pinecone/core-2020-05-10-deduplication huggingface dataset:
Drosophila arc Encodes a Novel Adherens Junction-Associated PDZ Domain Protein Required for Wing and Eye Development

AbstractLoss of arc function results in a downwardly curved wing and smaller eyes with a reduced number of ommatidia. Consistent with this phenotype, molecular analysis shows that arc mRNA and protein are expressed in the wing imaginal disc and in clusters of cells in the morphogenetic furrow of the eye imaginal disc. The 36-kb arc transcription unit contains 10 exons that are spliced to form a 5.5-kb mRNA. The encoded Arc protein is 143,000 Da and contains two PDZ (PSD-95, Discs large, ZO-1) domains; there is no close structural similarity to other PDZ proteins. In addition to its expression in imaginal discs, arc is expressed during embryogenesis in epithelia undergoing morphogenesis, including the invaginating posterior midgut, evaginating Malpighian tubule buds, elongating hindgut, invaginating salivary glands, intersegmental grooves, and developing tracheae. Arc protein colocalizes with Armadillo (β-catenin) to the apical (luminal) surface of these developing epithelia, indicating that it is associated with adherens junctions. Genes that are required for patterning of embryonic epithelia (e.g., tailless, Krüppel, fork head, and brachyenteron) or for progression of the morphogenetic furrow (i. e., hedgehog) are required to establish or maintain the regional expression of arc. Misexpression of arc in the eye imaginal discs results in rough and larger eyes with fused ommatidia. We propose that arc affects eye development by modulating adherens junctions of the developing ommatidium
Localization of gurken RNA in Drosophila Oogenesis Requires Elements in the 5′ and 3′ Regions of the Transcript

AbstractDuring Drosophila oogenesis, signaling between the germline and the soma leads to the establishment of polarity in the egg and embryo. This process involves the interaction of gurken (grk), a TGFα-like protein, with torpedo (top), the Drosophila EGF receptor (Egfr). In early stage egg chambers, grk RNA is present predominantly along the posterior cortex of the oocyte, and in mid stage egg chambers, the grk transcript becomes tightly localized to the future dorsal anterior corner of the oocyte. This localization of grk RNA restricts the distribution of Gurken protein and is critical in defining both the anterior–posterior and dorsal–ventral axes of the egg. We have determined the genomic sequence of the grk gene. By testing the requirement of various fragments of grk RNA in the localization process, we find localization signals present in both the 5′ and 3′ regions of the gene. Sequences in the 5′ noncoding region allow for accumulation of the transcript within the oocyte in early stage egg chambers, while signals in the coding region and the 3′UTR are necessary for localization in mid to late stage egg chambers. Active translation is not required for localization of the grk RNA. The mechanism of gurken RNA localization, therefore, differs from that of other localized RNAs studied to date
Spatially Restricted Factors Cooperate with Notch in the Regulation of Enhancer of split Genes

AbstractExpression of the Drosophila Enhancer of split [E(spl)] genes, and their homologues in other species, is dependent on Notch activation. The seven E(spl) genes are clustered in a single complex and their functions overlap significantly; however, the individual genes have distinct patterns of expression. To investigate how this regulation is acheived and to find out whether there is shared or cross regulation between E(spl) genes, we have analysed the enhancer activity of sequences from the adjacent E(spl)mβ, E(spl)mγ and E(spl)mδ genes and made comparisons to E(spl)m8. We find that although regulatory elements can be shared, most aspects of the expression of each individual gene are recapitulated by small (400–500 bp) evolutionarily conserved enhancers. Activated Notch or a Suppressor of Hairless-VP16 fusion are only sufficient to elicit transcription from the E(spl) enhancers in a subset of locations, indicating a requirement for other factors. In tissue culture cells, proneural proteins synergise with Suppressor of Hairless and Notch to promote expression from E(spl)mγ and E(spl)m8, but this synergy is only observed in vivo with E(spl)m8. We conclude that additional factors besides the proneural proteins limit the response of E(spl)mγ in vivo. In contrast to the other genes, E(spl)mβ exhibits little response to proneural proteins and its high level of activity in the wing imaginal disc suggests that wing-specific factors cooperate with Notch to activate the E(spl)mβ enhancer. These results demonstrate that Notch activity must be integrated with other transcriptional regulators and, since the activation of target genes is critical in determining the developmental consequences of Notch activity, provide a framework for understanding Notch function in different developmental contexts
An Essential Role of the Neuronal Cell Adhesion Molecule Contactin in Development of the Xenopus Primary Sensory System

