During previous studies investigating the formation of abdominal aortic aneurysms (AAA) induced by Ang II in ApoE−/− mice that had undergone irradiation and BMT to generate chimeric mice with different gene expression in BM-derived cells versus host cells, we observed that irradiation and BMT itself affects the degree of AAA development and rupture in ApoE−/− mice receiving ApoE−/− bone marrow. The gene discussed is APOE; the disease is abdominal aortic aneurysm.