pinecone/core-2020-05-10-deduplication huggingface dataset:
Interactions between the Foot and Bud Patterning Systems inHydra vulgaris

AbstractIn the freshwater coelenterate, hydra, asexual reproduction via budding occurs at the base of the gastric region about two-thirds of the distance from the head to the foot. Developmental gradients of head and foot activation and inhibition originating from these organizing centers have long been assumed to control budding in hydra. Much has been learned over the years about these developmental gradients and axial pattern formation, and in particular, the inhibitory influence of the head on budding is well documented. However, understanding of the role of the foot and potential interactions between the foot, bud, and head patterning systems is lacking. The purpose of this study was to investigate the role of the foot in the initiation of new axis formation during budding by manipulating the foot and monitoring effects on the onset of first bud evagination and the time necessary to reach the 50% budding point. Several experimental situations were examined: the lower peduncle and foot (PF) were injured or removed, a second PF was laterally grafted onto animals either basally (below the budding zone) or apically (above the budding zone), or both the head and PF were removed simultaneously. When the PF was injured or removed, the onset of first bud evagination was delayed and/or the time until the 50% budding point was reached was longer. The effects were more pronounced when the manipulation was performed closer to the anticipated onset of budding. When PF tissue was doubled, precocious bud evagination was induced, regardless of graft location. Removal of the PF at the same time as decapitation reduced the inductive effect of decapitation on bud evagination. These results are discussed in light of potential signals from the foot or interactions between the foot and head patterning systems that might influence bud axis initiation
Defective Vascularization of HIF-1α-Null Embryos Is Not Associated with VEGF Deficiency but with Mesenchymal Cell Death

AbstractHypoxia-inducible factor 1 (HIF-1) is a dimeric transcription factor composed of HIF-1α and HIF-1β subunits that plays an essential role in mammalian O2homeostasis. InHif1a−/−knockout mice, complete deficiency of HIF-1α resulted in cardiac and vascular malformations and embryonic lethality at E10.5. Between E8.75 and E9.25 striking vascular regression and abnormal remodeling occurred in the cephalic region concomitant with marked mesenchymal cell death. Similar vascular defects were observed in HIF-1α- and VEGF-deficient embryos and VEGF mRNA expression was not induced by hypoxia inHif1a−/−embryonic stem cells. Surprisingly,Hif1a−/−embryos demonstrated increased VEGF mRNA expression compared to wild-type embryos. In tissue culture cells, VEGF mRNA expression was induced by glucose deprivation independent of HIF-1α, providing a mechanism for increased VEGF mRNA expression inHif1a−/−embryos, in which absence of adequate tissue perfusion resulted in both O2and glucose deprivation. Rather than being associated with VEGF deficiency, the vascular defects inHif1a−/−embryos were spatially correlated with cell death, the onset of which preceded vascular regression
Characterization ofXenopusRalB and Its Involvement in F-Actin Control during Early Development

AbstractWe describe the characterization and a functional analysis inXenopusdevelopment of RalB, a small G protein. RalB RNA and protein are detectable during oogenesis and early development, but the gene is expressed only weakly in adult tissues. The RalB transcripts are processed by poly(A) extension during oocyte maturation and up to the gastrulation stage. Microinjection of wild-type or mutant RalB RNAs was performed in fertilized eggs in order to gain insight into the function of RalB during development. We show that during cleavage stages the activated GTP form of RalB specifically induces a cortical reaction that affects the localization of pigment granules. The use of different drugs suggests that this reaction is dependent on the outer cortical actin array. The relation between F-actin and RalB was shown by confocal analysis. Injection of mRNAs encoding the mutated activated form of RalB leads, at dependent doses, to a blocking of gastrulation or defects in closing of neural folding structures. In contrast, the inactivated form blocks only the closing of neural tube. Altogether, these observations suggest that RalB is part of a regulatory pathway that may affect the blastomere cytoskeleton and take part in early development
Evidence for the Involvement of a Src-Related Tyrosine Kinase inXenopusEgg Activation

