pinecone/core-2020-05-10-deduplication huggingface dataset:
Epithelial–Stromal Tissue Interaction in Paramesonephric (Müllerian) Epithelial Differentiation

AbstractDuring organogenesis, the middle to caudal portion of Müllerian epithelium differentiates into uterine and vaginal epithelia in females. Functional differentiation of uterine and vaginal epithelia occurs in adulthood, and is regulated by 17β-estradiol (E2) and progesterone. In this report, the roles of mesenchyme/stroma in differentiation of uterine and vaginal epithelia were studied in tissue recombination experiments. At birth, Müllerian epithelium was negative for uterine and vaginal epithelial markers. Tissue recombinant experiments showed that uterine and vaginal gene expression patterns were induced in neonatal Müllerian epithelium by the respective mesenchymes. Differentiated adult uterine and vaginal epithelia did not change their original gene expression in response to heterotypic mesenchymal induction. In the adult vagina, E2 induced expression of involucrin, a CCAAT/enhancer-binding protein β and cytokeratin 1 via estrogen receptor α (ERα). Tissue recombination experiments with wild-type and ERα knockout mice demonstrated that epithelial gene expression is regulated by E2 via epithelial–stromal tissue interactions. Uterine/vaginal heterotypic tissue recombinations demonstrated that functional differentiation of uterine and vaginal epithelia required organ-specific stromal factors. In contrast, stromal signals regulating epithelial proliferation appeared to be nonspecific in the uterus and vagina
Three Amphioxus Wnt Genes (AmphiWnt3, AmphiWnt5, and AmphiWnt6) Associated with the Tail Bud: the Evolution of Somitogenesis in Chordates

AbstractThe amphioxus tail bud is similar to the amphibian tail bud in having an epithelial organization without a mesenchymal component. We characterize three amphioxus Wnt genes (AmphiWnt3, AmphiWnt5, and AmphiWnt6) and show that their early expression around the blastopore can subsequently be traced into the tail bud; in vertebrate embryos, there is a similar progression of expression domains for Wnt3, Wnt5, and Wnt6 genes from the blastopore lip (or its equivalent) to the tail bud. In amphioxus, AmphiWnt3, AmphiWnt5, and AmphiWnt6 are each expressed in a specific subregion of the tail bud, tentatively suggesting that a combinatorial code of developmental gene expression may help generate specific tissues during posterior elongation and somitogenesis. In spite of similarities within their tail buds, vertebrate and amphioxus embryos differ markedly in the relation between the tail bud and the nascent somites: vertebrates have a relatively extensive zone of unsegmented mesenchyme (i.e., presomitic mesoderm) intervening between the tail bud and the forming somites, whereas the amphioxus tail bud gives rise to new somites directly. It is likely that presomitic mesoderm is a vertebrate innovation made possible by developmental interconversions between epithelium and mesenchyme that first became prominent at the dawn of vertebrate evolution
Exogenous Amino Acids Regulate Trophectoderm Differentiation in the Mouse Blastocyst through an mTOR-Dependent Pathway

AbstractAt the late blastocyst stage, the epithelial trophectoderm cells of the mammalian embryo undergo a phenotypic change that allows them to invade into the uterine stroma and make contact with the maternal circulation. This step can be regulated in vitro by the availability of amino acids. Embryos cultured in defined medium lacking amino acids cannot form trophoblast cell outgrowths on fibronectin, an in vitro model of implantation, but remain viable for up to 3 days in culture and will form outgrowths when transferred into complete medium. The amino acid requirement is a developmentally regulated permissive event that occurs during a 4- to 8-h period at the early blastocyst stage. Amino acids affect spreading competence specifically by regulating the onset of protrusive activity and not the onset of integrin activation. Rapamycin, a specific inhibitor of the kinase mTOR/FRAP/RAFT1, blocks amino acid stimulation of embryo outgrowth, demonstrating that mTOR is required for the initiation of trophectoderm protrusive activity. Inhibition of global protein translation with cycloheximide also inhibits amino acid-dependent signals, suggesting that mTOR regulates the translation of proteins required for trophoblast differentiation. Our data suggest that mTOR activity has a developmental regulatory function in trophectoderm differentiation that may serve to coordinate embryo and uterus at the time of implantation
Calmegin Is Required for Fertilin α/β Heterodimerization and Sperm Fertility

