bluuebunny/crossref_metadata_2025_split huggingface dataset:
6B4 proteoglycan/phosphacan is a repulsive substratum but promotes morphological differentiation of cortical neurons
Authors: Maeda Nobuaki , Noda Masaharu 
Published: April 2021

ABSTRACT
6B4 proteoglycan/phosphacan is one of the major phosphate-buffered saline-soluble chondroitin sulfate proteoglycans of the brain. Recently, this molecule has been demonstrated to be an extracellular variant of the proteoglycan-type protein tyrosine phosphatase, PTPζ (RPTPβ). The influence of the 6B4 proteoglycan, adsorbed onto the substratum, on cell adhesion and neurite outgrowth was studied using dissociated neurons from the cerebral cortex and thalamus. 6B4 proteoglycan adsorbed onto plastic tissue culture dishes did not support neuronal cell adhesion, but rather exerted repulsive effects on cortical and thalamic neurons. When neurons were densely seeded on patterned substrata consisting of a grid-like structure of alternating poly-L-lysine and 6B4 proteoglycan-coated poly-L-lysine domains, they were concentrated on the polyL-lysine domains. However, 6B4 proteoglycan did not retard the differentiation of neurons but rather promoted neurite outgrowth and development of the dendrites of cortical neurons, when neurons were sparsely seeded on poly-L-lysine-conditioned coverslips continuously coated with 6B4 proteoglycan. This effect of 6B4 proteoglycan on the neurite extension of cortical neurons was apparent even on coverslips co-coated with fibronectin or tenascin. By contrast, the neurite extension of thalamic neurons was not modified by 6B4 proteoglycan. Chondroitinase ABC or keratanase digestion of 6B4 proteoglycan did not affect its neurite outgrowth promoting activity, but a polyclonal antibody against 6B4 proteoglycan completely suppressed this activity, suggesting that a protein moiety is responsible for the activity. 6B4 proteoglycan transiently promoted tyrosine phosphorylation of an 85×103Mr protein in the cortical neurons, which correlated with the induction of neurite outgrowth. These results suggest that 6B4 proteoglycan/phosphacan modulates morphogenesis and differentiation of neurons dependent on its spatiotemporal distribution and the cell types in the brain.
The role of targeted secretion in the establishment of cell polarity and the orientation of the division plane in Fucus zygotes
Authors: Shaw Sidney L. , Quatrano Ralph S. 
Published: April 2021

ABSTRACT
In this study, we investigate the role of polar secretion and the resulting asymmetry in the cell wall in establishing polarity in Fucus zygotes. We have utilized brefeldin-A to selectively interrupt secretion of Golgi-derived material into the cell wall as assayed by toluidine blue O staining of sulfated fucoidin. We show that the polar secretion of Golgi-derived material is targeted to a cortical site of the zygote identified by the localization of actin filaments and dihydropyridine receptors. The deposition of Golgi-derived material into the cell wall at this target site is temporally coincident with and required for polar axis fixation. We propose that local secretion of Golgi-derived material into the cell wall transforms the target site into the fixed site of polar growth. We also found that polar secretion of Golgiderived material at the fixed site is essential for growth and differentiation of the rhizoid, as well as for the proper positioning of the first plane of cell division. We propose that the resulting asymmetry in the cell wall serves as positional information for the underlying cortex to initiate these polar events. Our data supports the hypothesis that cell wall factors in embryos, previously shown to be responsible for induction of rhizoid cell differentiation, are deposited simultaneously with and are responsible for polar axis fixation. Furthermore, the pattern of polar growth is attributable to a positional signal at the fixed site and appears to be independent of the orientation of the first cell division plane. Thus, the establishment of zygotic cell polarity and not the position of the first division plane, is critical for the formation of the initial embryonic pattern in Fucus.
Cooperative interactions between paired domain and homeodomain
Authors: Jun Susie , Desplan Claude 
Published: April 2021

