pinecone/core-2020-05-10-deduplication huggingface dataset:
Expression and Developmental Regulation of the Hydra-RFamide and Hydra-LWamide Preprohormone Genes inHydra:Evidence for Transient Phases of Head Formation

AbstractHydra magnipapillatahas three distinct genes coding for preprohormones A, B, and C, each yielding a characteristic set of Hydra-RFamide (Arg-Phe-NH2) neuropeptides, and a fourth gene coding for a preprohormone that yields various Hydra-LWamide (Leu-Trp-NH2) neuropeptides. Using a whole-mount double-labelingin situhybridization technique, we found that each of the four genes is specifically expressed in a different subset of neurons in the ectoderm of adultHydra.The preprohormone A gene is expressed in neurons of the tentacles, hypostome (a region between tentacles and mouth opening), upper gastric region, and peduncle (an area just above the foot). The preprohormone B gene is exclusively expressed in neurons of the hypostome, whereas the preprohormone C gene is exclusively expressed in neurons of the tentacles. The Hydra-LWamide preprohormone gene is expressed in neurons located in all parts ofHydrawith maxima in tentacles, hypostome, and basal disk (foot). Studies on animals regenerating a head showed that the prepro-Hydra-LWamide gene is expressed first, followed by the preprohormone A and subsequently the preprohormone C and the preprohormone B genes. This sequence of events could be explained by a model based on positional values in a morphogen gradient. Our head-regeneration experiments also give support for transient phases of head formation: first tentacle-specific preprohormone C neurons (frequently associated with a small tentacle bud) appear at the center of the regenerating tip, which they are then replaced by hypostome-specific preprohormone B neurons. Thus, the regenerating tip first attains a tentacle-like appearance and only later this tip develops into a hypostome. In a developing bud ofHydra,tentacle-specific preprohormone C neurons and hypostome-specific preprohormone B neurons appear about simultaneously in their correct positions, but during a later phase of head development, additional tentacle-specific preprohormone C neurons appear as a ring at the center of the hypostome and then disappear again. Nerve-freeHydraconsisting of only epithelial cells do not express the preprohormone A, B, or C or the LWamide preprohormone genes. These animals, however, have a normal phenotype, showing that the preprohormone A, B, and C and the LWamide genes are not essential for the basic pattern formation ofHydra
BMP7 Acts in Murine Lens Placode Development

AbstractTargeted inactivation of theBmp7gene in mouse leads to eye defects with late onset and variable penetrance (A. T. Dudleyet al.,1995,Genes Dev.9, 2795–2807; G. Luoet al.,1995,Genes Dev.9, 2808–2820). Here we report that the expressivity of theBmp7mutant phenotype markedly increases in a C3H/He genetic background and that the phenotype implicatesBmp7in the early stages of lens development. Immunolocalization experiments show that BMP7 protein is present in the head ectoderm at the time of lens placode induction. Using anin vitroculture system, we demonstrate that addition of BMP7 antagonists during the period of lens placode induction inhibits lens formation, indicating a role for BMP7 in lens placode development. Next, to integrateBmp7into a developmental pathway controlling formation of the lens placode, we examined the expression of several early lens placode-specific markers inBmp7mutant embryos. In these embryos,Pax6head ectoderm expression is lost just prior to the time when the lens placode should appear, while inPax6-deficient (Sey/Sey) embryos,Bmp7expression is maintained. These results could suggest a simple linear pathway in placode induction in whichBmp7functions upstream ofPax6and regulates lens placode induction. At odds with this interpretation, however, is the finding that expression ofsecreted Frizzled Related Protein-2(sFRP-2), a component of the Wnt signaling pathway which is expressed in prospective lens placode, is absent inSey/Seyembryos but initially present inBmp7mutants. This suggests a different model in whichBmp7function is required to maintainPax6expression after induction, during a preplacodal stage of lens development. We conclude thatBmp7is a critical component of the genetic mechanism(s) controlling lens placode formation
Histone Ubiquitination and Chromatin Remodeling in Mouse Spermatogenesis

