pinecone/core-2020-05-10-deduplication huggingface dataset:
Muscle Development and Lineage-Specific Expression of CiMDF, the MyoD-Family Gene of Ciona intestinalis

AbstractThe expression pattern of CiMDF, the MyoD-family gene of Ciona intestinalis, was analyzed in unmanipulated and microsurgically derived partial embryos. CiMDF encodes two transcripts during development (coding for distinct proteins), the smaller of which, CiMDFa, was detected in maternal RNA. Zygotic activity of CiMDF initiated in cleaving embryos of 32–64 cells. Both CiMDFa and CiMDFb transcripts were detected at this time; however, CiMDFa accumulated more rapidly before declining in abundance such that, by the early tail-formation stage, CiMDFb was more prevalent. Microsurgical isolations of various lineage blastomeres from the eight-cell stage were used to analyze CiMDF expression in the two embryonic lineages that give rise to larval tail muscle—autonomously specified primary cells and conditionally specified secondary cells. CiMDFa and CiMDFb transcripts were detected in both lineages, suggesting that neither functioned in a lineage-specific manner. The data also demonstrated that CiMDF expression was autonomous in the primary lineage (i.e., cells derived from the B4.1 blastomeres) and correlated with histospecific differentiation of muscle. In the secondary lineage (i.e., cells derived from the A4.1 and b4.2 blastomeres), CiMDF expression was conditional and, as in the primary lineage, correlated with muscle differentiation. These experiments reveal similar patterns of CiMDF activity in the primary and secondary muscle lineages and imply a requirement for the expression of this gene in both lineages during larval tail muscle development
Impaired Spermatogenic Ability of Testicular Germ Cells in Mice Deficient in the LIM-Kinase 2 Gene

AbstractLIM-Kinase (LIMK), including LIMK1 and LIMK2, is the only known catalytic protein among LIM-family molecules. It is well known that LIMK phosphorylates and inactivates cofilin, an actin-depolymerizing factor regulating actin reorganization, while in vivo functions have remained to be elucidated. In the present study, we generated Limk2 gene-deficient mice in which three LIMK2 isoforms were disrupted in a Cre-mediated fashion. Impaired cofilin phosphorylation was clearly observed in Limk2−/− fibroblasts stimulated with bradykinin or lysophosphatidic acid, thereby suggesting that Cdc42 or Rho-dependent LIMK activation did not occur. However, Limk2−/− mice did not exhibit embryonic lethality or any phenotypic abnormalities in postnatal growth and development, except for spermatogenesis in the testis. The testes of Limk2−/− mice were smaller in size and partial degeneration of spermatogenic cells in the seminiferous tubules was apparent in association with increased apoptosis. In addition, the viability of Limk2−/− spermatogenic cells, when cultured under stressed conditions, was diminished. Furthermore, the potential for germ cells to differentiate in a regenerative state was severely impaired in Limk2−/− testis. Experimental hyperthermia induced impairment of ADF/cofilin phosphorylation and the formation of intranuclear cofilin inclusions in mutant germ cells. Based on these findings, we propose that LIMK2, especially the testis-specific isoform tLIMK2, plays an important role in proper progression of spermatogenesis by regulation of cofilin activity and/or localization in germ cells
ced-10 Rac and mig-2 Function Redundantly and Act with unc-73 Trio to Control the Orientation of Vulval Cell Divisions and Migrations in Caenorhabditis elegans