AbstractRecently, we have purified a Src-related tyrosine kinase, namedXenopustyrosine kinase (Xyk), from oocytes ofXenopus laevisand found that the enzyme is activated within 1 min following fertilization [Satoet al.(1996)J. Biol. Chem.271, 13250–13257]. A concomitant translocation of a part of the activated enzyme from the membrane fraction to the cytosolic fraction was also observed. In the present study, we show that parthenogenetic egg activation by a synthetic RGDS peptide [Y. Iwao and T. Fujimura, T. (1996)Dev. Biol.177, 558–567], an integrin-interacting peptide, but not by electrical shock or the calcium ionophore A23187 causes the kinase activation, tyrosine phosphorylation, and translocation of Xyk. A synthetic tyrosine kinase-specific inhibitor peptide was employed to analyze the importance of the Xyk activity in egg activation. We found that the peptide inhibits the kinase activity of purified Xyk at IC50of 8 μM. Further, egg activation induced by sperm or RGDS peptide but not by A23187 was inhibited by microinjection of the peptide. In the peptide-microinjected eggs, penetration of the sperm nucleus into the egg cytoplasm and meiotic resumption in the egg were blocked. Indirect immunofluorescence study demonstrates that Xyk is exclusively localized to the cortex ofXenopuseggs, indicating that Xyk can function in close proximity to the sperm–egg or RGDS peptide–egg interaction site. Taken together, these data suggest that the tyrosine kinase Xyk plays an important role in the early events ofXenopusegg activation in a manner independent or upstream of calcium signaling
Isolation of Novel cDNAs by Subtractions between the Anterior Mesendoderm of Single Mouse Gastrula Stage Embryos

AbstractThe anterior mesendoderm of mid- to late primitive streak stage mouse embryos has the ability to induce anterior neuroectodermal fate in naive epiblast [S.-L. Ang and J. Rossant (1993)Development118, 139–149]. A number of genes have been found to be expressed in this tissue, notably the transcription factorLim1. Lim1-null mice have anterior mesendoderm defects that result in a lack of head formation. Thus, the anterior mesendoderm of gastrula stage mouse embryos should expressLim1-regulated genes that are essential for head development. To identifyLim1-regulated genes, a differential screen with subtraction was developed, using cDNA pools that were amplified from the anterior mesendoderm of single wild-type andLim1-null gastrula stage embryos. This novel screen strategy has yielded 22 cDNAs that show differential expression between anterior mesendoderm cells of wild-type andLim1-null embryos. The expression of one novel cDNA SII6 initially colocalizes withLim1in the anterior mesendoderm of gastrula stage embryos. Moreover, SII6 expression is undetectable in the anterior mesendoderm ofLim1-null embryos. This screen identifies a set of putativeLim1target genes that may have important roles in vertebrate head formation. Furthermore, this differential screen strategy should provide a broadly applicable approach to identify differences in gene expression between embryonic tissues of limiting quantity
EctopicMsx2Overexpression Inhibits andMsx2Antisense Stimulates Calvarial Osteoblast Differentiation

AbstractMsx2is believed to play a role in regulating bone development, particularly in sutures of cranial bone. In this study we investigated the effects of retroviral-mediated overexpression ofMsx2mRNA, in both sense and antisense orientations, on primary cultured chick calvarial osteoblasts. Unregulated overexpression of sense mRNA produced high levels ofMsx2protein throughout the culture period, preventing the expected fall as the cells differentiate. The continued high expression ofMsx2prevented osteoblastic differentiation and mineralization of the extracellular matrix. In contrast, expression of antisenseMsx2RNA decreased proliferation and accelerated differentiation. In other studies, we showed that theMsx2promoter was widely expressed during the proliferative phase of mouse calvarial osteoblast cultures but was preferentially downregulated in osteoblastic nodules. These results support a model in whichMsx2prevents differentiation and stimulates proliferation of cells at the extreme ends of the osteogenic fronts of the calvariae, facilitating expansion of the skull and closure of the suture
Altered Cell-Surface Targeting of Stem Cell Factor Causes Loss of Melanocyte Precursors inSteel17HMutant Mice

