pinecone/core-2020-05-10-deduplication huggingface dataset:
RNA Transport to the Vegetal Cortex ofXenopusOocytes

AbstractXcat-2 RNA, a component of the germ plasm inXenopus,localizes with the mitochondrial cloud material to the vegetal cortex in stage II oocytes.Vg1 RNA also localizes to the vegetal cortex, but later in stage III/IV oocytes, using a microtubule dependent pathway. To further analyze the mechanisms involved in RNA transport,in situhybridization and autoradiography were used to follow the localization of endogenousVg1 and injectedXcat-2 transcripts in stage IV oocytes. We show thatXcat-2 is competent to localize to the vegetal cortex quite independently of the mitochondrial cloud.Xcat-2 RNA appears to use the lateVg1 localization pathway, as depolymerization of microtubules by cold or nocodazole treatment prevented translocation ofXcat-2 transcripts, but did not result in the disruption ofXcat-2 anchored in the cortex. Furthermore, RNA transport was shown to be stage dependent for bothVg1 andXcat-2 RNAs, as they did not localize in fully grown stage VI oocytes after injection. RNA sequences both required and sufficient to directXcat-2 to the vegetal cortex were mapped to a sequence of 150 nt immediately adjacent to the open reading frame and additional sequences at the end of the 3′ untranslated region. Mapping was accomplished by injecting deletion mutant transcripts into stage IV oocytes and monitoring localization by RNase protection and autoradiography. All mutants competent for translocation were also capable of cortical anchoring, suggesting that the same signal is used for both steps. We speculate that two separate RNA pathways evolved during the course ofXenopusoogenesis. One pathway, specialized for the transport of germ plasm by way of the mitochondrial cloud, occurs early to ensure the segregation of the germ cell lineage. The other, late, pathway may serve as the more general transport system for localizing RNAs involved in somatic cell differentiation
Differentiation of Embryonal Stem Cells into Keratinocytes: Comparison of Wild-Type and β1Integrin-Deficient Cells

Abstractβ1Integrins are known to regulate terminal differentiation and morphogenesis in the adult epidermis. We have investigated their role in the embryonic development of keratinocytes by comparing the differentiation of wild-type and β1-null mouse embryonal stem (ES) cells. By 12–15 days in culture, differentiation of embryonic or simple epithelial cells occurred in both ES cell populations, as detected by expression of keratins 8, 18, and 19. From 21 days, expression of keratins 10 and 14 and of the cornified envelope precursor involucrin indicated that some of the wild-type cells had differentiated into keratinocytes. In contrast, keratinocyte markers were not expressed in β1-null cultures. The β1-null cells failed to express the α2and α3integrin subunits on the cell surface, consistent with the association of these α subunits with β1. Furthermore, α6and β4expression was reduced in the β1-null cultures. Although β1-null ES cells failed to undergo differentiation into keratinocytesin vitro,they did form keratinocyte cysts expressing α6β4, keratins 1 and 14, and involucrin when allowed to form teratomas by subcutaneous injection in mice; furthermore, β1-null keratinocytes were found in the epidermis of a wild-type/β1-null chimeric mouse. As judged by immunofluorescence microscopy, extracellular matrix assembly was severely impaired in β1-null ES cell cultures, but not in the teratomas or chimeric mouse skin. We therefore speculate that the failure of β1-null cells to differentiate into keratinocytesin vitromay reflect an inability to assemble a basement membrane
Effects of Intermediate Filament Disruption on the Early Development of the Peripheral Nervous System ofXenopus laevis

AbstractThe principal function of intermediate filaments is to strengthen cells. Their developmentally regulated, tissue-specific patterns of expression further suggest that they modulate cellular structural properties during development. To explore the role of intermediate filaments in development, we injected RNA encoding a truncated form of theXenopus laevismiddle-molecular-weight neurofilament protein (NF-M) into embryonic frog blastomeres at the 2-cell stage. A similar truncated form of mammalian NF-M disrupts neurofilaments (Type IV) and vimentin (Type III) intermediate filaments in transfected fibroblasts. In cultures made from dissociated neural tubes and their adjacent myotomes, the resultant protein disrupted both desmin filaments in muscle cells and neurofilaments in neurons during the first day of culture, which corresponds to stage 35/36 in the intact embryo. We next examined the effects of this truncated neurofilament protein on development of the nervous system. The greatest effects were seen on development of cranial and primary motor nerves, which were severely stunted as late as stage 37/38. In addition to these effects, ectopic neurons also appeared immediately beneath the epidermis along the flank of tadpoles expressing the truncated neurofilament protein. Whereas the former effects on peripheral nerve development were nearly identical to effects obtained with injected neurofilament antibodies, the ectopic neurons were novel, suggesting they resulted from the disruption of intermediate filaments other than the neurofilaments. These experiments thus implicate intermediate filaments in several functions important for normal neural development
Maturation of the Acetylcholine Receptor in Skeletal Muscle: Regulation of the AChR γ-to-ϵ Switch

