Muscle-specific filamin, which plays a central role in sarcomere assembly and organization (PubMed:34405687). Critical for normal myogenesis, it probably functions as a large actin-cross-linking protein with structural functions at the Z lines in muscle cells. May be involved in reorganizing the actin cytoskeleton in response to signaling events (By similarity). {ECO:0000250|UniProtKB:Q8VHX6, ECO:0000269|PubMed:34405687}. This is the function of ENSG00000128591 (FLNC, filamin C).