ABSTRACT
The Pax proteins are a family of transcriptional regulators involved in many developmental processes in all higher eukaryotes. They are characterized by the presence of a paired domain (PD), a bipartite DNA binding domain composed of two helix-turn-helix (HTH) motifs, the PAI and RED domains. The PD is also often associated with a homeodomain (HD) which is itself able to form homoand hetero-dimers on DNA. Many of these proteins therefore contain three HTH motifs each able to recognize DNA. However, all PDs recognize highly related DNA sequences, and most HDs also recognize almost identical sites. We show here that different Pax proteins use multiple combinations of their HTHs to recognize several types of target sites. For instance, the Drosophila Paired protein can bind, in vitro, exclusively through its PAI domain, or through a dimer of its HD, or through cooperative interaction between PAI domain and HD. However, prd function in vivo requires the synergistic action of both the PAI domain and the HD. Pax proteins with only a PD appear to require both PAI and RED domains, while a Pax-6 isoform and a new Pax protein, Lune, may rely on the RED domain and HD. We propose a model by which Pax proteins recognize different target genes in vivo through various combinations of their DNA binding domains, thus expanding their recognition repertoire.
Spatial regulation of a zebrafish patched homologue reflects the roles of sonic hedgehog and protein kinase A in neural tube and somite patterning
Authors: Concordet Jean-Paul , Lewis Katharine E. , Moore John W. , Goodrich Lisa V. , Johnson Ronald L. , Scott Matthew P. , Ingham Philip W. 
Published: April 2021

ABSTRACT
Signalling by members of the Hedgehog family of secreted proteins plays a central role in the development of vertebrate and invertebrate embryos. In Drosophila, transduction of the Hedgehog signal is intimately associated with the activity of protein kinase A and the product of the segment polarity gene patched. We have cloned a homologue of patched from the zebrafish Danio rerio and analysed the spatiotemporal regulation of its transcription during embryonic development in both wild-type and mutant animals. We find a striking correlation between the accumulation of patched1 transcripts and cells responding to sonic hedgehog activity both in the neurectoderm and mesoderm, suggesting that like its Drosophila counterpart, patched1 is regulated by sonic hedgehog activity. Consistent with this interpretation, mis-expression of sonic hedgehog results in ectopic activation of patched1 transcription. Using dominant negative and constitutively active forms of the protein kinase A subunits, we also show that expression of patched1 as well as of other sonic hedgehog targets, is regulated by protein kinase A activity. Taken together, our findings suggest that the mechanism of signalling by Hedgehog family proteins has been highly conserved during evolution.
Mammary gland morphogenesis is inhibited in transgenic mice that overexpress cell surface β1,4-galactosyltransferase
Authors: Hathaway Helen J. , Shur Barry D. 
Published: April 2021

ABSTRACT
Mammary gland morphogenesis is facilitated by a precise sequence of cell-cell and cell-matrix interactions, which are mediated in part through a variety of cell surface receptors and their ligands (Boudreau, N., Myers, C. and Bissell, M. J. (1995). Trends in Cell Biology 5, 1-4). Cell surface β1,4galactosyltransferase (GalTase) is one receptor that participates in a variety of cell-cell and cell-matrix interactions during fertilization and development, including mammary epithelial cell-matrix interactions (Barcellos-Hoff, M. H. (1992). Exp. Cell Res. 201, 225-234). To analyze GalTase function during mammary gland morphogenesis in vivo, we created transgenic animals that overexpress the long isoform of GalTase under the control of a heterologous promoter. As expected, mammary epithelial cells from transgenic animals had 2.3 times more GalTase activity on their cell surface than did wild-type cells. Homozygous transgenic females from multiple independent lines failed to lactate, whereas transgenic mice overexpressing the Golgi-localized short isoform of GalTase lactated normally. Glands from transgenic females overexpressing surface GalTase were characterized by abnormal and reduced ductal development with a concomitant reduction in alveolar expansion during pregnancy. The phenotype was not due to a defect in proliferation, since the mitotic index for transgenic and wild-type glands was similar. Morphological changes were accompanied by a dramatic reduction in the expression of milkspecific proteins. Immunohistochemical markers for epithelia and myoepithelia demonstrated that both cell types were present. To better understand how overexpression of surface GalTase impairs ductal morphogenesis, primary mammary epithelial cultures were established on basement membranes. Cultures derived from transgenic mammary glands were unable to form anastomosing networks of epithelial cells and failed to express milk-specific proteins, unlike wild-type mammary cultures that formed epithelial tubules and expressed milk proteins. Our results suggest that cell surface GalTase is an important mediator of mammary cell interaction with the extracellular matrix. Furthermore, perturbing surface GalTase levels inhibits the expression of mammary-specific gene products, implicating GalTase as a component of a receptor-mediated signal transduction pathway required for normal mammary gland differentiation.
Antagonizing cAMP-dependent protein kinase A in the dorsal CNS activates a conserved Sonic hedgehog signaling pathway
Authors: Epstein Douglas J. , Martí Elisa , Scott Matthew P. , McMahon Andrew P. 
Published: April 2021

