Compound Heterozygous Missense and Deep Intronic Variants in NDUFAF6 Unraveled by Exome Sequencing and mRNA Analysis

Biallelic mutations in NDUFAF6 have been identified as responsible for cases of autosomal recessive Leigh syndrome associated with mitochondrial complex I deficiency. Here, we report two siblings and two unrelated subjects with Leigh syndrome, in which we found the same compound heterozygous missense (c.532G>C:p.A178P) and deep intronic (c.420+784C>T) variants in NDUFAF6. We demonstrated that the identified intronic variant creates an alternative splice site, leading to production of an aberrant transcript. A detailed analysis of whole exome sequencing data together with functional validation based on mRNA analysis may reveal pathogenic variants even in non-exonic regions.