May be involved in the trafficking and exocytosis of secretory vesicles in non-neuronal tissues. Homodimer. Isoform 1 and isoform 2 are expressed in heart, lung, skeletal muscle and testis; not detected in brain, liver and kidney. Isoform 1 is expressed in spleen. Detected from 7 dpc. Neither C2 domains mediates Ca(2+)-dependent or Ca(2+)-independent phospholipid binding. May be due to intron retention. Belongs to the synaptotagmin family.