MAPK8 and Hepatic fibrosis: Ask1 inhibition reduces kidney and liver fibrosis [42] Cdc42 and Rac1 mediate JNK activation in the context of polycystin overexpression in cells [12,14] and activate Mlk2 and Mlk3 [37,43,44] However, in our model, Ask1 deletion (S2A Fig) or double deletion of Mlk2 and Mlk3 (S2B Fig) did not reduce cystic burden in Pkd2 mutants.