AbstractVulval development in the nematode Caenorhabiditis elegans can be divided into a fate specification phase controlled in part by let-60 Ras, and a fate execution phase involving stereotypical patterns of cell division and migration controlled in part by lin-17 Frizzled. Since the small GTPase Rac has been implicated as a downstream target of both Ras and Frizzled and influences cytoskeletal dynamics, we investigated the role of Rac signaling during each phase of vulval development. We show that the Rac gene ced-10 and the Rac-related gene mig-2 are redundantly required for the proper orientation of certain vulval cell divisions, suggesting a role in spindle positioning. ced-10 Rac and mig-2 are also redundantly required for vulval cell migrations and play a minor role in vulval fate specification. Constitutively active and dominant-negative mutant forms of mig-2 cause vulval defects that are very similar to those seen in ced-10;mig-2 double loss-of-function mutants, indicating that they interfere with the functions of both ced-10 Rac and mig-2. Mutations in unc-73 (a Trio-like guanine nucleotide exchange factor) cause similar vulval defects, suggesting that UNC-73 is an exchange factor for both CED-10 and MIG-2. We discuss the similarities and differences between the cellular defects seen in Rac mutants and let-60 Ras or lin-17 Frizzled mutants
The Caenorhabditis elegans EGL-26 Protein Mediates Vulval Cell Morphogenesis

AbstractIn screens for Caenorhabditis elegans mutants defective in vulval morphogenesis, we isolated multiple mutants in which the uterus and the vulva fail to make a functional connection, resulting in an egg-laying defective phenotype. Two of these connection of gonad defective (Cog) mutants carry alleles of the egl-26 gene. We demonstrate that vulval lineages in egl-26 mutant animals are normal, but one vulval cell, vulF, adopts an abnormal morphology. This results in formation of an abnormally thick layer of vulval tissue at the apex of the vulva and a physical blockage of the exit to the vulva from the uterus. egl-26 was cloned and is predicted to encode a novel protein. Mosaic analysis indicates that egl-26 activity is required in the primary vulval lineage for vulF morphogenesis. Expression of a functional translational fusion of EGL-26 to GFP was observed within the primary vulval lineage only in vulE, which neighbors vulF. EGL-26 is localized at the apical edge of the vulE cell. It is thus possible that vulE acts to instruct morphological changes in the neighboring cell, vulF, in an interaction mediated by EGL-26
A Transgenic Lef1/β-Catenin-Dependent Reporter Is Expressed in Spatially Restricted Domains throughout Zebrafish Development

AbstractThe Wnt/β-catenin signaling pathway plays multiple roles during embryonic development, only a few of which have been extensively characterized. Although domains of Wnt expression have been identified throughout embryogenesis, anatomical and molecular characterization of responding cells has been mostly unexplored. We have generated a transgenic zebrafish line that expresses a destabilized green fluorescent protein (GFP) variant under the control of a β-catenin responsive promoter. Early zygotic expression of this transgene (TOPdGFP) mirrors known domains of Wnt signaling in the embryo. Loss of Lef1 activity results in decreased reporter expression and posterior defects, while loss of Tcf3 (Headless, Hdl) activity does not alter reporter expression, even though it results in loss of forebrain structures. In addition, ectopic Wnt1 expression can activate the reporter. In older embryos, we identify a number of transgene-expressing cell populations as novel sites of β-catenin signaling. We conclude that our TOP-dGFP reporter line faithfully illustrates domains of β-catenin activity and enables the identification of responsive cell populations
Genetic Mosaic Analysis Indicates That the Bulb Region of Coat Hair Follicles Contains a Resident Population of Several Active Multipotent Epithelial Lineage Progenitors

AbstractThe hair follicle represents an excellent model system for exploring the properties of lineage-forming units in a dynamic epithelium containing multiple cell types. During its growth (anagen) phase, the proximal–distal axis of the mouse coat hair (pelage) follicle provides a historical record of all epithelial lineages generated from its resident stem cell population. An unresolved question in the field is whether the bulb region of anagen pelage follicles contains multipotential progenitors and whether their individual contribution to cellular census fluctuates over time. To address this issue, chimeric follicles were harvested in midanagen from three types of genetic mosaic mouse models. Analysis of the distribution of genotypic markers, including digital three-dimensional reconstruction of serially sectioned chimeric follicles, revealed that on average the bulb contains four or fewer active progenitors, each capable of giving rise to all six follicular epithelial fates. Moreover, analysis of mosaic pelage, as well as cultured whisker follicles provided evidence that bulb-associated progenitors can give rise to expanding descendant clones during midanagen, leading to the conclusion that the bulb contains dormant or symmetrically dividing stem cells. This latter feature resembles the behavior of hematopoietic stem cells after bone marrow transplantation, and raises the question of whether this property may be shared by stem cells in other self-renewing epithelia
Unseen Forces: The Influence of Bacteria on Animal Development

