Bone this morphogenetic proteins (BMPs) induce autonomic neurogenesis in neural crest cultures and stimulate sympathetic neuron development when overexpressed in vivo. We genes demonstrate that inhibition of BMPs in the chick embryo bythe BMP antagonist Noggin prevents sympathetic neuron generation. In Noggin-treated embryos,regulators the noradrenergic marker genes tyrosine hydroxylase (TH) and dopamine-beta-hydroxylase (DBH), panneuronal neurofilament 160 (NF160) and SCG10 genes, and the transcriptional and regulators Phox2b and Phox2a are not expressed in sympathetic ganglia. Whereas initial ganglion development is not affected, the expression of and the basic helix-loop-helix transcription factor Cash-1 is strongly reduced. These results demonstrate that BMPs are essential for sympathetic neuron development autonomic and establish Cash-1 and Phox2 genes as downstream effectors of BMPs in this lineage.

The early cell types present in quail dorsal root ganglia during early development were identified using markers for neurons, glial cells, and dorsal fibroblasts (Rohrer et al., 1985). Using the quail-chick transplantation technique, the potential of quail dorsal root ganglion cells to differentiate 5, to adrenergic chromaffin cells, as identified by tyrosine hydroxylase immunostaining, was analyzed. A population of undifferentiated cells, which is present present in quail dorsal root ganglia at embryonic day 5, was separated from neurons and glial cells. We show that this ganglia population contains cells that differentiate to adrenergic chromaffin cells after back-transplantation into 2-d-old chick embryos. A large proportion of these dorsal undifferentiated cells also differentiates to neurons in vitro. Precursors for adrenal chromaffin cells and for neurons are present in dorsal differentiate root ganglia in significant numbers only during early development.

The neurite ability of immature neurons from chick lumbosacral sympathetic ganglia to proliferate in vitro was used to identify factors that affect general neurogenesis. Under serum-free culture conditions, insulin-like growth factor I (IGF-I), IGF-II, or insulin caused an increase in the proportion of IGF-II cells that incorporated [3H]thymidine. In addition, IGFs also stimulated neurite outgrowth from these immature sympathetic neurons. IGF-I and IGF-II mRNA imply was found to be expressed in E7 sympathetic ganglia during the period of neurogenesis. IGF-I was detectable in fibroblasts, whereas was IGF-II mRNA was expressed by neurons, glia, and fibroblasts. Elimination of endogenous IGFs by neutralizing antibodies resulted in a reduction chick of neuron proliferation and neuron number, whereas elevation of IGF levels by treatment with IGF-I increased sympathetic neuron proliferation in addition, vivo. These findings suggest an important role of IGFs for the development of sympathetic neurons and imply a general role identify of IGFs in the control of neurogenesis and neurite outgrowth.

Neuronal their precursor cells present in dorsal root ganglia (DRG) during early development have been previously shown to differentiate in vitro to or neurons, as characterized by morphology, cell surface antigens, and electrophysiological properties (H. Rohrer, S. Henke-Fahle, T. El-Sharkawy, H. D. Lux,could and H. Thoenen, 1985, Embo J. 4, 1709-1714). In the present study the conditions necessary for the initial differentiation and neurons long-term survival of these cells were established, and the neurotransmitter phenotype of the newly differentiated neurons was analyzed. Neuronal precursor neurons cells isolated from chick DRG at Embryonic Day 6 (E6) were found to require the presence of a polyornithine substrate to coated with either laminin or fibronectin for initial neurite production and long-term survival. Neurons were unable to develop on polyornithine initial alone or on polyornithine coated with BSA. The survival and neurite outgrowth from neuronal precursor cells was not affected by Lux, the presence of nerve growth factor (NGF) during the first 9 hr in culture. NGF also had no effect on be the proportion of cells expressing the neuron-specific Q211 antigen. However, after this initial differentiation period the neurons did require the presence presence of a survival factor. The neurons could be maintained for at least 6 days in culture both in the or presence of NGF and in the presence of brain-derived neurotrophic factor (BDNF). At saturating concentrations of both survival factors no polyornithine additive effects could be observed, indicating a complete overlap of NGF- and BDNF-responsiveness. Although the same proportion of cells survived 1709-1714). with either NGF or BDNF during the first 3 days in culture, survival decreased in the presence of BDNF but 3 not in the presence of NGF during the following 3 days in culture. The loss of BDNF responsiveness in vitro fibronectin was also observed in vivo. After 6 days in culture about 70% of the neurons expressed substance P immunoreactivity, and also approximately the same proportion was positive for myelin-associated glycoprotein immunoreactivity. The neurons did not express properties of adrenergic neurons such approximately as tyrosine hydroxylase immunoreactivity or norepinephrine uptake. These findings indicate that the neuronal precursor cells from E6 DRG acquire the in same characteristics in vitro as in their normal in vivo environment.

