1. From the Department of Neurology (S.E.R., A.R.F., J.D., C.W.), Washington University in St. Louis, MO; John Walton Muscular Dystrophy Research Centre (S.L., F.W., M.S., J.D.-M.), Newcastle University and Newcastle Hospitals NHS Foundation Trusts, United Kingdom; and Division of Biology and Biological Engineering (T.-F.C.), California Institute of Technology, Pasadena.