A NEW MUTATION OF THE L1CAM GENE IN AN X-LINKED HYDROCEPHALUS FAMILY

X-linked hydrocephalus is a genetic form of hydrocephalus that frequen tly occurs in males. It is characterized by ventricular dilatation, me ntal retardation, deformity of the thumb and spastic paraparesis. Rece ntly, 23 different mutations of the gene for the neural cell adhesion molecule, L1CAM, located at chromosome region Xq28, have been reported , 16 of which were detected in families with X-linked hydrocephalus, W e sequenced the coding region of the L1CAM gene of patients from two d ifferent families with X-linked hydrocephalus and found a novel mutati on at nucleotide residue 1963 in one family. This mutation from adenin e to guanine results in an amino acid change from lysine to glutamic a cid at residue 655 of the L1CAM protein, which belongs to the fibronec tin type III domain. We report another method for the rapid identifica tion of the mutation based on the polymerase chain reaction. This muta tion was not detected among 70 X chromosomes from a healthy population . Ours is the first report demonstrating this gene mutation in X-linke d hydrocephalus in an Asian population. Our findings further emphasize the evolving genotypic heterogeneity in X-linked hydrocephalus.