pinecone/core-2020-05-10-deduplication huggingface dataset:
The Endoderm Plays an Important Role in Patterning the Segmented Pharyngeal Region in Zebrafish (Danio rerio)

AbstractThe development of the vertebrate head is a highly complex process involving tissues derived from all three germ layers. The endoderm forms pharyngeal pouches, the paraxial mesoderm gives rise to endothelia and muscles, and the neural crest cells, which originate from the embryonic midbrain and hindbrain, migrate ventrally to form cartilage, connective tissue, sensory neurons, and pigment cells. All three tissues form segmental structures: the hindbrain compartmentalizes into rhombomeres, the mesoderm into somitomeres, and the endoderm into serial gill slits. It is not known whether the different segmented tissues in the head develop by the same molecular mechanism or whether different pathways are employed. It is also possible that one tissue imposes segmentation on the others. Most recent studies have emphasized the importance of neural crest cells in patterning the head. Neural crest cells colonize the segmentally arranged arches according to their original position in the brain and convey positional information from the hindbrain into the periphery. During the screen for mutations that affect embryonic development of zebrafish, one mutant, called van gogh (vgo), in which segmentation of the pharyngeal region is absent, was isolated. In vgo, even though hindbrain segmentation is unaffected, the pharyngeal endoderm does not form reiterated pouches and surrounding mesoderm is not patterned correctly. Accordingly, migrating neural crest cells initially form distinct streams but fuse when they reach the arches. This failure to populate distinct pharyngeal arches is likely due to the lack of pharyngeal pouches. The results of our analysis suggest that the segmentation of the endoderm occurs without signaling from neural crest cells but that tissue interactions between the mesendoderm and the neural crest cells are required for the segmental appearance of the neural crest-derived cartilages in the pharyngeal arches. The lack of distinct patches of neural crest cells in the pharyngeal region is also seen in mutants of one-eyed pinhead and casanova, which are characterized by a lack of endoderm, as well as defects in mesodermal structures, providing evidence for the important role of the endoderm and mesoderm in governing head segmentation
FGF-2 Up-regulation and Proliferation of Neural Progenitors in the Regenerating Amphibian Spinal Cord in Vivo

AbstractRegeneration of the spinal cord occurs spontaneously in adult urodele amphibians. The key cells in this regenerative process appear to be the ependymal cells that following injury migrate and proliferate to form the ependymal tube from which the spinal cord regenerates. Very little is known about the signal(s) that initiates and maintains the proliferative response of these cells. Fibroblast growth factor 2 (FGF-2) has been shown to play a role in maintaining neural progenitor cell cycling in vitro and may be important for neuronal survival and axonal growth after injury. We have investigated its role in regeneration of the spinal cord in vivo following tail amputation in the adult salamander, Pleurodeles waltl. We show that only the low-molecular-weight form of FGF-2 is found in Pleurodeles and that in the normal cord it is expressed in a subset of neurons, but is hardly detectable in ependymal cells. Tail amputation results in induction of FGF-2 in the ependymal cells of the regenerating structure, and later in regeneration FGF-2 is up-regulated in some newborn neurons. FGF-2 pattern of expression in the ependymal tube parallels that of proliferation. Furthermore, exogenous FGF-2 significantly increases ependymal cell proliferation in vivo. Overall our results strongly support the view that one important role of FGF-2 during spinal cord regeneration in Pleurodeles is to induce proliferation of neural progenitor cells
The Mouse Mammary Gland Requires the Actin-Binding Protein Gelsolin for Proper Ductal Morphogenesis

