[1] Med Univ S Carolina, Dept Pediat, Charles P Darby Childrens Res Inst, Charleston, SC 29425 USA
[2] Med Univ S Carolina, Dept Neurosci, Charles P Darby Childrens Res Inst, Charleston, SC 29425 USA
[3] Washington Univ, Sch Med, Dept Neurol, St Louis, MO 63110 USA
[4] Univ Alabama Birmingham, Dept Genet, Birmingham, AL USA