Mutations in the INF2 gene account for a significant proportion of familial but not sporadic focal and segmental glomerulosclerosis

Mutations in the inverted formin 2 gene (INF2) have recently been identified as the most common cause of autosomal dominant focal and segmental glomerulosclerosis (FSGS). In order to quantify the contribution of various genes contributing to FSGS, we sequenced INF2 where all mutations have previously been described (exons 2 to 5) in a total of 215 probands and 281 sporadic individuals with FSGS, along with other known genes accounting for autosomal dominant FSGS (ACTN4, TRPC6 and CD2AP) in 213 probands. Variants were classified as disease-causing if they altered the amino acid sequence, were not found in control samples, and in families segregated with disease. Mutations in INF2 were found in a total of 20 of the 215 families (including those previously reported) in our cohort of autosomal dominant familial nephrotic syndrome or FSGS, thereby explaining disease in 9 percent. INF2 mutations were found in 2 of 281 individuals with sporadic FSGS. In contrast, ACTN4 and TRPC6-related disease accounted for 3 and 2 percent of our familial cohort, respectively. INF2-related disease showed variable penetrance, with onset of disease ranging widely from childhood to adulthood and commonly leading to ESRD in the third and fourth decade of life. Thus, mutations in INF2 are more common, although still minor, monogenic cause of familial FSGS when compared to other known autosomal dominant genes associated with FSGS.