TGFB1 and focal segmental glomerulosclerosis: We first examined TGF‐β1 expression in ADR‐induced FSGS and found that a massive Smad3 activation (phosphorylation) was evidenced in the glomeruli of ADR‐induced nephropathy (Figure9a), which was blocked by podocyte‐specific Btg2 knockout (Figure 9a).