pinecone/core-2020-05-10-deduplication huggingface dataset:
Interaction of Ihh and BMP/Noggin Signaling during Cartilage Differentiation

AbstractBone morphogenetic proteins (BMPs) have been implicated in regulating multiple stages of bone development. Recently it has been shown that constitutive activation of theBMP receptor-IAblocks chondrocyte differentiation in a similar manner as misexpression ofIndian hedgehog.In this paper we analyze the role of BMPs as possible mediators of Indian hedgehog signaling and useNogginmisexpression to gain insight into additional roles of BMPs during cartilage differentiation. We show by comparative analysis ofBMPandIhhexpression domains that the borders ofIndian hedgehogexpression in the chondrocytes are reflected in changes of the expression level of severalBMPgenes in the adjacent perichondrium. We further demonstrate that misexpression ofIndian hedgehogappears to directly upregulateBMP2andBMP4expression, independent of the differentiation state of the flanking chondrocytes. In contrast, changes inBMP5andBMP7expression in the perichondrium correspond to altered differentiation states of the flanking chondrocytes. In addition,NogginandChordin,which are both expressed in the developing cartilage elements, also change their expression pattern afterIhhmisexpression. Finally, we use retroviral misexpression ofNoggin,a potent antagonist of BMP signaling, to gain insight into additional roles of BMP signaling during cartilage differentiation. We find that BMP signaling is necessary for the growth and differentiation of the cartilage elements. In addition, this analysis revealed that the members of the BMP/Noggin signaling pathway are linked in a complex autoregulatory network
A HypomorphicMyogeninAllele Reveals DistinctMyogeninExpression Levels Required for Viability, Skeletal Muscle Development, and Sternum Formation

AbstractThe myogenic basic helix-loop-helix transcription factor myogenin plays an essential role in the differentiation of skeletal muscle and, secondarily, in rib and sternum formation during mouse development. However, virtually nothing is known about the quantitative requirements for myogenin in these processes. Here, we describe the generation of mice carrying a hypomorphic allele ofmyogenin,which expressesmyogenintranscripts at approximately one-fourth the level of the wild-typemyogeninallele. The hypomorphic allele in combination with wild-type andmyogenin-null alleles was used to create an allelic series. Embryos representing the complete range of genotypes from homozygous wild type to homozygous null were analyzed for their viability, ability to form normal ribs and sternum, and extent of skeletal muscle differentiation. Embryos carrying the hypomorphicmyogeninallele over a wild-type allele were normal. In embryos bearing homozygous hypomorphic alleles, the sternum developed normally and extensive skeletal muscle differentiation occurred. However, muscle hypoplasia and reduced muscle-specific gene expression were apparent in these embryos, and the mice were not viable as neonates. When the hypomorphic allele was placed over amyogenin-null allele, the resulting embryos had sternum defects resembling homozygousmyogenin-null embryos, and there was severe muscle hypoplasia. Our results demonstrate that skeletal muscle formation is highly sensitive to the absolute levels of myogenin and that correct sternum formation, skeletal muscle differentiation, and viability each require distinct threshold levels of myogenin
Influence of Centriole Behavior on the First Spindle Formation in Zygotes of the Brown AlgaFucus distichus(Fucales, Phaeophyceae)

AbstractThe influence of centrioles, derived from the sperm flagellar basal bodies, and the centrosomal material (MTOCs) on spindle formation in the brown algaFucus distichus(oogamous) was studied by immunofluorescence microscopy using anti-centrin and anti-β-tubulin antibodies. In contrast to a bipolar spindle, which is formed after normal fertilization, a multipolar spindle was formed in polyspermic zygote. The number of mitotic poles in polyspermic zygotes was double the number of sperm involved in fertilization. As an anti-centrin staining spot (centrioles) was located at these poles, the multipolar spindles in polyspermic zygotes were produced by the supplementary centrioles. When anucleate egg fragments were fertilized, chromosome condensation and mitosis did not occur in the sperm nucleus. Two anti-centrin staining spots could be detected, microtubules (MTs) radiated from nearby, but the mitotic spindle was never produced. When a single sperm fertilized multinucleate eggs (polygyny), abnormal spindles were also observed. In addition to two mitotic poles containing anti-centrin staining spots, extra mitotic poles without anti-centrin staining spots were also formed, and as a result multipolar spindles were formed. When karyogamy was blocked with colchicine, it became clear that the egg nucleus proceeded independently into mitosis accompanying chromosome condensation. A monoastral spindle could be frequently observed, and in rare cases a barrel-shaped spindle was formed. However, when a sperm nucleus was located near an egg nucleus, the two anti-centrin staining spots shifted to the egg nucleus from the sperm nucleus. In this case, a normal spindle was formed, the egg chromosomes arranged at the equator, and the associated MTs elongated from one pole of the egg spindle toward the sperm chromosomes which were scattered. From these results, it became clear that paternal centrioles derived from the sperm have a crucial role in spindle formation in the brown algae, such as they do during animal fertilization. However, paternal centrioles were not adequate for the functional centrosome during spindle formation. We speculated that centrosomal materials from the egg cytoplasm aggregate around the sperm centrioles and are needed for centrosomal activation
Development in the Absence of Skeletal Muscle Results in the Sequential Ablation of Motor Neurons from the Spinal Cord to the Brain

