Key calcium ion sensor involved in the Ca(2+)-triggered synaptic vesicle-plasma membrane fusion. Plays a role in the sarcolemma repair mechanism of both skeletal muscle and cardiomyocytes that permits rapid resealing of membranes disrupted by mechanical stress. Interacts with CAV3. Interacts with AHNAK; the interaction is direct and Ca(2+)-independent. Interacts with AHNAK2; the interaction is direct and Ca(2+)-independent (By similarity). Interacts with ANXA1; the interaction is Ca(2+)- and injury state-dependent. Interacts with ANXA2; the interaction is Ca(2+)- and injury state-dependent. Interacts with CACNA1S and PARVB. Interacts with TRIM72/MG53; interaction is required for transport to sites of cell injury during repair patch formation. Interacts with RIPOR2; this interaction occurs during early myogenic differentiation (By similarity). Colocalizes, during muscle differentiation, with BIN1 in the T-tubule system of myotubules and at the site of contact between two myotubes or a myoblast and a myotube (By similarity). Accumulates and colocalizes with fusion vesicles at the sarcolemma disruption sites. Wounding of myotubes led to its focal enrichment to the site of injury and to its relocalization in a Ca(2+)-dependent manner toward the plasma membrane (By similarity). Colocalizes with ANXA1 and ANXA2 at the sarcolemma in skeletal muscle. Colocalizes with PARVB at the sarcolemma of skeletal muscle (By similarity). Retained by caveolin at the plasmma membrane. Reaches the plasmma membrane through a caveolin-independent mechanism. Colocalizes, during muscle differentiation, with CACNA1S in the T-tubule system of myotubules. Detected on the apical plasma membrane of the syncytiotrophoblast (By similarity). Expressed in skeletal and cardiac muscles (at protein level). Expressed in skeletal muscle and heart. Also found in brain, liver and kidney. All seven C2 domains associate with lipid membranes in a calcium-dependent manner. Domains C2 1 and 3 have the highest affinity for calcium, the C2 domain 1 seems to be largely unstructured in the absence of bound ligands (By similarity). Defects in Dysf are the cause of a slowly progressive muscular dystrophy observed in SJL mice. It affects primarily the proximal muscles and it is inherited as autosomal recessive trait. Mice lacking Dysf maintain a functional dystrophin glycoprotein complex (DGC) but their muscle cells are defective in repairing the plasma membrane disruptions and accumulates vesicles at the sarcolemma. They develop a progressive muscular dystrophy and cardiomyopathy. Belongs to the ferlin family. The sequence differs significantly from amino acid position 1855.