To assess the role of HIF activation in FH-associated renal cystic disease, we determined if parallel inactivation of Hif-1α or Hif-2α would ameliorate the hyperplastic renal cystic phenotype in mice with renal tubule specific inactivation of Fh1 (Pollard et al., 2007). The gene discussed is EPAS1; the disease is cystic kidney disease.