Confirmation of Ath26 locus on chromosome 17 and identification of Cyp4f13 as an atherosclerosis modifying gene

Abstract

Background and aims: We previously demonstrated that Apoe^-/- mice on DBA/2 vs. AKR genetic background have >10-fold larger atherosclerotic lesions. Prior quantitative trait locus mapping via strain intercrossing identified a region on chromosome 17, Ath26, as the strongest atherosclerosis-modifying locus. We aimed to confirm Ath26, identify candidate genes, and validate the candidate gene effects on atherosclerosis.

Methods: We bred chromosome 17 interval congenic mice to confirm that Ath26 locus contains atherosclerosis modifying gene(s). Bone marrow derived macrophage transcriptomics was performed to identify candidate genes at this locus whose expression was correlated with lesions in a strain intercross. The Cyp4f13 candidate gene was tested via a gene knockout approach and in vivo and ex vivo phenotype analyses.

Results: A congenic mouse strain containing the DBA/2 interval on chromosome 17 on the AKR Apoe^-/- background demonstrated that this interval conferred increased lesion area. Transcriptomic analysis of bone marrow macrophages identified that expression of the Cyp4f13 gene, mapping to this locus, was highly associated with lesion area in an F2 cohort. AKR vs. DBA/2 macrophages had less Cyp4f13 mRNA expression, and their livers had lower leukotriene B4 (LTB4) 20-hydroxylase enzymatic activity. A Cyp4f13 knockout allele was bred onto the DBA/2 Apoe^-/- background and this conferred less enzymatic activity, decreased macrophage migration in response to LTB4, and smaller aortic root atherosclerotic lesions.

Conclusions: Allelic differences in the Cyp4f13 gene may in part be responsible for the Ath26 QTL conferring larger lesions in DBA/2 vs. AKR Apoe^-/- mice.

Keywords: Atherosclerosis; Cytochrome P-450 enzyme system; Inflammation; Leukotriene B4.