CLDN1 and focal segmental glomerulosclerosis: Previous studies reported reduced renal SIRT1 protein expression, especially in a model of diabetes, and these studies have examined the effect of proximal tubular SIRT1 and epigenetic regulation of claudin-1 in podocytes24,26,27 on diabetic kidney disease, but this interplay is still unclear in the context of nondiabetic FSGS, since tubular structures are not primarily affected in this condition.