Researchers first linked DDX3X to autism in 2014, and to intellectual disability the following year. The gene is located on the X chromosome, so mutations primarily affect girls; most boys with mutations in the gene are thought to die in utero.

Up to 3 percent of girls with unexplained intellectual disability have a mutation in DDX3X. About half of them are also likely to have autism, says co-lead investigator Elliott Sherr, professor of neurology at University of California, San Francisco. Read more here: Newly identified mutations clarify gene's link to autism, intellectual disability