AbstractGelsolin is an actin-binding/severing protein expressed in intracellular and secreted forms. It is a major regulator of the form and function of the actin cytoskeleton in most all cells. Here we demonstrate that female mice with a targeted deletion of the gelsolin gene (Gsn−/−) have defects in mammary gland morphogenesis. Two distinct defects were identified in the gelsolin-null mammary gland. First, the mammary anlage from Gsn−/− mice failed to elongate at the onset of puberty and remained rudimentary until approximately 9 weeks of age, early block (Gsn−/−EB). Second, after the mammary epithelium had filled the mammary fat pad, a complete lack of terminal branching, or late block, was observed (Gsn−/−LB). The Gsn−/−EB was seen in 70% of Gsn−/− mice and appeared to be dependent on a modifier gene(s) in addition to the loss of gelsolin. Gsn−/−LB was observed in all Gsn−/− mice. Terminal end buds (TEBs) were not evident in the mammary anlage from Gsn−/−EB mice until approximately 9 weeks of age. Cellular proliferation in the terminal ductal regions of Gsn−/−EB females was detected by bromodeoxyuridine incorporation, but was less than that found in the TEBs of age-matched controls. In mice deficient for gelsolin, mammary gland architecture was unaltered at the histological level. Lobuloalveolar development was delayed in response to pregnancy in mammary glands of Gsn−/− mice but was otherwise normal. Lactation and involution in the gelsolin-null animals were similar to those of wild-type mice. Transplantation of epithelium devoid of gelsolin into a wild-type (GsnWT) mammary fat pad resulted in proper arborization of the ductal tree. Transplantation of GsnWT epithelium into the Gsn−/− fat pad recapitulated the lack of terminal branching seen in Gsn−/− females. These results indicate that gelsolin is required in the mammary stroma for proper ductal morphogenesis. Our results provide the first evidence of an actin regulatory protein affecting mammary ductal growth through stromal–epithelial communication
VEGF Spatially Directs Angiogenesis during Metanephric Development in Vitro

AbstractVascular endothelial growth factor (VEGF) is required for endothelial cell differentiation, vasculogenesis, and normal glomerular vascularization. To examine whether VEGF plays a role as a chemoattractant for the developing kidney vasculature, avascular metanephric kidneys from rat embryos (E14) were cocultured with endothelial cells. To determine whether VEGF directly provides chemoattractive guidance for migration, we examined migration of endothelial cells toward VEGF-coated beads. Mouse glomerular endothelial cells expressing β-galactosidase (MGEC) were isolated from Flk-1(+/−) heterozygous mice and passaged 4–12 times. Upon 24 h culture on collagen I gels MGEC formed a lattice or capillary-like network. Embryonic metanephroi were cocultured with MGEC on collagen I gels for 1–6 days in defined media, stained for β-galactosidase, and examined by light microscopy. Metanephric organs induced a rearrangement of the endothelial cell lattice and attracted MGEC. MGEC invaded the metanephric organs forming capillary-like structures within and surrounding the forming nephrons. This process was accelerated and amplified by low oxygen (3% O2) and was prevented by anti-VEGF neutralizing antibodies. MGECs migrated toward VEGF-coated beads, whereas PBS-coated beads did not alter MGEC networks. We conclude that VEGF produced by the differentiating nephrons acts as a chemoattractant providing spatial direction to developing capillaries toward forming nephrons during metanephric development in vitro
The Caenorhabditis elegans Ldb/NLI/Clim Orthologue ldb-1 Is Required for Neuronal Function

AbstractLIM homeodomain (LIM-HD) and nuclear LIM-only proteins play important roles in a variety of developmental processes in animals. In some cases their activities are modulated by a nuclear LIM binding protein family called Ldb/NLI/Clim. Here we characterize the Ldb/NLI/Clim orthologue ldb-1 of the nematode Caenorhabditis elegans. Two alternatively spliced variants exist, which differ in their amino-termini. The ldb-1 orthologue of Caenorhabditis briggsae has the same structure as that of C. elegans and is highly conserved throughout the open reading frame, while conservation to fly and vertebrate proteins is restricted to specific domains: the dimerization domain, the nuclear localization sequence, and the LIM interaction domain. C. elegans ldb-1 is expressed in neurogenic tissues in embryos, in all neurons in larval and adult stages, and in vulval cells, gonadal sheath cells, and some body muscle cells. C. elegans LDB-1 is able to specifically bind LIM domains in yeast two-hybrid assays. RNA inactivation studies suggest that C. elegans ldb-1 is not required for the differentiation of neurons that express the respective LIM-HD genes or for LIM-HD gene autoregulation. In contrast, ldb-1 is necessary for several neuronal functions mediated by LIM-HD proteins, including the transcriptional activation of mec-2, the mechanosensory neuron-specific stomatin
The NED-8 Conjugating System in Caenorhabditis elegans Is Required for Embryogenesis and Terminal Differentiation of the Hypodermis