AbstractMale infertility inHR6Bknockout mice is associated with impairment of spermatogenesis. TheHR6Bgene is a mammalian, autosomal homolog of theSaccharomyces cerevisiaegeneRad6encoding a ubiquitin-conjugating enzyme. In addition, X-chromosomalHR6Ahas been identified, in human and mouse. RAD6 in yeast is required for a variety of cellular functions, including sporulation, DNA repair, and mutagenesis. Since RAD6 and its mammalian homologs can ubiquitinate histonesin vitro,we have investigated the pattern of histone ubiquitination in mouse testis. By immunoblot and immunohistochemical analysis of wild-type mouse testis, a high amount of ubiquitinated H2A (uH2A) was detected in pachytene spermatocytes. This signal became undetectable in round spermatids, but then increased again during a relatively short developmental period, in elongating spermatids. No other ubiquitinated histones were observed. In theHR6Bknockout mice, we failed to detect an overt defect in the overall pattern of histone ubiquitination. For somatic cell types, it has been shown that histone ubiquitination is associated with destabilization of nucleosomes, in relation to active gene transcription. Unexpectedly, the most intense uH2A signal in pachytene spermatocytes was detected in the sex body, an inactive nuclear structure that contains the heterochromatic X and Y chromosomes. The postmeiotic uH2A immunoexpression in elongating spermatids indicates that nucleosome destabilization induced by histone ubiquitination may play a facilitating role during histone-to-protamine replacement
Regulation of Meiosis during Mammalian Spermatogenesis: The A-Type Cyclins and Their Associated Cyclin-Dependent Kinases Are Differentially Expressed in the Germ-Cell Lineage

AbstractTo begin to examine the function of the A-type cyclins during meiosis in the male, we have examined the developmental and cellular distribution of the cyclin A1 and cyclin A2 proteins, as well as their candidate cyclin-dependent kinase partners, Cdk1 and Cdk2, in the spermatogenic lineage. Immunohistochemical localization revealed that cyclin A1 is present only in male germ cells just prior to or during the first, but not the second, meiotic division. By contrast, cyclin A2 was expressed in spermatogonia and was most abundant in preleptotene spermatocytes, cells which will enter the meiotic pathway. Immunohistochemical detection of Cdk1 was most apparent in early pachytene spermatocytes, while staining intensity diminished in diplotene and meiotically dividing spermatocytes, the cells in which cyclin A1 expression was strongest. Cdk2 was highly expressed in all spermatocytes. Notably, in cells undergoing the meiotic reduction divisions, Cdk2 appeared to localize specifically to the chromatin. This was not the case for spermatogonia undergoing mitotic divisions. In the testis, cyclin A1 has been shown to bind both Cdk1 and Cdk2 but we show here that cyclin A2 binds only Cdk2. These results indicate that the A-type cyclins and their associated kinases have different functions in the initiation and passage of male germ cells through meiosis
Gene Expression and Chromatin Organization during Mouse Oocyte Growth

AbstractMouse oocytes can be classified according to their chromatin organization and the presence [surrounded nucleolus (SN) oocytes] or absence [nonsurrounded nucleolus (NSN) oocytes] of a ring of Hoechst-positive chromatin around the nucleolus. Following fertilization only SN oocytes are able to develop beyond the two-cell stage. These studies indicate a correlation between SN and NSN chromatin organization and the developmental competence of the female gamete, which may depend on gene expression. In the present study, we have used the HSP70.1Luc transgene (murine HSP70.1 promoter + reporter gene firefly luciferase) to analyze gene expression in oocytes isolated from ovaries of 2-day- to 13-week-old females. Luciferase was assayed on oocytes after classification as SN or NSN type. Our data show that SN oocytes always exhibit a higher level of luciferase activity, demonstrating a higher gene expression in this category. Only after meiotic resumption, metaphase II oocytes derived from NSN or SN oocytes acquire the same level of transgene expression. We suggest that the limited availability of transcripts and corresponding proteins, excluded from the cytoplasm until GVBD in NSN oocytes, could explain why these oocytes have a lower ability to sustain embryonic development beyond the two-cell stage at which major zygotic transcription occurs. With this study we have furthered our knowledge of epigenetic regulation of gene expression in oogenesis
Misexpression of the Catenin p120ctn1A PerturbsXenopusGastrulation But Does Not Elicit Wnt-Directed Axis Specification

