MYH9 E1841K mutation augments proteinuria and podocyte injury and migration

Intronic variants of the MYH9 gene that encodes the nonmuscle myosin heavy chain IIA are associated with diabetic nephropathy in European Americans and with sickle cell disease–associated nephropathy. However, the causal functional variants of MYH9 have remained elusive. Rare missense mutations in MYH9 cause macrothrombocytopenia and are occasionally associated with development of nephropathy. The E1841K mutation is among the common MYH9 missense mutations and has been associated with nephropathy in some carriers. To determine the contribution of the E1841K mutation in kidney disease, we studied the effects of the E1841K mutation in mice subjected to high salt or angiotensin II (Ang II) as models of hypertension and in mice subjected to renal mass reduction as a model of CKD. Despite similar levels of BP among wild-type (MYH9^+/+) mice and mice heterozygous (MYH9^+/E1841K) and homozygous (MYH9^{E1841K/E1841K}) for the mutation in each model, MYH9^{E1841K/E1841K} mice exhibited mildly increased albuminuria in response to high salt; severe albuminuria, nephrinuria, FSGS, and podocyte foot effacement in Ang II–induced hypertension; and early mortality in the renal mass reduction model. Treatment with candesartan during Ang II–induced hypertension attenuated kidney disease development in MYH9^{E1841K/E1841K} mice. In vitro, isolated primary podocytes from MYH9^{E1841K/E1841K} mice exhibited increased lamellipodia formation and reorganization of F-actin stress fibers. Wound healing assays revealed that MYH9^+/+ podocytes had the lowest migration rate, followed by MYH9^+/E1841K then MYH9^{E1841K/E1841K} podocytes. In conclusion, the MYH9 E1841K variant alters podocyte cytoskeletal structure and renders podocytes more susceptible to injury after a damaging stimulus.