pinecone/core-2020-05-10-deduplication huggingface dataset:
The Drosophilaovarian tumorGene Is Required for the Organization of Actin Filaments during Multiple Stages in Oogenesis

AbstractTheovarian tumorgene is required during both early and late stages of oogenesis. Mutations produce a range of phenotypes, including agametic ovarioles, tumorous egg chambers, and late stage oogenic arrest. We demonstrate that each of these phenotypes is associated with specific aberrations in actin distribution. In the earliest case,ovarian tumormutations cause actin filaments to accumulate ectopically in the fusome. This correlates with abnormal fusome morphology and arrested germ cell development in the germaria. Similarly,ovarian tumorfunction is required for the localization of actin that is essential for the maturation of ring canals. This defect gives rise to tumorous egg chambers in which germ cell numbers and morphology are profoundly aberrant. We also confirm thatovarian tumoris required for the formation of the nurse cell cytoplasmic actin array that is essential for the nonspecific transport of cytoplasmic contents to the oocyte during late oogenesis. Our data suggest that at this stageovarian tumorcontrols the site where actin filaments initiate. Taken together, these studies suggest that the diverseovarian tumormutant phenotypes derive from the mislocalization of actin filaments, indicating a role for this gene in organizing the female germline cytoskeleton, and that the misregulation of actin can have profound effects on germ cell division and differentiation
Serotonin Plays an Early Role in the Metamorphosis of the HydrozoanPhialidium gregarium

AbstractHydrozoan larvae normally metamorphose in response to an obligate external environmental cue. Application of certain artificial chemical stimuli will also induce metamorphosis. These chemicals and their inhibitors have been used to define and order some of the signal transduction events involved in this process. Results from this study show that exogenous application of serotonin (5-HT) will induce metamorphosis and that 5-HT immunoreactive cells are present in larvae when they are competent to metamorphose. The 5-HT inhibitors ketanserin, clozapine, and 5,7-DHT prevent metamorphosis from occurring as a response to a natural inducing stimulus. Additionally, 5-HT signaling occurs prior to both an influx of external Ca2+from seawater and activation of protein kinase C, two other steps in the metamorphic signal transduction pathway. The neuropeptide LWamide, previously shown to induce metamorphosis in a related hydrozoan,Hydractinia echinata,also induced metamorphosis inPhialidium.When larvae were cotreated with LWamide and the 5-HT antagonist ketanserin, settlement occurred but was not followed by polyp morphogenesis. These results are used to present a model for the action of 5-HT during metamorphosis inPhialidium gregarium
Analysis of the Process of Localization of Fertilin to the Sperm Posterior Head Plasma Membrane Domain during Sperm Maturation in the Epididymis

AbstractFertilin is a heterodimeric (subunits α and β) sperm plasma membrane protein. Both subunits belong to the ADAM protein family of surface proteins that containa disintegrin anda metalloprotease domain. Fertilin functions in sperm–egg fusion by binding the sperm to the egg plasma membrane via a binding site in the disintegrin domain of fertilin β. On testicular sperm of guinea pig, fertilin is distributed on the plasma membrane over the entire sperm head, but is found only on the posterior head once sperm have passed through the epididymis. This redistribution of fertilin to the posterior head can be partially mimickedin vitroif testicular sperm are briefly treated with trypsin. In this study we used immunofluorescence and digital image analysis to analyze how fertilin becomes restricted to the posterior head. We found that fertilin became restricted to the posterior head by migration of anterior head fertilin molecules into the posterior head domain. Comparison of immunofluorescence patterns and immunoblots of fertilin from seven regions of the epididymis showed a temporal correlation between the beginning of fertilin's migration to the posterior head and the proteolytic processing of the full-length fertilin β precursor (the 85-kDa pro-β form) to a 75-kDa intermediate, pro-β*. Completion of the migration coincided with the further cleavage of pro-β* to the 25- to 28-kDa mature form. Our data suggest that the cleavage of fertilin pro-β to pro-β* may initiate fertilin's migration into the posterior head domain and, after localization to that membrane domain, pro-β* is cleaved to mature β. We also report evidence that a common mechanism may be used to change the localization pattern of other sperm surface molecules. Other surface proteins were shown to become localized to either the posterior or the anterior head membrane domains on sperm at the same time fertilin became localized to the posterior head. These restrictions of surface protein localizations were also shown to immediately precede the development of the sperm's ability to swim and undergo the acrosome reaction, and thus redistribution of surface proteins may be necessary before sperm become functional
Expression of T Protein in the Primitive Streak Is Necessary and Sufficient for Posterior Mesoderm Movement and Somite Differentiation

