Extrinsic signals in the developing nervous system: the role of neurokines during neurogenesis.
ABSTRACT Vertebrate neurogenesis involves many distinct differentiation stages that are regulated by extrinsic signals. Survival and differentiation effects on cultured neurons of several lineages are elicited by members of the neurokine family of growth factors, ciliary neurotrophic factor (CNTF) and the related avian factor, growth promoting activity (GPA). The selective actions of these factors are mediated through the activation of heteromeric receptor complexes and depend on the presence of the ligand-binding receptor subunits CNTFR alpha and GPAR alpha. The in vivo localization of CNTFR alpha and GPAR alpha is consistent with the previously assigned biological functions but also suggest novel functions for these receptors and their ligands during neurogenesis.
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ABSTRACT: Cholinergic properties in chick sympathetic neurons are detectable early during development of paravertebral ganglia and mature after target contact. The cholinergic marker choline acetyltransferase (ChAT) is first detectable at embryonic day 6 and its expression partly overlaps with that of the noradrenergic marker tyrosine hydroxylase (TH). At late embryonic stages, when sympathetic neurons have established target contact, ganglia consist of two major neuronal populations, TH-positive noradrenergic neurons and cholinergic neurons that at this stage express vasoactive intestinal peptide (VIP) in addition to ChAT. The maturation of sympathetic neurons is paralleled by changes in their response to the neurokine ciliary neurotrophic factor (CNTF). These findings suggest that expression of neurotransmitter properties is controlled differentially before and during target innervation.Mechanisms of Development 12/1997; 68(1-2):115-26. DOI:10.1016/S0925-4773(97)00135-4 · 2.24 Impact Factor
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ABSTRACT: In central neurons, glycine most commonly exerts inhibitory actions (Aprison, 1990). Nevertheless, recent reports have indicated that glycine may also cause neuronal depolarization (e.g. Reichling et al. 1994), particularly in developing neurons (Wang et al. 1994). In line with this idea, glycine has been found to elicit noradrenaline release from rat hippocampus in vitro (e.g. Schmidt & Taylor, 1990). In our cultures of chick sympathetic neurons, glycine also caused depolarization and transmitter release, at least in a subset (∼65%) of neurons. This was evidenced threefold: (i) glycine occasionally evoked spike-like currents that were abolished by the nicotinic blocking agent hexamethonium, suggesting synaptic release of endogenous acetylcholine (see O'Lague et al. 1974); (ii) glycine triggered Ca2+-dependent and TTX-sensitive [3H]noradrenaline release, which shows that glycine may depolarize the neurons to an extent sufficient to trigger Na+-carried action potentials (see Boehm & Huck, 1997); (iii) glycine raised intracellular Ca2+ concentrations as evidenced by increases in the ratio F340/F380 of the fura-2 fluorescence signal (Grynkiewicz et al. 1985), but only in 65% of the neurons. The observation that intracellular Ca2+ concentrations changed in only a proportion of the cultured sympathetic neurons indicates that the neuronal population is heterogeneous; this might relate to differences in either glycine receptor expression or Cl− equilibrium potentials. It remains to be shown whether this heterogeneity reflects neuronal subpopulations that can be distinguished in sympathetic ganglia (Heller, Ernsberger & Rohrer, 1996).The Journal of Physiology 11/1997; 504 ( Pt 3)(3):683-94. DOI:10.1111/j.1469-7793.1997.683bd.x · 4.54 Impact Factor
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ABSTRACT: The Dan gene was first identified as the putative rat tumor suppressor gene and encodes a protein structurally related to Cerberus and Gremlin in vertebrates. Xenopus DAN, as with Cerberus and Gremlin, was demonstrated to block bone morphogenetic protein (BMP) signaling by binding BMPs, and to be capable of inducing additional anterior structures by ectopic overexpression in Xenopus embryos. DAN, thus, is suggested to play pivotal roles in early patterning and subsequent organ development, as in the case of other BMP antagonists. In this report, we isolated the chicken counterpart of Dan. Chicken Dan is mainly expressed in the cephalic and somitic mesoderm and several placodes during organ development.Mechanisms of Development 01/2002; 109(2):363-5. DOI:10.1016/S0925-4773(01)00522-6 · 2.24 Impact Factor