pinecone/core-2020-05-10-deduplication huggingface dataset:
BMP Type II Receptor Is Required for Gastrulation and Early Development of Mouse Embryos

AbstractBone morphogenetic proteins (BMPs), members of the transforming growth factor-β superfamily, play a variety of roles during mouse development. BMP type II receptor (BMPR-II) is a type II serine/threonine kinase receptor, which transduces signals for BMPs through heteromeric complexes with type I receptors, including activin receptor-like kinase 2 (ALK2), ALK3/BMPR-IA, and ALK6/BMPR-IB. To elucidate the function of BMPR-II in mammalian development, we generated BMPR-II mutant mice by gene targeting. Homozygous mutant embryos were arrested at the egg cylinder stage and could not be recovered at 9.5 days postcoitum. Histological analysis revealed that homozygous mutant embryos failed to form organized structure and lacked mesoderm. The BMPR-II mutant embryos are morphologically very similar to the ALK3/BMPR-IA mutant embryos, suggesting that BMPR-II is important for transducing BMP signals during early mouse development. Moreover, the epiblast of the BMPR-II mutant embryo exhibited an undifferentiated character, although the expression of tissue-specific genes for the visceral endoderm was essentially normal. Our results suggest that the function of BMPR-II is essential for epiblast differentiation and mesoderm induction during early mouse development
Functional Analysis of Cdc42 in Actin Filament Assembly, Epithelial Morphogenesis, and Cell Signaling during Drosophila Development

AbstractCdc42, a member of the Rho family of GTP binding proteins, functions in the formation of polarized actin structures, in elongation of cell shape, and in cell signaling. Although genetic mutations previously have not been available in multicellular organisms, studies have attempted to discern Cdc42 functions in organisms, including Drosophila, using dominant active or interfering alleles. Here, for the first time, we examine the functions of Cdc42 in developing tissues using loss-of-function mutations in the Drosophila Cdc42 gene. We find that Cdc42− epithelial cells fail to elongate into a columnar cell shape and cannot maintain a monolayered epithelial structure. In contrast to previous studies, we find no requirement for Cdc42 in cell division or in activation of the Jun N-terminal kinase pathway. In addition, Cdc42 function is not required for cytoplasmic actin filament assembly in the nurse cells during oogenesis, although it may facilitate this process. Furthermore, our results indicate that Cdc42 plays a role in intercellular interactions between the germ line and the somatic follicle cells. These results confirm the role of Cdc42 in actin filament assembly and provide new insights into its functions in epithelial morphogenesis and regulating intercellular signaling events
Chondroitin Sulfates Affect the Formation of the Segmental Motor Nerves in Zebrafish Embryos

AbstractChondroitin sulfates have been implicated in the promotion and in the inhibition of axon growth. In the zebrafish embryo, chondroitin sulfates are present at the interface of the somites and the notochord where spinal motor axons extend ventrally to establish the midsegmental ventral motor nerves. Injection of chondroitinase ABC prior to motor axon outgrowth effectively removed all chondroitin sulfate immunoreactivity and induced abnormal axonal outgrowth in many (39%) of the ventral motor nerves. The most common abnormality was the formation of side branches, approximately half of which extended posteriorly, the others anteriorly. The effect was specific to the removal of chondroitin sulfates, since injections of vehicle solution or of heparinase III did not affect the ventral motor nerves. Electron microscopic examination demonstrated that the injections caused no damage to spinal cord, somite, and notochord. This suggests that chondroitin sulfates normally constrain the outgrowth of the ventral motor nerves. Consistent with this hypothesis, injections of soluble chondroitin sulfates, either as a mixture or individually, led to truncated or missing ventral motor nerves. Truncations were most frequent after injection of chondroitin sulfate-B (up to 23%) while chondroitin sulfate-A had a lesser, and chondroitin sulfate-C no apparent, effect
A Transient Specialization of the Microtubule Cytoskeleton Is Required for Differentiation of the Drosophila Visual System

