– Tropomyosin Alpha-3 Chain (TPM3) is a member of the Tropomyosin family. TPM3 exists as a heterodimer consisting of an alpha and a beta chain. TPM3 plays a central role in association with the Troponin complex and in the calcium dependent regulation of vertebrate striated muscle contraction. Defects in TPM3 are the cause of thyroid papillary carcinoma. Mutations in the TPM3 gene cause autosomal dominant nemaline myopathy, and oncogenes formed by chromosomal translocations involving this locus are linked with cancer.