Eric Topol, a cardiologist and genetics researcher at the clinic, spent a year studying their DNA. Each person's genome has millions of individual variations, but Topol was looking for something distinctive. The mutation he and his team finally spotted-in a gene called MEF2A-produced a faulty protein. "We knew we had something," Topol says. "But the question was: How does this sick protein, present at birth, lead to heart attacks 50 years later in life?