AbstractThe normal products of the murineSteel (Sl)andDominant white spotting (W)genes are essential for the development of melanocyte precursors, germ cells, and hematopoietic cells. TheSllocus encodes stem cell factor (SCF), which is the ligand of c-kit, a receptor tyrosine kinase encoded by theWlocus. One allele of theSlmutation,Sl17H,exhibits minor hematopoietic defects, sterility only in males, and a complete absence of coat pigmentation. TheSl17Hgene encodes SCF protein which exhibits an altered cytoplasmic domain due to a splicing defect. In this paper we analyzed the mechanism by which the pigmentation phenotype inSl17Hmutant mice occurs. We show that in embryos homozygous forSl17Hthe number of melanocyte precursors is severely reduced on the lateral neural crest migration pathway by e11.5 and can no longer be detected by e13.5 when they would enter the epidermis in wildtype embryos. The reduced number of dispersing melanocyte precursors correlates with a reduction of SCF immunoreactivity in mutant embryos in all tissues examined. Regardless of the reduced amount, functional SCF is present at the cell surface of fibroblasts transfected withSl17Hmutant SCF cDNA. Since SCF immunoreactivity normally accumulates in basolateral compartments of SCF-expressing embryonic epithelial tissues, we analyzed the localization of wildtype andSl17Hmutant SCF protein in transfected epithelial (MDCK) cellsin vitro.As expected, wildtype forms of SCF localize to and are secreted from the basolateral compartment. In contrast, mutant forms of SCF, which either lack a membrane anchor or exhibit theSl17Haltered cytoplasmic tail, localize to and are secreted from the apical compartment of the cultured epithelium. We suggest, therefore, that the loss of melanocyte precursors prior to epidermal invasion, and the loss of germ cells from mature testis, can be explained by the inability ofSl17Hmutant SCF to be targeted to the basolateral compartment of polarized epithelial keratinocytes and Sertoli cells, respectively
Notochord-Dependent Expression of MFH1 and PAX1 Cooperates to Maintain the Proliferation of Sclerotome Cells during the Vertebral Column Development

AbstractDuring axial skeleton development, the notochord is essential for the induction of the sclerotome and for the subsequent differentiation of cartilage forming the vertebral bodies and intervertebral discs. These functions are mainly mediated by the diffusible signaling molecule Sonic hedgehog. The products of the paired-box-containingPax1and the mesenchyme forkhead-1 (Mfh1) genes are expressed in the developing sclerotome and are essential for the normal development of the vertebral column. Here, we demonstrate thatMfh1likePax1expression is dependent on Sonic hedgehog signals from the notochord, andMfh1andPax1act synergistically to generate the vertebral column. InMfh1/Pax1double mutants, dorsomedial structures of the vertebrae are missing, resulting in extreme spina bifida accompanied by subcutaneous myelomeningocoele, and the vertebral bodies and intervertebral discs are missing. The morphological defects inMfh1/Pax1double mutants strongly correlate with the reduction of the mitotic rate of sclerotome cells. Thus, both theMfh1and thePax1gene products cooperate to mediate Sonic hedgehog-dependent proliferation of sclerotome cells
Disruption of Zebrafish Somite Development by Pharmacologic Inhibition of Hsp90

AbstractMembers of the Hsp90 family of molecular chaperones play important roles in allowing some intracellular signaling molecules and transcription factors to reach and maintain functionally active conformations. In the present study, we have utilized the specific Hsp90-binding agent, geldanamycin, to examine the requirement for Hsp90 during zebrafish development. We show that geldanamycin interacts with both the α and the β-isoforms of zebrafish Hsp90 and that geldanamycin-treated embryos consistently exhibit a number of defects in tissues which express either one of these genes. Within the somites, geldanamycin treatment results in the absence ofeng-2-expressing muscle pioneer cells. However, early development of adaxial cells, which give rise to muscle pioneers and which strongly express thehsp90α gene shortly before muscle pioneer formation, appeared unaffected. Furthermore, development of the notochord, which provides many of the signals required for proper somite patterning and which does not express detectable levels of eitherhsp90α orhsp90β mRNA, was similarly unaffected in geldanamycin-treated embryos. The data are consistent with there being a temporal and spatial requirement for Hsp90 function within somitic cells which is necessary for the formation ofeng-2-expressing muscle pioneers and possibly other striated muscle fiber types
Suppression of SHP-2 and ERK Signalling Promotes Self-Renewal of Mouse Embryonic Stem Cells

