Rare Brain Disorders Program, Department of Neurology (G.K., Q.M., G.A., V.J., A.D., L.B.G., J.M.P.), Department of Biochemistry (H.C., B.P.), Department of Pathology (J.Y.P.), Department of Physiology (J.M.P.), Department of Pediatrics (J.M.P.), and Eugene McDermott Center for Human Growth & Development/Center for Human Genetics (J.Y.P., J.M.P.), University of Texas Southwestern Medical Center, Dallas, Texas.