Scientists Uncover Trigger for Most Common Form of Intellectual Disability and Autism | Weill Cornell Newsroom | Weill Cornell Medical College

Scientists Uncover Trigger for Most Common Form of Intellectual Disability and Autism | Weill Cornell Newsroom | Weill Cornell Medical College: Fragile X syndrome occurs mostly in boys, causing intellectual disability as well as telltale physical, behavioral and emotional traits. While researchers have known for more than two decades that the culprit behind the disease is an unusual mutation characterized by the excess repetition of a particular segment of the genetic code, they weren't sure why the presence of a large number of these repetitions — 200 or more — sets the disease process in motion.

Using stem cells from donated human embryos that tested positive for fragile X syndrome, the scientists discovered that early on in fetal development, messenger RNA — a template for protein production — begins sticking itself onto the fragile X syndrome gene's DNA. This binding appears to gum up the gene, making it inactive and unable to produce a protein crucial to the transmission of signals between brain cells.