Global molecular analysis and APOE mutations in a cohort of autosomal dominant hypercholesterolemia patients in France

Abstract

Autosomal dominant hypercholesterolemia (ADH) is a human disorder characterized phenotypically by isolated high-cholesterol levels. Mutations in the low density lipoprotein receptor ( LDLR ), APOB, and proprotein convertase subtilisin/kexin type 9 ( PCSK9 ) genes are well known to be associated with the disease. To characterize the genetic background associated with ADH in France, the three ADHassociated genes were sequenced in a cohort of 120 children and 109 adult patients. Fifty-one percent of the cohort had a possible deleterious variant in LDLR, 3.1% in APOB, and 1.7% in PCSK9. We identifi ed 18 new variants in LDLR and 2 in PCSK9. Three LDLR variants, including two newly identifi ed, were studied by minigene reporter assay confi rming the predicted effects on splicing. Additionally, as recently an in-frame deletion in the APOE gene was found to be linked to ADH, the sequencing of this latter gene was performed in patients without a deleterious variant in the three former genes. An APOE variant was identifi ed in three patients with isolated severe hypercholesterolemia giving a frequency of 1.3% in the cohort. Therefore, even though LDLR mutations are the major cause of ADH with a large mutation spectrum, APOE variants were found to be signifi-cantly associated with the disease. Furthermore, using structural analysis and modeling, the identifi ed APOE sequence changes were predicted to impact protein function.