AbstractThis work has identified the enzymes involved in the activation and conjugation of the ubiquitin-like protein NED-8 in Caenorhabditis elegans. A C. elegans conjugating enzyme, UBC-12, is highly specific in its ability to utilize NED-8 as a substrate. Immunostaining shows that NED-8 is conjugated in vivo to a major target protein with a conjugate size of 90 kDa. While the amount of this conjugate is developmentally regulated with reduced levels in the larval stages, the mRNA encoding C. elegans UBC-12 is constitutively produced throughout development, as is NED-8 itself. The importance of the NED-8 conjugating system in C. elegans was determined by RNA interference (RNAi) assays using double-stranded RNA encoding NED-8, UBC-12, or the NED-8 activating enzyme component ULA-1. The progeny of both ned-8 and ubc-12 RNAi-treated hermaphrodites either arrested during embryonic development or underwent abnormal postembryonic development. The effect on postembryonic development was pleiotropic, the most frequent gross abnormality being vulval eversion during the L4 stage. Individuals with an everted vulva either burst at the L4 to adult molt or gave rise to adults incapable of egg laying. Additionally, both ned-8 and ubc-12 RNAi induced a striking abnormality in the alae, structures produced by the lateral hypodermal seam cells in the adult nematode. Affected alae were patchy and frequently diverged around a central space. Vulval defects were also produced by RNAi directed at C. elegans ula-1. This is the first demonstration of a requirement for NED-8 conjugation in metazoan development
The Drosophila Lissencephaly1 (DLis1) Gene Is Required for Nuclear Migration

AbstractNuclear movement is critical for several developmental processes in eukaryotes. Drosophila oogenesis provides a paradigmatic example in which localization of the nucleus generates a source of cellular asymmetry that is used in patterning both the anterior–posterior and the dorsal–ventral axes of the oocyte. In this study we show that mutations in the Drosophila Lissencephaly1 (DLis1) gene result in partial ventralization of the eggshell. DLis1 mutations affect the localization of gurken mRNA and protein in the oocyte. These defects are correlated with incorrect positioning of the oocyte nucleus, suggesting that DLis1 is required for nuclear migration. DLis1 shows significant sequence conservation across the evolutionary spectrum. Fungal cognates of DLis1 are involved in nuclear migration while homologs in humans and mice are implicated in neuronal migration. DLis1 shows genetic interactions with the Glued and Dynein heavy chain subunits of the dynein/dynactin complex, supporting the idea that the Lis1 family of proteins plays a role in microtubule motor-based nuclear motility
Gαs Family G Proteins Activate IP3–Ca2+ Signaling via Gβγ and Transduce Ventralizing Signals in Xenopus

AbstractDuring early embryonic development, IP3–Ca2+ signaling transduces ventral signaling at the time of dorsoventral axis formation. To identify molecules functioning upstream in this signal pathway, we examined effects of a panel of inhibitory antibodies against Gαq/11, Gαs/olf, or Gαi/o/t/z. While all these antibodies showed direct inhibition of their targets, their effects on redirection of the ventral mesoderm to a dorsal fate varied. Anti-Gαs/olf antibody showed strong induction of dorsal fate, anti-Gαi/o/t/z antibody did so weakly, and anti-Gαq/11 antibody was without effect. Injection of βARK, a Gβγ inhibitor, mimicked the dorsalizing effect of anti-Gαs/olf antibody, whereas injection of adenylyl cyclase inhibitors at a concentration which inhibited Gαs-coupled cAMP increase did not do so. The activation of Gαs-coupled receptor gave rise to Ca2+ transients. All these results suggest that activation of the Gαs-coupled receptor relays dorsoventral signal to Gβγ, which then stimulates PLCβ and then the IP3–Ca2+ system. This signaling pathway may play a crucial role in transducing ventral signals
Trk C Receptor Signaling Regulates Cardiac Myocyte Proliferation during Early Heart Development in Vivo

