The role of p21 in tubular senescence in DKD is in agreement with previous observations: (i) the level and duration of p21 induction determine the onset of cellular growth arrest; (ii) p21 expression is sufficient to induce senescence; (iii) p21 expression restricted to tubular cells is sufficient to induce renal fibrosis following acute kidney injury36,37; and (iv) p21 induces endoreduplication38, which may impair renal tubular cell recovery following acute kidney injury39,40. The gene discussed is CDKN1A; the disease is diabetic kidney disease.