AbstractThe diversity of developmental programs present in animal phyla first evolved within the world's oceans, an aquatic environment teeming with an abundance of microbial life. All stages in the life histories of these early animals became adapted to microorganisms bathing their tissues, and countless examples of animal–bacterial associations have arisen as a result. Thus far, it has been difficult for biologists to design ways of determining the extent to which these associations have influenced the biology of animals, including their developmental patterns. The following review focuses on an emerging field, the goal of which is to understand the influence of bacteria on animal developmental programs. This integrative area of research is undergoing a revolution that has resulted from advances in technology and the development of suitable animal–bacterial systems for the study of these complex associations. In this contribution, the current status of the field is reviewed and the emerging research horizons are examined
Bmp Activity Gradient Regulates Convergent Extension during Zebrafish Gastrulation

AbstractDuring vertebrate gastrulation, a ventral to dorsal gradient of bone morphogenetic protein (Bmp) activity establishes cell fates. Concomitantly, convergent extension movements narrow germ layers mediolaterally while lengthening them anteroposteriorly. Here, by measuring movements of cell populations in vivo, we reveal the presence of three domains of convergent extension movements in zebrafish gastrula. Ventrally, convergence and extension movements are absent. Lateral cell populations converge and extend at increasing speed until they reach the dorsal domain where convergence speed slows but extension remains strong. Using dorsalized and ventralized mutants, we demonstrate that these domains are specified by the Bmp activity gradient. In vivo cell morphology and behavior analyses indicated that low levels of Bmp activity might promote extension with little convergence by allowing mediolateral cell elongation and dorsally biased intercalation. Further, single cell movement analyses revealed that the high ventral levels of Bmp activity promote epibolic migration of cells into the tailbud, increasing tail formation at the expense of head and trunk. We show that high Bmp activity limits convergence and extension by negatively regulating expression of the wnt11 (silberblick) and wnt5a (pipetail) genes, which are required for convergent extension but not cell fate specification. Therefore, during vertebrate gastrulation, a single gradient of Bmp activity, which specifies cell fates, also regulates the morphogenetic process of convergent extension
Distinct Consequences of Sterol Sensor Mutations in Drosophila and Mouse patched Homologs

AbstractThe membrane protein Patched (Ptc) is a critical regulator of Hedgehog signaling. Ptc is among a family of proteins that contain a sterol sensor motif. The function of this domain is poorly understood, but some proteins that contain sterol sensors are involved in cholesterol homeostasis. In the SREBP cleavage-activating protein (SCAP), sterols inhibit the protein's activity through this domain. Mutations in two highly conserved residues in the SCAP sterol sensor have been identified that confer resistance to sterol regulation. We introduced the analogous mutations in the sterol sensor motif of fly Ptc and mouse Ptc1 and examined their effect on protein activity. In contrast to SCAP, the sterol sensor mutations had different affects on Drosophila Ptc; Ptc Y442C retained function, while Ptc D584N conferred dominant negative activity. In the wing imaginal disc, Ptc D584N overexpression induced Hedgehog targets by stabilizing Cubitus interruptus and inducing decapentaplegic. However, Ptc D584N did not induce collier, a gene that requires high levels of Hedgehog signaling. In mouse Ptc1, the Y438C and D585N mutations did not stimulate signaling in Shh-responsive cell lines but did complement murine ptc1−/− cells. The results suggest that mutations in sterol sensor motifs alter function differently between sterol sensor family members
Development of Anterior Gustatory Epithelia in the Palate and Tongue Requires Epidermal Growth Factor Receptor

