'Broken' heart caused by genetic mutation

Washington, Feb 16 (ANI)): Scientists have found that gene mutations that shorten the largest human protein are behind idiopathic dilated cardiomyopathy (DCM), a familial heart disease.

For decades, researchers have sought a genetic explanation for DCM, a weakening and enlargement of the heart that puts million of people at risk of heart failure each year.

Because idiopathic DCM occurs as a familial disorder, researchers have long searched for genetic causes, but for most patients the etiology for their heart disease remained unknown.

Now, new work from the lab of Christine Seidman, a Howard Hughes Investigator and the Thomas W. Smith Professor of Medicine and Genetics at Harvard Medical School and Brigham and Women's Hospital, and Jonathan Seidman, the Henrietta B. and Frederick H. Bugher Foundation Professor of Genetics at Harvard Medical School, has found that mutations in the gene TTN account for 18 percent of sporadic and 25 percent of familial DCM.

"Until the development of modern DNA sequencing platforms, the enourmous size of the TTN gene prevented a comprehensive analyses - but now we know TTN is a major cause of DCM," said Christine.

DCM may cause shortness of breath, chest pain, and limited exercise capacity. DCM increases the risk of developing heart failure, for which no cure is available, and the risk of stroke and sudden cardiac death.

These findings will not only help patients understand the cause of their DCM symptoms, but also help to screen family members who might be at risk of developing the condition. Early identification of those at risk allows early intervention with medications that reduce workload on the heart and help prevent the changes in heart muscle, called remodeling, that lead to heart failure.

As DCM progresses, remodeling of the heart tissue makes the heart more prone to disturbances in the normal heart rhythm that can lead to stroke, heart attack and sudden death.

Using next generation sequencing tools that substantially reduce the cost per base (the TTN sequence contains 100,000 bases) by orders of magnitude over earlier standards, the Seidmans were able to perform comprehensive screening for TTN mutations for the first time. They analyzed TTN in 312 DCM patients, 231 HCM patients, and 249 individuals with no disease. Of the many mutations identified, 72 make titin, the largest human protein, shorter.

Called TTN truncating variants, these specific mutations appeared almost exclusively in patients with DCM.

"Our hypothesis is that any variant that shortens titin is going to cause DCM, which will lead to heart failure by the same mechanism," said Jonathan.

A better understanding of pathological mechanism may lead to better and more direct therapies for treatment and prevention of DCM.

The findings have been reported in the New England Journal of Medicine. (ANI)