AbstractContactin is a glycosylphosphatidylinositol-anchored immunoglobulin-like neuronal cell adhesion molecule that has been implicated in cellular interaction during development of the vertebrate central nervous system. Here we report evidence for an essential role of contactin in development of the Xenopus nervous system. Contactin mRNA is detectable by in situ hybridization in subsets of neurons in the brain, primary sensory neurons in the spinal cord, and cells along the trigeminal nerves of tailbud embryos. Contactin immunoreactivities preferentially distribute on axon tracts of the brain, the spinal cord, and the trigeminal sensory nerves. Most prominently, cell bodies and peripheral and spinal axons of primary sensory neurons, Rohon-Beard (RB) cells, are strongly contactin positive. Injection of the contactin overexpression vector into one blastomere of two-cell stage embryos leads to misdirected elongation of the peripheral axons of RB neurons in the injected half. Overexpression of antisense transcript causes depletion of contactin mRNA accumulation and abnormal development of RB neurons. In 52.3% of the injected embryos, RB neurons decrease in number and their peripheral axons in dorsal lateral tracts are defasciculated. These results demonstrate that contactin plays an essential role in development of the Xenopus primary sensory system
Pax-6 expression and activity are induced in the reepithelializing cornea and control activity of the transcriptional promoter for matrix metalloproteinase gelatinase B

Recent evidence supports the idea that matrix metalloproteinases (MMPs) act as morphogenetic regulators in embryonic and adult events of tissue remodeling. MMP activity is controlled primarily at the level of gene expression. In a recent study we characterized the transcriptional promoter of the MMP gene, gelatinase B (gelB), in transgenic mice, demonstrating the requirement for DNA sequences between -522 and +19 for appropriate activity. In this study we investigated factors required for gelB promoter activity in the developing eye and reepithelializing adult cornea. Pax-6 is a homeobox and paired domain transcription factor that acts at the top of the hierarchy of genes controlling eye development. Pax-6 is also expressed in the adult eye. We show here that the tissue expression pattern of Pax-6 overlaps extensively with gelB promoter activity in the developing and adult eye. In addition Pax-6 is observed to be upregulated in repairing corneal epithelium, as is gelB promoter activity. In cell culture transfection experiments, we identified two promoter regions which mediate positive response to Pax-6. By electrophoretic mobility shift assay, we further pinpoint two Pax-6 binding sites within these response regions and demonstrate direct interaction of the Pax-6 paired domain with one of these sites. These data suggest a mechanism by which Pax-6 may direct gelB expression in an eye-specific manner
Overexpression of FGF-2 alters cell fate specification in the developing retina of Xenopus laevis

The developing vertebrate retina produces appropriate ratios of seven phenotypically and functionally distinct cell types. Retinal progenitors remain multipotent up until the last cell division, favoring the idea that extrinsic cues direct cell fate. We demonstrated previously that fibroblast growth factor (FGF) receptors are necessary for transduction of signals in the developing Xenopus retina that bias cell fate decisions (S. McFarlane et al., 1998, Development 125, 3967-3975). However, the precise identity of the signal remains unknown. To test whether an FGF signal is sufficient to influence cell fate choices in the developing retina, FGF-2 was overexpressed in Xenopus retinal precursors by injecting, at the embryonic 16-cell stage, a cDNA plasmid encoding FGF-2 into cells fated to form the retina. We found that FGF-2 overexpression in retinal precursors altered the relative numbers of transgene-expressing retinal ganglion cells (RGC) and Miiller glia; RGCs were increased by 35% and Muller glia decreased by 50%. In contrast, the proportion of retinal precursors that became photoreceptors was unchanged. Within the photoreceptor population, however, we found a twofold increase in rod photoreceptors at the expense of cone photoreceptors. These data are consistent with an endogenous FGF signal influencing cell fate decisions in the developing vertebrate retina
Negative Autoregulation of Mash1 Expression in CNS Development