AbstractThe propagation of pluripotent mouse embryonic stem (ES) cells depends on signals transduced through the cytokine receptor subunit gp130. Signalling molecules activated downstream of gp130 in ES cells include STAT3, the protein tyrosine phosphatase SHP-2, and the mitogen-activated protein kinases, ERK1 and ERK2. A chimaeric receptor in which tyrosine 118 in the gp130 cytoplasmic domain was mutated did not engage SHP-2 and failed to activate ERKs. However, this receptor did support ES cell self-renewal. In fact, stem cell colonies formed at 100-fold lower concentrations of cytokine than the unmodified receptor. Moreover, altered ES cell morphology and growth were observed at high cytokine concentrations. These indications of deregulated signalling in the absence of tyrosine 118 were substantiated by sustained activation of STAT3. Confirmation that ERK activation is not required for self-renewal was obtained by propagation of pluripotent ES cells in the presence of the MEK inhibitor PD098059. In fact, the growth of undifferentiated ES cells was enhanced by culture in PD098059. Thus activation of ERKs appears actively to impair self-renewal. These data imply that the self-renewal signal from gp130 is a finely tuned balance of positive and negative effectors
Developmental Morphology of the Head Mesoderm and Reevaluation of Segmental Theories of the Vertebrate Head: Evidence from Embryos of an Agnathan Vertebrate, Lampetra japonica

AbstractDue to the peculiar morphology of its preotic head, lampreys have long been treated as an intermediate animal which links amphioxus and gnathostomes. To reevaluate the segmental theory of classical comparative embryology, mesodermal development was observed in embryos of a lamprey, Lampetra japonica, by scanning electron microscopy and immunohistochemistry. Signs of segmentation are visible in future postotic somites at an early neurula stage, whereas the rostral mesoderm is unsegmented and rostromedially confluent with the prechordal plate. The premandibular and mandibular mesoderm develop from the prechordal plate in a caudal to rostral direction and can be called the preaxial mesoderm as opposed to the caudally developing gastral mesoderm. With the exception of the premandibular mesoderm, the head mesodermal sheet is secondarily regionalized by the otocyst and pharyngeal pouches into the mandibular mesoderm, hyoid mesoderm, and somite 0. The head mesodermal components never develop into cephalic myotomes, but the latter develop only from postotic somites. These results show that the lamprey embryo shows a typical vertebrate phylotype and that the basic mesodermal configuration of vertebrates already existed prior to the split of agnatha–gnathostomata; lamprey does not represent an intermediate state between amphioxus and gnathostomes. Unlike interpretations of theories of head segmentation that the mesodermal segments are primarily equivalent along the axis, there is no evidence in vertebrate embryos for the presence of preotic myotomes. We conclude that mesomere-based theories of head metamerism are inappropriate and that the formulated vertebrate head should possess the distinction between primarily unsegmented head mesoderm which includes preaxial components at least in part and somites in the trunk which are shared in all the known vertebrate embryos as the vertebrate phylotype
Interferon Regulatory Transcription Factors Are Constitutively Expressed and Spatially Regulated in the Mouse Lens

AbstractInterferon regulatory factors (IRFs) are a family of transcription factors involved in regulation of cell growth and immunological responses. Nine IRFs have been described and they are expressed in a variety of cells, except for ICSBP and LSIRF/Pip, which are thought to be expressed exclusively in immune cells. Here, we show that IRF-1, IRF-2, ICSBP, and LSIRF/Pip are constitutively expressed in the mouse lens. These IRFs are present in both the cytoplasm and the nuclei of lens cells. However, the nuclear and cytoplasmic proteins exhibit distinct mobilities on SDS/PAGE. We further show that in the developing mouse lens, IRF-1 and IRF-2 are expressed at high levels in differentiated lens fiber cells with very low and barely detectable levels in undifferentiated lens epithelial cells. Although the level of ICSBP expression is very low in the normal mouse lens, in transgenic mice with constitutive expression of interferon γ in the lens, its level is markedly elevated and ICSBP expression is detected exclusively in the nuclei of undifferentiated lens cells. Taken together, our data suggest that expression of IRF transcription factors is spatially regulated in the lens and that distinct IRFs may contribute to differential gene regulation in the epithelial and fiber compartments of the vertebrate lens
Activin Family Members in the Developing Chick Retina: Expression Patterns, Protein Distribution, andin VitroEffects