ABSTRACT
Hedgehog (Hh) signaling plays a significant role in defining the polarity of a variety of tissue types along the anterior/posterior and dorsal/ventral axes in both vertebrate and invertebrate organisms. The pathway through which Hh transduces its signal is still obscure, however, recent data have implicated the cyclic AMP-dependent protein kinase A as a negative regulator of the Hh signal transduction pathway. One of the vertebrate Hh family members, Sonic hedgehog (Shh), can induce ventral neural cell types both in vivo and in vitro; high concentrations induce floor plate and lower concentrations motor neurons. To investigate whether PKA plays an active role in the suppression of ventral neural differentiation, we generated transgenic embryos expressing a dominant negative form of PKA (dnPKA) in primarily dorsal aspects of the mouse CNS. Similar to our earlier results with Shh, we observed the induction of floor plate and motor neuron markers in embryos expressing the dominant negative PKA transgene and the loss of dorsal gene expression at rostral levels. Thus suppression of PKA activity is sufficient to activate targets of the Shh signaling pathway in the vertebrate CNS suggesting that induction of ventral cell types occurs via the antagonistic action of Shh on PKA activity. Two mammalian target genes that are strongly expressed in ectopic dorsal locations in response to dnPKA are Ptc and Gli. As both of these are targets of Drosophila Hh signaling, our data point to an evolutionary conservation in both the mechanisms of signaling and the effectors of the signaling pathway.
Cadherins regulate aggregation of pancreatic β-cells in vivo
Authors: Dahl Ulf , Sjödin Anders , Semb Henrik 
Published: April 2021

ABSTRACT
It is thought that the cadherin protein family of cell adhesion molecules regulates morphogenetic events in multicellular organisms. In this study we have investigated the importance of β-cell cadherins for cell-cell interactions mediating the organization of endocrine cells into pancreatic islets of Langerhans. To interfere with endogenous cadherin activity in β-cells during pancreatic development, we overexpressed a dominant negative mutant of mouse Ecadherin, lacking nearly all extracellular amino acids, in pancreatic β-cells in transgenic mice. Expression of the truncated E-cadherin receptor displaced both Eand Ncadherin from pancreatic β-cells. As a result, the initial clustering of β-cells, which normally begins at 13.5–14.5 days postcoitum, was perturbed. Consequently, the clustering of endocrine cells into islets, which normally begins at 17.5-18 days postcoitum, was abrogated. Instead, transgenic β-cells were found dispersed in the tissue as individual cells, while α-cells selectively aggregated into islet-like clusters devoid of β-cells. Furthermore, expression of truncated E-cadherin in β-cells resulted in an accumulation of β-catenin in the cytoplasm. Thus, we have for the first time shown in vivo that cadherins regulate adhesive properties of β-cells which are essential for the aggregation of endocrine cells into islets.
Sequence and developmental expression of AmphiDll, an amphioxus Distalless gene transcribed in the ectoderm, epidermis and nervous system: insights into evolution of craniate forebrain and neural crest
Authors: Holland Nicholas D. , Panganiban Grace , Henyey Erika L. , Holland Linda Z. 
Published: April 2021

