Essential for myoblast fusion in developing embryos and pupae, and consequently is essential for muscle formation in adults (PubMed:17537424, PubMed:25797154). Required for progression past the pre-fusion complex stage of myoblast fusion (PubMed:17537424). In embryos, expressed in the muscle founder cells (FCs) and the fusion-competent myoblasts (FCMs) (PubMed:17537424). Expressed in myoblasts of stage 13 embryos (PubMed:17537424, PubMed:25797154). Expressed in the visceral mesoderm from stage 10 and the somatic mesoderm from stage 11, and expression persists until stage 13 (PubMed:17537424). By Mef2 during myoblast fusion in developing muscles of embryos and pupae. RNAi-mediated knockdown in pupae is adult lethal (PubMed:25797154). Pupae develop to the pharate adult stage and die before eclosion from the pupal case (PubMed:25797154). In pupae, fusion-competent myoblasts (FCMs) fail to fuse with the muscle founder templates (PubMed:25797154). Pharate adults display adherent muscle formation; only partially developed dorsal longitudinal muscles appear to be present but they are smaller and their nuclei are reduced in number and clustered together (PubMed:25797154). RNAi-mediated knockdown in embryos reduces myoblast fusion (PubMed:17537424). In RNAi pupae, there is no effect on myoblast proliferation, migration of the FCMs to the founder templates and initiation of myoblast fusion (PubMed:25797154). Named 'singles bar' based upon the accumulation of single myoblasts in mutant embryos.