Probable transcription factor required for muscle structure (PubMed:12808046, PubMed:7348600). Its dual subcellular localization suggests that it may function both as a muscle adhesion complex protein and as a transcription factor, or work together with transcription factors, to influence gene expression (PubMed:12808046). Thought to act as a molecular bridge between unc-97 and myo-3 at the M-line of muscles, possibly in a signaling role (PubMed:17158957). Plays a role in the formation of muscle connections, also called muscle arm extensions, between the body wall and the motor axons in the dorsal and ventral cord (PubMed:27123983). Interacts with hum-6, mep-1, myo-3, unc-96 and unc-97/PINCH. Localized in body wall muscle M-lines, dense bodies and muscle nuclei. Expressed in embryos from 1.5- to 2-fold stage in myofibrils. In larvae and adults, it is expressed in body wall muscle, and in addition, anal depressor muscle and vulval muscles. More specifically it is found in the thick filaments of muscle fibers. The N-terminal part (1-106) mediates the nuclear localization, while the fourth zinc finger is required for the localization to M-lines and dense bodies. Disorganised A and I bands in body-wall muscle structure (PubMed:7348600). Defective extension of body wall muscle connections or arms towards the ventral nerve cord (PubMed:27123983). Double knockout with madd-3 results in severe muscle arm extension defects (PubMed:27123983).