pinecone/core-2020-05-10-deduplication huggingface dataset:
Germ-Layer Surface Tensions and “Tissue Affinities” inRana pipiensGastrulae: Quantitative Measurements

AbstractThe morphogenetic properties causing germ-layer spreading and stratification in amphibian gastrulation were called “tissue affinities” by Holtfreter. The differential adhesion hypothesis (DAH) attributes such liquidlike tissue rearrangements to forces generated by intercellular adhesions within and between the migrating cell populations. This theory predicts that, among the primary germ layers, the cohesiveness of deep ectoderm should be the greatest, that of deep mesoderm should be intermediate, and that of deep endoderm should be the least. Also, the cohesiveness of differentiating neural ectoderm should increase after induction, causing it to internalize and segregate from epidermis. The DAH also explains why the cohesiveness of “liquid” tissues, whose cells are free to rearrange, should be measurable as tissue surface tensions. Using a specially designed tissue surface tensiometer, we demonstrate that (i) aggregates ofRana pipiensdeep germ layers do possess liquid-like surface tensions, (ii) their surface tension values lie in precisely the sequence necessary to account for germ-layer stratificationin vitroandin vivo,and (iii) the surface tension of deep ectoderm just underlain by the archenteron roof is twice that of not-yet-underlain deep ectoderm. These measurements provide direct, quantitative evidence that the “tissue affinities” governing germ-layer flow during early stages of vertebrate morphogenesis are reflected in tissue surface tensions
Protein Tyrosine Kinase Activity Following Fertilization Is Required to Complete Gastrulation, but Not for Initial Differentiation of Endoderm and Mesoderm in the Sea Urchin Embryo

AbstractThe egg activation process functions to implement developmental programs that act much later in embryogenesis. One example of this is the fact that application of protein tyrosine kinase inhibitors to the fertilized sea urchin egg for a 15-min period results in a defect in the gastrulation process occurring over 24 h later (Kinsey, W. H.,Dev. Biol.172, 704–707, 1995). In the present study, we show that the window of sensitivity is not due to differential uptake of inhibitor, and establish that the inhibitor inhibits tyrosine kinase activity at the time of application. We also demonstrate that inhibition of protein tyrosine kinase activity in the zygote causes a specific defect in the morphogenetic movements associated with gastrulation without interfering with the initial specification and differentiation of endoderm and mesoderm. Differentiation events occurring concurrent with or subsequent to gastrulation were also suppressed in embryos derived from treated zygotes. These findings indicate that fertilization initiates a signaling cascade involving protein tyrosine kinase actitvity that is required specifically for events at gastrulation. This signaling event is required to complete the developmental program of both endoderm and mesoderm, but is different from those events necessary for initial specification of endodermal and mesodermal cell fate
The Cut-Homeodomain Transcriptional Activator HNF-6 Is Coexpressed with Its Target Gene HNF-3β in the Developing Murine Liver and Pancreas

AbstractMurine hepatocyte nuclear factor-3β (HNF-3β) protein is a member of a large family of developmentally regulated transcription factors that share homology in the winged helix/fork headDNA binding domain and that participate in embryonic pattern formation. HNF-3β also mediates cell-specific transcription of genes important for the function of hepatocytes, intestinal and bronchiolar epithelial, and pancreatic acinar cells. We have previously identified a liver-enriched transcription factor, HNF-6, which is required for HNF-3β promoter activity and also recognizes the regulatory region of numerous hepatocyte-specific genes. In this study we used the yeast one-hybrid system to isolate the HNF-6 cDNA, which encodes a cut-homeodomain-containing transcription factor that binds with the same specificity as the liver HNF-6 protein. Cotransfection assays demonstrate that HNF-6 activates expression of a reporter gene driven by the HNF-6 binding site from either the HNF-3β or transthyretin (TTR) promoter regions. We used interspecific backcross analysis to determine that murineHnf6gene is located in the middle of mouse chromosome 9.In situhybridization studies of staged specific embryos demonstrate that HNF-6 and its potential target gene, HNF-3β, are coexpressed in the pancreatic and hepatic diverticulum. More detailed analysis of HNF-6 and HNF-3β's developmental expression patterns provides evidence of colocalization in hepatocytes, intestinal epithelial, and in the pancreatic ductal epithelial and exocrine acinar cells. The expression patterns of these two transcription factors do not overlap in other endoderm-derived tissues or the neurotube. We also found that HNF-6 is also abundantly expressed in the dorsal root ganglia, the marginal layer, and the midbrain. At day 18 of gestation and in the adult pancreas, HNF-6 and HNF-3β transcripts colocalize in the exocrine acinar cells, but their expression patterns diverge in other pancreatic epithelium. HNF-6, but not HNF-3β, expression continues in the pancreatic ductal epithelium, whereas only HNF-3β becomes restricted to the endocrine cells of the islets of Langerhans. We discuss these expression patterns with respect to specification of hepatocytes and differentiation of the endocrine and exocrine pancreas
GDNF Induces Branching and Increased Cell Proliferation in the Ureter of the Mouse

