Scientists have mapped and described the function of cells in six regions of the adult heart, providing a new foundation for studying heart disease. New research examines why some children born with heart defects also have developmental disabilities. HHMI researchers have designed an inhibitor that can reduce the expression of the mutated gene that causes hypertrophic cardiomyopathy, a potentially fatal heart condition.  New research shows that about 10 percent of severe cases of congenital heart disease are caused by genetic mutations that are absent in the parents of affected children. Defects in the gene that encodes the human body’s largest protein are responsible for more cases of dilated cardiomyopathy than are caused by all other known mutations associated with the heart disorder.