AbstractWe have investigated whether the activin family of growth factors is involved in the regulation of retinal cell differentiation. Immunocytochemistry andin situhybridization have shown that activin/inhibin subunits α, βA, and βB; receptors II and IIB; follistatin; and a follistatin-like gene are expressed in different regions of the chick embryo retina in developmentally regulated patterns. When tested in dissociated retinal cultures, activin did not appear to affect cell survival or proliferation, but it exerted marked inhibitory effects on the differentiation of photoreceptors, while stimulating the differentiation of nonphotoreceptor neurons; both effects were concentration-dependent and follistatin-sensitive. The results are consistent with the possibility that activin family members play significant roles in the regulation of retinal development
NT-3, like NGF, Is Required for Survival of Sympathetic Neurons, but Not Their Precursors

AbstractSuperior cervical ganglia of postnatal mice with a targeted disruption of the gene for neurotrophin-3 have 50% fewer neurons than those of wild-type mice. In culture, neurotrophin-3 increases the survival of proliferating sympathetic precursors. Both precursor death (W. ElShamy et al., 1996, Development 122, 491–500) and, more recently, neuronal death (S. Wyatt et al., 1997, EMBO J. 16, 3115–3123) have been described in mice lacking NT-3. Consistent with the second report, we found that, in vivo, neurogenesis and precursor survival were unaffected by the absence of neurotrophin-3 but neuronal survival was compromised so that only 50% of the normal number of neurons survived to birth. At the time of neuron loss, neurotrophin-3 expression, assayed with a lacZ reporter, was detected in sympathetic target tissues and blood vessels, including those along which sympathetic axons grow, suggesting it may act as a retrograde neurotrophic factor, similar to nerve growth factor. To explore this possibility, we compared neuron loss in neurotrophin-3-deficient mice with that in nerve growth factor-deficient mice and found that neuronal losses occurred at approximately the same time in both mutants, but were less severe in mice lacking neurotrophin-3. Eliminating one or both neurotrophin-3 alleles in mice that lack nerve growth factor does not further reduce sympathetic neuron number in the superior cervical ganglion at E17.5 but does alter axon outgrowth and decrease salivary gland innervation. Taken together these results suggest that neurotrophin-3 is required for survival of some sympathetic neurons that also require nerve growth factor
Developmental Expression and Cellular Origin of the Laminin α2, α4, and α5 Chains in the Intestine

AbstractLaminins are extracellular matrix glycoproteins that are involved in various cellular functions, including adhesion, proliferation, and differentiation. In this study, we examine the expression patterns and the cellular origins of the laminin α2, α4, and α5 chains in the developing mouse intestine and inin vitromouse/chick or chick/mouse interspecies hybrid intestines.In situhybridization and Northern blot analysis revealed that mRNA levels for all three laminin α chains are highest in the fetal intestine undergoing intense morphogenetic movements. Laminin α4 mRNA and polypeptide are associated with mesenchyme-derived cell populations such as endothelium and smooth muscle. In contrast, laminin α2 and α5 chains participate in the structural organization of the subepithelial basement membrane and, in the mature intestine, show a complementary pattern of expression. All three laminin α chains occur in the smooth muscle basement membrane, with a differential expression of laminin α5 chain in the circular and longitudinal smooth muscle layers. The cellular origin of laminin α2 and α5 chains found in the subepithelial cell basement membrane was studied by immunocytochemical analysis of mouse/chick or chick/mouse interspecies hybrid intestines at various stages of development using mouse-specific antibodies. Laminin α2 was found to be deposited into the basement membrane exclusively by mesenchymal cells, while the laminin α5 chain was deposited by both epithelial and mesenchymal cells in an apparently developmentally regulated pattern. We conclude that (1) multiple laminin α chains are expressed in the intestine, implying specific roles for individual laminin isoforms during intestinal development, and (2) reciprocal epithelial/mesenchymal interactions are essential for the formation of a structured subepithelial basement membrane