HIF1A and ischemia: Hif1α−/− mice are embryonically lethal whereas Hif1α heterozygotes (Hif1α+/−), although viable, are defective in expressing the angiogenic factor vascular endothelial growth factor (VEGF) and fail to induce adaptive arteriogenesis in the mouse hindlimb ischemia model (Bosch-Marce et al., 2007).