The discovery, published in Nature Communications, explains why not all people with the genetic mutation develop the disease—called autosomal dominant leukodystrophy (ADLD)—and has significant implications for diagnosis and genetic counseling. It also explains why the mutation only affects one type of cell, despite being expressed in most cells in the body.

“The function of gene silencers is only now being understood and, in this case, it is allowing us to tell some patients who previously would have been given a fatal prognosis that they will not die of a cruel and debilitating disease,” said senior author Quasar Padiath, M.B.B.S., Ph.D., professor and chair of Pitt Public Health’s Department of Human Genetics. “Our discovery also explains the mystery of why a gene duplication expressed in most cells of the body could result in a disease that only affects one type of cell.”