AbstractThe secreted signaling molecule GDNF is expressed in the metanephric mesenchyme and has recently been implicated as a factor necessary for development of the metanephric kidney. We have examined the effects of GDNF on mouse kidney explants. We show that GDNF increases cell proliferation in ureter tips. There is an increase in the number of ureter tips and expansion and fusion of adjacent tips and some tips appear to grow toward the source of GDNF. These events are accompanied by transcriptional upregulation of several genes localized to the tips, including its own receptor,c-ret,the transcription factorSox9,and the signalWnt-11.These results support a model in which GDNF supplied by the mesenchyme regulates growth and branching in the metanephric kidney through the local regulation of ureter tip-specific factors
Early Postnatal Lethality inHoxa-5Mutant Mice Is Attributable to Respiratory Tract Defects

AbstractTo uncover roles for theHoxa-5gene during embryogenesis, we have focused on identifying structural and functional defects in organ systems underlying the perinatal lethality inHoxa-5homozygous mutants. Analysis of the mutant phenotype shows thatHoxa-5is essential for normal organogenesis and function of the respiratory tract. In homozygous newborn mutants, improper tracheal and lung morphogenesis can lead to tracheal occlusion, and to respiratory distress associated with a marked decrease in the production of surfactant proteins. Collectively, these defects likely underlie the pronounced mortality of homozygous mutant pups. Furthermore, the loss ofHoxa-5function results in alteredTTF-1, HNF-3β,and N-mycgene expression in the pulmonary epithelium. Since expression ofHoxa-5is confined to the mesenchymal component of the developing trachea and lung, the effects observed in epithelial cells may result from a disruption of normal epithelial–mesenchymal interactions
Embryonic and Uterine Expression Patterns of Peptidylglycine α-Amidating Monooxygenase Transcripts Suggest a Widespread Role for Amidated Peptides in Development

AbstractPosttranslational processing of peptide precursors frequently includes COOH-terminal amidation by the bifunctional enzyme peptidylglycine α-amidating monooxygenase (PAM). We examined the ontogeny of PAM gene expression usingin situhybridization and detected expression in the cardiogenic region beginning at embryonic day 9 (e9) and in decidualizing uterine endometrium and myometrial smooth muscle at even earlier postimplantation stages. PAM expression in the CNS at e10 was highest in the dorsal spinal cord and floor plate and exhibited complex patterning in several CNS regions, including the ventricular zone, over the next several days with PAM expression first detected in neurons at e13. High levels of PAM expression characterized several nonneural cell populations as well, including limb mesoderm and the mesenchyme immediately adjacent to nasal, maxillary, palatal, and dental epithelia during tissue fusion and remodeling. Since alternative splicing generates PAM transcripts encoding proproteins that are differentially localized and processed, we used probes that distinguish major subsets of PAM transcripts to determine that transcripts encoding integral membrane PAM isoforms predominate in most, if not all, PAM-expressing cell types throughout development. Further, transcripts that encode soluble and cleavable PAM isoforms are essentially absent from two CNS areas that are rich in transcripts encoding integral membrane, bifunctional PAM: the ependymal region of the spinal cord and the ventricular zone of the hippocampus. These results provide evidence for widespread expression and cell-type-specific alternative splicing of PAM during development and raise the possibility that region-specific amidation of PAM substrates contributes significantly to several developmental processes
Establishment of a BMP-4 Morphogen Gradient by Long-Range Inhibition