AbstractWe characterized the gustatory phenotypes of neonatal mice having null mutations for epidermal growth factor receptor (egfr−/−), brain-derived neurotrophic factor (bdnf−/−), or both. We counted the number and diameter of fungiform taste buds, the prevalence of poorly differentiated or missing taste cells, and the incidence of ectopic filiform-like spines, each as a function of postnatal age and anterior/posterior location.Egfr−/− mice and bdnf−/− mice had similar reductions in the total number of taste buds on the anterior portions of the tongue and palate. Nonetheless, there were significant differences in their gustatory phenotypes. EGFR deficiency selectively impaired the development of anterior gustatory epithelia in the mouth. Only bdnf−/− mice had numerous taste buds missing from the foliate, vallate, and posterior fungiform papillae. Only egfr−/− fungiform taste papillae had robust gustatory innervation, markedly reduced cytokeratin 8 expression in taste cells, and a high incidence of a filiform-like spine. Egfr/bdnf double-null mutant mice had a higher frequency of failed fungiform taste bud differentiation. In bdnf−/− mice taste cell development failed because of sparse gustatory innervation. In contrast, in young egfr−/− mice the abundance of axons innervating fungiform papillae and the normal numbers of geniculate ganglion neurons implicate gustatory epithelial defects rather than neural defects
CABYR, a Novel Calcium-Binding Tyrosine Phosphorylation-Regulated Fibrous Sheath Protein Involved in Capacitation

AbstractTo reach fertilization competence, sperm undergo an incompletely understood series of morphological and molecular maturational processes, termed capacitation, involving, among other processes, protein tyrosine phosphorylation and increased intracellular calcium. Hyperactivated motility and an ability to undergo the acrosome reaction serve as physiological end points to assess successful capacitation. We report here that acidic (pI 4.0) 86-kDa isoforms of a novel, polymorphic, testis-specific protein, designated calcium-binding tyrosine phosphorylation-regulated protein (CABYR), were tyrosine phosphorylated during in vitro capacitation and bound 45Ca on 2D gels. Acidic 86-kDa calcium-binding forms of CABYR increased during in vitro capacitation, and calcium binding to these acidic forms was abolished by dephosphorylation with alkaline phosphatase. Six variants of CABYR containing two coding regions (CR-A and CR-B) were cloned from human testis cDNA libraries, including five variants with alternative splice deletions. A motif homologous to the RII dimerization domain of PK-A was present in the N-terminus of CR-A in four CABYR variants. A single putative EF handlike motif was noted in CR-A at aas 197–209, while seven potential tyrosine phosphorylation-like sites were noted in CR-A and four in CR-B. Pro-X-X-Pro (PXXP) modules were identified in the N- and C-termini of CR-A and CR-B. CABYR localizes to the principal piece of the human sperm flagellum in association with the fibrous sheath and is the first demonstration of a sperm protein that gains calcium-binding capacity when phosphorylated during capacitation
Sonic Hedgehog Inhibits the Terminal Differentiation of Limb Myoblasts Committed to the Slow Muscle Lineage

AbstractThe proliferation, differentiation, and fusion of a small number of myogenic precursor cells must be precisely regulated during development to ensure the proper size, organization, and function of the limb musculature. We have examined the role of Sonic hedgehog (Shh) in these processes by both augmentation and inhibition of the Shh-mediated signaling pathway. Our data show that Shh regulates muscle development by repressing the terminal differentiation of early myogenic precursor cells and does not function as a myoblast mitogen. Shh function in hypaxial muscle appears to be spatially restricted to the early myoblast population within the ventral muscles of the posterior region of the limb. Furthermore, Shh appears to act as a permissive, rather than an inductive, signal for slow MyHC expression in myoblasts. Our data thus provide the foundation for a new hypothesis for Shh function in hypaxial skeletal muscle development
Overexpression of the CT GalNAc Transferase in Skeletal Muscle Alters Myofiber Growth, Neuromuscular Structure, and Laminin Expression

