what amounts. TheDrosophila slowpokeCa2+-activated K+channel gene has four distinct promoters. Here we assess the role that a downstream intronic region, called the C2/C3 region, plays in modulating Promoter C1 and Promoter C2 activity. Promoter C1 and Promoter C2 appear to be responsible for all neuronal and muscle expression, respectively. Transgenic flies were used to determine the expression pattern from each promoter in the presence and absence of the C2/C3 region. Deletion of this region silences Promoter C1 in adult but not larval CNS and causes a substantial reduction in Promoter C2 activity in adult but not larval muscle. The C2/C3 region also activates Promoter C1 in the animal's eye. By placing the C2/C3 region adjacent to a basal HSP70 promoter we have demonstrated that it contains elements that can specifically activate a heterologous promoter in the eye and in adult but not larval muscle. These results demonstrate that the C2/C3 region has a important role in regulatingslowpokedevelopmental expression in the CNS and musculature and in regulating eye expression
The Enzymatic Activity ofDrosophilaAWD/NDP Kinase Is Necessary but Not Sufficient for Its Biological Function

AbstractTheDrosophila abnormal wing discs(awd) gene encodes the subunit of a protein that has nucleoside diphosphate kinase (NDP kinase) activity. Null mutations of theawdgene cause lethality after puparium formation. Larvae homozygous for such mutations have small imaginal discs, lymph glands, and brain lobes. Neither the imaginal discs nor the ovaries from such null mutant larvae are capable of further growth or normal differentiation when transplanted into suitable host larvae. This null mutant phenotype can be entirely rescued by one copy of a transgene that has 750 bp ofawdupstream regulatory DNA fused to a full-lengthawdcDNA. Tissue-specific expression of AWD protein from this rescue transgene is identical to tissue-specific expression of β-galactosidase from a reporter transgene that has the same regulatory region fused to the bacteriallac Zgene. However, this rescue transgene or reporter transgene expression pattern is only a subset of the endogenous pattern of expression detected by eitherin situhybridization or immunohistochemistry. This suggests thatawdis normally expressed in some tissues where it is not required. The null mutant phenotype cannot be rescued at all by a transgene that has 750 bp ofawdupstream regulatory DNA fused to a full-lengthawdcDNA with a mutation that eliminates NDP kinase activity by replacement of the active site histidine with alanine. This suggests that the enzymatic activity of the AWD protein is necessary for its biological function. The human genesnm23-H1andnm23-H2encode NDP kinase A and B subunits, respectively. The protein subunit encoded by either humannm23gene is 78% identical to that encoded by theDrosophila awdgene. Transgenes that have the 750-bpawdupstream regulatory DNA fused to humannm23-H2cDNA but not tonm23-H1cDNA can rescue the imaginal disc phenotype and the zygotic lethality caused by homozygosis for anawdnull mutation as efficiently as anawdtransgene. However, rescue of female sterility requires twice as muchnm23-H2expression asawdexpression. This implies that the enzymatic activity of the AWD protein is not sufficient for its biological function. The biological function may require nonconserved residues of the AWD protein that allow it to interact with other proteins
Activation ofXenopusEggs by RGD-Containing Peptides Accompanied by Intracellular Ca2+Release

AbstractTo investigate the mechanism of egg activation inXenopus,unfertilized eggs were treated with various oligopeptides related to the RGD sequence-containing peptides. When dejellied eggs were treated with RGDS at concentrations higher than 250 μM,the eggs produced a positive-going activation potential concomitant with intracellular Ca2+release. The eggs underwent cortical granule breakdown, cortical contraction, and resumption of meiosis. The activation by RGDS was independent of the voltage of egg membranes. GRGD, GRGDTP, and RGPFPI caused activation in some eggs, but RGES, RFDS, GPRP amide, and GPA did not. Denuded eggs were activated by Sepharose beads bound to RGDS, indicating an interaction of the RGD sequence with receptor molecules on the egg plasma membrane. The activation by RGDS did not occur under a Ca2+- and Mg2+-free condition, but occurred in a Ca2+-free solution containing Mg2+, concomitant with an intracellular Ca2+release. These results indicate that a receptor of the RGD sequence on egg plasma membrane causes egg activation through an intracellular signal transduction system. A sperm agonist including the RGD sequence may play an important role in egg activation through the egg membrane receptor during the normal fertilization process
Ezrin Becomes Restricted to Outer Cells Following Asymmetrical Division in the Preimplantation Mouse Embryo

