Identification of Three Novel Mutations in the FRMD7 Gene for X-linked Idiopathic Congenital Nystagmus

Idiopathic congenital nystagmus (ICN) consists of involuntary and periodic ocular motility, often with seriously reduced visual acuity. To identify the genetic defects associated with X-linked ICN, we performed PCR-based DNA direct sequencing of two candidate genes, FRMD7 and GPR143, in four families. Mutation analysis led to identification of three novel mutations, p.S260R, p.Q487X, and p.V549Y fsX554, in FRMD7 in three of the recruited families. Results from structural modeling indicated that the p.S260R may potentially disrupt FRMD7 function through loss of a phosphorylation site and/or interference with protein-protein interactions. Both p.Q487X, and p.V549Y fsX554 mutations were predicted to generate nonfunctional truncated proteins. Using a capture next generation sequencing method, we excluded CASK as the responsible gene for the remaining family. Combining sequence analysis and structural modeling, we report three novel mutations in FRMD7 in three independent families with XLICN, and provide molecular insights for future XLICN diagnosis and treatment.