Novel mutations of the FRMD7 gene in X-linked congenital motor nystagmus.

PURPOSE Congenital motor nystagmus (CMN) is a relatively common oculomotor disorder characterized by bilateral uncontrollable ocular oscillations. Recently, the FRMD7 gene mutation has been identified as the genetic cause of CMN. The purpose of this study was to identify mutations of the FRMD7 gene in Chinese patients with CMN. METHODS Clinical data and genomic DNA of three Chinese CMN families were collected after informed consent. Genescan by two-point linkage analysis combined with haplotype analysis was performed and mutation screening of the FRMD7 gene was conducted by direct sequencing. RESULTS Maximum two-point LOD scores of 2.00, 1.76, and 1.16 at theta=0.00 were obtained with markers in proximity to the FRMD7 gene on chromosome Xp26 in the three CMN families. Mutation screening in the FRMD7 gene identified two novel missense mutations (c.781C>G and c.886G>C) and one reported nonsense mutation (c.1003C>T). These nucleotide alterations were not seen in unaffected members of the families or in 100 unrelated control subjects. CONCLUSIONS This study widens the mutation spectrum of the FRMD7 gene.