Positively regulates actin filament organization and provides mechanical stability to the myofibrils during body wall muscle contraction (PubMed:16597697). Required for the organization of sarcomeric actin filaments and myosin protein myo-3 in striated body wall muscle cells (PubMed:31411810). Not required for assembly of dense bodies, which are a type of integrin-based adhesion structure that link the plasma membrane to thin filaments of myofibrils, in body wall muscle (PubMed:31411810). Not required for the atn-1 protein to localize to the dense bodies (PubMed:31411810). Interacts (via Ig-like domains) with F-actin. Localizes to sarcomeres in a punctate pattern (PubMed:31411810). Localizes to actin filaments (thin filaments) close to dense bodies in body wall muscle (PubMed:16597697). Co-localizes with actin filaments in embryos and adults (PubMed:16453162, PubMed:31411810). Expressed in the pharyngeal, body wall, and anal depressor muscles (PubMed:16597697, PubMed:10669599, PubMed:16453162). Expression in these muscles is higher in hermaphrodites than in males (PubMed:10669599). Expressed in the vulva and the myoepithelial sheath of the proximal ovary (PubMed:16597697). Expressed in the proximal gonad of males (PubMed:10669599). Not expressed in the dense bodies of the obliquely striated body wall muscle (PubMed:16453162). First expressed in body wall muscle at the comma stage of embryonic development and co-localizes with actin at the early stage of myofibril assembly (PubMed:16597697). At the two-fold stage, it is expressed in body wall muscles and in the pharynx (PubMed:16597697). At the two-fold embryonic stage, assembles into continuously organized myofibrils (PubMed:31411810). Highly expressed in the body wall muscle and pharynx in three-fold stage embryos (PubMed:16597697, PubMed:31411810). In larvae, highly expressed in the pharyngeal, body wall, and anal depressor muscles (PubMed:10669599, PubMed:31411810). Lethal during the larval stage of development with body elongation defects (PubMed:31411810). L1 stage larvae have severely disorganized actin filaments in the striated body wall muscle whereby actin filaments and tropomyosin assemble into thicker and fewer disorganized bundles (PubMed:31411810). Furthermore, the sarcomeric organization of actin and myo-3 is disrupted in body wall muscle cells (PubMed:31411810). RNAi-mediated knockdown reduces the brood size and results in a defective body wall muscle contractility (PubMed:16597697). RNAi-mediated knockdown results in small round actin aggregates or unusual accumulations of actin in body wall muscle in 23% of animals (PubMed:16597697). Larger actin aggregates form more frequently at the cell periphery in 94% of animals in response to tetramisole, an agonist of acetylcholine receptors (PubMed:16597697). RNAi-mediated knockdown enhances the disorganization of the actin filaments and results in larger actin aggregates in an atn-1 ok84 mutant background (PubMed:16597697).