pinecone/core-2020-05-10-deduplication huggingface dataset:
Alignment of Centrosomal and Growth Axes Is a Late Event during Polarization ofPelvetia compressaZygotes

AbstractZygotes and embryos of the fucoid brown algaPelvetia compressaundergo a series of asymmetric cleavages. We are interested in the developmental role of these cleavages and the mechanism controlling their alignment. To assess the importance of division plane alignment, the orientation of the first asymmetric division was altered and the effects on subsequent embryo elongation rates were analyzed. Although this division is normally oriented transversely (90°) to the growth axis, deviations up to 45° had no significant effects on embryo elongation. However, division planes that were parallel with the growth axis (0–45°) had drastic effects. Embryo elongation was severely inhibited and the wall often bifurcated and avoided the rhizoid tip. The orientation of the division plane is determined by the position of the centrosomes. We therefore investigated centrosomal position and function during the first cell cycle within the three-dimensional context of the cell. We found that, after karyogamy, microtubule organization changed from a radially symmetric circumnuclear array into a bipolar centrosomal array. The reorganization coincided with the migration of the centrosomes around the nucleus. The centrosomes separated slowly and asynchronously until they reached opposite sides of the nuclear envelope. At this time the centrosomal axis, defined by the position of the two centrosomes, was oriented randomly with respect to the cortical growth axis. The centrosomal axis then rotated into alignment parallel with the growth axis late in the first cell cycle. These results indicate that the growth axis and the centrosomal axis develop independently of each other and that the centrosomal axis does not align with the growth axis until just prior to mitosis
ThemuscleblindGene Participates in the Organization of Z-Bands and Epidermal Attachments ofDrosophilaMuscles and Is Regulated byDmef2

AbstractWe report the embryonic phenotype ofmuscleblind(mbl), a recently describedDrosophilagene involved in terminal differentiation of adult ommatidia.mblis a nuclear protein expressed late in the embryo in pharyngeal, visceral, and somatic muscles, the ventral nerve cord, and the larval photoreceptor system. All threemblalleles studied exhibit a lethal phenotype and die as stage 17 embryos or first instar larvae. These larvae are partially paralyzed, show a characteristically contracted abdomen, and lack striation of muscles. Our analysis of the somatic musculature shows that the pattern of muscles is established correctly, and they form morphologically normal synapses. Ultrastructural analysis, however, reveals two defects in the terminal differentiation of the muscles: inability to differentiate Z-bands in the sarcomeric apparatus and reduction of extracellular tendon matrix at attachment sites to the epidermis. Failure to differentiate both structures could explain the partial paralysis and contracted abdomen phenotype. Analysis ofmblexpression in embryos that are either mutant forDmef2or ectopically expressDmef2placesmbldownstream ofDmef2function in the myogenic differentiation program.mbl, therefore, may act as a critical element in the execution of twoDmef2-dependent processes in the terminal differentiation of muscles
Expression of atwist-Related Gene,Bbtwist,during the Development of a Lancelet Species and Its Relation to Cephalochordate Anterior Structures

AbstractMesoderm formation plays a crucial role in the establishment of the chordate body plan. In this regard, lancelet embryos develop structures such as the anteriorly extended notochord and the lateral divertecula in their anterior body. To elucidate the developmental basis of these structures, we examined the expression pattern of a lancelettwist-related gene,Bbtwist,from the late gastrula to larval stages. In late-gastrula embryos, the transcripts ofBbtwistwere detected in the presumptive first pair of somites and the middorsal wall of the primitive gut. The expression ofBbtwistwas then upregulated in the lateral wall of somites and the notochord. At the late-neurula stage, it was also expressed in the anterior wall of the primitive gut, as well as in the evaginating lateral diverticula. No signal was detected in the left lateral diverticulum when it was separated from the gut, while in the right one, the gene was expressed later during the formation of the head coelom in knife-shaped larvae, and in the anterior part of the notochord in the same larvae. In 36-h larvae, only faint expression was detected in the differentiating notochordal and paraxial mesoderm in the caudal region. These expression patterns suggest thatBbtwistis involved in early differentiation of mesodermal subsets as seen inDrosophilaand vertebrates. The expression in the anterior notochord may be related to its anterior expansion. The expression in the anterior wall of the primitive gut and its derivative, the lateral diverticula, suggests that lancelets share the capability to produce a mesodermal population from the tip of the primitive gut with nonchordate deuterostome embryos
Changes in Cyclin B during Oocyte Maturation and Early Embryonic Cell Cycle in the Newt,Cynops pyrrhogaster: Requirement of Germinal Vesicle for MPF Activation