AbstractCarbohydrates have been shown to mediate or modulate a number of important events in the development of the nervous system; however, there is little evidence that they participate directly in the development of synapses. One carbohydrate structure that is likely to be important in synaptic development of the neuromuscular junction is the CT carbohydrate antigen {GalNAcβ1,4[NeuAcα2,3]Galβ1(-3GalNAc or -4GlcNAc)}. The synaptic localization of the CT antigen is due to the presence of the terminal β1,4 GalNAc linkage, and such linkages are localized to the neuromuscular junction in many species. Here we show that an enzyme that can create the synaptic CT structure, the CT GalNAc transferase, is also confined to the neuromuscular junction in mice. Using transgenic mice, we show that overexpression of the CT GalNAc transferase in extrasynaptic regions in skeletal myofibers caused as much as a 60% reduction in the diameter of adult myofibers and an order of magnitude increase in satellite cells. Neuromuscular junctions of transgenic mice had severely reduced numbers of secondary folds, Schwann cell processes were present in the synaptic cleft, and secondary folds were often misaligned with active zones. In addition, multiple presynaptic specializations occurred on individual myofibers. In addition, some normally synaptic proteins, including laminin α4, laminin α5, utrophin, and NCAM, were expressed along extrasynaptic regions of myofibers. One of the muscle proteins that displayed increased glycosylation with the CT antigen in the transgenic mice was α-dystroglycan. These experiments provide the first in vivo evidence that a synaptic carbohydrate antigen has important roles in the development of the neuromuscular synapse and suggest that the CT antigen is involved in controlling the expression of synaptic molecules
Otx2 Is Required to Respond to Signals from Anterior Neural Ridge for Forebrain Specification

AbstractPrevious analysis employing chimeric and transgenic rescue experiments has suggested that Otx2 is required in the neuroectoderm for development of the forebrain region. In order to elucidate the precise role of Otx2 in forebrain development, we attempted to generate an allelic series of Otx2 mutations by Flp- and Cre-mediated recombination for the production of conditional knock-out mice. Unexpectedly, the neo-cassette insertion created a hypomorphic Otx2 allele; consequently, the phenotype of compound mutant embryos carrying both a hypomorphic and a null allele (Otx2frt-neo/−) was analyzed. Otx2frt-neo/− mutant mice died at birth, displaying rostral head malformations. Molecular marker analysis demonstrated that Otx2frt-neo/− mutant embryos appeared to undergo anterior–posterior axis generation and induction of anterior neuroectoderm normally; however, these mutants subsequently failed to correctly specify the forebrain region. As the rostral margin of the neural plate, termed the anterior neural ridge (ANR), plays crucial roles with respect to neural plate specification, we examined expression of molecular markers for the ANR and the neural plate; moreover, neural plate explant studies were performed. Analyses revealed that telencephalic gene expression did not occur in mutant embryos due to defects of the neural plate; however, the mutant ANR bore normal induction activity on gene expression. These results further suggest that Otx2 dosage may be crucial in the neural plate with respect to response to inductive signals primarily from the ANR for forebrain specification
The Zebrafish trilobite Gene Is Essential for Tangential Migration of Branchiomotor Neurons

AbstractNewborn neurons migrate extensively in the radial and tangential directions to organize the developing vertebrate nervous system. We show here that mutations in zebrafish trilobite (tri) that affect gastrulation-associated cell movements also eliminate tangential migration of motor neurons in the hindbrain. In the wild-type hindbrain, facial (nVII) and glossopharyngeal (nIX) motor neurons are induced in rhombomeres 4 and 6, respectively, and migrate tangentially into r6 and r7 (nVII) and r7 (nIX). In all three tri alleles examined, although normal numbers of motor neurons are induced, nVII motor neurons are found exclusively in r4, and nIX-like motor neurons are found exclusively in r6. The migration of other neuronal and nonneuronal cell types is unaffected in tri mutants. Rhombomere formation and the development of other hindbrain neurons are also unaffected in tri mutants. Furthermore, tangential neuronal migration occurs normally in the gastrulation mutant knypek, indicating that the trilobite neuron phenotype does not arise nonspecifically from aberrant gastrulation-associated movements. We conclude that trilobite function is specifically required for two types of cell migration that occur at different stages of zebrafish development