AbstractDrosophila β3-tubulin is an essential isoform expressed during differentiation of many cell types in embryos and pupae. We report here that during pupal development transient β3 expression demarcates a unique subset of neurons in the developing adult visual system. β3 is coassembled into microtubules with β1, the sole β-tubulin isoform in the permanent microtubule cytoskeleton of the adult eye and brain. Examination of β3 mutant phenotypes showed that β3 is required for axonal patterning and connectivity and for spatial positioning within the optic lobe. Comparison of the phenotypes of β3 mutations with those that result from disruption of the Hedgehog signaling pathway shows that β3 functions early in the establishment of the adult visual system. Our data support the hypothesis that β3 confers specialized properties on the microtubules into which it is incorporated. Thus a transient specialization of the microtubule cytoskeleton during differentiation of a specific subset of the neurons has permanent consequences for later cell function
Down-regulation of the Inositol 1,4,5-Trisphosphate Receptor in Mouse Eggs Following Fertilization or Parthenogenetic Activation

AbstractFertilization in mammalian eggs is characterized by the presence of intracellular calcium ([Ca2+]i) oscillations. In mouse eggs, these oscillations cease after a variable period of time and this is accompanied by a decrease in inositol 1,4,5-trisphosphate receptor (IP3R) responsiveness and down-regulation of the IP3R type 1 (IP3R-1). To investigate the signaling pathway responsible for inducing IP3R-1 down-regulation during fertilization, mouse eggs were exposed to or injected with several Ca2+-releasing agonists and the amounts of IP3R-1 immunoreactivity evaluated by Western blotting. Exposure to ethanol or ionomycin, which induce a single [Ca2+]i rise, failed to signal down-regulation of IP3R-1. However, [Ca2+]i oscillations induced by injection of boar sperm fractions (SF), which presumably stimulate production of IP3, or adenophostin A, an IP3R agonist, both induced down-regulation of IP3R-1 of a magnitude similar to or greater than that observed after fertilization. Exposure to thimerosal, an oxidizing agent that modifies the IP3R without stimulating production of IP3, also initiated down-regulation of IP3R-1, although oscillations initiated by SrCl2 failed to evoke down-regulation of IP3R-1. The degradation of IP3R-1 in mouse eggs appears to be mediated by the proteasome pathway because it was inhibited by preincubation with lactacystin, a very specific proteasome inhibitor. We therefore suggest that persistent stimulation of the phosphoinositide pathway in mouse eggs by the sperm during fertilization or by injection of SF leads to down-regulation of the IP3R-1
Imaginal Pioneers Prefigure the Formation of Adult Thoracic Muscles in Drosophila melanogaster

AbstractIn insects, specialized mesodermal cells serve as templates to organize myoblasts into distinct muscle fibers during embryogenesis. In the grasshopper embryo, large mesodermal cells called muscle pioneers extend between the epidermal attachment points of future muscle fibers and serve as foci for myoblast fusion. In the Drosophila embryo, muscle founder cells serve a similar function, organizing large numbers of myoblasts into larval muscles. During the metamorphosis of Drosophila, nearly all larval muscles degenerate and are replaced by a set of de novo adult muscles. The extent to which specialized mesodermal cells homologous to the founders and pioneers of the insect embryo are involved in the development of adult-specific muscles has yet to be established. In the larval thorax, the majority of imaginal myoblasts are associated with the imaginal discs. We report here the identification of a morphologically distinct class of disc-associated myoblasts, which we call imaginal pioneers, that prefigures the formation of at least three adult-specific muscles, the tergal depressor of the trochanter and dorsoventral muscles I and II. Like the muscle pioneers of the grasshopper, the imaginal pioneers attach to the epidermis at sites where the future muscle insertions will arise and erect a scaffold for developing adult muscles. These findings suggest that a prior segregation of imaginal myoblasts into at least two populations, one of which may act as pioneers or founders, must occur during development
Participation of a K+ Channel Modulated Directly by cGMP in the Speract-Induced Signaling Cascade of Strongylocentrotus purpuratus Sea Urchin Sperm