AbstractNeurotrophin-3 (NT-3) is a member of the neurotrophin family of growth factors, best characterized by its survival- and differentiation-inducing effects on developing neurons bearing the trk C receptor tyrosine kinase. Through analysis of NT-3 and trk C gene-targeted mice we have identified NT-3 as critically regulating cardiac septation, valvulogenesis, and conotruncal formation. Although these defects could reflect cardiac neural crest dysfunction, the expression of NT-3 and trk C by cardiac myocytes prior to neural crest migration prompted analysis of cell-autonomous actions of NT-3 on cardiac myocytes. Retroviral-mediated overexpression of truncated trk C receptor lacking kinase activity was used to inhibit activation of trk C by endogenous NT-3, during early heart development in ovo. During the first week of chicken development, expression of truncated trk C reduced myocyte clone size by more than 60% of control clones. Direct mitogenic actions of NT-3 on embryonic cardiac myocytes were demonstrated by analysis of BrdU incorporation or PCNA immunoreactivity in control and truncated trk C-expressing clones. Inhibition of trk C signaling reduced cardiac myocyte proliferation during the first week of development, but had no effect at later times. These studies demonstrate that endogenous NT-3:trk C signaling regulates cardiac myocyte proliferation during cardiac looping and the establishment of ventricular trabeculation but that myocyte proliferation becomes NT-3 independent during the second week of embryogenesis
brother of rhomboid, a rhomboid-Related Gene Expressed during Early Drosophila Oogenesis, Promotes EGF-R/MAPK Signaling

AbstractThe Drosophila rhomboid (rho) gene participates in localized activation of EGF-receptor signaling in various developmental settings. The Rhomboid protein has been proposed to promote presentation and/or processing of the membrane-bound Spitz (mSpi) EGF-related ligand to generate an active diffusible form of the ligand. Here, we report on a new rhomboid-related gene identified by sequence similarity searching that we have named brother of rhomboid (brho). In contrast to rho, which is expressed in complex patterns during many stages of development, brho appears to be expressed only during oogenesis. brho transcripts are present in early oocytes and abut posterior follicle cells which exhibit high levels of MAPK activation. brho, like rho, collaborates with Star to promote signaling through the EGF-R/MAPK pathway, and genetic evidence indicates that Brho can activate both the mSpi and the Grk precursor EGF ligands in the wing. We propose that endogenous brho may activate the oocyte-specific Gurken ligand and thereby participate in defining posterior cell fates in the early follicular epithelium
Voltage-Gated Calcium Channels Direct Neuronal Migration in Caenorhabditis elegans

AbstractCalcium signaling is known to be important for regulating the guidance of migrating neurons, yet the molecular mechanisms underlying this process are not well understood. We have found that two different voltage-gated calcium channels are important for the accurate guidance of postembryonic neuronal migrations in the nematode Caenorhabditis elegans. In mutants carrying loss-of-function alleles of the calcium channel gene unc-2, the touch receptor neuron AVM and the interneuron SDQR often migrated inappropriately, leading to misplacement of their cell bodies. However, the AVM neurons in unc-2 mutant animals extended axons in a wild-type pattern, suggesting that the UNC-2 calcium channel specifically directs migration of the neuronal cell body and is not required for axonal pathfinding. In contrast, mutations in egl-19, which affect a different voltage-gated calcium channel, affected the migration of the AVM and SDQR bodies, as well as the guidance of the AVM axon. Thus, cell migration and axonal pathfinding in the AVM neurons appear to involve distinct calcium channel subtypes. Mutants defective in the unc-43/CaM kinase gene showed a defect in SDQR and AVM positioning that resembled that of unc-2 mutants; thus, CaM kinase may function as an effector of the UNC-2-mediated calcium influx in guiding cell migration
Mechanisms Underlying Olfactory Neuronal Connectivity in Drosophila—The Atonal Lineage Organizes the Periphery while Sensory Neurons and Glia Pattern the Olfactory Lobe

AbstractPatterning of the antennal lobe of adult Drosophila occurs through a complex interaction between sensory neurons, glia, and central neurons of larval and adult origin. Neurons from the olfactory sense organs are organized into distinct fascicles lined by glial cells. The glia originate from one of the three types of sensory lineages—specified by the proneural gene atonal. Gain-of-function as well as loss-of-function analysis validates a role for cells of the Atonal lineage in the ordered fasciculation of sensory neurons. Upon entry of the antennal nerve to central regions, sensory neurons at first remain closely associated with central glia which lie around the periphery of the lobe anlage. Coincident with the arrival of sensory neurons into the brain, glial precursors undergo mitosis and neural precursors expressing Dachshund appear around the lobe. Sensory neurons and glial cells project into the lobe at around the same time and are likely to coordinate the correct localization of different glomeruli. The influence of sensory neurons on the development of the olfactory lobe could serve to match and lock peripheral and central properties important for the generation of olfactory behavior
Regional Specification during Embryogenesis in the Craniiform Brachiopod Crania anomala

