Population genetics of chronic kidney disease: The evolving story of APOL1

Advances in human genome sequencing and generation of public databases of genomic diversity enable nephrologists to re-examine the genetics of common, complex kidney diseases. Non-diabetic kidney diseases prevalent in African ancestry populations and the allelic variation described in chromosome 22q12.3 is one such illustrative example. Newly available genomic database information enabled research groups to discover common functional DNA sequence risk variants in the APOL1 gene. These variants (termed G1 and G2) evolved to confer protection from a species of trypanosomal infection and thus achieved high prominence in many geographic regions of Africa and have been carried over to African diaspora communities worldwide. Since these discoveries two years ago, new insights have been gained: localization of APOL1 in normal and disease kidney tissues; influence of the APOL1 variants on the histopathology of HIV kidney disease; possible association with kidney transplant durability; onset of kidney failure at a younger age; association with blood lipid concentrations; more precise geographic localization of individuals with these variants to western and southern African ancestry; and the absence of the variants and kidney disease predisposition in Ethiopians. The definition of APOL1 nephropathy also confirms the long-held assumption by many clinicians that kidney disease attributed to hypertension in African populations represents an underlying glomerulopathy. Still awaited is the delineation of the biologic mechanisms of cellular injury related to these variants, to provide biologic proof of the APOL1 association and to provide potential targets for preventive and therapeutic intervention.