Calcineurin is a calcium/calmodulin-dependent serine-threonine phosphatase that plays an important role in transducing calcium-dependent signals in a variety of cell types.

Calsarcin-1 encodes a 263-amino acid protein, which shows the highest sequence homology with calsarcin-2 in the N and C termini. Northern blot analysis of human tissues revealed a highly striated muscle-specific expression pattern of both genes. Calsarcins 1 and 2 are expressed in developing cardiac and skeletal muscle during embryogenesis, but calsarcin-1 is expressed specifically in adult cardiac and slow-twitch skeletal muscle as 1.6- and 2.6-kb transcripts, whereas calsarcin-2 is expressed only in fast skeletal muscle as a 1.6-kb transcript.