AbstractDuring preimplantation development in the mouse, two phenotypically distinct cell populations appear at the 16-cell stage: nonpolarized inner cells that give rise to the inner cell mass and polarized outer cells that give rise mainly to the trophectoderm. The divergence of these two cell lineages is due to asymmetrical cell divisions during the transition from the 8- to the 16 cell stage which can occur following blastomere polarization. During compaction, at the 8-cell stage, cytoplasmic organelles accumulate in the apical domain, a surface pole of microvilli forms, and blastomeres flatten onto one another. During the division from the 8- to the 16-cell stage, the only asymmetrical structure maintained is the pole of microvilli. At the 16-cell stage, only blastomeres inheriting a large part of this apical structure can reestablish a polarized organization. The mechanisms involved in the formation and stabilization of the apical pole of microvilli are still unknown. Ezrin is an actin-associated protein that has been proposed to play a role in the formation of microvillous structures. This led us to study the expression of ezrin during early development of the mouse embryo. We observed that ezrin mRNA and protein are present in the mouse oocyte and throughout preimplantation embryo development, although the amount of protein present decreases continuously during early development, particularly after the 8-cell stage, at the time of compaction. Two isoforms of ezrin phosphorylated on tyrosine residues are present during all of preimplantation development while a third non-tyrosine-phosphorylated isoform appears at the 8-cell stage and its relative amount increases from the 8-cell stage to the blastocyst stage. Before compaction, ezrin is distributed around the cell cortex. However ezrin becomes restricted to the microvilli of the apical pole after compaction. At later stages, ezrin is found in the microvilli of the apical surface of outer cells. Finally, ezrin remains associated with the microvillous pole during the transition from the 8- to 16-cell stage and is found only in the outer cells after division. Thus, ezrin is the first cytocortical protein described that is totally segregated in outer cells at the 16-cell stage after an asymmetrical division
Neural Crest Formation inXenopus laevis:Mechanisms ofXslugInduction

AbstractA study of the induction of the prospective neural crest inXenopus laevisembryos has been carried out, using the expression ofXslugas a specific marker for the neural crest. We have analyzed the competence and the specification of the neural crest. The competence to expressXslugwas analyzed using two different approaches: (1)in vitroculture of conjugates of dorsal mesoderm and ectoderm taken from embryos at different ages and (2) grafts of equivalent pieces of ectoderm in the neural fold region of a gastrula or a neurula. Similar results were obtained with both methods: the ectoderm loses the competence to respond to neural fold induction at the end of gastrulation. Neural crest specification was analyzed by culturing a region of the ectoderm that contained the prospective neural crest and analyzingXslugexpression. Our results show that neural folds are specified autonomously to expressXslugby the end of gastrulation. By grafting labeled neural plate into lateral epidermis we have shown that neural crest can be induced by an interaction between neural plate and epidermis. Furthermore, neural crest cells come from both tissues. We have discarded the possibility that these neural crest cells are induced by a signal coming from the underlying lateral plate, by a homeogenetic signal coming from the host neural plate, or by regeneration of crest cells from the dissected neural plate. We propose a model to explain how the neural crest cells are induced at the border of the neural plate inX. laevis
Eggshell Assembly inDrosophila:Processing and Localization of Vitelline Membrane and Chorion Proteins

AbstractTheDrosophilaeggshell consists of three major proteinaceous layers: the vitelline membrane, the inner chorionic layer, and the outer endochorion. During the latter stages of oogenesis, the proteins that comprise these layers are synthesized and secreted by epithelial follicle cells which surround the maturing oocyte. While there is considerable knowledge of the structural units which comprise the eggshell layers, there is little knowledge of how individual proteins function or interact with one another to form the structure. Immunoelectron microscopy was used to follow the distribution of four different eggshell proteins in the assembling and mature eggshell. sV23 and sV17, follicle cell proteins synthesized during the early stages of eggshell formation (stages 8–10), were distributed within the vitelline membrane layer at all stages. Despite marked temporal differences in their accumulation profiles, s36 and s18, putative chorion proteins, were similarly distributed throughout the floor, pillars, and roof of the endochorion. Although the vitelline membrane appears to be morphologically complete by stage 11, developmental Western blots and immunolocalization data indicate that molecular dynamism persists within the layer throughout the subsequent choriogenic stages. During early chorion formation the vitelline membrane appears to act as a reservoir for chorion proteins since s36 was found predominantly in the vitelline membrane layer of stage 12 egg chambers. During the late choriogenic stages (13–14), both sV17 and sV23 are processed to smaller derivatives. Interactions between the eggshell layers were suggested by ultrastructural analysis of a sV23 protein null mutant which showed that the structural integrity of the outer chorion is dependent upon the presence of a vitelline membrane component
Phenotypic Maturation of Neurons and Continuous Precursor Migration in the Formation of the Peduncle Nerve Net inHydra