AbstractMash1, a neural-specific bHLH transcription factor, is essential for the formation of multiple CNS and PNS neural lineages. Transcription from the Mash1 locus is elevated in mice null for Mash1, suggesting that MASH1 normally acts to repress its own transcription. This activity is contrary to the positive autoregulation of other proneural bHLH proteins. To investigate the mechanisms involved in this process, sequences flanking the Mash1 gene were tested for the ability to mediate negative autoregulation. A Mash1/lacZ transgene containing 36 kb of cis-regulatory sequence exhibits an increase in lacZ expression in the Mash1 mutant background, which phenocopies the observation of transcriptional autoregulation at the endogenous Mash1 locus. Using Mash1/lacZ lines with progressively less cis-acting sequence, autoregulatory responsive elements were demonstrated to colocalize with a previously characterized 1.2-kb CNS enhancer. Mutations of E-box sites within this enhancer did not result in an apparent loss of autoregulation, suggesting that MASH1 does not directly repress its own transcription. Interestingly, these mutations did not indicate any underlying positive auto- or cross-regulation of Mash1. Furthermore, the loss of autoregulation in the Mash1 mutant background is reminiscent of a loss of lateral inhibitory signaling. However, mutations in HES consensus sites, the likely purveyors of Notch-mediated lateral inhibition, do not support a role for these sites in negative autoregulation. We hypothesize that MASH1 normally inhibits its own expression indirectly, possibly through a HES-mediated repression of positive regulators or through novel HES binding sites
Microphthalmia due to p53-mediated apoptosis of anterior lens epithelial cells in mice lacking the CREB-2 transcription factor

CREB-2 (also called ATF4, TAXREB67, or C/ATF) is an evolutionarily conserved member of the CREB/ATF family of basic-leucine zipper transcription factors. CREB-2 is expressed ubiquitously in the adult mouse and can function as both a transcriptional activator and a repressor. However, little was understood about the normal function of CREB-2 in mammalian development or organ physiology. In this report we have used gene targeting to produce CREB-2-deficient (CREB-2-/-) mice. Adult (CREB-2-/-) mice displayed microphthalmia due to the complete absence of a lens. Early embryonic lens development including formation of the optic vesicle, primary lens fibers, and proliferating anterior epithelial cells occurred normally in these mice. However, beginning at ED 14.5 the CREB-2-deficient anterior epithelial lens cells underwent massive and synchronous apoptosis. This was followed by the complete resorption of the developing lens. Consistent with this defect in anterior epithelial cell survival, in situ hybridization studies showed that CREB-2 is expressed at high levels in wild-type anterior epithelial lens cells at ED 14.5. The defect in lens formation seen in the CREB-2-/- mice was not associated with qualitative defects in the expression of Pax-6, αA-crystallin, c-maf, or PDGF-Rα. However, apoptosis of the anterior epithelial cells was mediated by a p53-dependent cell death pathway because ablation of the p53 gene rescued anterior epithelial cell death and allowed the formation of a lens in the absence of CREB-2. Taken together, these results identify CREB-2 as an important regulator of mammalian lens development
Cortical Actin Filaments Form Rapidly during Photopolarization and Are Required for the Development of Calcium Gradients in Pelvetia compressa Zygotes