AbstractRecent work suggests that signaling molecules such as activin are capable of acting at long range to establish a morphogen gradient in the amphibian embryo and that responding cells activate different genes at distinct threshold levels of activin. Other signaling molecules like BMP-4 and Xnr-2 also exert concentration-dependent effects, but these factors appear to diffuse less freely. This raises the question of whether gradients of these inducing factors are indeed established, and if so, how they are generated. In this paper we demonstrate directly that BMP-4 elicits graded responses in gastrula-stage embryos. We then show that an effective BMP-4 gradient is established not by diffusion of BMP-4 protein but by the long-range effects of two BMP-4 inhibitors, noggin and chordin. This provides a novel mechanism for the establishment of a morphogen gradient in vertebrate embryos
Novel Segment Polarity Gene Interactions during Embryonic Head Development inDrosophila

AbstractIn the trunk of theDrosophilaembryo, the segment polarity genes are initially activated by the pair-rule genes, and later maintain each other's expression through a complex network of cross-regulatory interactions. These interactions, which are critical to cell fate specification, are similar in each of the trunk segments. To determine whether segment polarity gene expression is established differently outside the trunk, we studied the regulation of the geneshedgehog(hh),wingless(wg), andengrailed(en) in each of the segments of the developing head. We show that the cross-regulatory relationships among these genes, as well as their initial mode of activation, in the anterior head are significantly different from those in the trunk. In addition, each head segment exhibits a unique network of segment polarity gene interactions. We propose that these segment-specific interactions evolved to specify the high degree of structural diversity required for head morphogenesis
The Expression Patterns of Guidance Receptors, DCC and Neogenin, Are Spatially and Temporally Distinct throughout Mouse Embryogenesis

AbstractTo gain a better understanding of the role of DCC and Neogenin in neural and nonneural tissues during vertebrate development we have carried outin situhybridization studies to determine their expression patterns throughout the mid to late stages of mouse embryogenesis. This analysis revealed striking contrasts in both the spatial and temporal expression patterns of these closely related molecules. While DCC mRNA expression was predominately restricted to the developing central nervous system (CNS), Neogenin mRNA was detected in a broad spectrum of embryonic tissues. Outside the CNS, Neogenin expression was observed mainly in mesodermal derivatives such as organ primordia and cartilage condensations of many developing embryonic structures. Within the CNS, initiation of DCC expression correlated with the onset of neurogenesis and was maintained at high levels in all regions of the developing CNS actively undergoing neurogenesis. By E18.5, DCC expression was detected only in structures such as the olfactory bulb, the hippocampus, and the cerebellum, that are known to sustain active neurogenesis well into postnatal life. In contrast, Neogenin expression was weak in the early developing CNS but broadened and intensified as neurogenesis proceeded. In summary, these observations indicate that Neogenin is the predominant member of this subfamily in mesodermal tissues, while DCC and Neogenin may play complementary roles in the generation of the fully functional CNS
HNF-6 Is Expressed in Endoderm Derivatives and Nervous System of the Mouse Embryo and Participates to the Cross-Regulatory Network of Liver-Enriched Transcription Factors

AbstractHepatocyte nuclear factor-6 (HNF-6) is a liver-enriched transcription factor that contains a single cut domain and a novel type of homeodomain. Here we have studied the developmental expression pattern of HNF-6 in the mouse.In situhybridization experiments showed that HNF-6 mRNA is detected in the liver at embryonic day (E) 9, at the onset of liver differentiation. HNF-6 mRNA disappeared transiently from the liver between E12.5 and E15. In transfection experiments HNF-6 stimulated the expression of HNF-4 and of HNF-3β, two transcription factors known to be involved in liver development and differentiation. HNF-6 was detected in the pancreas from E10.5 onward, where it was restricted to the exocrine cells. HNF-6 was also detected in the developing nervous system. Both the brain and the spinal cord started to express HNF-6 at E9–9.5 in postmitotic neuroblasts. Later on, HNF-6 was restricted to brain nuclei, to the retina, to the ventral horn of the spinal cord, and to dorsal root ganglia. Our observations that HNF-6 contributes to the control of the expression of transcription factors and is expressed at early stages of liver, pancreas, and neuronal differentiation suggest that HNF-6 regulates several developmental programs
ARNT-Deficient Mice and Placental Differentiation