AbstractSperact, a decapeptide from Strongylocentrotus purpuratus sea urchin eggs, transiently stimulates a membrane guanylyl cyclase and activates a K+-selective channel that hyperpolarizes sperm. However, previous studies of sperm and of sperm membrane vesicles reached conflicting conclusions about the mechanisms that open these channels. We find that speract hyperpolarizes and increases the cGMP content of flagellar vesicles. We confirm previous findings that intravesicular GTPγS and GTP enhance this hyperpolarization, but not GDPβS. The G protein activators AlF−4 and mastoparan also are ineffective. Thus, it is unlikely that a G protein participates in the speract response. In contrast, hyperpolarization responses to speract are increased by 3-isobutyl-1-methylxanthine, which preferentially inhibits cGMP-selective phosphodiesterases of sperm, and the 8Br-cGMP derivative hyperpolarizes vesicles in the absence of speract. The responses to speract and to 8Br-cGMP have similar ionic selectivities (K+ > Rb+ > > Li+ > Na+) and sensitivities to the channel blockers 4-aminopiridine and 3,4-dichlorobenzamil, indicating that they likely result from opening of the same K+ channel. Inhibitors that preferentially inhibit cAMP-selective phosphodiesterases do not alter responses to speract, and permeant cAMP analogs do not hyperpolarize vesicles. In addition, inhibitors of protein kinases and phosphatases fail to alter vesicle hyperpolarization by speract. The increase in vesicular cGMP content produced by speract therefore may directly mediate opening of the channel that hyperpolarizes sperm membrane vesicles. Similar mechanisms presumably operate in intact sperm
nhr-25, the Caenorhabditis elegans Ortholog of ftz-f1, Is Required for Epidermal and Somatic Gonad Development

AbstractWe have analyzed the expression and function of the Caenorhabditis elegans gene nhr-25, a member of the widely conserved FTZ-F1 family of nuclear receptors. The gene encodes two protein isoforms, only one of which has a DNA binding domain. nhr-25 is transcribed during embryonic and larval development. A nhr-25::GFP fusion gene is expressed in the epidermis, the developing somatic gonad, and a subset of other epithelial cells. RNA-mediated interference indicates a requirement for nhr-25 function during development: disruption of nhr-25 function leads to embryonic arrest due to failure of the epidermally mediated process of embryo elongation. Animals that survive to hatching arrest as misshapen larvae that occasionally exhibit defects in shedding molted cuticle. In addition, somatic gonad development is defective in these larvae. These results further establish the importance of FTZ-F1 nuclear receptors in molting and developmental control across evolutionarily distant phyla
Drosophila PTEN Regulates Cell Growth and Proliferation through PI3K-Dependent and -Independent Pathways

AbstractThe control of cell and organ growth is fundamental to the development of multicellular organisms. Here, we show that dPTEN, a Drosophila homolog of the mammalian PTEN tumor suppressor gene, plays an essential role in the control of cell size, cell number, and organ size. In mosaic animals, dPTEN− cells proliferate faster than their heterozygous siblings, show an autonomous increase in cell size, and form organs of increased size, whereas overexpression of dPTEN results in opposite phenotypes. The loss-of-function phenotypes of dPTEN are suppressed by mutations in the PI3K target Dakt1 and the translational initiation factor eif4A, suggesting that dPTEN acts through the PI3K signaling pathway to regulate translation. Although activation of PI3K and Akt has been reported to increase rates of cellular growth but not proliferation, loss of dPTEN stimulates both of these processes, suggesting that PTEN regulates overall growth through PI3K/Akt-dependent and -independent pathways. Furthermore, we show that dPTEN does not play a major role in cell survival during Drosophila development. Our results provide a potential explanation for the high frequency of PTEN mutation in human cancer
MyoD−/− Satellite Cells in Single-Fiber Culture Are Differentiation Defective and MRF4 Deficient