AbstractLoss of the endoplasmic reticulum resident chaperone calmegin leads to the production of sterile sperm that do not bind to the egg zona pellucida (M. Ikawa et al., 1997, Nature 387, 607–611). In the present study, we demonstrate that calmegin −/− sperm were defective in migrating into the oviducts and in binding to the egg plasma membrane. Despite the impaired adhesive function, calmegin −/− sperm could fertilize eggs when zonae pellucidae were partially dissected, and eggs fertilized in this manner could develop normally to term. Since these sperm characteristics were similar to those found in fertilin β −/− sperm, we investigated the interaction of calmegin with fertilin β. Using immunoprecipitation techniques, calmegin was found to bind to sperm membrane proteins, fertilin α and β, during spermatogenesis. The binding was specific to calmegin: another endoplasmic reticulum chaperone calnexin, a calmegin homologue, was not able to bind to fertilin α and β. In the calmegin −/− mice, a loss of heterodimerization of fertilin α and β was observed and fertilin β was not detectable in mature sperm. The data not only explain why the calmegin and fertilin β knockout mouse lines share a common infertile phenotype, but also reveal the importance of the maturation of sperm membrane proteins in the endoplasmic reticulum
Neuron–Glia Communication via Nitric Oxide Is Essential in Establishing Antennal-Lobe Structure in Manduca sexta

AbstractNitric oxide synthase recently has been shown to be present in olfactory receptor cells throughout development of the adult antennal (olfactory) lobe of the brain of the moth Manduca sexta. Here, we investigate the possible involvement of nitric oxide (NO) in antennal-lobe morphogenesis. Inhibition of NO signaling with a NO synthase inhibitor or a NO scavenger early in development results in abnormal antennal lobes in which neuropil-associated glia fail to migrate. A more subtle effect is seen in the arborization of dendrites of a serotonin-immunoreactive neuron, which grow beyond their normal range. The effects of NO signaling in these types of cells do not appear to be mediated by activation of soluble guanylyl cyclase to produce cGMP, as these cells do not exhibit cGMP immunoreactivity following NO stimulation and are not affected by infusion of a soluble guanylyl cyclase inhibitor. Treatment with Novobiocin, which blocks ADP-ribosylation of proteins, results in a phenotype similar to those seen with blockade of NO signaling. Thus, axons of olfactory receptor cells appear to trigger glial cell migration and limit arborization of serotonin-immunoreactive neurons via NO signaling. The NO effect may be mediated in part by ADP-ribosylation of target cell proteins
Transcription Factors of the Anterior Neural Plate Alter Cell Movements of Epidermal Progenitors to Specify a Retinal Fate

AbstractThe embryonic progenitors that give rise to the vertebrate retina acquire their cell fate identity through a series of transitions that ultimately determine their final, differentiated retinal cell fates. In Xenopus, these transitions have been broadly defined as competence, specification, and determination. The expression of several transcription factors within the anterior neural plate at the time when the presumptive eye field separates from other neural derivatives suggests that these genes function to specify competent embryonic progenitors toward a retinal fate. In support of this, we demonstrate that some transcription factors expressed in the anterior neural ectoderm and/or presumptive eye field (otx2, pax6, and rx1) change the fate of competent, ventral progenitors, which normally do not contribute to the retina, from an epidermal to a retinal fate. Furthermore, the expression of these factors changes the morphogenetic movements of progenitors during gastrulation, causing ventral cells to populate the native anterior neural plate. In addition, we experimentally demonstrate that the efficacy of pax6 to specify retinal cells depends on the position of the affected cell relative to the field of neural induction. Thereby, otx2, pax6, and rx1 mediate early steps of retinal specification, including the regulation of morphogenetic cell movements, that are dependent on the level of neural-inductive signaling
MAP Kinase Converts MyoD into an Instructive Muscle Differentiation Factor in Xenopus