AbstractMice lacking the transcription factorsMyf-5andMyoDlack all skeletal muscle and therefore present a unique opportunity to investigate the dependence of nervous system development on myogenesis. Motor neurons arose normally in the spinal cord of mutant embryos and by birth all somatic motor neurons were eliminated by apoptosis. By contrast, interneurons were not affected. Proprioceptive sensory neurons in the dorsal root ganglia underwent apoptosis. The facial motor nucleus was ablated of motor neurons and contained large numbers of apoptotic bodies. Surprisingly, giant pyramidal neurons were absent in the motor cortex without any corresponding evidence of apoptosis. The epaxial and cutaneous component of dorsal ramus failed to form in the absence of the myotome. Therefore, we conclude that nervous development is more intimately coupled to skeletal myogenesis than has previously been understood
TheciDMutation Encodes a Chimeric Protein Whose Activity Is Regulated by Wingless Signaling

AbstractThe Drosophilacubitus interruptus(ci) gene encodes a sequence-specific DNA-binding protein that regulates transcription of Hedgehog (Hh) target genes. Activity of the Ci protein is posttranslationally regulated by Hh signaling. In animals homozygous for theciDmutation, however, transcription of Hh target genes is regulated by Wingless (Wg) signaling rather than by Hh signaling. We show thatciDencodes a chimeric protein composed of the regulatory domain of dTCF/Pangolin (Pan) and the DNA binding domain of Ci. Pan is a Wg-regulated transcription factor that is activated by binding of Armadillo (Arm) to its regulatory domain. Arm is thought to activate Pan by contributing a transactivation domain. We find that a constitutively active form of Arm potentiates activity of a CiD transgene and coimmunoprecipitates with CiD protein. The Wg-responsive activity of CiD could be explained by recruitment of the Arm transactivation function to the promoters of Hh-target genes. We suggest that wild-type Ci also recruits a protein with a transactivation domain as part of its normal mechanism of activation
Evidence That a Starfish Egg Src Family Tyrosine Kinase Associates with PLC-γ1 SH2 Domains at Fertilization

AbstractThe initiation of calcium release at fertilization in the eggs of most animals relies on the production of IP3, implicating the activation of phospholipase C. Recent work has demonstrated that injection of PLC-γ SH2 domain fusion proteins into starfish eggs specifically inhibits the initiation of calcium release in response to sperm, indicating that PLC-γ is necessary for Ca2+release at fertilization [Carrollet al.(1997)J. Cell Biol.138, 1303–1311]. Here we investigate how PLC-γ may be activated, by using the PLC-γ SH2 domain fusion protein as an affinity matrix to identify interacting proteins. A tyrosine kinase activity and an egg protein of ca.Mr58 K that is recognized by an antibody directed against Src family tyrosine kinases associate with PLC-γ SH2 domains in a fertilization-dependent manner. These associations are detected by 15 s postfertilization, consistent with a function in releasing Ca2+. Calcium ionophore treatment of eggs did not cause association of the kinase activity or of the Src family protein with the PLC-γ SH2 domains. These data identify an egg Src family tyrosine kinase as a potential upstream regulator of PLC-γ in the activation of starfish eggs
The Role of Cell Adhesion Molecules inDrosophilaHeart Morphogenesis:Faint Sausage, Shotgun/DE-Cadherin, andLaminin AAre Required for Discrete Stages in Heart Development