AbstractWe used homologous recombination in embryonic stem cells to generate mice heterozygous for an aryl hydrocarbon nuclear translocator (ARNT) null mutation. These mice were intercrossed, but no live homozygousArnt−/− knockout mice were produced among 64 newborns. Homozygotes diein uterobetween 9.5 and 10.5 days of gestation. Abnormalities included neural tube closure defects, forebrain hypoplasia, delayed rotation of the embryo, placental hemorrhaging, and visceral arch abnormalities. However, the primary cause of lethality appears to be failure of the embryonic component of the placenta to vascularize and form the labyrinthine spongiotrophoblast. This may be related to ARNT's known role in hypoxic induction of angiogenesis. We found no defects in yolk sac circulation
Faithful Expression of the Myf-5 Gene during Mouse Myogenesis Requires Distant Control Regions: A Transgene Approach Using Yeast Artificial Chromosomes

AbstractMyf-5, a member of the family of four muscle-specific basic helix–loop–helix (bHLH) transcription factors is the first to be expressed in somites, branchial arches, and limb buds during prenatal mouse development. However, little is known about control mechanisms which actually regulate Myf-5 gene activity within these various muscle-forming domains. To identify control regions that contribute to the correct spatiotemporal activity pattern of the Myf-5 gene during mouse embryogenesis, here we report the characterization of yeast artificial chromosomes (YACs) which faithfully direct muscle-specific expression of the gene in chimeric mouse embryos. Forty-five kilobases of sequence 5′ to the Myf-5 gene together with 500 kb of 3′ flanking DNA drives the correct Myf-5 expression in the mesenchyme of the visceral arches and in somites but not in the hypaxial muscles of limb buds. An additional 50 kb of DNA at the 5′ end is required to activate Myf-5 gene expression in developing limbs. These results demonstrate for the first time that unexpectedly distant regions of the Myf-5 gene are necessary to recapitulate its precise developmental expression pattern. We also show that Myf-5 expression in hypaxial muscles and in somites and visceral arches is regulated by separate and distinct far upstream regions. The identification of these remote regulatory elements on YACs carrying the mouse Myf-5 gene constitutes the first important step toward further dissection of the complex mechanisms by which cell-autonomous and external cues control Myf-5 expression during skeletal muscle formation in the mouse embryo
Mindin/F-spondin Family: Novel ECM Proteins Expressed in the Zebrafish Embryonic Axis

AbstractF-spondin is a secreted protein expressed at high levels by the floor plate cells. The C-terminal half of the protein contains six thrombospondin type 1 repeats, while the N-terminal half exhibited virtually no similarity to any other protein until recently, when aDrosophilagene termedM-spondinwas cloned; its product was found to share two conserved domains with the N-terminal half of F-spondin. We report the molecular cloning of four zebrafish genes encoding secreted proteins with these conserved domains. Two are zebrafish homologs ofF-spondin,while the other two, termedmindin1andmindin2,encode mutually related novel proteins, which are more related to theDrosophilaM-spondin than to F-spondin. During embryonic development, all four genes are expressed in the floor plate cells. In addition to the floor plate,mindin1is expressed in the hypochord cells, whilemindin2is expressed in the sclerotome cells. When ectopically expressed, Mindin proteins selectively accumulate in the basal lamina, suggesting that Mindins are extracellular matrix (ECM) proteins with high affinity to the basal lamina. We also report the spatial distribution of one of the F-spondin proteins, F-spondin2. F-spondin2 is localized to the thread-like structure in the central canal of the spinal cord, which is likely to correspond to Reissner's fiber known to be present in the vertebrate phylum. In summary, our study has defined a novel gene family of ECM molecules in the vertebrate, all of which may potentially be involved in development of the midline structure
Neuronal and Neuroendocrine Expression oflim3,a LIM Class Homeobox Gene, Is Altered in Mutant Zebrafish with Axial Signaling Defects