AbstractDuring the development of the mammalian neuromuscular junction, acetylcholine receptors (AChRs) become localized to the postsynaptic muscle membrane. As this process nears completion, the fetal form of the receptor, containing a γ subunit (composition α2βγδ) is gradually replaced by an ϵ subunit-containing adult form (α2βϵδ). To understand how this transition is controlled, we compared the expression and regulation of the AChR γ and ϵ subunits in developing, adult, and cultured muscles. Immunostaining with subunit-specific antibodies showed that replacement of γ subunit- by ϵ subunit-containing AChRs occurs largely during the first postnatal week in fast-twitch muscles, and occurs homogeneously throughout individual endplates. In the slow-twitch soleus, however, this transition is delayed, and in the multiply innervated slow fibers of extraocular muscle, γ subunit expression persists into adulthood. The transcriptional bases of the AChR subunit transition, and of these intermuscular variations, were demonstrated in mice bearing transgenes containing promoter elements from the AChR γ and ϵ subunit genes, each coupled to a nuclear-localized β-galactosidase (nlacZ) reporter. We show that transgene expression is stimulated by the nerve-derived inducer of AChR expression, ARIA, in myotubes cultured from γ–nlacZ as well as ϵ–nlacZ mice. However, the expression of γ–nlacZ, but not ϵ–nlacZ, is increased by treatment of myotubes with TTX, and the ARIA sensitivity of γ–nlacZ is dependent on the electrical state of the myotube. Thus, the promoters of the γ and ϵ subunit genes may integrate ARIA- and activity-dependent signals in different ways to generate their complementary patterns of expression
Interleukin-7 Is Trophic for Embryonic Neurons and Is Expressed in Developing Brain

AbstractInterleukin-7 (IL7) is a hematopoietic cytokine with critical functions in both B- and T-lymphocyte development. In this study, we find that IL7 exhibits trophic properties in the developing brain as well. Treatment of cultures of embryonic brain with exogenous IL7 increases neuronal survival and results in greater numbers of cells manifesting neurite outgrowth. As demonstrated with single-cell cultures, IL7 acts directly to promote neuronal survival. Expression of the mRNA encoding the high-affinity IL7 receptor (IL7R) is observedin vitroin neurons as well as in subventricular zone progenitor cells. Phosphorylation of p59fyn, which is activated by IL7 in pre-B cells and is thought to be important in neural development, occurs rapidly following IL7 treatment of cultured embryonic neurons. Additionally, the expression of c-mycmRNA, which is modulated by IL7 in lymphoid cells, is upregulated by IL7 in the same CNS cultures. Finally, the messenger RNAs encoding IL7 and IL7R are expressedin vivoin developing brain. The direct neurotrophic properties of IL7 combined with the expression of ligand and receptor in developing brain suggest that IL7 may be a neuronal growth factor of physiological significance during central nervous system (CNS) ontogeny
Laminin and Heparan Sulfate Proteoglycan Mediate Epithelial Cell Polarization in Organotypic Cultures of Embryonic Lung Cells: Evidence Implicating Involvement of the Inner Globular Region of Laminin β 1 Chain and the Heparan Sulfate Groups of Heparan Sulfate Proteoglycan