AbstractPrevious research has shown that cortical gradients of cytosolic Ca2+ are formed during the photopolarization of Pelvetia compressa zygotes, with elevated Ca2+ on the shaded hemisphere that will become the site of rhizoid germination. We report here that the marine sponge toxin, latrunculin B, which blocks photopolarization at nanomolar concentrations, inhibited the formation of the light-driven Ca2+ gradients. Using low concentrations of microinjected fluorescent phalloidin as a tracer for actin filaments, we found that exposure to light induced a striking increase in actin filaments in the cells as indicated by an increase in fluorescence. The increase was quantified in the cortex, where it was most apparent, and the fluorescence there was found to increase by about a factor of 3. This increase in cortical phalloidin fluorescence was inhibited by latrunculin B at the same concentration required to inhibit Ca2+ gradient formation and photopolarization. The distribution of the increasing phalloidin fluorescence was uniform with respect to the developing rhizoid–thallus axis during the formation of the axis, and no intense patches of fluorescence were observed. After germination, fluorescence suggestive of an apical ring of actin filaments was seen near the rhizoid tip. Finally, inhibitor studies indicated that myosin may be involved in the photopolarization process
Combinatorial Activity of Pair-Rule Proteins on the Drosophila gooseberry Early Enhancer

The early expression of the Drosophila segment polarity gene gooseberry (gsb) is under the control of the pair-rule genes. We have identified a 514-bp enhancer which reproduces the early gsb expression pattern in transgenic flies. The transcription factor Paired (Prd) is the main activator of this enhancer in all parasegments of the embryo. It binds to paired- and homeodomain-binding sites, which are segregated on the enhancer. Using site-directed mutagenesis, we have identified sites critical for Prd activity. Negative regulation of this enhancer is mediated by the Even-skipped protein (Eve) in the odd-numbered parasegments and by the combination of Fushi-tarazu (Ftz) and Odd-skipped proteins in the even-numbered parasegments. The organisation of the Prd-binding sites, as well as the necessity for intact DNA binding sites for both paired- and homeodomains, suggests a molecular model whereby the two DNA-binding domains of the Prd protein cooperate in transcriptional activation of gsb. This positive activity appears to be in competition with Eve and Ftz on Prd homeodomain-binding sites
Analysis of Mouse Fertilin in Wild-Type and Fertilin β−/− Sperm: Evidence for C-terminal Modification, α/β Dimerization, and Lack of Essential Role of Fertilin α in Sperm–Egg Fusion

AbstractThe sperm surface protein fertilin functions in sperm–egg interaction. On guinea pig and bovine sperm, fertilin is a heterodimer of α and β subunits. Both subunits are initially synthesized as precursors and then proteolytically processed by removing N-terminal domains. Since the mouse is currently the main mammalian species in which fertilization is studied, in the present report, we analyzed the structure, processing, and expression of fertilin in mouse. We found that the processing of mouse fertilin β occurs during epididymal maturation and involves changes in the cytoplasmic tail domain as well as the N-terminal domains. Although we (R. Yuan et al., 1997, J. Cell Biol. 137, 105–112) and others (M. S. Chen et al., 1999, J. Cell Biol. 144, 549–561) have previously reported that mature fertilin β is 55–57 kDa, here we show that 55 kDa is an unrelated protein in the sperm extract which cross-reacts with an antibody that recognizes precursor, but not mature, fertilin β. Comparison of Western blots of wild-type and fertilin β knockout sperm revealed that authentic, mature fertilin β is 45 kDa. We also obtained direct evidence that mouse fertilin α and β exist as a heterodimer. In addition, we found that in mice lacking the fertilin β subunit, fertilin α is absent from mature sperm. A widely proposed model for sperm–egg fusion suggests that fertilin α is the sperm component that promotes membrane fusion by undergoing a conformational change that exposes a virus-like, hydrophobic fusion peptide. Because sperm lacking fertilin α and fertilin β can fuse with eggs at 50% the wild-type rate, this model is called into question. The results suggest instead that other gamete surface molecules act to promote membrane fusion and that fertilin's role in gamete fusion is in sperm–egg plasma membrane adhesion
Essential functions of DNA topoisomerase I in Drosophila melanogaster

