A duplication in the L1CAM gene associated with X-linked hydrocephalus

Recently, a mutation in the gene for the neural cell adhesion molecule L1CAM, located at chromosome Xq28, was found in a family with X-linked hydrocephalus (HSAS). However, as the L1CAM mutation could only be identified in one HSAS family, it remained unclear whether or not L1CAM was the gene responsible for HSAS. We have conducted a mutation analysis of L1CAM in 25 HSAS families. The mutation reported previously was not found in any of these families. In one family, however, a 1.3 kilobases (kb) genomic duplication was identified, cosegregating with HSAS and significantly changing the intracellular domain of the L1CAM protein. These results confirm that L1CAM is the HSAS gene.