AbstractA fate map has been constructed for the embryo of Crania. The animal half of the egg forms the ectodermal epithelium of the larva's apical lobe. The vegetal half of the egg forms endoderm, mesoderm, and the ectoderm of the mantle lobe. The vegetal pole is the site of gastrulation; this site becomes the posterior ventral region of the mantle lobe of the larva. The plane of the first cleavage goes through the animal–vegetal axis of the egg; it bears no relationship to the future plane of bilateral symmetry of the larva. The timing of regional specification was examined by isolating animal, vegetal, or meridional halves from oocytes, eggs, or embryos from prior to germinal vesicle breakdown through gastrulation. Animal halves isolated from oocytes formed either the epithelium of the apical lobe or a larva with all three germ layers. Animal halves isolated from unfertilized eggs and eight-cell embryos formed only apical lobe epithelium. Beginning at the blastula stage, animal halves formed mantle in addition to apical lobe epithelium. In animal halves isolated after gastrulation, the mantle lobe was always truncated. Vegetal halves isolated at all stages prior to gastrulation gastrulated and formed apical and mantle lobes with endoderm and mesoderm; however, the relative size of the apical lobe that formed decreased substantially when vegetal halves were isolated at later developmental stages. When meridional halves were isolated from unfertilized eggs and two- to four-cell embryos, both halves frequently formed normally proportioned larvae. Beginning at the blastula stage, a number of pairs frequently had a member that lacked dorsal setae on its mantle lobe while the other member of the pair formed setae, indicating that the dorsoventral axis had been set up. The process of regional specification in Crania is compared to those of Discinisca and Glottidia in the brachiopod subphylum Linguliformea and Phoronis in the phylum Phoronida
Programmed Cell Death in Zebrafish Rohon Beard Neurons Is Influenced by TrkC1/NT-3 Signaling

AbstractRohon Beard (RB) cells are embryonic primary sensory neurons that are removed by programmed cell death during larval development in zebrafish. RB somatosensory functions are taken over by neurons of the dorsal root ganglia (DRG), suggesting that RB cell death may be triggered by the differentiation of these ganglia, as has been proposed to be the case in Xenopus. However, here we show that the timing of RB cell death correlates with reduced expression of trkC1, the receptor for neurotrophin NT-3, but not with the appearance of DRG, which differentiate only after most RB cells die. trkC1 is expressed in subpopulations of RB neurons during development, and cell death is initiated only in trkC1-negative neurons, suggesting a role for TrkC1 and its ligand, NT-3, in RB cell survival. In support of this, antibodies that deplete NT-3 induce RB cell death while exogenous application of NT-3 reduces death. In addition, we show that RB cell death can be prevented using a caspase inhibitor, zVADfmk, showing that during normal development, RB cells die by a caspase-dependent programmed cell death pathway possibly triggered by reduced signaling via TrkC1
A Role for E-cadherin in Mouse Primordial Germ Cell Development

AbstractIn this study we show that mouse primordial germ cells and fetal germ cells at certain stages of differentiation express E-cadherin and α and β catenins. Moreover, we demonstrate that the formation of germ cell aggregates that rapidly occurs when monodispersed germ cell populations are released from embryonic gonads in culture is E-cadherin mediated, developmentally regulated, and dependent on the sex of the germ cells. Immunoblotting analyses indicate that the lower ability to form aggregates of primordial germ cells in comparison to fetal germ cells is not due to gross changes in E-cadherin expression, altered association with β catenin, or changes in β catenin phosphorylation. Investigating possible functions of E-cadherin-mediated adhesion in primordial germ cell development, we found that E-cadherin-mediated adhesion may stimulate the motility of primordial germ cells. Moreover, treatment of primordial germ cells cultured on STO cell monolayers with an anti-E-cadherin antibody caused a significant decrease in their number and markedly reduced their ability to form colonies in vitro. The same in vitro treatment of explanted undifferentiated gonadal ridges cultured for 4 days results in decreased numbers and altered localization of the germ cell inside the gonads. Taken together these results suggest that E-cadherin plays an important role in primordial germ cell migration and homing and may act as a modulator of primordial germ cell development