AbstractMechanisms of nerve net formation inHydrawere analyzed using a monoclonal antibody (L96) directed against neurons of the peduncle, the basal end of the polyp's body axis. L96+neurons express RFamide neuropeptides and constitute 70–80% of all ectodermal neurons in the lower peduncle. L96+neurons arise from neuronal precursors which immigrate from the gastric region into the upper peduncle and first differentiate into neurons lacking the L96 antigen. By tissue movement, these L96−neurons become displaced to the lower peduncle where L96 antigen expression is initiated. The entire L96 neuron differentiation pathway requires about 4 days, but regeneration stimuli shorten it to only 36 hr. Our experiments indicate that local extrinsic signals released by epithelial cells in the peduncle control the L96+neuron differentiation pathway. Ectopic L96+neuron differentiation can be induced by LiCl treatment, which also stimulates ectopic feet in the gastric region. Further experiments show that intrinsic signals are also involved in the L96+neuron differentiation pathway. Neurons of the gastric region become continuously displaced to the peduncle by tissue movement, but these “old” neurons fail to express the L96 antigen in response to the altered epithelial environment. Gastric neurons also fail to express the L96 antigen after LiCl treatment or regeneration in stem cell-depleted polyps. Thus, the competence of neurons to respond to environmental cues with L96 antigen expression is strongly age-dependent. We define this age-dependent acquisition of the neuronal phenotype as phenotypic maturation controlled by the target tissue
TheDrosophilaSecreted Protein Argos Regulates Signal Transduction in the Ras/MAPK Pathway

AbstractTheDrosophila argosgene encodes a secreted protein with an EGF motif which acts as an inhibitor of cellular differentiation in multiple developmental processes. To investigate the cellular pathways regulated by Argos, we screened for mutations which could modify the phenotype caused by overexpression ofargos.We show that the effects ofargosoverexpression on the eye and wing vein development are suppressed by gain-of-function mutations of the MAPKK/D-MEK gene (Dsor1/D-mek) and the MAPK/ERK-A gene (rolled) and were enhanced by loss-of-function mutations ofStar.Loss-of-function mutations in components of the Ras/MAPK signaling cascade act as dominant suppressors of the phenotype caused by theargosnull mutation. A loss-of-functionargosmutation enhanced the overproduction of R7 neurons caused by gain-of-function alleles ofSon of sevenlessandDsor1.Conversely, overexpression ofargosinhibited formation of the extra R7 cells that was caused by high-level MAPK/ERK-A activity. A phenotype of thesev;argosdouble mutants revealed thatsevis epistatic toargos.These results provide evidence that Argos negatively regulates signal transduction events in the Ras/MAPK cascade
brainiacEncodes a Novel, Putative Secreted Protein That Cooperates with Grk TGFα in the Genesis of the Follicular Epithelium

Abstractbrainiac (brn)is involved in a number of developmental events. In addition to being required zygotically for segregation of neuroblasts from epidermoblasts, it is essential for a series of critical steps during oogenesis which also depend upongurken (grk),a TGFα homolog. Animals harboring strong mutations of eithergrkor EGF receptor tyrosine kinase (Egfr) or doubly mutant forbrnand weakgrkorEgfrmutations produce ovarian follicles with multiple sets of nurse cell–oocyte complexes. These follicles frequently have discontinuities in the follicular epithelium that uncover nurse cells but not the oocyte. Gaps first appear in the germarium, suggesting that some nurse cells lack affinity for invading prefollicular cells. This is the first evidence thatgrk,in addition to its involvement in the genesis of anterior–posterior and dorsal–ventral polarity, is also required for Egfr-dependent development of the follicular epithelium that surrounds each nurse cell/oocyte cluster to form an egg chamber. We have used restriction fragment length polymorphisms to localizebrnto a 10-kb region within a 300-kb stretch of DNA on the X-chromosome, and we have identified thebrngene by means of RNA rescue.brncodes for a putative secreted protein.brnis expressed in germ cells at the time follicle cells first surround the nurse cell–oocyte complex. Our genetic data suggest thatbrnacts in a parallel, but partially overlapping pathway to the Grk–Egfr signaling pathway. Thebrnpathway may help to provide specificity to TGFα–Egfr function during oogenesis