AbstractA characteristic abnormality of chimeras composed of wildtype andT/T(Brachyury) mutant embryonic stem cells is the aggregation and accumulation of mutant cells in the primitive streak and its descendant, the tail bud (V. Wilson, L. Manson, W. C. Skarnes, and R. S. P. Beddington (1995).Development121, 877–886). To demonstrate that this aberrant behaviour of mutant cells in the streak is due only to the absence of wild-type T protein and to investigate dosage effects of T function on cell deployment during gastrulation, a vector expressingTunder the control of its own promoter (which results inTexpression in the primitive streak but not in the notochord) was introduced intoT/Tmutant ES cells carrying a ubiquitouslacZlineage marker. Four clones (TR clones) that express T appropriately in the streak and rescue abnormal chimeric morphology were recovered. In chimeras, these four clones fall into two distinct categories with respect to their ability to exit from the primitive streak and their subsequent tissue colonisation profile. TR1 and TR4 descendants no longer accumulated in the tail bud and gave rise to all types of mesoderm as well as colonising ventral neurectoderm. Interestingly, TR2 and TR5 cells (which express higher levels of T protein than TR1 and TR4in vitro) tended to exit the streak prematurely, showed a marked reduction in posterior mesoderm colonisation, and were virtually excluded from ventral neurectoderm. However, while descendants of all four TR clones can colonise dermomyotome at all axial levels, the parentT/Tmutant cells only contribute to this tissue rostral to the forelimb bud and are completely excluded from more caudal dermomyotome. These results show that the abnormal aggregation of mutant cells homozygous for theBrachyurydeletion (∼200 kb) can be ascribed solely to the lack of wild-type T protein, as can the failure ofT/Tcells to colonise caudal dermomyotome. They also suggest that patterns of cell recruitment from the streak can be influenced by the level of T expression
glide/gcmIs Expressed and Required in the Scavenger Cell Lineage

AbstractGlial cell differentiation inDrosophila melanogasterrequires the activity ofglide/gcm(glial cell deficient/glial cell missing). The role of this gene is to direct the cell fate switch between neurons and glial cells by activating the glial developmental program in multipotent precursor cells of the nervous system. In this paper, we show thatglide/gcmis also expressed and required in the lineage of hemocytes/macrophages, scavenger cells that phagocytose cells undergoing programmed cell death. In addition, we show that, as for glial cells,glide/gcmplays an instructive role in hemocyte differentiation. Interestingly, it has been shown that in the development of the fly adult nervous system the role of scavenger cells is played by glial cells. These data and our findings on the dual role ofglide/gcmindicate that glial cells and hemocytes/macrophages are functionally and molecularly related
The Differential Effects of 12-O-Tetradecanoylphorbol-13-acetate on the Gap Junctions and Connexins of the Developing Mammalian Lens

