Common genetic variants do not associate with CAD in familial hypercholesterolemia

In recent years, multiple loci dispersed on the genome have been shown to be associated with coronary artery disease (CAD). We investigated whether these common genetic variants also hold value for CAD prediction in a large cohort of patients with familial hypercholesterolemia (FH). We genotyped a total of 41 single-nucleotide polymorphisms (SNPs) in 1701 FH patients, of whom 482 patients (28.3%) had at least one coronary event during an average follow up of 66 years. The association of each SNP with event-free survival time was calculated with a Cox proportional hazard model. In the cardiovascular disease risk factor adjusted analysis, the most significant SNP was rs1122608:G>T in the SMARCA4 gene near the LDL-receptor (LDLR) gene, with a hazard ratio for CAD risk of 0.74 (95% CI 0.49–0.99; P-value 0.021). However, none of the SNPs reached the Bonferroni threshold. Of all the known CAD loci analyzed, the SMARCA4 locus near the LDLR had the strongest negative association with CAD in this high-risk FH cohort. The effect is contrary to what was expected. None of the other loci showed association with CAD.     

A rare variant in MCF2L identified using exclusion linkage in a pedigree with premature atherosclerosis

Cardiovascular disease (CVD) is a major cause of death in Western societies. CVD risk is largely genetically determined. The molecular pathology is, however, not elucidated in a large number of families suffering from CVD. We applied exclusion linkage analysis and next-generation sequencing to elucidate the molecular defect underlying premature CVD in a small pedigree, comprising two generations of which six members suffered from premature CVD. A total of three variants showed co-segregation with the disease status in the family. Two of these variants were excluded from further analysis based on the prevalence in replication cohorts, whereas a non-synonymous variant in MCF.2 Cell Line Derived Transforming Sequence-like protein (MCF2L, c.2066A>G; p.(Asp689Gly); {"type":"entrez-nucleotide","attrs":{"text":"NM_001112732.1","term_id":"163644324","term_text":"NM_001112732.1"}}NM_001112732.1), located in the DH domain, was only present in the studied family. MCF2L is a guanine exchange factor that potentially links pathways that signal through Rac1 and RhoA. Indeed, in HeLa cells, MCF2L689Gly failed to activate Rac1 as well as RhoA, resulting in impaired stress fiber formation. Moreover, MCF2L protein was found in human atherosclerotic lesions but not in healthy tissue segments. In conclusion, a rare functional variant in MCF2L, leading to impaired DH function, was identified in a small pedigree with premature CVD. The presence of MCF2L in human atherosclerotic plaque specimen lends further support to its potential role in atherosclerosis.     

Identification of a homozygous recessive variant in PTGS1 resulting in a congenital aspirin-like defect in platelet function

We have identified a rare missense variant on chromosome 9, position 125145990 (GRCh37), in exon 8 in prostaglandin endoperoxide synthase 1 (PTGS1) (the gene encoding cyclo-oxygenase 1 [COX-1], the target of anti-thrombotic aspirin therapy). We report that in the homozygous state within a large consanguineous family this variant is associated with a bleeding phenotype and alterations in platelet reactivity and eicosanoid production. Western blotting and confocal imaging demonstrated that COX-1 was absent in the platelets of three family members homozygous for the PTGS1 variant but present in their leukocytes. Platelet reactivity, as assessed by aggregometry, lumi-aggregometry and flow cytometry, was impaired in homozygous family members, as were platelet adhesion and spreading. The productions of COXderived eicosanoids by stimulated platelets were greatly reduced but there were no changes in the levels of urinary metabolites of COX-derived eicosanoids. The proband exhibited additional defects in platelet aggregation and spreading which may explain why her bleeding phenotype was slightly more severe than those of other homozygous affected relatives. This is the first demonstration in humans of the specific loss of platelet COX-1 activity and provides insight into its consequences for platelet function and eicosanoid metabolism. Notably despite the absence of thromboxane A² formation by platelets, urinary thromboxane A² metabolites were in the normal range indicating these cannot be assumed as markers of in vivo platelet function. Results from this study are important benchmarks for the effects of aspirin upon platelet COX-1, platelet function and eicosanoid production as they define selective platelet COX-1 ablation within humans.