AbstractThe extracellular matrix and in particular the basement membrane (BM) play an important role in the induction of organotypic rearrangement of cells in culture. This process involves cell aggregation, sorting into epithelial and mesenchymal components, epithelial cell polarization, and lumen formation. In this study, a combination of laminin (LM) and heparan sulfate proteoglycan (HSPG), two major BM constituents, induced organotypic rearrangement of embryonic mouse lung cells. In the absence of LM/HSPG supplementation, the cells sorted into epithelial and mesenchymal compartments but epithelial cell polarization and lumen formation did not occur. Neither LM nor HSPG alone could trigger this process. Synthetic peptide F-9, representing an amino acid sequence from the inner globular region of the laminin β1 chain (RYVVLPRPVCFEKGMNYTVR) induced organotypic cell rearrangement when substituted for LM. Exogenous LM as well as peptide F-9 were localized at the epithelial–mesenchymal interface of organotypic cultures, where a BM-like structure is formedde novo.Organotypic cell rearrangement was blocked by heparin, heparan sulfate, or antibodies against peptide F-9. Binding assays indicated that peptide F-9 interacts with HSPG but not with LM or type IV collagen. Preincubation of embryonic lung cells with peptide F-9 resulted in a significant increase in cell attachment to HSPG but not to other major BM constituents. These findings suggest that the interaction between LM and BM HSPG is critical for the development of epithelial cell polarization and lumen formation. This interaction occurs at the epithelial–mesenchymal interface and is mediated by a site in the LM molecule represented by peptide F-9 and the heparan sulfate groups of HSPG
Role of Galectin-1 in the Developing Mouse Olfactory System

AbstractPrimary sensory olfactory neurons reside in a neuroepithelium lining the nasal cavity and project topographically onto the surface of the olfactory bulb, a rostral extension of the telencephalon. Galectin-1, a bivalent galactose-binding vertebrate lectin, is expressed in the developing rodent olfactory system. In the present study, the mouse olfactory neuron cell line 4.4.2 was used to examine the role of galectin-1 in neurite outgrowthin vitro.Recombinant galectin-1 has neurite outgrowth-promoting activity when used as a substrate for 4.4.2 cells. When either galectin-1 or lactose was added to the culture media, the neurite outgrowth-promoting activity was abolished. These results demonstrate that galectin-1 can modulate neurite growthin vitro.Thein vivorole of galectin-1 was investigated by examining the topographical organization of the olfactory pathway in mice carrying a null mutation for galectin-1. UsingDolichos biflorusagglutinin as a convenient histochemical marker of a subpopulation of primary sensory olfactory neurons which project topographically to the dorsomedial olfactory bulb, we show an aberrant topography of olfactory axons in the null mutants. A subset of primary sensory olfactory axons failed to project to their correct target sites in the caudal olfactory bulb. These data indicate that galectin-1 is involved in the growth and/or guidance of primary sensory olfactory axons between the nasal cavity and the olfactory bulb. This is the first demonstration that a lectin has neurite outgrowth-promoting activity and plays a role in neuronal pathfinding in the mammalian nervous system
Expression of CCAAT Enhancer Binding Protein-α (C/EBPα) in the Rat Ovary: Implications for Follicular Development and Ovulation

AbstractThe development of follicles from the antral to the preovulatory stage in the mammalian ovary involves both proliferation and differentiation of cells. These processes are coordinated by endocrine, paracrine, and autocrine factors in a time- and cell-specific pattern. Each stage of development is characterized by expression of specific genes the products of which are involved in different cellular processes, e.g., signal transduction (cAMP-dependent protein kinases), steroidogenesis (cytochrome P450 enzymes). At the nuclear level, the signaling pathway from external stimuli converges to modify the mechanisms of transcription factors. One such factor, CCAAT enhancer binding protein-α (C/EBPα), participates in differentiation processes of several organs, e.g., liver, adipose tissue, and gut. We have previously demonstrated that C/EBPα is expressed in rat ovarian follicles in a cell-, time-, and hormone-specific manner. This increase in granulosa cells was concomitant with the more differentiated phenotype. The aim of the present study was to explore the function of C/EBPα in the rat ovary. To achieve this, the expression of C/EBPα in follicular cells was attenuatedin vivoby the local administration of antisense oligonucleotides (AS) into the ovarian bursa, i.e., the sac-like structure surrounding the ovary of immature rats. This administration resulted in an impaired response to subsequent injections of exogenous gonadotropins (PMSG, hCG) with an attenuated expression of C/EBPα protein and finally a decreased ovulation rate. Furthermore, the morphology of the AS-treated ovary was altered with large, oocyte-containing follicles at a time when ovaries exposed to sense (S) oligonucleotides demonstrated newly formed corpora lutea. AS also affected the expression of the proto-oncogene c-myc, which was elevated by this treatment. The administration of S was without effects. Thus, C/EBPα seems to be a necessary factor for follicular development in the rat ovary
TGF-β Receptor Type II Deficiency Results in Defects of Yolk Sac Hematopoiesis and Vasculogenesis

