The expression of dopamine beta-hydroxylase, tyrosine hydroxylase, and Phox2 transcription factors in sympathetic neurons: evidence for common regulation during noradrenergic induction and diverging regulation later in development

During differentiation of sympathetic neurons in chick embryos, tyrosine hy droxylase (TH) and dopamine beta-hydroxylase (DBH) mRNAs become detectable during the same developmental period and are both induced by BMP 4. Later d uring sympathetic ganglion development, DBH is detectable in TH-positive an d -negative cells. Moreover, BMPs reduce DBH mRNA in cultures of sympatheti c neurons while leaving TH unaffected. The data provide evidence for a comm on regulation of TH and DBH early during sympathetic neuron differentiation and indicate that BMPs promote their initial expression but not the mainte nance during later development. The time course of Phox2a and 2b expression suggests an evolutionary conserved role in noradrenergic induction. In add ition, Phox2a, Phox2b, and c-ret may be involved in the differentiation of cholinergic sympathetic neurons. (C) 2000 Elsevier Science Ireland Ltd. All rights reserved.