AbstractLIM class homeobox genes code for a family of transcriptional regulators that encode important determinants of cell lineage and cell type specificity. Thelim3gene from the zebrafish,Danio rerio,is highly conserved in sequence and expression pattern compared to its homologs in other vertebrates. In this paper we report immunocytochemical analysis of Lim3 protein expression in the pituitary, pineal, hindbrain, and spinal cord of the embryo, revealing an asymmetrical, lateral and late program of pituitary development in zebrafish, distinct from the pattern in other vertebrates. We studied Lim3 expression inno tail, floating head,andcyclopsmutant embryos, all of which have midline defects, with special reference to spinal cord differentiation where Lim3 marks mostly motoneurons.cyclopsembryos showed essentially normal Lim3 expression in the hindbrain and spinal cord despite the absence of the floor plate, whileno tailmutant embryos, which lack a differentiated notochord, displayed an excess of Lim3-expressing cells in a generally normal pattern. In contrast, Lim3-positive cells largely disappeared from the posterior spinal cord infloating headmutants, except in patches that correlated with remnants of apparent floor plate cells. These results support the view that either notochord or floor plate signaling can specify Lim3-positive motoneurons in the spinal cord
A 5.5-kb Enhancer Is both Necessary and Sufficient for Regulation ofWnt-1Transcriptionin Vivo

AbstractWnt-1encodes a secreted signaling molecule which is required for development of the midbrain and anterior hindbrain in the mouse.Wnt-1expression is initiated early in the development of the central nervous system in a region predicted to give rise to the midbrain. Later in developmentWnt-1expression is restricted to regions of the forebrain, midbrain, and spinal cord. Previous studies identified a 5.5-kb enhancer in theWnt-1locus which is sufficient to activate transcription of a reporter gene in a pattern very similar to that of the endogenousWnt-1gene. Here we have assessed if this enhancer is an important component of the endogenous regulatory sequences ofWnt-1by gene targeting and by testing if it is able to expressWnt-1in a pattern which is sufficient to rescue the phenotype of loss ofWnt-1.Our results show that the 5.5-kb enhancer is both necessary and sufficient forWnt-1expressionin vivo
A Study of the Potential of the Embryonic Rat Telencephalon to Generate Oligodendrocytes

AbstractA major question in neural development is whether each part of the telencephalon has an equal potential to generate each cell type. In this study, we address this question specifically in regard to the generation of oligodendrocytes. We cultured precursor cells from two different regions of the rat embryonic telencephalon—the ganglionic eminence and the anlage of the cerebral cortex—from different stages of development, and labeled the cells with a retroviral vector to follow their fate. We discovered that multipotential precursor cells from E13 ganglionic eminence have several orders of magnitude higher capacity to generate oligodendrocyte than the equivalent cells from E13 cerebral cortex. This failure of cortical precursor cells to generate oligodendrocytes at early developmental stages (E12–E13) could not be reversed by growth factors, permissive growth media, or a permissive striatal cell environment. A combination of striatal contact and plus specific growth factors, however, did induce the production of oligodendrocytes. We conclude that telencephalic precursor cells do have the potential to generate oligodendrocytes, but that this potential is significantly greater in striatal than cortical multipotential precursor cells
The Effects of Angiotensin II and Specific Angiotensin Receptor Blockers on Embryonic Cardiac Development and Looping Patterns

AbstractThe role of angiotensin II (Ang II) in the early embryonic development of the heart has not been examined. We have used RT–PCR to identify mRNA for angiotensinogen, angiotensin-converting enzyme, and the Ang II AT1 and AT2 receptors in embryonic day 10.25 Sprague–Dawley rats, and have used confocal microscopy to localize the AT1 receptor to the greater curvature of the developing ventricle in these animals at embryonic days (ED) 9.25 and 10.25. The antibodies used in immunolocalization studies did not distinguish between the AT1a and AT1b receptor subtypes. In whole embryo culture, Ang II added to the culture media resulted in increased ventricular growth and myocyte hypertrophy when treated embryos were compared to cultured littermate controls. Use of Losartan and PD123,319 to block the Ang II AT1 and AT2 receptors resulted in reduced ventricular development and cardiac dilation when compared to control and Ang II-treated embryos. Addition of Ang II and PD123,319 to the culture media also resulted in cardiac loop inversions which may be associated with disruption of normal myofibrillar development. These results clearly indicate an important role for Ang II in the early embryonic development of the heart