AbstractMyoD-deficient mice are without obvious deleterious muscle phenotype during embryogenesis and fetal development, and adults in the laboratory have grossly normal skeletal muscle and life span. However, a previous study showed that in the context of muscle degeneration on a mdx (dystrophin null) genetic background, animals lacking MyoD have a greatly intensified disease phenotype leading to lethality not otherwise seen in mdx mice. Here we have examined MyoD−/− adult muscle fibers and their associated satellite cells in single myofiber cultures and describe major phenotypic differences found at the tissue, cellular, and molecular levels. The steady-state number of satellite cells on freshly isolated MyoD−/− fibers was elevated and abnormal branched fiber morphologies were observed, the latter suggesting chronic muscle regeneration in vivo. Single-cell RNA coexpression analyses were performed for c-met, m-cadherin, and the four myogenic regulatory factors (MRFs.) Most mutant satellite cells entered the cell cycle and upregulated expression of myf5, both characteristic early steps in satellite cell maturation. However, they later failed to normally upregulate MRF4, displayed a major deficit in m-cadherin expression, and showed a significant diminution in myogenin-positive status compared with wildtype. MyoD−/− satellite cells formed unusual aggregate structures, failed to fuse efficiently, and showed greater than 90% reduction in differentiation efficiency relative to wildtype. A further survey of RNAs encoding regulators of growth and differentiation, cell cycle progression, and cell signaling revealed similar or identical expression profiles for most genes as well as several noteworthy differences. Among these, GDF8 and Msx1 were identified as potentially important regulators of the quiescent state whose expression profile differs between mutant and wildtype. Considered together, these data suggest that activated MyoD−/− satellite cells assume a phenotype that resembles in some ways a developmentally “stalled” cell compared to wildtype. However, the MyoD−/− cells are not merely developmentally immature, as they also display novel molecular and cellular characteristics that differ from any observed in wild-type muscle precursor counterparts of any stage
A large targeted deletion of Hoxb1-Hoxb9 produces a series single-segment anterior homeotic transformations

Hox genes regulate axial regional specification during animal embryonic development and are grouped into four clusters. The mouse HoxB cluster contains 10 genes, Hoxb to Hoxb9 and Hoxb13, which are transcribed in the same direction. We have generated a mouse strain with a targeted 90-kb deletion within the HoxB cluster from Hoxb1 to Hoxb9. Surprisingly, heterozygous mice show no detectable abnormalities. Homozygous mutant embryos survive to term and exhibit an ordered series of one-segment anterior homeotic transformations along the cervical and thoracic vertebral column and defects in sternum morphogenesis. Neurofilament staining indicates abnormalities in the IXth cranial nerve. Notably, simultaneous deletion of Hoxb1 to Hoxb9 resulted in the sum of phenotypes of single HoxB gene mutants. Although a higher penetrance is observed, no synergistic or new phenotypes were observed, except for the loss of ventral curvature at the cervicothoracic boundary of the vertebral column. Although Hoxb13, the most 5′ gene, is separated from the rest by 70 kb, it has been suggested to be expressed with temporal and spatial colinearity. Here, we show that the expression pattern of Hoxb13 is not affected by the targeted deletion of the other 9 genes Thus, Hoxb13 expression seems to be independent of the deleted region, suggesting that its expression pattern could be achieved independent of the colinear pattern of the cluster or by a regulatory element located 5′ of Hoxb9
Expression and Regulation of Type I BMP Receptors during Early Avian Sympathetic Ganglion Development

AbstractWe have investigated the expression and regulation of the mRNAs for the type I BMP receptors, BMPR-IA and BMPR-IB, in quail embryos in vivo and in neural crest cultures in vitro. BMPR-IB mRNA was expressed in the primordial sympathetic ganglia at stage 17, soon after the first expression of Cash-1 mRNA, the avian homolog of the Drosophila transcription factor achaete-scute. BMP-4 mRNA was detected in the dorsal aorta at stage 17, coincident with BMPR-IB mRNA expression in the sympathetic ganglia. BMPR-IA mRNA was first expressed in the sympathetic ganglia at stage 18. Moreover, BMP-4 ligand mRNA was detected in the sympathetic ganglia starting at stage 18. BMPR-IA and BMPR-IB were differentially regulated in cultured neural crest cells. BMPR-IB was expressed in primary outgrowths of neural crest cells but was downregulated after primary outgrowths were harvested and replated in secondary cultures. In secondary cultures of neural crest cells, exogenous BMP-2 and BMP-4 increased the expression of BMPR-IA but decreased the expression of BMPR-IB. The expression of both type I BMP receptors was inhibited by exogenous TGF-β1. Our results suggest distinct roles for BMPR-IA and BMPR-IB in the development of the sympathoadrenal phenotype from cells of the neural crest
The L63 Gene Is Necessary for the Ecdysone-Induced 63E Late Puff and Encodes CDK Proteins Required for Drosophila Development