AbstractWhen full-grown oocytes of the newtCynops pyrrhogasterwere treated with progesterone in O-R2 solution containing antibiotics, approximately 85% of the oocytes completed meiosis synchronously. Maturation-promoting factor (MPF) activity appeared just before germinal vesicle breakdown (GVBD) and the oocytes maintained high MPF activity throughout metaphase I and metaphase II of meiosis. A slight decrease of MPF activity was observed at the first polar body emission. The distribution of cyclin B1 was investigated with anti-cyclin B1 antibody. No cyclin B1 was found in the oocytes before progesterone treatment. Cyclin B1 appeared in the cortex of animal hemispheres, especially around and inside germinal vesicle just before GVBD. A large amount of cyclin B1 accumulated at metaphase I, approximately half disappeared at the first polar body emission, and then cyclin B1 accumulated again at metaphase II. An inactive form of cdc2 kinase was observed in both the germinal vesicles and the oocyte cytoplasm, while an active form appeared at the M phase. No MPF was observed in the oocytes from which the germinal vesicle had been removed. A cdk7-like molecule was localized in the germinal vesicle, but not in oocyte cytoplasm, indicating that inactive cdc2 kinase associated with cyclin B1 derived from cytoplasm is activated by phosphorylation in the germinal vesicle. The changes in the amount of cyclin B1 were synchronous with the first cell cycle after fertilization. Cyclin B1 was primarily localized in the cortex of the animal hemisphere. A shift in band mobility upon electrophoresis of cyclin B1 was observed from samples taken during the cell cycle; this shift was probably due to the protein's phosphorylation state
Stomata Patterning on the Hypocotyl ofArabidopsis thalianaIs Controlled by Genes Involved in the Control of Root Epidermis Patterning

AbstractStomata complexes are epidermal specialized structures typical of the upper aerial part of plants (shoot). In the model plantArabidopsis thaliana,we show that in the hypocotyl (the junction between the shoot and the root), stomata are organized according to a clear pattern reminiscent of the root epidermis pattern. Although stomata complexes are typical of the shoot epidermis, their pattern on the hypocotyl is under the control of genes involved in root epidermis patterning. Moreover, we have isolated a GFP marker line for the hypocotyl epidermal cells which do not differentiate stomata complexes. In this line the root and the hypocotyl epidermal patterns are similar. Our data support the existence of interactions between developmental mechanisms involved in the control of the apical/basal polarity and the radial symmetry of the plant body
Developmental Regulation of Mossy Fiber Afferent Interactions with Target Granule Cells

AbstractIn anin vitromodel system based on purified target cerebellar granule neurons and explants of afferents, pontine mossy fiber afferents stop growing through contact-mediated mechanisms when they encounter granule neurons. Here we studied the developmental regulation of the stop signal posed by granule cells and the response of mossy fibers to the stop signal in two culture systems. Granule neurons presented in slices or as dissociated cells from postnatal day (P) 4 and P7 cerebellum were more potent in the arrest of P0 pontine neurites than younger (P0-P2) or older (up to P14) granule neurons. In contrast, pontine neurites at embryonic day (E) 18, during their period of normal growth toward the cerebellum, grew extensively on both cerebellar slices of all ages from P0 to P10 and dissociated P4 granule neurons. When E18 explants were maintained for 2 days before plating in medium conditioned by neonatal cerebellar cells, E18 pontine explants were rendered more responsive to the stop signal from P4 granule cells. These results indicate that the stop signal, and the response of afferents to it, are developmentally regulated. Moreover, factors within the target region may initiate these interactions
A Key Function for αv Containing Integrins in Mesodermal Cell Migration duringPleurodeles waltlGastrulation