AbstractEpithelial cells in primary ovine lens cultures express the gap junction proteins connexin43 (Cx43) and connexin49 (Cx49; a.k.a. MP70), a homologue of mouse connexin50. In contrast, lens cultures of differentiated, fiber-like cells (termed lentoid cells) express Cx49 and connexin46 (Cx46), but not Cx43. To investigate the regulation of lens cell gap junctions by protein kinase C (PKC), differentiating lens cultures were treated with the PKC activator 12-O-tetradecanoylphorbol-13-acetate (β-TPA). Within 10 min, β-TPA significantly inhibited the transfer of Lucifer Yellow dye between epithelial, but not lentoid, cells. This inhibition was correlated with the phosphorylation of Cx43 and was followed by the gradual disappearance of Cx43 from cell interfaces. The protein kinase inhibitor staurosporine prevented Cx43 phosphorylation and the loss of Cx43 from intercellular junctions. Following treatment of cultures with β-TPA for 2–6 hr, Cx49 disappeared from epithelial cell interfaces, and by 24 hr of β-TPA treatment, levels of Cx49 detected on immunoblots of purified epithelial membrane fractions had also diminished significantly. The β-TPA-induced loss of Cx49 both from regions of epithelial cell contact and from isolated membranes was correlated with the disappearance of Cx49 mRNA. In contrast to the epithelial connexins, the lentoid connexins Cx49 and Cx46 were unaffected by even extended β-TPA treatment. In spite of lentoid dye transfer being refractory to β-TPA, significant levels of PKC-α (a β-TPA-sensitive isoform) were detected in the lentoid cell. The response of lens gap junctions to β-TPA depends upon the stage of differentiation and the complement of connexins expressed. The contrasting effects of β-TPA on Cx43 and Cx49 in lens epithelial cells indicate a fundamental difference in the regulation of these connexin proteins in the developing mammalian lens
Mesodermal Guidance of Pioneer Axon Growth

AbstractPioneer axons in insect legs are experimentally accessible model systems for the molecular identification and cellular localization of guidance cues regulating the path of axon growth. A detailed study of the Fe2 pioneer axons in the legs of the cockroach was performed to examine the diversity of guidance mechanisms. A detailed microscopic analysis of the axons at various points in their trajectory indicates that the Fe2 axons grow on a mesodermal substratum which contains the cues guiding their growth along a stereotyped path. An identified pair of muscle pioneer cells (MPC) are likely to play an important role in enabling the Fe2 growth cones to respond to mesodermal guidance cues. The addition of heparan sulfate, heparitinase, and phosphatidylinositol-specific phospholipase C to the medium perturbs thein situpath of growth of the Fe2 axons and the location of the MPC in cultured embryos. This indicates a role for heparan sulfate proteoglycans and glycosylphosphatidylinositol-anchored proteins in axon guidance. When these results are compared to those of similar experiments performed on the well-characterized Ti1 axons, they indicate significant differences in the mechanisms that are used for axon guidance. The Fe2 neurons are a good model for elucidating the mechanisms used to guide axon growth on nonmuscle mesodermal substrates often encountered in the periphery of vertebrate embryos
Separate Elements in the 3′ Untranslated Region of the Mouse Protamine 1 mRNA Regulate Translational Repression and Activation during Murine Spermatogenesis

AbstractThe mouse protamine mRNAs,Prm-1andPrm-2,are translationally repressed for several days during male germ cell differentiation. The translational delay of mousePrm-1mRNA has previously been shown to be dependent uponcis-acting elements that reside in the last 62 nucleotides of thePrm-13′ untranslated region (3′ UTR). We have previously identified a 48/50-kDa protein that binds the 3′ UTRs of bothPrm-1andPrm-2mRNAs in a sequence-specific manner, is present in cytoplasmic fractions of postmeiotic round spermatids where the protamine mRNAs are translationally silent, and is markedly reduced in elongated spermatids where the protamine mRNAs become activated for translation. Surprisingly, the binding site for this activity maps to a region of thePrm-13′ UTR not contained within the functional 62 nucleotides described above. In this report we show that the binding site for the 48/50-kDa protein can also delay translation of a reporter RNAin vivo,suggesting that the 48/50-kDa protein can repress the translation ofPrm-1mRNA during murine spermatogenesis. This observation proves that two separate regions of thePrm-13′ UTR are sufficient to repressPrm-1translation. In addition, immunocytochemistry and polysome analysis have revealed that this transgenic reporter mRNA fails to undergo proper translational activation. These results suggest that an additional region of thePrm-13′ UTR is required for proper translational activation and thatPrm-1translational repression elements can be separated from those involved in translational activation
Graded and Lamina-Specific Distributions of Ligands of EphB Receptor Tyrosine Kinases in the Developing Retinotectal System

