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Largest human gene linked to cases of heart disease

20 February 2012
Appeared in BioNews 645

A mutation in the largest human gene causes 25 percent of a type of inherited heart disease, according to scientists in the USA. The information could be incorporated into current genetic tests to provide early diagnosis and clinical intervention.

The condition, known as familial dilated cardiomyopathy (DCM), causes the heart to become enlarged, losing the ability to pump blood efficiently, and can lead to heart failure by middle age.

Study co-leader Dr Jonathan Seidman of Harvard Medical School explained that the gene, called TTN, has been implicated in the disease before, but due to its large size it has been very difficult to sequence and analyse.

The TTN gene produces a protein called titin that acts as a scaffold for assembling contractile proteins in muscle cells and regulates the production of contractile force in heart muscle cells.

The study, published in the New England Journal of Medicine, screened the entire sequence of the TTN gene in 312 people with dilated cardiomyopathy, 231 with another form of heart disease and 249 without heart disease. This identified 72 mutations in the TTN gene, resulting in a shorter version of titin, which lacked regions important for regulating contraction in cardiac muscle cells.

'Early diagnosis of any disease, including DCM, can allow interventions that may prevent some of the devastating outcomes, such as sudden cardiac death from an arrhythmia or development of heart failure', said study co-leader Dr Christine Seidman of Brigham and Women's Hospital. 'By knowing that TTN mutations account for a substantial amount of idiopathic DCM, we now will have the opportunity for early diagnosis in lots of at-risk individuals, and any person who has a family member with idiopathic DCM'.

Dr Jonathan Seidman added that half of the DCM patients had a first degree relative with a TTN mutation and of these 95 percent had some sign of heart disease by age 40.

Dr Gordon Tomaselli, president of the American Heart Association and chief of cardiology at Johns Hopkins Medicine in Baltimore, said that the study is important for both researchers and patients. Currently, genetic tests are available that screen for the other known causes of cardiomyopathy. According to Dr Tomaselli we could expect to see TTN testing being added to current genetic screens within months.

Gene Mutation Linked to Heart Failure Discovered
Daily RX |  15 February 2012
Mutations in Gigantic Gene Responsible for Common Heart Muscle Disease
Health Canal |  16 February 2012
Study Finds Gene Behind Inherited Cases of Enlarged Heart
HealthDay News |  15 February 2012
Truncations of Titin Causing Dilated Cardiomyopathy
New England Journal of Medicine |  16 February 2012
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