rs629301 CELSR2 polymorphism confers a ten-year equivalent risk of critical stenosis assessed by coronary angiography.

BACKGROUND AND AIMS: Novel genetic determinants associated with coronary artery disease (CAD) have been discovered by genome wide association studies. Variants encompassing the CELSR2- PSRC1-SORT1 gene cluster have been associated with CAD. This study is aimed to investigate the rs629301 polymorphism association with the extent of CAD evaluated by coronary angiography (CAG), and to evaluate its associations with an extensive panel of lipid and lipoprotein measurements in a large Italian cohort of 2429 patients. METHODS AND RESULTS: The patients were collected by four Intensive Care Units located in Palermo and Verona (Italy). Clinical Records were filed, blood samples were collected, lipids and apolipoproteins (apo) were measured in separate laboratories. CAD was defined by the presence of stenotic arteries (>50% lumen diameter) by CAG. The presence of CAD was associated with the rs629301 genotype. Patients with CAD were 78% and 73% (p = 0.007) of the T/T vs. T/G + G/G genotype carriers respectively. T/T genotype was also correlated with the number of stenotic arteries, with a 1.29 (1.04-1.61) risk to have a three-arteries disease. T/T genotype correlated with higher levels of LDL-, non-HDL cholesterol, apoB, apoE and apoCIII, and lower HDL-cholesterol. Logistic Regression confirmed that rs629301was associated with CAD independently from the common risk factors, with a risk similar to that conferred by ten years of age [odds ratios were 1.43 (1.04-1.96) and 1.39 (1.22-1.58) respectively]. CONCLUSIONS: rs629301 risk allele was independently associated with the extension and severity of CAD and positively with apoE and apoB containing lipoproteins.

PCSK9-D374Y mediated LDL-R degradation can be functionally inhibited by EGF-A and truncated EGF-A peptides: An in vitro study.

BACKGROUND AND AIMS: Proprotein convertase subtilisin/kexin type 9 (PCSK9) binds to low density lipoprotein receptor (LDLR) through the LDLR epidermal growth factor-like repeat A (EGF-A) domain and induces receptor internalization and degradation. PCSK9 has emerged as a novel therapeutic target for hypercholesterolemia. Clinical studies with PCSK9 inhibiting antibodies have demonstrated strong LDL-c lowering effects, but other therapeutic approaches using small molecule inhibitors for targeting PCSK9 functions may offer supplementary therapeutic options. The aim of our study was to evaluate the effect of synthetic EGF-A analogs on mutated (D374Y) PCSK9-D374Y mediated LDLR degradation in vitro. METHODS: Huh7 human hepatoma cells were transiently transfected to overexpress the gain-of-function D374Y PCSK9 mutation, which has been associated with severe hypercholesterolemia in humans. RESULTS: Transient transfection of cells with PCSK9-D374Y expression vector very effectively enhanced degradation of mature LDLR in Huh7. Treatment with both EGF-A and EGF-A truncated peptides inhibited this effect and showed increased LDLR protein in Huh7 cells transfected with PCSK9-D374Y in a clear concentration dependent manner. Huh7 transfected cells treated with increasing concentration of EGF-A analogs also showed an increase internalization of labeled Dil-LDL. CONCLUSIONS: The result of our study shows that EGF-A analogs are able to effectively hamper the enhanced degradation of LDLR in liver cells expressing PCSK9-D374Y.

Genetic epidemiology of autosomal recessive hypercholesterolemia in Sicily: Identification by next-generation sequencing of a new kindred.