AbstractThe pulse of ecdysone that triggers Drosophila metamorphosis activates six early genes in a primary response made visible by polytene chromosome puffs. The secondary response is detected by the induction of over 100 late puffs, only a few of which have been subject to molecular genetic analysis. We present a molecular and mutational analysis of the L63 gene responsible for the late puff at 63E. This gene contains overlapping L63A, B, and C transcription units of which the A unit encodes two isoforms and the B unit three. The C unit, which exhibits little activity, encodes one of the B isoforms. Evidence that L63B, but not L63A, transcription is ecdysone responsive derives from their developmental transcription profiles and from P-element mutagenesis showing that ecdysone induction of the 63E puff requires sequences adjacent to the 5′ end of L63B but not those adjacent to the 5′ end of L63A. L63-specific lethal mutations showed that L63 is required not only for metamorphosis, but also maternally and for embryonic and larval development. The L63 proteins contain a common C-terminal 294-aa sequence that is 71% identical to the CDK sequence of the murine PFTAIRE protein. In vivo tests of L63 proteins altered by site-directed mutagenesis showed that they exhibit CDK functions. L63 proteins are widely distributed among late larval and prepupal tissues and are unlikely to be involved in cell cycle functions
CHE-3, a Cytosolic Dynein Heavy Chain, Is Required for Sensory Cilia Structure and Function in Caenorhabditis elegans

AbstractForward genetic screens using novel assays of nematode chemotaxis to soluble compounds identified three independent transposon-insertion mutations in the gene encoding the Caenorhabditis elegans dynein heavy chain (DHC) 1b isoform. These disruptions were mapped and cloned using a newly developed PCR-based transposon display. The mutations were demonstrated to be allelic to the che-3 genetic locus. This isoform of dynein shows temporally and spatially restricted expression in ciliated sensory neurons, and mutants show progressive developmental defects of the chemosensory cilia. These results are consistent with a role for this motor protein in the process of intraflagellar transport; DHC 1b acts in concert with a number of other proteins to establish and maintain the structural integrity of the ciliated sensory endings in C. elegans
Krüppel-homolog, a Stage-Specific Modulator of the Prepupal Ecdysone Response, Is Essential for Drosophila Metamorphosis

AbstractWe have characterised a P-element-induced prepupal mutant of Drosophila melanogaster which after an apparently normal embryonic and larval development fails to complete head eversion, an essential step in metamorphosis. The P-element insertion disrupts an ecdysone-regulated transcript which, although expressed during embryonic and larval stages, appears critical for preparing the late prepupal response to ecdysone. By a combination of molecular and genetic studies, in which we recovered new alleles, we show that the locus is complex, containing at least two distinct promoters. Its transcripts contain a short region described previously by R. Schüh et al. (1986, Cell 47, 1025–1032), who screened for homologues of the Krüppel gene. Our studies on the corresponding gene, named Krüppel-homolog (Kr-h), add to a growing body of evidence that specific isoforms of a number of key genes are implicated in both embryogenesis and metamorphosis
Functional Analysis of an Eye Enhancer of the Drosophila eyes absent Gene: Differential Regulation by Eye Specification Genes

AbstractGenes involved in eye development are highly conserved between vertebrates and Drosophila. Given the complex genetic network controlling early eye development, identification of regulatory sequences controlling gene expression will provide valuable insights toward understanding central events of early eye specification. We have focused on defining regulatory elements critical for Drosophila eyes absent (eya) expression. Although eya has a complex expression pattern during development, analysis of eye-specific mutations in the gene revealed a region selectively deleted in the eye-specific alleles. Here we have performed detailed analysis of the region deleted in the eye-specific eya2 allele. This analysis shows that this region can direct earlyeya gene expression in a pattern consistent with that of normal eya in eye progenitor cells. Functional studies indicate that this element will restore appropriate eya transcript expression to rescue the eye-specific allele. We have examined regulation of this element during eye specification, both in normal eye development and in ectopic eye formation. These studies demonstrate that the element was activated upon ectopic expression of the eye specification genes eyeless and dachshund, but does not respond to ectopic expression of eya or sine oculis. The differential regulation of this element by genes involved during early retinal formation reveals new aspects of the genetic hierarchy of eye development