AbstractIn amphibian development, muscle is specified in the dorsal lateral marginal zone (DLMZ) of the gastrula embryo. Two critical events specify the formation of skeletal muscle: the expression of the myogenic transcription factor, XMyoD, and the secretion of bone morphogenetic protein (BMP) antagonists by the adjacent Spemann organizer. Inhibition of BMP signaling during early gastrula stages converts XMyoD protein into an instructive differentiation factor in the DLMZ. Yet, the intracellular signaling factors connecting BMP antagonism and activation of XMyoD remain unknown. Our data show that BMP antagonism induces the activity of mitogen-activated protein kinase (MAPK), and that the activity of MAPK is necessary for muscle-specific differentiation. Treatment of gastrula-stage DLMZ explants with MAPK pathway inhibitors ventralized mesoderm and prevented muscle differentiation. Expression of XMyoD in ventral mesoderm weakly induced muscle formation; however, the coexpression of a constitutively active MEK1 with XMyoD efficiently induced muscle differentiation. Activation of the MAPK pathway did not induce the transcription of XMyoD, but increased its protein levels and transcriptional activity. Thus, MAPK activation is subsequent to BMP antagonism, and participates in the dorsalization of mesoderm by converting the XMyoD protein into a potent differentiation factor
Apoptosis Is Required for the Proper Formation of the Ventriculo-Arterial Connections

AbstractThe role of apoptosis in cardiac morphogenesis has not been directly tested. Cardiomyocyte apoptosis is prevalent during the remodeling of the embryonic chicken cardiac outflow tract (OFT) in the transition from a single to a dual circulation. We tested the hypothesis that OFT cardiomyocyte apoptosis drives the shortening and rotation of the embryonic cardiac OFT and is required to achieve the mature ventriculo-arterial configuration. Chick embryos were treated with the peptide Caspase inhibitors zVAD-fmk or DEVD-cho at HH stages 15–20 (looped heart). Morphology of control and experimental embryos was assessed at HH stage 35, at which time the control hearts have developed a dual circulation. Infection of the hearts with a recombinant adenovirus expressing green fluorescent protein was used to follow the fate of the OFT cardiomyocytes. Affected embryos displayed abnormal persistence of a long infundibulum (OFT myocardial remnant) beneath the great vessels, indicating failure of OFT shortening. In some instances, the infundibulum connected both great vessels to the right ventricle in a side-by-side arrangement with transposition of the aorta, indicating a failure of rotation of the OFT, and modeling human congenital double outlet right ventricle. Defects were also observed at other sites in the heart where apoptosis is prevalent, such as in the formation of the cardiac valves and trabeculae. To more specifically target the apoptosis of the OFT cardiomyocytes, recombinant adenovirus was used to express the X-linked inhibitor of apoptosis protein in these cells. This resulted in an effect on outflow tract shortening and rotation similar to that of the peptide inhibitors, while the effects on the other cardiac structures were not observed. These results demonstrate that elimination of OFT cardiomyocytes by apoptosis is necessary for the proper formation of the ventriculo-arterial connections, and suggest apoptosis as a potential target of teratogens and genetic defects that are associated with congenital human conal heart defects
Roles for Zebrafish Focal Adhesion Kinase in Notochord and Somite Morphogenesis

AbstractWe have cloned zebrafish focal adhesion kinase (Fak) and analyzed its subcellular localization. Fak protein is localized at the cortex of notochord cells and at the notochord–somite boundary. During somitogenesis, Fak protein becomes concentrated at the basal region of epithelial cells at intersomitic boundaries. Phosphorylated Fak protein is seen at both the notochord–somite boundary and intersomitic boundaries, consistent with a role for Fak in boundary formation and maintenance. The localization of Fak protein to the basal region of epithelial cells in knypek;trilobite double mutant embryos shows that polarization of Fak distribution in the somite border cells is independent of internal mesenchymal cells. In addition, we show that neither Notch signaling through Suppressor of Hairless (SuH) nor deltaD is necessary for the wild-type segmental pattern of fak mRNA expression in the anterior paraxial mesoderm. However, nonsegmental expression of fak mRNA occurs with ectopic activation of Notch signaling through SuH and also in fused somite and beamter mutant embryos, indicating that there are multiple regulators of fak mRNA expression. Our results suggest that Fak plays a central role in notochord and somite morphogenesis
Perturbing Nuclear Transport in Drosophila Eye Imaginal Discs Causes Specific Cell Adhesion and Axon Guidance Defects

