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(1/16085) Inhibition of in vitro enteric neuronal development by endothelin-3: mediation by endothelin B receptors.

The terminal colon is aganglionic in mice lacking endothelin-3 or its receptor, endothelin B. To analyze the effects of endothelin-3/endothelin B on the differentiation of enteric neurons, E11-13 mouse gut was dissociated, and positive and negative immunoselection with antibodies to p75(NTR )were used to isolate neural crest- and non-crest-derived cells. mRNA encoding endothelin B was present in both the crest-and non-crest-derived cells, but that encoding preproendothelin-3 was detected only in the non-crest-derived population. The crest- and non-crest-derived cells were exposed in vitro to endothelin-3, IRL 1620 (an endothelin B agonist), and/or BQ 788 (an endothelin B antagonist). Neurons and glia developed only in cultures of crest-derived cells, and did so even when endothelin-3 was absent and BQ 788 was present. Endothelin-3 inhibited neuronal development, an effect that was mimicked by IRL 1620 and blocked by BQ 788. Endothelin-3 failed to stimulate the incorporation of [3H]thymidine or bromodeoxyuridine. Smooth muscle development in non-crest-derived cell cultures was promoted by endothelin-3 and inhibited by BQ 788. In contrast, transcription of laminin alpha1, a smooth muscle-derived promoter of neuronal development, was inhibited by endothelin-3, but promoted by BQ 788. Neurons did not develop in explants of the terminal bowel of E12 ls/ls (endothelin-3-deficient) mice, but could be induced to do so by endothelin-3 if a source of neural precursors was present. We suggest that endothelin-3/endothelin B normally prevents the premature differentiation of crest-derived precursors migrating to and within the fetal bowel, enabling the precursor population to persist long enough to finish colonizing the bowel.  (+info)

(2/16085) A Wnt5a pathway underlies outgrowth of multiple structures in the vertebrate embryo.

Morphogenesis depends on the precise control of basic cellular processes such as cell proliferation and differentiation. Wnt5a may regulate these processes since it is expressed in a gradient at the caudal end of the growing embryo during gastrulation, and later in the distal-most aspect of several structures that extend from the body. A loss-of-function mutation of Wnt5a leads to an inability to extend the A-P axis due to a progressive reduction in the size of caudal structures. In the limbs, truncation of the proximal skeleton and absence of distal digits correlates with reduced proliferation of putative progenitor cells within the progress zone. However, expression of progress zone markers, and several genes implicated in distal outgrowth and patterning including Distalless, Hoxd and Fgf family members was not altered. Taken together with the outgrowth defects observed in the developing face, ears and genitals, our data indicates that Wnt5a regulates a pathway common to many structures whose development requires extension from the primary body axis. The reduced number of proliferating cells in both the progress zone and the primitive streak mesoderm suggests that one function of Wnt5a is to regulate the proliferation of progenitor cells.  (+info)

(3/16085) Retinoids are produced by glia in the lateral ganglionic eminence and regulate striatal neuron differentiation.

In order to identify molecular mechanisms involved in striatal development, we employed a subtraction cloning strategy to enrich for genes expressed in the lateral versus the medial ganglionic eminence. Using this approach, the homeobox gene Meis2 was found highly expressed in the lateral ganglionic eminence and developing striatum. Since Meis2 has recently been shown to be upregulated by retinoic acid in P19 EC cells (Oulad-Abdelghani, M., Chazaud, C., Bouillet, P., Sapin, V., Chambon, P. and Dolle, P. (1997) Dev. Dyn. 210, 173-183), we examined a potential role for retinoids in striatal development. Our results demonstrate that the lateral ganglionic eminence, unlike its medial counterpart or the adjacent cerebral cortex, is a localized source of retinoids. Interestingly, glia (likely radial glia) in the lateral ganglionic eminence appear to be a major source of retinoids. Thus, as lateral ganglionic eminence cells migrate along radial glial fibers into the developing striatum, retinoids from these glial cells could exert an effect on striatal neuron differentiation. Indeed, the treatment of lateral ganglionic eminence cells with retinoic acid or agonists for the retinoic acid receptors or retinoid X receptors, specifically enhances their striatal neuron characteristics. These findings, therefore, strongly support the notion that local retinoid signalling within the lateral ganglionic eminence regulates striatal neuron differentiation.  (+info)

(4/16085) Deletion analysis of the Drosophila Inscuteable protein reveals domains for cortical localization and asymmetric localization.

The Drosophila Inscuteable protein acts as a key regulator of asymmetric cell division during the development of the nervous system [1] [2]. In neuroblasts, Inscuteable localizes into an apical cortical crescent during late interphase and most of mitosis. During mitosis, Inscuteable is required for the correct apical-basal orientation of the mitotic spindle and for the asymmetric segregation of the proteins Numb [3] [4] [5], Prospero [5] [6] [7] and Miranda [8] [9] into the basal daughter cell. When Inscuteable is ectopically expressed in epidermal cells, which normally orient their mitotic spindle parallel to the embryo surface, these cells reorient their mitotic spindle and divide perpendicularly to the surface [1]. Like the Inscuteable protein, the inscuteable RNA is asymmetrically localized [10]. We show here that inscuteable RNA localization is not required for Inscuteable protein localization. We found that a central 364 amino acid domain - the Inscuteable asymmetry domain - was necessary and sufficient for Inscuteable localization and function. Within this domain, a separate 100 amino acid region was required for asymmetric localization along the cortex, whereas a 158 amino acid region directed localization to the cell cortex. The same 158 amino acid fragment could localize asymmetrically when coexpressed with the full-length protein, however, and could bind to Inscuteable in vitro, suggesting that this domain may be involved in the self-association of Inscuteable in vivo.  (+info)

(5/16085) JunB is essential for mammalian placentation.

