Two members of a family who suffered progressive hearing loss and then underwent heart transplants got Christine Seidman, a Harvard professor of medicine, interested in the strange connection.
Their hearing loss began early in life. It progressed for at least 10 years before they started to experience shortness of breath, chest pains, and other symptoms of congestive heart failure. This condition, in which heart muscles become too weak to pump enough blood to the lungs and heart, kills about 260,000 people a year.
However, the heart transplants received by these two people were successful and they are now living healthy lives.
Taking the novel connection to heart, Seidman and her colleagues set out to find the cause. Their studies of family members with the syndrome revealed that they shared a mutation in a gene called eya4.
“The importance of this discovery goes beyond finding the cause of an unusual human mutation,” Seidman notes. Many genes that cause heart failure have been found by her team and other investigators, but they code for individual tasks such as making a heart beat or building an ear bone. In contrast, eya4 takes part in regulation of a large repertoire of genes needed for normal heart function. Thus, “studying eya4 gives us a new tool to overview the whole of heart function,” Seidman says. “That’s the real excitement of this work.”
Seidman is intrigued about learning why a gene that has survived hundreds of million of years of evolution from fish to humans got involved in both hearing and heart beats. “The heart and ear don’t seem to have much in common,” she says. “But, if an efficient way to regulate gene expression evolves in an organ such as the ear, evolution might well want to conserve it and use it for other purposes in other tissues. A fuller understanding of what happens when a critical regulator like eya 4 doesn’t function normally can lead us to novel and creative ways to redress medical problems that involve both the heart and hearing.”