FSGS is characterized by the presence of partial sclerosis of some but not all glomeruli. Studies of familial FSGS have been instrumental in identifying podocytes as critical elements in maintaining glomerular function, but underlying mutations have not been identified for all forms of this genetically heterogeneous condition. Here, exome sequencing in members of an index family with dominant FSGS revealed a nonconservative, disease-segregating variant in the PAX2 transcription factor gene. Sequencing in probands of a familial FSGS cohort revealed seven rare and private heterozygous single nucleotide substitutions (4% of individuals). Further sequencing revealed seven private missense variants (8%) in a cohort of individuals with congenital abnormalities of the kidney and urinary tract. As predicted by in silico structural modeling analyses, in vitro functional studies documented that several of the FSGS-associated PAX2 mutations perturb protein function by affecting proper binding to DNA and transactivation activity or by altering the interaction of PAX2 with repressor proteins, resulting in enhanced repressor activity. Thus, mutations in PAX2 may contribute to adult-onset FSGS in the absence of overt extrarenal manifestations. These results expand the phenotypic spectrum associated with PAX2 mutations, which have been shown to lead to congenital abnormalities of the kidney and urinary tract as part of papillorenal syndrome. Moreover, these results indicate PAX2 mutations can cause disease through haploinsufficiency and dominant negative effects, which could have implications for tailoring individualized drug therapy in the future.
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