AbstractHeart development in theDrosophilaembryo starts with the specification of cardiac precursors from the dorsal edge of the mesoderm through signaling from the epidermis. Cardioblasts then become aligned in a single row of cells that migrate dorsally. After contacting their contralateral counterparts, cardioblasts undergo a cytoskeletal rearrangement and form a lumen. Its simple architecture and cellular composition makes the heart a good system to study mesodermal patterning, intergerm layer signaling, and the function of cell adhesion molecules (CAMs) during morphogenesis. In this paper we focus on three adhesion molecules,faint sausage (fas), shotgun/DE-cadherin (shg/DE-Cad), andlaminin A (lam A),that are essential for heart development.fasencodes an Ig-like CAM and is required for the correct number of cardioblasts to become specified, as well as proper alignment of cardioblasts.shg/DE-Cad is expressed and required at a later stage thanfas;in embryos lacking this gene, cardioblasts are specified normally and become aligned, but do not form a lumen. Additionally, cardioblasts ofshgmutant embryos show a redistribution of phosphotyrosine as well as a loss of Armadillo from the membrane, indicating defects in cell polarity. Theshgphenotype could be phenocopied by applying EGTA or cytochalasin D, supporting the view that Ca2+-dependent adhesion and the actin cytoskeleton are instrumental for heart lumen formation. As opposed to cell–cell adhesion, cell–substrate adhesion mechanisms are not required for heart morphogenesis, but only for maintenance of the differentiated heart. Embryos lacking thelam Agene initially developed a normal heart, but showed twists and breaks of cardioblasts at late embryonic stages. We discuss our findings in light of recent results that elucidate the function of different adhesion systems in vertebrate heart development
Hoxa5Gene Regulation: A Gradient of Binding Activity to a Brachial Spinal Cord Element

AbstractTheHoxgenes cooperate in providing positional information needed for spatial and temporal patterning of the vertebrate body axis. However, the biological mechanisms behind spatialHoxexpression are largely unknown. In transgenic mice, gene fusions betweenHoxa5(previously calledHox-1.3) 5′ flanking regions and the lacZ reporter gene show tissue- and time-specific expression in the brachial spinal cord in day 11–13 embryos. A 604-bp regulatory region with enhancer properties directs this spatially specific expression. Fine-detail mapping of the enhancer has identified several elements involved in region-specific expression, including an element required for expression in the brachial spinal cord. Factors in embryonic day 12.5 nuclear extracts bind this element in electrophoretic mobility shift assays (EMSA) and protect three regions from DNase digestion. All three sites contain an AAATAA sequence and mutations at these sites reduce or abolish binding. Furthermore, this element binds specific individual embryonic proteins on a protein blot. The binding activity appears as a gradient along the anterior-posterior axis with two- to threefold higher levels observed in extracts from anterior regions than from posterior regions. In parallel with the EMSA, the proteins on the protein blot also show reduced binding to probes with mutations at the AAATAA sites. Most importantly, transgenic mice carrying Hoxa5/lacZ fusions with the three AAATAA sites mutated either do not express the transgene or have altered transgene expression. The brachial spinal cord element and its binding proteins are likely to be involved in spatial expression ofHoxa5during development
Paracrine-Mediated Apoptosis in Reproductive Tract Development

AbstractIn mammalian development, the signaling pathways that couple extracellular death signals with the apoptotic machinery are still poorly understood. We chose to examine Müllerian duct regression in the developing reproductive tract as a possible model of apoptosis during morphogenesis. The TGFβ-like hormone, Müllerian inhibiting substance (MIS), initiates regression of the Müllerian duct or female reproductive tract anlagen; this event is essential for proper male sexual differentiation and occurs between embryonic days (E) 14 and 17 in the rat. Here, we show that apoptosis occurs during Müllerian duct regression in male embryos beginning at E15. Female Müllerian ducts exposed to MIS also exhibited prominent apoptosis within 13 h, which was blocked by a caspase inhibitor. In both males and females the MIS type-II receptor is expressed exclusively in the mesenchymal cell layer surrounding the duct, whereas apoptotic cells localize to the epithelium. In addition, tissue recombination experiments provide evidence that MIS does not act directly on the epithelium to induce apoptosis. Based on these data, we suggest that MIS triggers cell death by altering mesenchymal–epithelial interactions
A Novel BMP Expressed in Developing Mouse Limb, Spinal Cord, and Tail Bud Is a Potent Mesoderm Inducer inXenopusEmbryos