AbstractDuring cleavage ofPleurodeles waltlamphibian embryos, inner cells of the blastocoel roof (presumptive ectodermal and mesodermal cells) organize a fibrillar extracellular matrix (ECM) containing fibronectin on their basal surface by a β1-integrin-dependent process. This matrix is used as a migratory substrate by mesodermal cells during gastrulation. While α5β1 integrin is expressed on both ectodermal and mesodermal cell surface, we have shown previously that αv containing integrins are essentially restricted to the surface of mesodermal cells (Alfandari, D., Whittaker, C. A., DeSimone, D. W., and Darribère, T.,Dev. Biol.170, 249–261, 1995). To investigate the function of αv integrins during gastrulation, we have generated a function blocking antibody directed against the extracellular domain of thePleurodelesintegrin αv subunit. The antibody did not prevent fibronectin fibril formation, whereas an antibody against the α5β1 integrin did. When injected into the blastocoel, the antibody against integrin αv subunit perturbed gastrulation and further development in a stage-dependent manner. Developmental defects were correlated to an abnormal positioning of the mesoderm layer.In vitro,the antibody blocked spreading of mesodermal cell to fibronectin or blastocoel roof ECM but not their attachment. In contrast, the antibody directed against the α5β1 integrin inhibited both cell attachment and spreading to the same substrates. We propose that the α5β1 integrin is required for fibronectin assembly into fibrils and mesodermal cell attachment to the blastocoel roof ECM, while the αv containing integrins are necessary for cell spreading, and possibly migration, on this complex network
BMP1-Related Metalloproteinases Promote the Development of Ventral Mesoderm in Early Xenopus Embryos

AbstractBone morphogenetic protein 1 (BMP1) is a metalloproteinase closely related toDrosophilaTolloid (Tld). Tld regulates dorsoventral patterning in earlyDrosophilaembryos by enhancing the activity of Dpp, a member of the TGF-β family most closely related to BMP2 and BMP4. InXenopusBMP4 appears to play an essential role in dorsoventral patterning, promoting the development of ventral fates during gastrula stages. To determine if BMP1 has a role in regulating the activity of BMP4, we have isolated cDNAs forXenopusBMP1 and a novel closely related gene that we have calledxolloid(xld). Whereasxbmp1is uniformly expressed at all stages tested, the initial uniform expression ofxldbecomes localized to two posterior ectodermal patches flanking the neural plate and later to the inner ectoderm of the developing tailbud.xldis also expressed in dorsal regions of the brain during tailbud stages and is especially abundant in the ventricular layer of the dorsal hindbrain caudal to the otic vesicle. Overexpression of either gene inhibits the development of dorsoanterior structures in whole embryos and ventralizes activin-induced dorsal mesoderm in animal caps. Since ventralization of activin-induced animal caps can be blocked by coinjecting a dominant-inhibitory receptor for BMP2 and BMP4, we suggest a role for BMP1 and Xld in regulating the ventralizing activity of these molecules
Microtubule Organization during the Early Development of the Parthenogenetic Egg of the HymenopteranMuscidifurax uniraptor

AbstractThe origin of the zygotic centrosome is an important step in developmental biology. It is generally thought that sperm at fertilization plays a central role in forming the functional centrosome which subsequently organizes the first mitotic spindle. However, this view is not applicable in the case of parthenogenetic eggs which develop without the sperm contribution. To clarify the problem of the origin of the zygotic centrosome during parthenogenetic development, we studied a hymenopteran,Muscidifurax uniraptor.Antitubulin antibody revealed that after activation several asters assembled in the egg cytoplasm. The number of asters varied in relation to the cell cycle. They became visible from anaphase of the first meiotic division and increased in number as meiosis progressed, reaching a maximum at the first mitosis. From anaphase–telophase of the first mitosis they decreased in number and were no longer found during the third mitotic division. To elucidate the nature of these asters we performed an ultrastructural study with transmission electron microscopy and immunofluorescence with antibodies against anti-γ-tubulin and CP190. In this way we showed the presence in these asters of centrosomal components and centrioles. Our observations suggest that the cytoplasm ofMuscidifuraxeggs contains a pool of inactive centrosomal precursor proteins becoming able to nucleate microtubules into well-defined asters containing centrioles after activation
Knock-in Mutation of Transcription Factor GATA-3 into the GATA-1 Locus: Partial Rescue of GATA-1 Loss of Function in Erythroid Cells