ABSTRACT
The dynamic expression patterns of the single amphioxus Distal-less homolog (AmphiDll) during development are consistent with successive roles of this gene in global regionalization of the ectoderm, establishment of the dorsoventral axis, specification of migratory epidermal cells early in neurulation and the specification of forebrain. Such a multiplicity of Distal-less functions probably represents an ancestral chordate condition and, during craniate evolution, when this gene diversified into a family of six or so members, the original functions evidently tended to be parcelled out among the descendant genes. In the amphioxus gastrula, AmphiDll is expressed throughout the animal hemisphere (presumptive ectoderm), but is soon downregulated dorsally (in the presumptive neural plate). During early neurulation, AmphiDll-expressing epidermal cells flanking the neural plate extend lamellipodia, appear to migrate over it and meet mid-dorsally. Midway in neurulation, cells near the anterior end of the neural plate begin expressing AmphiDll and, as neurulation terminates, these cells are incorporated into the dorsal part of the neural tube, which forms by a curling of the neural plate. This group of AmphiDll-expressing neural cells and a second group expressing the gene a little later and even more anteriorly in the neural tube demarcate a region that comprises the anterior three/fourths of the cerebral vesicle; this region of the amphioxus neural tube, as judged by neural expression domains of craniate Distal-less-related genes, is evidently homologous to the craniate forebrain. Our results suggest that craniates evolved from an amphioxus-like creature that had the beginnings of a forebrain and possibly a precursor of neural crest – namely, the cell population leading the epidermal overgrowth of the neural plate during early neurulation.
Disruption of gastrulation and oral-aboral ectoderm differentiation in the Lytechinus pictus embryo by a dominant/negative PDGF receptor
Authors: Ramachandran Ravi K. , Wikramanayake Athula H. , Uzman J. Akif , Govindarajan Venkatesh , Tomlinson Craig R. 
Published: April 2021

ABSTRACT
Little is known about the cell signaling involved in forming the body plan of the sea urchin embryo. Previous work suggested that PDGF-like and EGF-like receptor-mediated signaling pathways are involved in gastrulation and spicu-logenesis in the Lytechinus pictus embryo. Here we show that expression of the human PDGF receptor-β lacking the cytoplasmic domain disrupted development in a manner consistent with a dominant/negative mechanism. The truncated PDGF receptor-β inhibited gut and spicule formation and differentiation along the oral-aboral axis. The most severely affected embryos arrested at a develop-mental stage resembling mesenchyme blastula. Coinjection into eggs of RNA encoding the entire human PDGF receptor-β rescued development. The truncated PDGF receptor-β caused the aboral ectoderm-specific genes LpS1 and LpC2 to be repressed while an oral ectoderm-specific gene, Ecto-V, was expressed in all ectoderm cells. The results support the hypothesis that a PDGF-like signaling pathway plays a key role in the intercellular communica-tion required for gastrulation and spiculogenesis, and in cell commitment and differentiation along the oral-aboral axis.
Clonal dispersion and evidence for asymmetric cell division in ferret cortex
Authors: Reid Christopher B. , Tavazoie Sohail F. , Walsh Christopher A. 
Published: April 2021

ABSTRACT
Cell lineage analysis with retroviral libraries suggests that clonal progeny disperse widely in rodent cortex. To determine whether widespread dispersion is a general mammalian plan and to investigate phylogenetic differences in cortical development, we analyzed cell lineage in the ferret, a carnivore and near relative of the cat. The ferret possesses a highly developed, folded cerebral cortex, characteristic of higher mammalian species. Progenitor cells of the ferret cerebral cortex were tagged with an amphotropic retroviral library encoding alkaline phos-phatase, and sibling relationships were determined using the polymerase chain reaction. Neuronal clones were single neurons (52%) or large clones (48%; average, 7 neurons) containing neurons and glia in widespread cortical locations. Neuronal clones in the ferret labeled at middle to late neurogenesis (embryonic day 33-35) contained large numbers of neurons and showed little tendency to cluster. The large proportion of single neuron clones, contrasted with the large size of multicell clones, suggests that some progenitors divide asymmetrically, producing a postmitotic neuron and regenerating a multipotential cell.
Induction of cardiac myogenesis in avian pregastrula epiblast: the role of the hypoblast and activin
Authors: Yatskievych Tatiana A. , Ladd Andrea N. , Antin Parker B. 
Published: April 2021