AbstractMolecular gradients have been postulated to control the topographic mapping of retinal axons in their central targets. Based initially on their expression patterns, and more recently on functional studies, members of the EphA subfamily of receptor tyrosine kinases and their ephrin-A ligands have been implicated in the guidance of retinal axons along the anterior–posterior axis of the chick optic tectum. The report that a receptor of the EphB subfamily, EphB2/Cek5/Nuk/Sek3, is expressed in a high ventral to low dorsal gradient in the developing chick retina and is present on ganglion cell axons suggests that it may be involved in the mapping of retinal axons along the corresponding dorsal–ventral axis of the tectum. To address this issue, we have determined the expression and distribution of ephrin-B1/LERK-2/Cek5-L and ephrin-B2/LERK-5/Htk-L/ELF-2, ligands for EphB2, in the developing chick retinotectal system using riboprobes, immunocytochemistry, and receptor affinity probes. Both ephrin-B1 and ephrin-B2 transcripts are expressed in a high dorsal to low ventral gradient in the developing retina, complementary to the distribution of EphB2. Ephrin-B1 and ephrin-B2 proteins are predominantly found in the developing plexiform layers, suggesting a role in the development of intraretinal connections. Neither protein is detected on ganglion cell axons. In tectum, ephrin-B1 transcripts are expressed in a high dorsal to low ventral gradient in the neuroepithelium and the protein is present along the processes of radial glia and is concentrated at their endfeet in the stratum opticum, at the time retinal axons are growing through it. This distribution of ephrin-B1 suggests that it influences retinal axon mapping along the dorsal–ventral tectal axis and may also be involved in intratectal development. In contrast, ephrin-B2 transcripts and protein are localized to the deeper retinorecipient laminae in the tectum at the time retinal axons begin to arborize in them, suggesting that this ligand may influence the laminar patterning of retinal axon terminations
GFP-Moesin Illuminates Actin Cytoskeleton Dynamics in Living Tissue and Demonstrates Cell Shape Changes during Morphogenesis inDrosophila

AbstractMoesin, ezrin, and radixin (MER) are components of the cortical actin cytoskeleton and membrane processes such as filopodia and microvilli. Their C-terminal tails contain an extended region that is predicted to be helical, an actin binding domain, and a region(s) that participates in self-association. We engineered anin vivofluorescent actin binding protein (GFP-moe) by joining sequences that encode the jellyfish green fluorescent protein (GFP) to sequences that encode the C-terminal end of the soleDrosophilaMER homolog, moesin [Moesin-likegene product, referred to previously as the D17 MER-like protein; Edwardset al.,1994,Proc. Natl. Acad. Sci. USA91, 4589], andDmoesin[McCartney and Fehon, 1996,J. Cell Biol.133, 843]. Transgenic flies expressing this fusion protein under control of thehsp70promoter were generated and used for analysis of cell shape changes during morphogenesis of various developmental stages and tissues. Following heat shock, high levels of stable fusion protein are produced by all somatic tissues. GFP-moe localizes to the cortical actin cytoskeleton, providing a strongin vivomarker for cell shape and pattern during epithelial morphogenesis. The protein also becomes highly enriched in pseudopods, microvilli, axons, denticles, the border cell process, and other membrane projections, potentially by binding to endogenous moesin as well as actin. We show that GFP-moe can be used to examine the development and behavior of these dynamic structures in live specimens. We observe a bright green fluorescent, presumably actin-rich, polar cell proboscis that inserts itself into the forming micropyle and appears to maintain an opening for sperm passage around which the chorion is formed. We also confirm the existence of an actin-rich purse string at the leading edge of the lateral epidermis and provide a dynamic analysis of its behavior as it migrates during dorsal closure. Observations of embryos, larvae, and pupae show that GFP-moe is also useful for labeling the developing nervous system and will be a good general marker of dynamic cell behavior during morphogenesis in live tissues and demonstrate that fusion of a subcellular localization signal to GFP greatly increases its utility as a cell marker
Distinct Neuronal Lineages of the Ascidian Embryo Revealed by Expression of a Sodium Channel Gene