AbstractModulators of cadherin function are of great interest given that the cadherin complex actively contributes to the morphogenesis of virtually all tissues. The catenin p120ctn(formerly p120cas) was first identified as a src- and receptor-protein tyrosine kinase substrate and later shown to interact directly with cadherins. In common with β-catenin and plakoglobin (γ-catenin), p120ctncontains a central Armadillo repeat region by which it binds cadherin cytoplasmic domains. However, little is known about the function of p120ctnwithin the cadherin complex. We examined the role of p120ctn1A in early vertebrate development via its exogenous expression inXenopus.Ventral overexpression of p120ctn1A, in contrast to β-catenin, did not induce the formation of duplicate axial structures resulting from the activation of the Wnt signaling pathway, nor did p120ctnaffect mesoderm induction. Rather, dorsal misexpression of p120ctnspecifically perturbed gastrulation. Lineage tracing of cells expressing exogenous p120ctnindicated that cell movements were disrupted, whilein vitrostudies suggested that this may have been a consequence of reduced adhesion between blastomeres. Thus, while cadherin-binding proteins β-catenin, plakoglobin, and p120ctnare members of the Armadillo protein family, it is clear that these proteins have distinct biological functions in early vertebrate development. This work indicates that p120ctnhas a role in cadherin function and that heightened expression of p120ctninterferes with appropriate cell–cell interactions necessary for morphogenesis
Incompetence of Preovulatory Mouse Oocytes to Undergo Cortical Granule Exocytosis Following Induced Calcium Oscillations

AbstractImmature oocytes of many species are incompetent to undergo cortical granule (CG) exocytosis upon fertilization. In mouse eggs, CG exocytosis is dependent primarily on an inositol 1,4,5-trisphosphate (IP3)-mediated elevation of intracellular calcium ([Ca2+]i). While deficienciesupstreamof [Ca2+]irelease are known, this study examined whetherdownstreamdeficiencies also contribute to the incompetence of preovulatory mouse oocytes to release CGs. The experimental strategy was to bypass upstream deficiencies by inducing normal, fertilization-like [Ca2+]ioscillations in fully grown, germinal vesicle (GV) stage oocytes and determine if the extent of CG exocytosis was restored to levels observed in mature, metaphase II (MII)-stage eggs. Because IP3does not stimulate a normal Ca2+response in GV-stage oocytes, three alternate methods were used to induce oscillations: thimerosal treatment, electroporation, and sperm factor injection. Long-lasting oscillations from thimerosal treatment resulted in 64 and 10% mean CG release at the MII and GV stages, respectively (P< 0.001). Three electrical pulses induced mean [Ca2+]ielevations of approximately 730 and 650 nM in MII- and GV-stage oocytes, respectively, and 31% CG release in MII-stage eggs and 9% in GV-stage oocytes (P< 0.001). Sperm factor microinjection resulted in 86% CG release in MII-stage eggs, while similarly treated GV-stage oocytes exhibited < 1% CG release (P< 0.001). Taken together, these results demonstrate a deficiency downstream of [Ca2+]irelease which is developmentally regulated in the 12 h prior to ovulation
Germ Cell Development in the XXY Mouse: Evidence That X Chromosome Reactivation Is Independent of Sexual Differentiation

