A C. elegans E/Daughterless bHLH protein marks neuronal but not striated muscle development.

The E proteins of mammals, and the related Daughterless (DA) protein of Drosophila, are ubiquitously expressed helix-loop-helix (HLH) transcription factors that play a role in many developmental processes. We report here the characterization of a related C. elegans protein, CeE/DA, which has a dynamic and restricted distribution during development. CeE/DA is present embryonically in neuronal precursors, some of which are marked by promoter activity of a newly described Achaete-scute-like gene hlh-3. In contrast, we have been unable to detect CeE/DA in CeMyoD-positive striated muscle cells. In vitro gel mobility shift analysis detects dimerization of CeE/DA with HLH-3 while efficient interaction of CeE/DA with CeMyoD is not seen. These studies suggest multiple roles for CeE/DA in C. elegans development and provide evidence that both common and alternative strategies have evolved for the use of related HLH proteins in controlling cell fates in different species.