Girls with Rett syndrome develop normally for about 18 months and then begin to regress.  Eventually, they have difficulty walking, speaking, and using their hands. With the help of affected girls and their families, Dr. Zoghbi and her collaborators found the gene responsible for this neurological disorder. The gene, called MECP2, encodes a protein essential to the normal functioning of nerve cells in the brain. Dr. Zoghbi discusses how identification of this gene should lead to better methods for diagnosing and treating Rett syndrome. From the Series:HHMI’s Understanding Biomedical Research Series