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TNNI2 gene

troponin I2, fast skeletal type

Normal Function

The TNNI2 gene provides instructions for making one form of a protein called troponin I. The troponin I protein produced from the TNNI2 gene is found in skeletal muscles, which are the muscles used for movement. Troponin I is one of three proteins that make up the troponin complex in muscle cells. The troponin complex, along with calcium, helps regulate muscle tensing (contraction).

The troponin complex is part of a structure called the sarcomere, which is the basic unit of muscle contraction. Sarcomeres contain thick and thin filaments. The overlapping thick and thin filaments attach (bind) to each other and release, which allows the filaments to move relative to one another so that muscles can contract.

When calcium levels are low, the troponin complex blocks the binding between the thick and thin filaments that is needed for muscle contraction. An increase in calcium levels causes structural changes in the troponin complex, which exposes the binding sites and allows the thick and thin filaments to interact, leading to muscle contraction.

Health Conditions Related to Genetic Changes

Sheldon-Hall syndrome

At least eight TNNI2 gene mutations have been identified in people with Sheldon-Hall syndrome. This disorder affects muscle and skeletal development before birth and is characterized by joint deformities (contractures) that restrict movement in the hands and feet. Researchers suggest that the TNNI2 gene mutations that cause Sheldon-Hall syndrome may prevent the troponin complex from blocking thick and thin filament binding to control muscle contractions, resulting in the contractures and other muscle and skeletal abnormalities associated with Sheldon-Hall syndrome.

More About This Health Condition

Other Names for This Gene

  • AMCD2B
  • DA2B
  • FSSV
  • fsTnI
  • troponin I fast twitch 2
  • troponin I type 2 (skeletal, fast)
  • troponin I, fast skeletal muscle
  • troponin I, fast skeletal muscle isoform 1
  • troponin I, fast skeletal muscle isoform 2
  • troponin I, fast-twitch isoform
  • troponin I, fast-twitch skeletal muscle isoform
  • troponin I, skeletal, fast

Additional Information & Resources

Tests Listed in the Genetic Testing Registry

Scientific Articles on PubMed

Catalog of Genes and Diseases from OMIM

Gene and Variant Databases


  • Beck AE, McMillin MJ, Gildersleeve HI, Kezele PR, Shively KM, Carey JC, Regnier M, Bamshad MJ. Spectrum of mutations that cause distal arthrogryposis types 1 and 2B. Am J Med Genet A. 2013 Mar;161A(3):550-5. doi: 10.1002/ajmg.a.35809. Epub 2013 Feb 7. Citation on PubMed or Free article on PubMed Central
  • Drera B, Zoppi N, Barlati S, Colombi M. Recurrence of the p.R156X TNNI2 mutation in distal arthrogryposis type 2B. Clin Genet. 2006 Dec;70(6):532-4. doi: 10.1111/j.1399-0004.2006.00713.x. No abstract available. Citation on PubMed
  • Ochala J. Thin filament proteins mutations associated with skeletal myopathies: defective regulation of muscle contraction. J Mol Med (Berl). 2008 Nov;86(11):1197-204. doi: 10.1007/s00109-008-0380-9. Epub 2008 Jun 24. Citation on PubMed
  • Toydemir RM, Bamshad MJ. Sheldon-Hall syndrome. Orphanet J Rare Dis. 2009 Mar 23;4:11. doi: 10.1186/1750-1172-4-11. Citation on PubMed or Free article on PubMed Central

The information on this site should not be used as a substitute for professional medical care or advice. Contact a health care provider if you have questions about your health.