Specifically required for survival and integrity of the larval musculature: the maintenance of appropriate synaptic retrograde communication and the stabilization of muscle cell architecture or physiology. May play a role in anchoring the cytoskeleton to the plasma membrane. Component of the dystrophin associated protein complex (DAPC). Interacts with Dg, via the Dg WW domain binding sites. Expressed predominantly in all body wall muscle fibers during embryogenesis and in third instar larvae. Expression is also seen in the embryonic and larval ventral midline and larval brain. Flies exhibit muscle degeneration and lethality. Flies that have reduced expression of all isoforms (due to transgenic RNA interference targeting the common C-terminal region) exhibit severe muscle degeneration in larvae and adult flies. Muscles were either ruptured, absent or the fibers were detached from their attachment sites at tendon cells. These are necrotic, not apoptotic processes.