The chromaffin cell and its development.

This article summarizes some of the recent progress in understanding the development of chromaffin cells. These cells are derivatives of the neural crest and are intimately associated with the sympathetic nervous system. Although a common sympathoadrenal (SA) progenitor cell for chromaffin cells and sympathetic neurons has been postulated, there is evidence to suggest that chromaffin progenitors are already distinct, at least in part, from neuronal SA progenitors prior to invading the adrenal gland. The concept of an essential role of glucocorticoid signalling for chromaffin cell development has been shaken by the observation that chromaffin cells in mice lacking the glucocorticoid receptor develop largely normal. Distinct developmental requirements of chromaffin cells and sympathetic neurons must also be assumed based on the analyses of mice carrying targeted mutations of the genes for two transcription factors, MASH1 and Phox2B. Both genes are expressed by SA progenitors, but are distinctly required for the development of chromaffin cells and sympathetic neurons. There is an ongoing search for molecules selectively operating at the sites, where chromaffin cells develop. Such molecules may be candidates for triggering the distinct developmental pathway of chromaffin cells, as opposed to sympathetic neurons.