It has not been fully elucidated whether the DSL ligand source is vascular endothelial cells, vascular smooth muscle cells, or their common progenitor, angioblasts, although SM22-Cre-mediated smooth muscle cell-conditional Jag1 knockout resulted in more severe jaundice than VE-Cadherin-Cre-mediated endothelial cell-conditional Jag1 knockout [21]. The gene discussed is JAG1; the disease is Jaundice.