AbstractTranscription factors of the GATA-family are essential for proper development of diverse tissues or cell types. GATA-1 is required for differentiation of two hematopoietic lineages (red blood cells and megakaryocytes), whereas GATA-3 is essential for T-cell development. Functional studies suggest that many properties of the GATA-family of proteins are shared and largely interchangeable. To test whether the function of GATA-1 in erythroid differentiation can be replaced by another GATA-factor, we generated a knock-in mutation of the GATA-1 locus in which GATA-3 cDNA was introduced by gene targeting. Mutant embryos (designated G1G3ki), though embryonic lethal, exhibit partial rescue, characterized by increased survival of erythroid precursor cells and improved hemoglobin production. The basis for the incomplete extent of rescue is likely to be complex, but may be accounted for, in part, by insufficient accumulation of GATA-3 protein (compared with the normal level of GATA-1). Our findings suggest that GATA-3 protein is functional when expressed in an erythroid environment and is competent to act on at least a subset of erythroid-expressed target genesin vivo
Morphological Diversity of the Avian Foot Is Related with the Pattern ofmsxGene Expression in the Developing Autopod

AbstractThe formation of the digits in amniota embryos is accompanied by apoptotic cell death of the interdigital mesoderm triggered through BMP signaling. Differences in the intensity of this apoptotic process account for the establishment of the different morphological types of feet observed in amniota (i.e., free-digits, webbed digits, lobulated digits). The molecular basis accounting for the differential pattern of interdigital cell death remains uncertain since the reduction of cell death in species with webbed digits is not accompanied by a parallel reduction in the pattern of expression ofbmpgenes in the interdigital regions. In this study we show that the duck interdigital web mesoderm exhibits an attenuated response to both BMP-induced apoptosis and TGFβ-induced chondrogenesis in comparison with species with free digits. The attenuated response to these signals is accompanied by a reduced pattern of expression ofmsx-1andmsx-2genes. Local application of FGF in the duck interdigit expands the domain ofmsx-2expression but not the domain ofmsx-1expression. This change in the expression ofmsx-2is followed by a parallel increase in spontaneous and exogenous BMP-induced interdigital cell death, while the chondrogenic response to TGFβs is unchanged. The regression of AER, as deduced by the pattern of extinction offgf-8expression, takes place in a similar fashion in the chick and duck regardless of the differences in interdigital cell death andmsxgene expression. Implantation of BMP-beads in the distal limb mesoderm induces AER regression in both the chick and duck. This finding suggests an additional role for BMPs in the physiological regression of the AER. It is proposed that the formation of webbed vs free-digit feet in amniota results from a premature differentiation of the interdigital mesoderm into connective tissue caused by a reduced expression ofmsxgenes in the developing autopod
Multiple Roles of theeyes absentGene inDrosophila

AbstractTheeyes absent(eya) gene plays an essential role in the events that lead to formation of theDrosophilaeye; without expression ofeyain retinal progenitor cells, they undergo programmed cell death just prior to the morphogenetic furrow, leading to an eyeless or reduced eye phenotype. Theeyagene has recently been found to be highly conserved to humans, defining a new gene family. Insights into the gene's function in the fly, therefore, are likely to be relevant to the role of its homologs in vertebrates. Detailed studies at the subcellular level indicate that the Eya protein is localized to the nucleoplasm, suggesting a role in control of nuclear events. Theeyagene shows expression and roles in tissues other than the eye, including subsets of cells of the adult visual system, brain, and ovary, as well as an elaborate expression pattern in the embryo. Various mutations in theeyagene cause loss of ocelli, female sterility, or lethality. Analysis of the embryonic lethal phenotype indicates that mutant alleles show defects in head morphogenesis. These data indicate thateyahas critical roles in morphogenesis of a number of tissues in the animal, in addition to its role in early eye formation. Despite multiple roles at multiple stages of development of the fly, both the type I and type II forms of the protein, when expressed ectopically during larval development, can direct eye formation
Formation of Functional Tight Junctions inXenopusEmbryos