AbstractPrior to entry into meiosis, XX germ cells in the fetal ovary undergo X chromosome reactivation. The signal for reactivation is thought to emanate from the genital ridge, but it is unclear whether it is specific to the developing ovary. To determine whether the signals are present in the developing testis as well as the ovary, we examined the expression of X-linked genes in germ cells from XXY male mice. To facilitate this analysis, we generated XXY and XX fetuses carrying X chromosomes that were differentially marked and subject to nonrandom inactivation. This pattern of nonrandom inactivation was maintained in somatic cells but, in XX as well as XXY fetuses, both parental alleles were expressed in germ cell-enriched cell populations. Because testis differentiation is temporally and morphologically normal in the XXY testis and because all germ cells embark upon a male pathway of development, these results provide compelling evidence that X chromosome reactivation in fetal germ cells is independent of the somatic events of sexual differentiation. Proper X chromosome dosage is essential for the normal fertility of male mammals, and abnormalities in germ cell development are apparent in the XXY testis within several days of X reactivation. Studies of exceptional germ cells that survive in the postnatal XXY testis demonstrated that surviving germ cells are exclusively XY and result from rare nondisjunctional events that give rise to clones of XY cells
Treatment of Mouse Oocytes with PI-PLC Releases 70-kDa (pI 5) and 35- to 45-kDa (pI 5.5) Protein Clusters from the Egg Surface and Inhibits Sperm–Oolemma Binding and Fusion

AbstractThe effect of phosphatidyinositol-specific phospholipase C (PI-PLC) on mouse sperm–egg interaction was investigated in this study to determine if glycosyl-phosphatidylinositol (GPI)-anchored proteins are involved in mammalian fertilization. When both sperm and zona-intact oocytes were pretreated with a highly purified preparation of PI-PLC and coincubated, there was no significant effect on sperm–zona pellucida binding; however, fertilization was reduced from 59.6% (control group) to 2.8% (treatment group). A similar reduction in fertilization rates was found when zona-intact oocytes were treated with PI-PLC and washed prior to incubation with untreated sperm. The effect of PI-PLC on sperm binding and fusion with zona-free oocytes was then investigated. Treatment of sperm with PI-PLC had no significant effect on sperm–egg binding or fusion. However, treatment of eggs with PI-PLC significantly reduced sperm–egg binding and fusion from 6.2 bound and 2.1 fused sperm per egg in the control group to 2.1 bound and 0.02 fused sperm per egg in the treatment group. This decrease in sperm–egg binding and fusion depended on the dose of PI-PLC employed, with a maximal inhibitory effect on binding and fusion at 5 and 1 U/ml, respectively. PI-PLC-treated oocytes could be artificially activated by calcium ionophore, demonstrating that the oocytes were functionally viable following treatment. Furthermore, treatment of oocytes with PI-PLC did not reduce the immunoreactivity of the non-GPI-anchored egg surface integrin, α6β1. Taken together, these observations support the hypothesis that PI-PLC affects fertilization by specifically releasing GPI-anchored proteins from the oolemma. In order to identify the oolemmal GPI-anchored proteins involved in fertilization, egg surface proteins were labeled with sulfo-NHS biotin, treated with PI-PLC, and analyzed by two-dimensional gel electrophoresis followed by avidin blotting. A prominent high-molecular-weight protein cluster (∼70 kDa, pI 5) and a lower molecular weight (∼35–45 kDa, pI 5.5) protein cluster were released from the oolemmal surface as a result of PI-PLC treatment. It is likely that these GPI-anchored egg surface proteins are required for sperm–egg binding and fusion
OtxExpression during Lamprey Embryogenesis Provides Insights into the Evolution of the Vertebrate Head and Jaw

AbstractAgnathan or jawless vertebrates, such as lampreys, occupy a critical phylogenetic position between the gnathostome or jawed vertebrates and the cephalochordates, represented by amphioxus. In order to gain insight into the evolution of the vertebrate head, we have cloned and characterized a homolog of the head-specific geneOtxfrom the lampreyPetromyzon marinus.This lampreyOtxgene is a clear phylogenetic outgroup to both the gnathostomeOtx1andOtx2genes. Like its gnathostome counterparts, lampreyOtxis expressed throughout the presumptive forebrain and midbrain. Together, these results indicate that the divergence ofOtx1andOtx2took place after the gnathostome/agnathan divergence and does not correlate with the origin of the vertebrate brain. Intriguingly,Otxis also expressed in the cephalic neural crest cells as well as mesenchymal and endodermal components of the first pharyngeal arch in lampreys, providing molecular evidence of homology with the gnathostome mandibular arch and insights into the evolution of the gnathostome jaw
Dynamic Expression oflunatic fringeSuggests a Link betweennotchSignaling and an Autonomous Cellular Oscillator Driving Somite Segmentation

