LDLR and coronary atherosclerosis: However, since apo E deficient mice are on the C57BL/6N background and LDLr deficient mice are on the C57BL/6J background, this mutation does not explain the presence of coronary atherosclerosis in C57BL/6N apo E−/− TAC mice and the absence of coronary atherosclerosis in C57BL/6J LDLr−/− TAC mice.