Two rat homologues of Drosophila achaete-scute specifically expressed in neuronal precursors

Abstract

IN vertebrates, the peripheral nervous system is embryologically derived from the neural crest¹. Although the earliest neural crest cells seem to be multipotent^2,3, the molecular mechanisms responsible for the restriction of these cells to different sublineages⁴ are not understood. We therefore searched for developmental control genes expressed in crest cells or their derivatives. One important class of regulatory molecules comprises proteins with common DNA-binding and dimerization domains, the basic helix–loop–helix (B-HLH) region⁵. Members of this family include MyoD (ref. 6), a mammalian myogenic determination molecule, and proteins encoded by genes of the achaete-scute complex^7–9 of Drosophila, which have an important role in neuronal determination¹⁰. From a sympathetic neuronal precursor cell line derived from the neural crest¹¹ we have now isolated two different mammalian genes that are homologous to genes of the achaete-scute complex. The sequence of the B-HLH-encoding region of these genes is more similar to that of the genes of the achaete-scute complex than it is to that of other, mammalian members of the B-HLH family. At least one of these genes is transiently expressed in the embryonic rat nervous system, is not detected in non-neuronal tissues or cell lines, and is induced by nerve growth factor in PC 12 cells.