AbstractDNA topoisomerase I (topo I) is an essential enzyme involved in replication, transcription, and recombination. To probe the functions of topo I during Drosophila development, we used topl-deficient flies with heat-shock-inducible topl transgenes and were able to observe both zygotic and maternal functions of topl. A critical period for the zygotic function is in the late larval and early pupal stages. Topo I is required for larval growth and cell proliferation in imaginal disc tissues. The maternal functions consist of two aspects: oogenesis and early embryogenesis. During oogenesis, topo I is detected in the nuclei of early germ-line cells and follicle cells. The mutant ovary exhibits abnormal proliferation and defective nuclear morphology in these cells. There are extranumeral germ-line cells in individual egg chambers, while the follicle cells are underreplicated. Topo I is also stored maternally in early embryos. It localizes to the nuclei during interphase and prophase, but disperses into the cytoplasm at metaphase. Embryos from the mutant mother frequently show disrupted nuclear divisions with defects in chromosome condensation and segregation. The cytological and genetic analysis of the topl mutant demonstrates that in Drosophila, topo I plays critical roles in many developmental stages active in cell proliferation
cDNA subtraction cloning reveals novel genes whose temporal and spatial expression indicates association with trophoblast invasion

Trophoblast invasion is a critical process in development of most mammals that shares similarities with the invasive behavior of tumor cells. In the present investigation, a cDNA subtraction library was constructed between invasive trophoblast at day 8 of murine development and mature noninvasive placenta at day 18 of gestation. One of the differentially expressed clones, Epcs26, was mapped to the X chromosome and revealed no homology to any known gene. It was predominantly expressed in parietal endoderm, undifferentiated cells of the ectoplacental cone, and a few trophoblast giant cells. Another gene, designated Epcs50, was mapped to chromosome 19. It exhibited homologies to the mouse Mps1 gene and, like Mps1, may have a distant relationship to the lyric protein perforin. High expression was detected in parietal endoderm cells and in a subset of secondary trophoblast giant cells. Two sequences, Epcs24 and Epcs68, exhibited an extensive open reading frame that shared the common features of the cysteine proteinase cathepsin L. Expression was confined to an undefined subpopulation of trophoblast giant cells. Both genes were mapped to chromosome 13 in close proximity to cathepsins L and J. The known functions of MPS1 and cathepsin L proteins indicate that the related proteins EPCS50, EPCS24, and EPCS68 participate in conferring invasive properties to the mouse trophoblast
Locally released retinoic acid repatterns the first branchial arch cartilages in vivo

AbstractThe fates of cranial neural crest cells are unique compared to trunk neural crest. Cranial neural crest cells form bone and cartilage and ultimately these cells make up the entire facial skeleton. Previous studies had established that exogenous retinoic acid has effects on neurogenic derivatives of cranial neural crest cells and on segmentation of the hindbrain. In the present study we investigated the role of retinoic acid on the skeletal derivatives of migrating cranial neural crest cells. We wanted to test whether low doses of locally applied retinoic acid could respecify the neural crest-derived, skeletal components of the beak in a reproducible manner. Retinoic acid-soaked beads were positioned at the presumptive mid-hindbrain junction in stage 9 chicken embryos. Two ectopic cartilage elements were induced, the first a sheet of cartilage ventral and lateral to the quadrate and the second an accessory cartilage rod branching from Meckel's cartilage. The accessory rod resembled a retroarticular process that had formed within the first branchial arch domain. In addition the quadrate was often displaced laterally and fused to the retroarticular process. The next day following bead implantation, expression domains of Hoxa2 and Hoxb1 were shifted in an anterior direction up to the mesencephalon and Msx-2 was slightly down-regulated in the hindbrain. Despite down-regulation in neural crest cells, the onset of Msx-2 expression in the facial prominences at stage 18-20 was normal. This correlates with normal distal beak morphology. Focal labeling of neural crest with Dil showed that instead of migrating in a neat group toward the second branchial arch, a cohort of labeled cells from r4 spread anteriorly toward the proximal first arch region. AP-2 expression data confirmed the uninterrupted presence of AP-2-expressing cells from the anterior mesencephalon to r4. The morphological changes can be explained by mismigration of r4 neural crest into the first arch, but at the same time maintenance of their identity. Up-regulation of the Hoxa2 gene in the first branchial arch may have encouraged r4 cells to move in the anterior direction. This combination of events leads to the first branchial arch assuming some of the characteristics of the second branchial arch