AbstractTo study nucleocytoplasmic transport during multicellular development, we developed a sensitive nuclear protein import assay in living blastoderm embryos. We show that dominant negative truncations of the human nuclear transport receptor karyopherinβ/Importinβ (DNImpβ) disrupt mRNA export and protein import in Drosophila. To test the sensitivity of different developmental processes to nuclear trafficking perturbations, we expressed DNImpβ behind the morphogenetic furrow of the eye disc, at a time when photoreceptors are patterned and project their axons to the brain. DNImpβ expression does not disrupt the correct specification of different photoreceptors, but causes a defect in cell adhesion that leads to some photoreceptors descending below the layer of ommatidia. The photoreceptors initially project their axons correctly to the posterior, but later their axons are unable to enter the optic stalk en route to the brain and continue to project an extensive network of misguided axons. The axon guidance and cell adhesion defects are both due to a disruption in the function of Ketel, the Drosophila ortholog of Importinβ. We conclude that cell adhesion and axon guidance in the eye have specific requirements for nucleocytoplasmic transport, despite involving processes that occur primarily at the cell surface
Targeted Mutagenesis of Smad1 Reveals an Essential Role in Chorioallantoic Fusion

AbstractThe Smad family of intracellular signaling intermediates transduce signals downstream from the transforming growth factor beta (TGF-β) family of receptor serine threonine kinases. The original member of this family, Smad1, has been shown to mediate signals from receptors for the bone morphogenetic proteins (BMPs), a large group of ligands in the TGF-β superfamily that mediate important developmental events. We have targeted the Smad1 gene in mice and created mutants null at this locus. Smad1 mutant mice die at approximately 9.5 days postcoitum due to defects in allantois formation. In Smad1 mutant mice, the allantois fails to fuse to the chorion, resulting in a lack of placenta and failure to establish a definitive embryonic circulation. Although vasculogenesis is initiated in the mutant allantois, the vessels formed are disorganized, and VCAM-1 protein, a marker for distal allantois development, is not expressed. Smad1 null fibroblasts are still able to respond to BMP2, however, suggesting that the defect observed in the developing extraembryonic tissue is caused by a very specific loss of transcriptional activity regulated by Smad1. Our data further demonstrate that although highly similar structurally, Smad proteins are not functionally homologous
otx2 Expression in the Ectoderm Activates Anterior Neural Determination and Is Required for Xenopus Cement Gland Formation

AbstractWe previously showed that otx2 regulates Xenopus cement gland formation in the ectoderm. Here, we show that otx2 is sufficient to direct anterior neural gene expression, and that its activity is required for cement gland and anterior neural determination. otx2 activity at midgastrula activates anterior and prevents expression of posterior and ventral gene expression in whole embryos and ectodermal explants. These data suggest that part of the mechanism by which otx2 promotes anterior determination involves repression of posterior and ventral fates. A dominant negative otx2-engrailed repressor fusion protein (otx2-En) ablates endogenous cement gland formation, and inhibits expression of the mid/hindbrain boundary marker engrailed-2. Ectoderm expressing otx2-En is not able to respond to signals from the mesoderm to form cement gland, and is impaired in its ability to form anterior neural tissue. These results compliment analyses in otx2 mutant mice, indicating a role for otx2 in the ectoderm during anterior neural patterning
Regulation of Endochondral Cartilage Growth in the Developing Avian Limb: Cooperative Involvement of Perichondrium and Periosteum

AbstractThe perichondrium and periosteum have recently been suggested to be involved in the regulation of limb growth, serving as potential sources of signaling molecules that are involved in chondrocyte proliferation, maturation, and hypertrophy. Previously, we observed that removal of the perichondrium and periosteum from tibiotarsi in organ culture resulted in an overall increase in longitudinal cartilage growth, suggesting negative regulation originating from these tissues. To determine if the perichondrium and periosteum regulate growth through the production of diffusible factors, we have tested various conditioned media from these tissues for the ability to modify cartilage growth in tibiotarsal organ cultures from which these tissues have been removed. Both negative and positive regulatory activities were detected. Negative regulation was observed with conditioned medium from (1) cell cultures of the region bordering both the perichondrium and the periosteum, (2) co-cultures of perichondrial and periosteal cells, and (3) a mixture of conditioned media from perichondrial cell cultures and periosteal cell cultures. The requirement for regulatory factors from both the perichondrium and periosteum suggests a novel mechanism of regulation. Positive regulation was observed with conditioned media from several cell types, with the most potent activity being from articular perichondrial cells and hypertrophic chondrocytes
The Secreted Glycoprotein Noelin-1 Promotes Neurogenesis in Xenopus

