Leigh syndrome associated with mitochondrial complex I deficiency due to a novel mutation in the NDUFS1 gene.

BACKGROUND Mutations in the nuclear-encoded subunits of complex I of the mitochondrial respiratory chain are a recognized cause of Leigh syndrome (LS). Recently, 6 mutations in the NDUFS1 gene were identified in 3 families. OBJECTIVE To describe a Spanish family with LS, complex I deficiency in muscle, and a novel mutation in the NDUFS1 gene. DESIGN Using molecular genetic approaches, we identified the underlying molecular defect in a patient with LS with a complex I defect. PATIENT The proband was a child who displayed the clinical features of LS. RESULTS Muscle biochemistry results showed a complex I defect of the mitochondrial respiratory chain. Sequencing analysis of the mitochondrial DNA-encoded ND genes, the nuclear DNA-encoded NDUFV1, NDUFS1, NDUFS2, NDUFS4, NDUFS6, NDUFS7, NDUFS8, and NDUFAB1 genes, and the complex I assembly factor CIA30 gene revealed a novel homozygous L231V mutation (c.691C-->G) in the NDUFS1 gene. The parents were heterozygous carriers of the L231V mutation. CONCLUSIONS Identifying nuclear mutations as a cause of respiratory chain disorders will enhance the possibility of prenatal diagnosis and help us understand how molecular defects can lead to complex I deficiency.