AbstractThe bone morphogenetic proteins (BMPs) play critical roles in patterning the early embryo and in the development of many organs and tissues. We have identified a new member of this multifunctional gene family,BMP-11,which is most closely related toGDF-8/myostatin.During mouse embryogenesis,BMP-11is first detected at 9.5 dpc in the tail bud with expression becoming stronger as development proceeds. At 10.0 dpc,BMP-11is expressed in the distal and posterior region of the limb bud and later localizes to the mesenchyme between the skeletal elements.BMP-11is also expressed in the developing nervous system, in the dorsal root ganglia, and dorsal lateral region of the spinal cord. To assess the biological activity of BMP-11, we tested the protein in theXenopusectodermal explant (animal cap) assay. BMP-11 induced axial mesodermal tissue (muscle and notochord) in a dose-dependent fashion. At higher concentrations, BMP-11 also induced neural tissue. Interestingly, the activin antagonist, follistatin, but not noggin, an antagonist of BMPs 2 and 4, inhibited BMP-11 activity on animal caps. Our data suggest that inXenopusembryos, BMP-11 acts more like activin, inducing dorsal mesoderm and neural tissue, and less like other family members such as BMPs 2, 4, and 7, which are ventralizing and anti-neuralizing signals. Taken together, these data suggest that during vertebrate embryogenesis, BMP-11 plays a unique role in patterning both mesodermal and neural tissues
Distinct Neural Stem Cells Proliferate in Response to EGF and FGF in the Developing Mouse Telencephalon

AbstractMultipotent, self-renewing neural stem cells reside in the embryonic mouse telencephalic germinal zone. Using anin vitroneurosphere assay for neural stem cell proliferation, we demonstrate that FGF-responsive neural stem cells are present as early as E8.5 in the anterior neural plate, but EGF-responsive neural stem cells emerge later in development in a temporally and spatially specific manner. By separately blocking EGF and FGF2 signaling, we also show that EGF alone and FGF2 alone can independently elicit neural stem cell proliferation and at relatively high cell densities separate cell nonautonomous effects can substantially enhance the mitogen-induced proliferation. At lower cell densities, neural stem cell proliferation is additive in the presence of EGF and FGF2 combined, revealing two different stem cell populations. However, both FGF-responsive and EGF-responsive neural stem cells retain their self-renewal and multilineage potential, regardless of growth factor conditions. These results support a model in which separate, lineage-related EGF- and FGF-responsive neural stem cells are present in the embryonic telencephalic germinal zone
Multiple Developmental Roles for CRAC, a Cytosolic Regulator of Adenylyl Cyclase

AbstractReceptor-mediated activation of adenylyl cyclase (ACA) inDictyosteliumrequires CRAC protein. Upon translocation to the membrane, this pleckstrin homology (PH) domain protein stimulates ACA and thereby mediates developmental aggregation. CRAC may also have roles later in development since CRAC-null cells can respond to chemotactic signals and participate in developmental aggregation when admixed with wild-type cells, but they do not complete development within such chimeras. To test whether the role of CRAC in postaggregative development is related to the activation of ACA, chemotactic aggregation was bypassed in CRAC-null cells by activating the cAMP-dependent protein kinase (PKA). While such strains formed mounds, they did not complete fruiting body morphogenesis or form spores. Expression of CRAC in the prespore cells of these strains rescued sporulation and fruiting body formation. This later function of CRAC does not appear to require its PH domain since the C-terminal portion of the protein (CRAC-ΔPH) can substitute for full-length CRAC in promoting spore cell formation and morphogenesis. No detectable ACA activation was observed in any of the CRAC-null strains rescued by PKA activation and expression of CRAC-ΔPH. Finally, we found that the development of CRAC-null ACA-null double mutants could be rescued by the activation of PKA together with the expression of CRAC-ΔPH. Thus, there appears to be a required function for CRAC in postaggregative development that is independent of its previously described function in the ACA activation pathway
Spatiotemporal Characterization of Intracellular Ca2+Rise during the Acrosome Reaction of Mammalian Spermatozoa Induced by Zona Pellucida