AbstractNeurogenesis in Xenopus neural ectoderm involves multiple gene families, including basic helix-loop-helix transcription factors, which initiate and control primary neurogenesis. Equally important, though less well understood, are the downstream effectors of the activity of these transcription factors. We have investigated the role of a candidate downstream effector, Noelin-1, during Xenopus development. Noelin-1 is a secreted glycoprotein that likely forms large multiunit complexes. In avians, overexpression of Noelin-1 causes prolonged and excessive neural crest migration. Our studies in Xenopus reveal that this gene, while highly conserved in sequence, has a divergent function in primary neurogenesis. XenopusNoelin-1 is expressed mainly by postmitotic neurogenic tissues in the developing central and peripheral nervous systems, first appearing after neural tube closure. Its expression is upregulated in ectopic locations upon overexpression of the neurogenic genes X-ngnr-1 and XNeuroD. Noelin-1 expression in animal caps induces expression of neural markers XBrn-3d and XNeuroD, and co-expression of secreted Noelin-1 with noggin amplifies noggin-induced expression of XBrn-3d and XNeuroD. Furthermore, in animal caps neuralized by expression of noggin, co-expression of Noelin-1 causes expression of neuronal differentiation markers several stages before neurogenesis normally occurs in this tissue. Finally, only secreted forms of the protein can activate sensory marker expression, while all forms of the protein can induce early neurogenesis. This suggests that the cellular localization of Noelin-1 may be important to its function. Thus, Noelin-1 represents a novel secreted factor involved in neurogenesis
Sgn1, a Basic Helix-Loop-Helix Transcription Factor Delineates the Salivary Gland Duct Cell Lineage in Mice

AbstractThe salivary system in mammals is comprised of three independently developed pairs of organs, the parotid, submaxillar, and sublingual glands. Each gland is composed of various ductal and acinar cell types that fulfill multiple roles. However, the molecular mechanisms regulating their biogenesis and functions are still largely unknown. In this paper, we report that two class B basic helix-loop-helix (bHLH) transcriptional regulators delineate the ductal and the acinar cells in salivary glands. Sgn1, a novel class B bHLH factor, is specifically expressed in the salivary duct cells, while the acinar cells are characterized by the expression of another class B bHLH factor, Mist1. The molecular nature of Sgn1 was also investigated: it binds to specific sequences of DNA as a dimer with a class A bHLH factor and acts as a negative transcriptional regulator against other bHLH factors. This study provides an important cue towards better understanding of the generation and function of multiple cell types in salivary glands. In addition, Sgn1 expression exhibits a reverse relationship with the development of male phenotypes, suggesting its role in gender dimorphism in the salivary glands
Structure and Function of the Egg Cortex from Oogenesis through Fertilization

Abstract•WHAT IS THE CORTEX?•The Egg Cortex•The Scope of This Review•STORING INFORMATION AND BUILDING THE CORTEX DURING OOGENESIS•Localizing Maternal Determinants in the Cortex•Structuring and Positioning Information in the Cortex•Cortical Polarity and Storage of Information in Other Oocytes•The Cortex during Vitellogenesis•MATURATION PREPARES THE CORTEX FOR FERTILIZATION•Restructuring Cortical Endoplasmic Reticulum and Organelles during Maturation•Restructuring the Cytoskeleton during Maturation•Relocalization of Cortical mRNAs and Domains during Maturation•The Cortex as the Site of Attachment and Fusion of Sperm and Egg•FERTILIZATION TRANSFORMS THE EGG CORTEX•Sperm-Induced Calcium Waves and Membranes•Waves of Exocytosis and Endocytosis at Fertilization•Fertilization-Induced Microfilament Reorganizations•The Fertilized Egg Cortex•WHAT THE CORTEX IS•The Cortex as a Repository for Spatiotemporal Information•The Questions That Remai