AbstractThe metameric organization of the vertebrate trunk is a characteristic feature of all members of this phylum. The origin of this metamerism can be traced to the division of paraxial mesoderm into individual units, termed somites, during embryonic development. Despite the identification of somites as the first overt sign of segmentation in vertebrates well over 100 years ago, the mechanism(s) underlying somite formation remain poorly understood. Recently, however, several genes have been identified which play prominent roles in orchestrating segmentation, including the novel secreted factorlunatic fringe.To gain further insight into the mechanism by whichlunatic fringecontrols somite development, we have conducted a thorough analysis oflunatic fringeexpression in the unsegmented paraxial mesoderm of chick embryos. Here we report thatlunatic fringeis expressed predominantly in somite −II, where somite I corresponds to the most recently formed somite and somite −I corresponds to the group of cells which will form the next somite. In addition, we show thatlunatic fringeis expressed in a highly dynamic manner in the chick segmental plate prior to somite formation and thatlunatic fringeexpression cycles autonomously with a periodicity of somite formation. Moreover, the murine ortholog oflunatic fringeundergoes a similar cycling expression pattern in the presomitic mesoderm of somite stage mouse embryos. The demonstration of a dynamic periodic expression pattern suggests thatlunatic fringemay function to integrate notch signaling to a cellular oscillator controlling somite segmentation
A Subpopulation of Apoptosis-Prone Cardiac Neural Crest Cells Targets to the Venous Pole: Multiple Functions in Heart Development?

AbstractA well-described population of cardiac neural crest (NC) cells migrates toward the arterial pole of the embryonic heart and differentiates into various cell types, including smooth muscle cells of the pharyngeal arch arteries (but not the coronary arteries), cardiac ganglionic cells, and mesenchymal cells of the aortopulmonary septum. Using a replication-incompetent retrovirus containing the reporter gene LacZ, administered to the migratory neural crest of chicken embryos, we demonstrated another population of cardiac neural crest cells that employs the venous pole as entrance to the heart. On the basis of our present data we cannot exclude the possibility that precursors of these cells might not only originate from the dorsal part of the posterior rhombencephalon, but also from the ventral part. These NC cells migrate to locations surrounding the prospective conduction system as well as to the atrioventricular (AV) cushions. Concerning the prospective conduction system, the tagged neural crest cells can be found in regions where the atrioventricular node area, the retroaortic root bundle, the bundle of His, the left and right bundle branches, and the right atrioventricular ring bundle are positioned. The last area connects the posteriorly located AV node area with the retroaortic root bundle, which receives its neural crest cells through the arterial pole in concert with the cells giving rise to the aortopulmonary septum. The NC cells most probably do not form the conduction system proper, as they enter an apoptotic pathway as determined by concomitant TUNEL detection. It is possible that the NC cells in the heart become anoikic and, as a consequence, fail to differentiate further and merely die. However, because of the perfect timing of the arrival of crest cells, their apoptosis, and a change in electrophysiological behavior of the heart, we postulate that neural crest cells play a role in the last phase of differentiation of the cardiac conduction system. Alternatively, the separation of the central conduction system from the surrounding working myocardium is mediated by apoptotic neural crest cells. As for the presence of NC cells in both the outflow tract and the AV cushions, followed by apoptosis, a function is assigned in the muscularization of both areas, resulting in proper septation of the outflow tract and of the AV region. Failure of normal neural crest development may not only play a role in cardiac outflow tract anomalies but also in inflow tract abnormalities, such as atrioventricular septal defects