Involved in myogenesis, in cooperation with transcription factors unc-120 and hnd-1 (PubMed:2175254, PubMed:15892873, PubMed:17142668). Acts redundantly with fozi-1 to promote body wall muscle cell and coelomocyte specification in postembryonic mesoderm progenitors, probably through suppression of sem-2 (PubMed:21307099). Efficient DNA binding requires dimerization with another bHLH protein. Body wall muscle cells; in clonal muscle precursors, in a set of early embryonic blastomeres (the ms-granddaughters), and in six glial-like cells called GLRS. RNAi-mediated knockdown results in a low frequency of embryonic lethality, with embryos arresting paralyzed at the two-fold stage; increases in frequency significantly on an hnd-1 or unc-120 mutant background (PubMed:15892873). Many embryos that survive to hatch become uncoordinated, dumpy larvae (PubMed:15892873). Double RNAi-mediated knockdown with sem-2 results in no sex myoblast production (PubMed:21307099).