From the Program in Vascular Cell Engineering, Institute for Cell Engineering and the McKusick-Nathans Institute of Genetic Medicine (B.D.K., K.H., Z.C., S.B.-D., A.R., Z.Y., G.L.S.) and the Departments of Ophthalmology and Neuroscience (S.F.H., Y.O., P.A.C.), Johns Hopkins University School of Medicine, Baltimore, Md. (At 2003-11-28)