ABSTRACT
An in vitro assay has been developed to investigate tissue interactions regulating myocardial cell specification in birds. Explants from the posterior region of stage XI-XIV blastulas were found to form heart muscle at high frequency with a timing that corresponded to onset of cardiac myocyte differentiation in vivo. Isolation and recombination experiments demonstrated that a signal from the hypoblast was required to induce cardiac myogenesis in the epiblast, and regional differences in epiblast responsiveness and hypoblast inductiveness restrict appearance of cardiac myocytes to the posterior region. Explantation studies provided evidence that myocardial cell specification is underway by stage 3, indicating that the hypoblast-derived signal occurs shortly before specification is detected. Recombinations were also performed to compare cardiac-inducing capacities of pregastrula hypoblast and stage 5 anterior lateral endoderm. The hypoblast possessed broad capacity to induce heart muscle cells in pregastrula and mid-gastrula epiblast, and modest ability to induce cardiac myogenesis in stage 4 posterior primitive streak. Stage 5 anterior lateral endoderm, in contrast, showed no ability to induce heart development in epiblast cells but was a potent inducer of cardiac myogenesis in cells from stage 4 posterior primitive streak. These findings suggest that the hypoblast-derived signal likely acts upstream of proposed heart-inducing signals provided by anterior lateral endoderm. Experiments were also performed to investigate whether activin, or an activin-like molecule, is involved in regulating cardiac myogenesis. Follistatin blocked cardiac myogenesis in stage XI-XIV posterior region explants and activin induced cardiac myogenesis in a dose-dependent fashion in posterior epiblast. These findings indicate that activin, or an activin-like molecule, is required for and is sufficient to stimulate cardiac myogenesis in posterior region pregastrula epiblast. Three models are presented to explain these results.
Genes that guide growth cones along the C. elegans ventral nerve cord
Authors: Wightman Bruce , Baran Renee , Garriga Gian 
Published: April 2021

ABSTRACT
During nervous system development, growth cone pioneering and fasciculation contribute to nerve bundle structure. Pioneer growth cones initially navigate along neuroglia to establish an axon scaffold that guides later extending growth cones. In C. elegans, the growth cone of the PVPR neuron pioneers the left ventral nerve cord bundle, providing a path for the embryonic extensions of the PVQL and AVKR growth cones. Later during larval development, the HSNL growth cone follows cues in the left ventral nerve cord bundle provided by the PVPR and PVQL axons. Here we show that mutations in the genes enu-1, fax-1, unc-3, unc-30, unc-42 and unc-115 disrupt pathfinding of growth cones along the left ventral nerve cord bundle. Our results indicate that unc-3 and unc-30 function in ventral nerve cord pioneering and that enu-1, fax-1, unc-42 and unc-115 function in recognition of the PVPR and PVQL axons by the AVKR and HSNL growth cones.
Mothers against dpp participates in a DPP/TGF-β responsive serine-threonine kinase signal transduction cascade
Authors: Newfeld Stuart J. , Mehra Arun , Singer Matthew A. , Wrana Jeffrey L. , Attisano Liliana , Gelbart William M. 
Published: April 2021

ABSTRACT
Mothers against dpp (Mad) is the prototype of a family of genes required for signaling by TGF-β related ligands. In Drosophila, Mad is specifically required in cells responding to Decapentaplegic (DPP) signals. We further specify the role of Mad in DPP-mediated signaling by utilizing tkvQ199D, an activated form of the DPP type I receptor serine-threonine kinase thick veins (tkv). In the embryonic midgut, tkvQ199D mimics DPP-mediated inductive interactions. Homozygous Mad mutations block signaling by tkvQ199D. Appropriate responses to signaling by tkvQ199D are restored by expression of MAD protein in DPP-target cells. Endogenous MAD is phosphorylated in a ligand-dependent manner in Drosophila cell culture. DPP overexpression in the embryonic midgut induces MAD nuclear accumulation; after withdrawal of the overexpressed DPP signal, MAD is detected only in the cytoplasm. However, in three different tissues and developmental stages actively responding to endogenous DPP, MAD protein is detected in the cytoplasm but not in the nucleus. From these observations, we discuss possible roles for MAD in a DPP-dependent serine-threonine kinase signal transduction cascade integral to the proper interpretation of DPP signals.