BACKGROUND: Autosomal recessive hypercholesterolemia (ARH) is a rare inherited lipid disorder. In Sardinia, differently from other world regions, the mutated allele frequency is high. It is caused by mutations in the low-density lipoprotein receptor adaptor protein 1 gene. Fourteen different mutations have been reported so far; in Sardinia, 2 alleles (ARH1 and ARH2) explain most of the cases. Four ARH patients, all carriers of the ARH1 mutation, have been identified in mainland Italy and 2 in Sicily. OBJECTIVE: The objectives of the study were to improve the molecular diagnosis of familial hypercholesterolemia (FH) and to estimate the frequency of the ARH1 allele in 2 free-living Sicilian populations. METHODS: We sequenced by targeted next-generation sequencing 20 genes related to low-density lipoprotein metabolism in 50 hypercholesterolemic subjects. Subjects from 2 free-living populations from Northern (Ventimiglia Heart Study, 848 individuals) and Southern Sicily (Zabut Zabùt Aging Project, 1717 individuals) were genotyped for ARH1 allele. RESULTS: We identified 1 homozygous carrier of the ARH1 mutation among the 50 hypercholesterolemic outpatients. Population-based genotyping of ARH1 in 2565 subjects allowed the identification of 1 heterozygous carrier. The overall estimated allele frequency of ARH1 in Sicily was 0.0002 (0.02%). CONCLUSIONS: The identification of a new case of ARH in Sicily among 50 clinically diagnosed FH highlights the importance of next-generation sequencing analysis as tool to improve the FH diagnosis. Our results also indicate that ARH1 carrier status is present in ∼1:2500 of Sicilian inhabitants, confirming that ARH is extremely rare outside Sardinia.

Identification of a novel LMF1 nonsense mutation responsible for severe hypertriglyceridemia by targeted next-generation sequencing.

BACKGROUND: Severe hypertriglyceridemia (HTG) may result from mutations in genes affecting the intravascular lipolysis of triglyceride (TG)-rich lipoproteins. OBJECTIVE: The aim of this study was to develop a targeted next-generation sequencing panel for the molecular diagnosis of disorders characterized by severe HTG. METHODS: We developed a targeted customized panel for next-generation sequencing Ion Torrent Personal Genome Machine to capture the coding exons and intron/exon boundaries of 18 genes affecting the main pathways of TG synthesis and metabolism. We sequenced 11 samples of patients with severe HTG (TG>885 mg/dL-10 mmol/L): 4 positive controls in whom pathogenic mutations had previously been identified by Sanger sequencing and 7 patients in whom the molecular defect was still unknown. RESULTS: The customized panel was accurate, and it allowed to confirm genetic variants previously identified in all positive controls with primary severe HTG. Only 1 patient of 7 with HTG was found to be carrier of a homozygous pathogenic mutation of the third novel mutation of LMF1 gene (c.1380C>G-p.Y460X). The clinical and molecular familial cascade screening allowed the identification of 2 additional affected siblings and 7 heterozygous carriers of the mutation. CONCLUSIONS: We showed that our targeted resequencing approach for genetic diagnosis of severe HTG appears to be accurate, less time consuming, and more economical compared with traditional Sanger resequencing. The identification of pathogenic mutations in candidate genes remains challenging and clinical resequencing should mainly intended for patients with strong clinical criteria for monogenic severe HTG.

Novel CREB3L3 Nonsense Mutation in a Family With Dominant Hypertriglyceridemia.

OBJECTIVE: Cyclic AMP responsive element-binding protein 3-like 3 (CREB3L3) is a novel candidate gene for dominant hypertriglyceridemia. To date, only 4 kindred with dominant hypertriglyceridemia have been found to be carriers of 2 nonsense mutations in CREB3L3 gene (245fs and W46X). We investigated a family in which hypertriglyceridemia displayed an autosomal dominant pattern of inheritance. APPROACH AND RESULTS: The proband was a 49-year-old woman with high plasma triglycerides (≤1300 mg/dL; 14.68 mmol/L). Her father had a history of moderate hypertriglyceridemia, and her 51-year-old brother had triglycerides levels as high as 1600 mg/dL (18.06 mmol/L). To identify the causal mutation in this family, we analyzed the candidate genes of recessive and dominant forms of primary hypertriglyceridemia by direct sequencing. The sequencing of CREB3L3 gene led to the discovery of a novel minute frame shift mutation in exon 3 of CREB3L3 gene, predicted to result in the formation of a truncated protein devoid of function (c.359delG-p.K120fsX20). Heterozygosity for the c.359delG mutation resulted in a severe phenotype occurring later in life in the proband and her brother and a good response to diet and a hypotriglyceridemic treatment. The same mutation was detected in a 13-year-old daughter who to date is normotriglyceridemic. CONCLUSIONS: We have identified a novel pathogenic mutation in CREB3L3 gene in a family with dominant hypertriglyceridemia with a variable pattern of penetrance.