An eQTL analysis between DBA/2J and AKR/J mice strains on the ApoE null background was done in bone marrow derived macrophages and endothelial cells to identify modifier genes that affect atherosclerosis susceptibility. Overall design: DBA/2J mice were crossed with AKR/J mice and their offspring crossed with each other to yield an F2 generation. Bone marrow derived macrophages were cultured and gene expression quantified using Illumina's MouseRef-8 v2 arrays in 170 F2 mice for an eQTL study. In addition primary endothelial cells derived from the aorta of 48 male F2 mice were also assayed using arrays for eQTL mapping. Lesion area in the aortic root was also quantified in these samples.