AbstractThe mammalian sperm acrosome reaction (AR) is an essential event prior to sperm–egg fusion at fertilization, and it is primarily dependent on an increase in intracellular Ca2+concentration ([Ca2+]i). Spatiotemporal aspects of the [Ca2+]iincrease during the AR induced by solubilized zona pellucida (ZP) in hamster spermatozoa were precisely investigated with a Ca2+imaging technique using confocal laser scanning microscopy with two fluorescent Ca2+indicators. A rapid rise in [Ca2+]ioccurred immediately after the application of ZP solution through a micropipette. The rise was always initiated in the sperm head, even when the application was directed toward the tail. The elevated [Ca2+]iwas little attenuated during measurement for 30–40 s. Acrosomal exocytosis was detected as a sudden decrease of fluorescence in the acrosomal vesicle ∼20 s after the onset of the [Ca2+]irise. High-resolution imaging revealed that the [Ca2+]irise in the sperm head began at the region around the equatorial segment and spread over the posterior region of the head within 0.6 s, whereas Ca2+concentration in the acrosomal vesicle appeared to be unaltered. The [Ca2+]irise was completely abolished under Ca2+-free extracellular conditions, indicating that it is totally attributable to Ca2+influx. Nifedipine, an inhibitor of L-type Ca2+channels, did not affect the rising phase of the ZP-induced Ca2+response, but accelerated the decline of the [Ca2+]irise and inhibited acrosomal exocytosis. The present study provides implicative information about the spatial organization of functional molecules involved in the signal transduction in mammalian AR
A BMP-Inducible Gene, Dlx5, Regulates Osteoblast Differentiation and Mesoderm Induction

AbstractBone morphogenetic proteins (BMPs), members of the transforming growth factor β superfamily, have been identified by their ability to induce cartilage and bone from nonskeletal cells and have been shown to act as a ventral morphogen inXenopusmesoderm. We isolated a murine homeobox-containing gene, distal-less 5 (mDlx5), as a BMP-inducible gene in osteoblastic MC3T3-E1 cells. Stable transfectants of MC3T3-E1 that overexpress mDlx5 mRNA showed increase in various osteogenic markers, a fourfold increase in alkaline phosphatase activity, a sixfold increase in osteocalcin production, and appearance in mineralization of extracellular matrix. Furthermore, mDlx5 was induced orthotopically in mouse embryos treated with BMP-4 and in fractured bone of adult mice. Consistent with these observations, we also found that injection of mDlx5 mRNA into dorsal blastomeres enhanced the ventralization ofXenopusembryos. These findings suggest that mDlx5 is a target gene of the BMP signaling pathway and acts as an important regulator of both osteogenesis and dorsoventral patterning of embryonic axis
Activation ofXenopusEggs by Proteases: Possible Involvement of a Sperm Protease in Fertilization

AbstractEgg activation in cross-fertilization betweenXenopuseggs andCynopssperm may be caused by a protease activity against Boc-Gly-Arg-Arg-MCA in the sperm acrosome. To determine the role of the sperm protease in fertilization, the protease was purified fromCynopssperm using several chromatographic techniques. We found that purified sperm protease readily hydrolyzes Boc-Gly-Arg-Arg-MCA and Z-Arg-Arg-MCA, that protease activity was inhibited by the trypsin inhibitors aprotinin and leupeptin, and that not only the purified protease, but also cathepsin B, induces activation inXenopuseggs. We inseminated unfertilizedXenopuseggs with homologous sperm in the presence of various peptidyl MCA substrates or protease inhibitors and demonstrated that trypsin inhibitors or MCA substrates containing Arg-Arg-MCA reversibly inhibited fertilization of both fully jellied and denuded eggs. Sperm motility was not affected by the reagents. An extract obtained fromXenopussperm showed hydrolytic activity against Boc-Gly-Arg-Arg-MCA, Z-Arg-Arg-MCA, and Arg-MCA. These results suggest that the tryptic protease inXenopussperm is involved in fertilization, most likely by participating in egg activation
Drosophila Src42AIs a Negative Regulator of RTK Signaling

AbstractThe Src family of nonreceptor tyrosine kinases has been implicated in many signal transduction pathways. However, due to a possible functional redundancy in vertebrates, there is no genetic loss-of-function evidence that any individual Src family member has a crucial role for receptor tyrosine kinase (RTK) signaling. Here we show that an extragenic suppressor ofRaf, Su(Raf)1,encodes aDrosophilaSrc family geneSrc42A.Characterization ofSrc42Amutations shows that Src42A acts independent of Ras1 and that it is, unexpectedly, a negative regulator of RTK signaling. Our study provides the first evidence that Src42A defines a negative regulatory pathway parallel to Ras1 in the RTK signaling cascade. A possible model for Src42A function is discussed