AbstractTGF-β signaling is mediated through two types of serine/threonin kinase-containing receptors, type I (TGF-βRI) and type II (TGF-βRII), which form a heteromeric complex. In this signaling complex, ligand binding TGF-βRII phosphorylates and thereby activates the TGF-βRI to signal downstream pathways. To determine the role of TGF-βRII in embryogenesis, we have generated a TGF-βRII gene (Tgfbr2) knockout mouse line. The heterozygousTgfbr2knockout mice are developmentally normal. The homozygousTgfbr2mutation causes defects in the yolk sac hematopoiesis and vasculogenesis, resulting in an embryonic lethality around 10.5 days of gestation. This phenotype is indistinguishable from the previously reported embryonic lethality by the homozygous TGF-β1 gene (Tgfb1) null mutation. In addition, we have generated chimeric mice using aTgfbr2(−/−) embryonic stem cell line. Some chimeric mice showed several types of congenital anomalies, suggesting that TGF-βRII is important for normal development in a variety of organs
Scatter Factor/Hepatocyte Growth Factor (SF/HGF) Induces Emigration of Myogenic Cells at Interlimb Levelin Vivo

AbstractThe initiating event in the migration of myogenic cells to the limb buds is an epitheliomesenchymal transformation of cells located at the lateral edge of the dermomyotome. Recently, a targeted mutation ofc-metin mice demonstrated an essential role of this tyrosine kinase receptor and its ligand, scatter factor/hepatocyte growth factor (SF/HGF), in the migration of myogenic cells to the limb buds. Here, we show that ectopic application of exogenous SF/HGF induces emigration ofPax-3-positive myogenic cells into the lateral plate mesoderm. During this process, the lateral portions of the dermomyotomes deepithelialize and the basement membrane disintegrates. Detaching myogenic cells do not lose N-cadherin from their surfaces. We conclude that an HGF/SF- andc-met-mediated signal detaches myogenic precursor cells from the somites and thus plays a necessary role in the initiation of myoblast migration
Disruption of Cell Adhesion inXenopusEmbryos by Pagliaccio, an Eph-Class Receptor Tyrosine Kinase

AbstractPagliaccio (Pag) is a receptor tyrosine kinase of the Eph family that is expressed inXenopusembryos in a diverse set of localized tissues. Pag is theXenopushomolog of Hek-8 (human), Sek-1 (mouse), cek8 (chicken), and RTK-1 (zebrafish). We have investigated the function of this protein by injecting RNA encoding an epidermal growth factor receptor–Pag chimera into earlyXenopusembryos. Activation of the chimeric receptor results in a kinase-dependent loss of cell–cell adhesion. This dissociation can be reversed by co-injection of RNA encoding C-cadherin, suggesting that one or more cadherins could be the functional targets for Pag activity
Structural Change of the Endoplasmic Reticulum during Fertilization: Evidence for Loss of Membrane Continuity Using the Green Fluorescent Protein

AbstractGreen fluorescent protein (GFP) was targeted to the lumen of the endoplasmic reticulum (ER) of starfish eggs by injecting mRNA coding for a chimeric protein containing a signal sequence and the KDEL ER retention sequence. By confocal microscopy, the GFP chimeric protein was localized in intracellular cisternae (membrane sheets) and the nuclear envelope, showing that it had been successfully targeted to the ER. The labeling pattern closely resembled that produced by the fluorescent dicarbocyanine DiI, which has been used previously to label the ER (Jaffe and Terasaki,Dev. Biol.164, 579–587, 1994). Eggs expressing the GFP chimera were used to examine whether there is a loss of ER continuity at fertilization. The time required for recovery of fluorescence after photobleaching for both the GFP chimera and DiI was much longer in eggs at 1 min postfertilization than in unfertilized eggs or in 20-min-postfertilized eggs. This result provides strong evidence for a transient loss of continuity of the ER associated with Ca release at fertilization
Dual Origins of Mesoderm in a Basal Spiralian: Cell Lineage Analyses in the Polyclad TurbellarianHoploplana inquilina