AbstractFormation of the blastocoel in earlyXenopusembryos was studied with a novel biotin-permeability assay and newly generated tight junction markers. The blastocoel forms at the first cleavage division since functional tight junctions which excluded biotin and established a segregated intraembryonic compartment were found at the 2-cell and all subsequent developmental stages. Unexpectedly, tight junctions before the 64-cell stage were not at their normal apical positions, but were found deep in the embryos, up to 200 μm from the apical surface. In these positions, the tight junctions left large areas of ion permeable lateral membranes exposed to the extraembryonic environment, explaining why electrophysiological experiments record a decrease in embryonic input resistances concomitant with early cleavage stages. Immunohistochemistry revealed that the recessed tight junctions did not influence the distribution of C-cadherin and Na+,K+ATPase. Both markers were present apical to recessed tight junctions, indicating that the maintenance of polarization of these basolateral markers does not require tight junctions. With further development, tight junctions assumed an increasingly apical location until, by the 2000-cell stage, they occupied their conventional positions between the blastomeres at the apical/lateral membrane boundaries
The Paternal Effect Genems(3)sneakyIs Required for Sperm Activation and the Initiation of Embryogenesis inDrosophila melanogaster

AbstractAlthough a large number of maternal factors are known to be essential for fertilization or the earliest stages of embryogenesis inDrosophila melanogaster, the role of paternally supplied products is not clearly understood. Paternal effect mutations provide a means to identify factors specifically required by the sperm after its entry into the egg. Here we describe the third strict paternal effect gene to be identified inDrosophila, ms(3)sneaky(snky), which defines the earliest developmental arrest phenotype so far described. Characterization of two independently isolatedsnkymutations showed that they affected male fertility, but not viability or female fertility. Cytological analyses showed that spermatogenesis proceeded normally insnkymales. However, thesnkydefect was evident after sperm entry into the egg;snkysperm did not undergo nuclear decondensation, form a functional male pronucleus, or initiate mitotic divisions in the egg. Immunolocalization of tubulin and Drosophila Centrosomin, a known centrosomal component, showed thatsnky-inseminated eggs failed to reconstitute a microtubule-organizing center. In addition,snkysperm chromatin retained the histochemical properties of mature sperm chromatin for several hours after sperm entry, showed reduced staining with membrane-impermeant nuclear dyes, and failed to replicate. We conclude that thesnky+product is required for the initial response of the sperm to cytoplasmic cues in the egg and for the subsequent initiation of embryogenesis inDrosophila. We suggest that all of thesnkydefects can be explained by the failure of the sperm plasma membrane to break down after entry into the egg
FGF Is an Essential Regulator of the Fifth Cell Division in Preimplantation Mouse Embryos

AbstractFibroblast growth factor (FGF) signaling is required prior to gastrulation in the mouse embryo. To test for the spatial and temporal requirements of FGF signaling, a dominant negative FGF receptor (dnFGFR) was used to make transgenic mouse embryos. In mosaic embryos, cell division ceased at the fifth cell division in all cells that expressed the mutant receptor, but cell death did not increase. After the fifth cell division, the progeny of unaltered cells and cells expressing lacZ continued to accumulate at the same rate, suggesting that the FGF requirement is cell autonomous. In mosaic embryos, lacZ, but not dnFGFR expression was detected in mitotic trophoblasts adjacent to the ICM. Conversely, dnFGFR-expressing extraembryonic ectoderm cells were detected at the abembryonic pole in postmitotic cells. In blastocysts expressing the dnFGFR in all cells, the morphology appeared normal and inner cell masses (ICMs) formed, but resultant embryos had only one-third the number of cells as control embryos. In these blastocysts, cell division had also ceased at the fifth cell division, but cavitation, a concurrent morphogenetic event, initiated and progressed normally. To test for the continuing requirement of FGF, FGFR-3 was overexpressed in all cells and resulted in an increase in cell numbers after the fifth cell cycle. In a model for postimplantation development, addition of FGF-4 to blastocyst outgrowths increased the number of extraembryonic ectoderm cells, suggesting a continuing role for FGF. Thus, FGF signaling induces the cell division of embryonic and extraembryonic cells in the preimplantation mouse embryo starting at the fifth cell division. The signal requirement for FGF is cell autonomous, but is not required to prevent cell death. This provides the first evidence for the necessity of a growth factor before implantation