Pattern formation during vulval development in C. elegans

A bipotential neuroendocrine precursor whose choice of cell fate is determined by NGF and glucocorticoids

Adrenal medullary endocrine (chromaffin) cells and sympathetic neurons both derive from the neural crest. We have found that the embryonic adrenal medulla and sympathetic ganglia are both initially populated by precursors expressing neural-specific genes. By birth, however, the medulla consists largely of chromaffin cells. In primary culture, the medullary precursors have three developmental fates: in NGF they continue to mature into neurons and survive, whereas in glucocorticoid they either extinguish their neuronal properties and exhibit an endocrine phenotype, or else continue to develop into neurons but then die. These data suggest that, in vivo, the adrenal medulla develops through both the glucocorticoid-induced differentiation of bipotential progenitors and the degeneration of committed neuronal precursors, which have migrated into the gland.

A gene involved in the development of the posterior body region of C. elegans

Many regional differences in Caenorhabditis elegans body pattern are generated after hatching. Here I describe a gene, mab-5, that is required for the postembryonic development of nearly all ectodermal and mesodermal features that normally characterize a posterior body region. In addition, this gene is necessary for most cell migrations toward the posterior, but not for cell migrations toward the anterior. mab-5+ activity is cell-autonomous. In animals carrying a mutation in the gene lin-22, increases or decreases in mab-5+ gene dosage produce corresponding increases or decreases in the size of the region in which cells adopt posterior-specific fates. The model that best explains the data is that during postembryonic development, posterior-specific patterns of cell differentiation and cell migration are initiated by graded positional information, and that a common step in the different cellular responses to this information is mediated by mab-5 activity.