AbstractEvolutionary modifications in the origins and organization of the mesoderm represent significant events in the diversification of metazoan body plans. Within the Spiralia, mesoderm comprises ectomesoderm, which typically is generated by derivatives of the second and third quartets of micromeres, and endomesoderm, which is formed from the fourth quartet micromere of the D quadrant (4d). It has been held that endomesoderm generates the majority of adult mesodermal derivatives, while larval mesoderm is formed primarily from ectomesoderm. The evolutionary history of these mesodermal sources could be clarified by examining basal members of the Spiralia such as the polyclad turbellarians, whose embryos exhibit canonical quartet spiral cleavage. Using the fluorescent lineage tracer DiI, we show that larval mesoderm is derived from only two cells, one from the ventral embryonic quadrant (2b, the “mesectoblast” cell), and the other from the dorsal quadrant (4d, the mesentoblast cell). We compare these results with mesodermal origins in other spiralian phyla and conclude that a dual origin of mesoderm is a primitive feature of spiralian development. We also argue that ectomesoderm and endomesoderm should not be considered as the exclusive precursors of larval and adult mesoderm, respectively
Gene Expression in thelimblessMutant: Polarized Gene Expression in the Absence of Shh and an AER

AbstractLimb buds in thelimblesschick begin to form normally but fail to form an AER and ultimately degenerate. Wnt7a and LMX-1, which are restricted to the dorsal half of a normal limb bud, are expressed throughout the ectoderm and mesenchyme of the mutant buds, respectively. Engrailed-1, normally expressed in ventral limb ectoderm, is not expressed in thelimblessbud. This defect precedes the normal period of AER formation and no localized expression of genes normally found in the AER is observed inlimblessbuds. Consistent with the lack of molecular specialization of an AER, Shh and BMP-2 are not expressed in the ZPA of the mutant bud. Despite the lack of Shh, FGF-4, or BMP-2 expression, the hoxd genes are expressed at low levels in the posterior mesenchyme of the bud. Forced expression of Shh fails to rescue the positive feedback loop between the AER and the ZPA and does not lead to distal outgrowth. However, Shh does maintain the part of the bud formed during pre-AER stages. These results support the importance of the dorsal/ventral boundary in the initiation of AER formation and imply that Shh is not required for the initial activation of polarized hoxd gene expression during limb development
Local Delivery of TGF β2 Can Substitute for Placode Epithelium to Induce Mesenchymal Condensation during Skin Appendage Morphogenesis

AbstractDevelopment of skin appendages requires interactions between the epithelium and mesenchyme. Without the epithelium, dermal condensations cannot develop, and those already formed will disintegrate. Here we explored the molecular basis of this epithelial requirement and tried to identify the molecule(s) responsible by using the chick feather bud development as a model. TGF β2 is a likely candidate because its message is predominantly expressed in the feather bud epithelium, and the protein is enriched in the dermal–epidermal junction within the bud. We tested this hypothesis by placing TGF β-soaked beads on skin explants. We found that TGF β2, but not TGF β1, beads placed on top of epithelially stripped mesenchymes can induce dermal condensations. NCAM and tenascin-C (Tn-C) are expressed and protein kinase C is suppressed in the normal feather bud domain. This molecular organization is lost in denuded mesenchyme but can be restored by TGF β2-coated beads. Subsequently, the TGF β2-induced dermal condensations can induce nascent epithelium to form skin appendages. Together with our recent findings that ectopic Sonic hedgehog (Shh) expression causes wider TGF β expression and larger dermal condensation, these results strongly suggest that TGF β2 produced by epithelial placode is downstream to Shh and plays a key role in the induction of dermal condensation by activating the expression of NCAM and Tn-C, and by suppressing PKC expression
Neurotrophin and Neurotrophin Receptors in Human Fetal Kidney

AbstractVertebrate kidney development involves a series of complex interactions between the ureteric bud and undifferentiated mesenchyme resulting in the production of the nephron unit. These interactions are thought to be dependent on a variety of locally derived soluble factors, including peptide growth factors and their receptors. We have extensively analyzed the neurotrophins (NT) and their receptors during human kidney development. The neurotrophin receptors p75 and trk were both present within cells of early glomerular/tubular structures but absent from uninduced mesenchyme. Later in organogenesis, the NTs NT-3 and BDNF colocalized with their respective receptors in differentiated tubules. These findings suggested that the NT:receptor complex was not involved in the early inductive events of renal development but was responsible for postinductive tubulogenesis and epithelial integrity.In situhybridization confirmed selective localization for the expression of trk B and trk C receptors and Western blot identified a full-length (kinase-active) trk receptor during human kidney development