Exome Sequencing and Directed Clinical Phenotyping Diagnose Cholesterol Ester Storage Disease Presenting as Autosomal Recessive Hypercholesterolemia.
ABSTRACT Autosomal recessive hypercholesterolemia is a rare inherited disorder, characterized by extremely high total and low-density lipoprotein cholesterol levels, that has been previously linked to mutations in LDLRAP1. We identified a family with autosomal recessive hypercholesterolemia not explained by mutations in LDLRAP1 or other genes known to cause monogenic hypercholesterolemia. The aim of this study was to identify the molecular pathogenesis of autosomal recessive hypercholesterolemia in this family.
We used exome sequencing to assess all protein-coding regions of the genome in 3 family members and identified a homozygous exon 8 splice junction mutation (c.894G>A, also known as E8SJM) in LIPA that segregated with the diagnosis of hypercholesterolemia. Because homozygosity for mutations in LIPA is known to cause cholesterol ester storage disease, we performed directed follow-up phenotyping by noninvasively measuring hepatic cholesterol content. We observed abnormal hepatic accumulation of cholesterol in the homozygote individuals, supporting the diagnosis of cholesterol ester storage disease. Given previous suggestions of cardiovascular disease risk in heterozygous LIPA mutation carriers, we genotyped E8SJM in >27 000 individuals and found no association with plasma lipid levels or risk of myocardial infarction, confirming a true recessive mode of inheritance.
By integrating observations from Mendelian and population genetics along with directed clinical phenotyping, we diagnosed clinically unapparent cholesterol ester storage disease in the affected individuals from this kindred and addressed an outstanding question about risk of cardiovascular disease in LIPA E8SJM heterozygous carriers.
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ABSTRACT: Background Familial hypercholesterolaemia (FH) is an autosomal dominant disease of lipid metabolism, which leads to early coronary heart disease. Mutations in LDLR, APOB and PCSK9 can be detected in 80% of definite FH (DFH) patients. This study aimed to identify novel FH-causing genetic variants in patients with no detectable mutation. Methods and results Exomes of 125 unrelated DFH patients were sequenced, as part of the UK10K project. First, analysis of known FH genes identified 23 LDLR and two APOB mutations, and patients with explained causes of FH were excluded from further analysis. Second, common and rare variants in genes associated with low-density lipoprotein cholesterol (LDL-C) levels in genome-wide association study (GWAS) meta-analysis were examined. There was no clear rare variant association in LDL-C GWAS hits; however, there were 29 patients with a high LDL-C SNP score suggestive of polygenic hypercholesterolaemia. Finally, a gene-based burden test for an excess of rare (frequency <0.005) or novel variants in cases versus 1926 controls was performed, with variants with an unlikely functional effect (intronic, synonymous) filtered out. Conclusions No major novel locus for FH was detected, with no gene having a functional variant in more than three patients; however, an excess of novel variants was found in 18 genes, of which the strongest candidates included CH25H and INSIG2 (p<4.3x10(-4) and p<3.7x10(-3), respectively). This suggests that the genetic cause of FH in these unexplained cases is likely to be very heterogeneous, which complicates the diagnostic and novel gene discovery process.Journal of Medical Genetics 07/2014; 51(8). DOI:10.1136/jmedgenet-2014-102405 · 5.64 Impact Factor
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ABSTRACT: The analysis of rich catalogues of genetic variation from population-based sequencing provides an opportunity to screen for functional effects. Here we report a rare variant in APOC3 (rs138326449-A, minor allele frequency ~0.25% (UK)) associated with plasma triglyceride (TG) levels (-1.43 s.d. (s.e.=0.27 per minor allele (P-value=8.0 × 10(-8))) discovered in 3,202 individuals with low read-depth, whole-genome sequence. We replicate this in 12,831 participants from five additional samples of Northern and Southern European origin (-1.0 s.d. (s.e.=0.173), P-value=7.32 × 10(-9)). This is consistent with an effect between 0.5 and 1.5 mmol l(-1) dependent on population. We show that a single predicted splice donor variant is responsible for association signals and is independent of known common variants. Analyses suggest an independent relationship between rs138326449 and high-density lipoprotein (HDL) levels. This represents one of the first examples of a rare, large effect variant identified from whole-genome sequencing at a population scale.Nature Communications 09/2014; 5:4871. DOI:10.1038/ncomms5871 · 10.74 Impact Factor
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ABSTRACT: A novel electrochemical sensor for cholesterol (CHO) detection based on molecularly imprinted polymer (MIP) membranes on a glassy carbon electrode (GCE) modified with multi-walled carbon nanotubes (MWNTs) and Au nanoparticles (AuNPs) was constructed. p-Aminothiophenol (P-ATP) and CHO were assembled on the surface of the modified GCE by the formation of Au-S bonds and hydrogen-bonding interactions, and polymer membranes were formed by electropolymerization in a polymer solution containing p-ATP, HAuCl4, tetrabutylammonium perchlorate (TBAP) and the template molecule CHO. Cyclic voltammetry (CV) and differential pulse voltammetry (DPV) measurements were used to monitor the electropolymerization process and its optimization, which was further characterized by scanning electron microscopy (SEM). The linear response range of the MIP sensor was between 1×10(-13) and 1×10(-9)molL(-1), and the limit of detection (LOD) were 3.3×10(-14)molL(-1). The proposed system has the potential for application in clinical diagnostics of cholesterol with high-speed real-time detection capability, low sample consumption, high sensitivity, low interference and good stability. Copyright © 2014 Elsevier B.V. All rights reserved.Biosensors & Bioelectronics 04/2015; 66:590-5. DOI:10.1016/j.bios.2014.12.014 · 6.45 Impact Factor