Troponin I is the ATPase inhibitory subunit of troponin in the thin filament regulatory complex. Involved in the development and maintenance of muscle and nervous system. May also be involved in the cytoskeletal apparatus. Binds to actin and tropomyosin. Exon 3 is either present or absent, exon 6 has 4 mutually exclusive forms (6a1, 6a2, 6b1 and 6b2) and C-terminal exons 9 and 10 are mutually exclusive. All isoforms are expressed in somatic muscle. Isoforms containing exon 6a1 (isoforms 1 and 2) are expressed in all muscles but highest expression is in abdominal muscle and splanchnic muscle of the gut. Isoforms containing exon 6b1 (isoforms 5, 6, 9 and 10) are highly expressed in the tergal depressor of trochanter (TDT) muscle. Isoforms containing exon 3 (isoform 9 and isoform 10) are expressed in adults. Isoforms containing exon 6a1 (isoforms 1 and 2) are expressed at all developmental stages. Isoforms containing exon 6a2 (isoforms 3 and 4) are weakly expressed in embryos and larvae and very weakly in adults. Isoforms containing exon 6b1 (isoforms 5, 6, 9 and 10) are weakly expressed in larva and increase during metamorphosis. Isoforms containing exon 6b2 (isoforms 7 and 8) are weakly expressed in embryos and larvae and at a higher level in adults. Belongs to the troponin I family.