AbstractThe ascidian larva contains tubular neural tissue, one of the prominent anatomical features of the chordates. The cell-cleavage pattern and cell maps of the nervous system have been described in the ascidian larva in great detail. Cell types in the neural tube, however, have not yet been defined due to the lack of a suitable molecular marker. In the present work, we identified neuronal cells in the caudal neural tube of theHalocynthiaembryo by utilizing a voltage-gated Na+channel gene, TuNa I, as a molecular marker. Microinjection of a lineage tracer revealed that TuNa I-positive neurons in the brain and in the trunk epidermis are derived from the a-line of the eight-cell embryo, which includes cell fates to epidermal and neural tissue. On the other hand, TuNa I-positive cells in the more caudal part of the neural tissue were not stained by microinjection into the a-line. These neurons are derived from the A-line, which contains fates of notochord and muscle, but not of epidermis. Electron microscopic observation confirmed that A-line-derived neurons consist of motor neurons innervating the dorsal and ventral muscle cells. Isolated A-line blastomeres have active membrane excitability distinct from those of the a-line-derived neuronal cells after culture under cleavage arrest, suggesting that the A-line gives rise to a neuronal cell distinct from that of the a-lineage. TuNa I expression in the a-line requires signals from another cell lineage, whereas that in the A-line occurs without tight cell contact. Thus, there are at least two distinct neuronal lineages with distinct cellular behaviors in the ascidian larva: the a-line gives rise to numerous neuronal cells, including sensory cells, controlled by a mechanism similar to vertebrate neural induction, whereas A-line cells give rise to motor neurons and ependymal cells in the caudal neural tube that develop in close association with the notochord or muscle lineage, but not with the epidermal lineage
The Intracellular Calcium Increase at Fertilization inUrechis caupoOocytes: Activation without Waves

AbstractThe intracellular Ca2+(Cai) increase at fertilization of the marine wormUrechis caupo(Echiura) was studied with conventional and confocal epifluorescence microscopy in oocytes microinjected with calcium green dextran or dually labeled with the calcium-insensitive dye tetramethylrhodamine dextran. Calcium green fluorescence was also measured with a photomultiplier system while the oocyte membrane potential was recorded and manipulated. The results show that Cairises simultaneously around the oocyte cortex and peaks slightly later in the nucleoplasm. The Cairise coincides with the initiation of the fertilization potential and we conclude that it is due primarily to external Ca2+entering through the voltage-gated Ca2+action potential channels that open during the fertilization potential because: (1) current clamping the oocyte membrane potential to positive values in the absence of sperm produces a similar Caiincrease, (2) external Ca2+is required, (3) and the confocal images are consistent with this mechanism. External application of sperm acrosomal peptide (P23) also caused a Caiincrease that was inhibited in the presence of CoCl2. Caiand pHi(measured with BCECF dextran) were manipulated in experiments employing microinjection of BAPTA (to chelate Cai), external application of NH4Cl (to increase pHi) and CoCl2(to block Ca2+channels), and fertilization of eggs in pH 7 seawater (Caiincrease without pHiincrease). The results showed that increases in both Caiand pHiare required for GVBD; neither alone is sufficient. However, although nuclear and cytoplasmic Ca2+levels tended to parallel each other in oocytes fertilized at pH 7, and during the initial Cairesponse in oocytes fertilized at pH 8, there was a disproportionate fluorescence increase in the nucleoplasm of the latter prior to GVBD which could not be explained by any artifact we tested, suggesting there may be a selective increase in nuclear Ca2+associated with GVBD. Finally, electrophysiological experiments with BAPTA-injected oocytes showed that the opening of the fertilization potential Na+channels was Ca2+-independent, (although they did not close at the normal time). These and earlier results suggest thatUrechissperm may activate oocytes by interacting directly with the Na+channels or associated receptors