Lack of JunB, an immediate early gene product and member of the AP-1 transcription factor family causes embryonic lethality between E8.5 and E10.0. Although mutant embryos are severely retarded in growth and development, cellular proliferation is apparently not impaired. Retardation and embryonic death are caused by the inability of JunB-deficient embryos to establish proper vascular interactions with the maternal circulation due to multiple defects in extra-embryonic tissues. The onset of the phenotypic defects correlates well with high expression of junB in wild-type extra-embryonic tissues. In trophoblasts, the lack of JunB causes a deregulation of proliferin, matrix metalloproteinase-9 (MMP-9) and urokinase plasminogen activator (uPA) gene expression, resulting in a defective neovascularization of the decidua. As a result of downregulation of the VEGF-receptor 1 (flt-1), blood vessels in the yolk sac mesoderm appeared dilated. Mutant embryos which escape these initial defects finally die from a non-vascularized placental labyrinth. Injection of junB-/- embryonic stem (ES) cells into tetraploid wild-type blastocysts resulted in a partial rescue, in which the ES cell-derived fetuses were no longer growth retarded and displayed a normal placental labyrinth. Therefore, JunB appears to be involved in multiple signaling pathways regulating genes involved in the establishment of a proper feto-maternal circulatory system.  (+info)

(6/16085) Cloning of a novel gene specifically expressed in clonal mouse chondroprogenitor-like EC cells, ATDC5.

We cloned a full-length cDNA encoding a novel mouse protein, A-C2, by differential display method using mouse embryonic fibroblast C3H10T1/2 cells and mouse chondroprogenitor-like EC cells, ATDC5. The deduced amino acid sequence of A-C2 consisted of 106 amino acids with no significant homology to the sequences previously reported. Northern blot analysis showed two major bands of 2.1 and 1.8 kb sizes. Expression of A-C2 mRNA was exclusive to ATDC5 cells at their undifferentiated stage. None of ATDC5 cells at their differentiated stage and adult mice tissues examined expressed A-C2 gene.  (+info)

(7/16085) Reciprocal control of T helper cell and dendritic cell differentiation.

It is not known whether subsets of dendritic cells provide different cytokine microenvironments that determine the differentiation of either type-1 T helper (TH1) or TH2 cells. Human monocyte (pDC1)-derived dendritic cells (DC1) were found to induce TH1 differentiation, whereas dendritic cells (DC2) derived from CD4+CD3-CD11c- plasmacytoid cells (pDC2) induced TH2 differentiation by use of a mechanism unaffected by interleukin-4 (IL-4) or IL-12. The TH2 cytokine IL-4 enhanced DC1 maturation and killed pDC2, an effect potentiated by IL-10 but blocked by CD40 ligand and interferon-gamma. Thus, a negative feedback loop from the mature T helper cells may selectively inhibit prolonged TH1 or TH2 responses by regulating survival of the appropriate dendritic cell subset.  (+info)

(8/16085) Endothelial cells modulate the proliferation of mural cell precursors via platelet-derived growth factor-BB and heterotypic cell contact.

Embryological data suggest that endothelial cells (ECs) direct the recruitment and differentiation of mural cell precursors. We have developed in vitro coculture systems to model some of these events and have shown that ECs direct the migration of undifferentiated mesenchymal cells (10T1/2 cells) and induce their differentiation toward a smooth muscle cell/pericyte lineage. The present study was undertaken to investigate cell proliferation in these cocultures. ECs and 10T1/2 cells were cocultured in an underagarose assay in the absence of contact. There was a 2-fold increase in bromodeoxyuridine labeling of 10T1/2 cells in response to ECs, which was completely inhibited by the inclusion of neutralizing antiserum against platelet-derived growth factor (PDGF)-B. Antisera against PDGF-A, basic fibroblast growth factor, or transforming growth factor (TGF)-beta had no effect on EC-stimulated 10T1/2 cell proliferation. EC proliferation was not influenced by coculture with 10T1/2 cells in the absence of contact. The cells were then cocultured so that contact was permitted. Double labeling and fluorescence-activated cell sorter analysis revealed that ECs and 10T1/2 cells were growth-inhibited by 43% and 47%, respectively. Conditioned media from contacting EC-10T1/2 cell cocultures inhibited the growth of both cell types by 61% and 48%, respectively. Although we have previously shown a role for TGF-beta in coculture-induced mural cell differentiation, growth inhibition resulting from contacting cocultures or conditioned media was not suppressed by the presence of neutralizing antiserum against TGF-beta. Furthermore, the decreased proliferation of 10T1/2 cells in the direct cocultures could not be attributed to downregulation of the PDGF-B in ECs or the PDGF receptor-beta in the 10T1/2 cells. Our data suggest that modulation of proliferation occurs during EC recruitment of mesenchymal cells and that heterotypic cell-cell contact and soluble factors play a role in growth control during vessel assembly.  (+info)