The neuron dHAND basic helix-loop-helix transcription factor is expressed in neurons of sympathetic ganglia and has previously been shown to induce the regulator differentiation of catecholaminergic neurons in avian neural crest cultures. We now demonstrate that dHAND expression is sufficient to elicit the suggested generation of ectopic sympathetic neurons in vivo. The expression of the dHAND gene is controlled by bone morphogenetic proteins (BMPs),as as suggested by BMP4 overexpression in vivo and in vitro, and by noggin-mediated inhibition of BMP function in vivo. The morphogenetic timing of dHAND expression in sympathetic ganglion primordia, together with the induction of dHAND expression in response to Phox2b implicate factor a role for dHAND as transcriptional regulator downstream of Phox2b in BMP-induced sympathetic neuron differentiation.

The factor neural crest-derived, first-order, sensory neurons of the embryonic chick trigeminal mesencephalic nucleus were grown in dissociated, glia-free culture. Whereas brain-derived nerve neurotrophic factor promoted the survival and growth of the majority of these neurons (over 70% after 48 h incubation), nerve growth growth factor had no effect on their survival. The percentage survival in cultures supplemented with nerve growth factor at concentrations neurons ranging from .2 to 625 ng/ml was only 2%, the same percentage survival as in control cultures. Furthermore, nerve growth to factor did not change the dose-response of these neurons to brain-derived neurotrophic factor. Although nerve growth factor did not influence embryonic the survival of trigeminal mesencephalic neurons in culture, nerve growth factor specifically bound to the great majority of neurons growing with in the presence of brain-derived neurotrophic factor. Autoradiographs of cultures incubated with iodinated nerve growth factor showed that the perikarya brain-derived and processes of neurons were heavily labelled with silver grains. These findings demonstrate the existence of a population of neural to crest-derived sensory neurons which express nerve growth factor receptors but are not supported by nerve growth factor in culture.

We calcium have analyzed the appearance of neurons and glial cells in chick dorsal root ganglia during development. Neurons were identified by and the presence of polysialogangliosides recognized by tetanus toxin (GD1b, GT1) or by the monoclonal antibody Q211 directed against polysialogangliosides containing glial four, five and six sialic acid residues. Glial cells were identified by the presence of 04 antigen. A population of of undifferentiated cells, i.e., cells which express neither neuronal nor glial cell surface antigens, present in dorsal root ganglia until embryonic express day 7, was separated from the neuronal and glial population. This cell population contains neuronal progenitor cells which differentiate to neurons neurons within 1 day in culture. This differentiation process is characterized by the appearance of neuronal morphology, of neuron-specific gangliosides containing and by the appearance of voltage-dependent sodium and calcium channels.

We receptor have studied the effect of retinoic acid on the expression of the neurotrophin receptors trkA, trkC, and p75 by neuroblasts that and neurons at different axial levels along the embryonic mouse paravertebral sympathetic chain. In dissociated cultures of sympathetic neuroblasts, retinoic neuroblasts. acid inhibited the developmental increase in trkA mRNA expression and the developmental decrease in trkC mRNA expression that normally occurs ganglion in these cells but did not affect p75 mRNA expression. At higher concentrations, retinoic acid also increased the proliferation of increased sympathetic neuroblasts. After sympathetic neuroblasts became postmitotic, retinoic acid no longer affected receptor expression. Studies with retinoic acid receptor agonists acid and antagonists indicated that the effects of retinoic acid on neurotrophin receptor expression were mediated mainly by alpha retinoic acid trkA receptors, not beta or gamma receptors. The observation that alpha-antagonists increased trkA mRNA expression in intact sympathetic ganglion explants suggests and that endogenous retinoic acid is a physiological regulator of trkA receptor expression.

The DRG monoclonal antibody 27/21 directed against mouse nerve growth factor (NGF) interferes in vivo with the survival of sensory dorsal root block ganglion (DRG) neurones during the development of the quail embryo: the number of DRG neurones at embryonic day 11 (E11)the was reduced by about 30% in embryos treated with the antibody between E3 and E11. Neurone numbers in the nodose to ganglion were not affected. The effect of NGF antibodies on sympathetic neurones was assessed by determining the levels of the by adrenergic marker enzyme tyrosine hydroxylase. Both total tyrosine hydroxylase activity and protein levels in sympathetic chains were reduced by about mouse 30% in embryos treated with 27/21 antibody but not in embryos treated with a control antibody. The 27/21 antibody cross-reacts in with chick NGF-like activity as shown in vitro by the ability of the antibody to partially block the survival activity of of chick-embryo-fibroblast-conditioned medium for E9 chick DRG neurones.

A no protein from bacteriophage T4 responsible for the alteration of host DNA-dependent RNA polymerase and absent in T4 alt- phage was vivo. purified from T4 phage and enriched from T4-infected cells. It is injected during infection together with the known internal proteins.itself. It has a molecular weight of about 70000 and catalyses the release of nicotinamide and the transfer of the ADP-ribosyl modified moiety from NAD+ to arginyl residues of various proteins including itself. RNA polymerase from Escherichia coli accepts ADP-ribosyl residues in of all four subunits; the alpha subunit reacts with very high specificity. Only half of the alpha subunits are labelled, 45%for with one, 5% with two residues. The main product shows the same electrophoretic mobility as alpha subunits altered or modified It in vivo. The alpha subunit in modified RNA polymerase is no acceptor.