1. From the Institute of Human Genetics (H.M.P., V.H., J.D.P., B.C., D.J.H.), Newcastle University, Newcastle upon Tyne, UK; Medical Research Council Mammalian Genetics Unit (J.N.M.), Harwell, Oxon, UK; and Department of Molecular Genetics (K.K.), Institute of Biomedical Sciences, Fukushima Medical University School of Medicine, Fukushima, Japan.