Although the genetic polymorphisms which create strain-specific variations in collateral numbers are unknown, vascular endothelial growth factor (VEGF), A disintegrin and metalloprotease Family Members (ADAM) 10 and 17 as well as chloride intracellular channel (Clic4) have been shown to regulate collateral density and diameter during development as well as remodeling after ischemia [9, 18–20]. The gene discussed is VEGFA; the disease is ischemia.