Serum concentrations of total cholesterol, low-density lipoprotein cholesterol (LDL-C), high-density lipoprotein cholesterol (HDL-C), and triglycerides (TG) are among the most important risk factors for coronary artery disease (CAD) and are targets for therapeutic intervention. We screened the genome for common variants associated with serum lipids in >100,000 individuals of European ancestry. Here we report 95 significantly associated loci (P < 5 × 10-8), with 59 showing genome-wide significant association with lipid traits for the first time. The newly reported associations include single nucleotide polymorphisms (SNPs) near known lipid regulators (e.g., CYP7A1, NPC1L1, and SCARB1) as well as in scores of loci not previously implicated in lipoprotein metabolism. The 95 loci contribute not only to normal variation in lipid traits but also to extreme lipid phenotypes and impact lipid traits in three non-European populations (East Asians, South Asians, and African Americans). Our results identify several novel loci associated with serum lipids that are also associated with CAD. Finally, we validated three of the novel genes—GALNT2, PPP1R3B, and TTC39B—with experiments in mouse models. Taken together, our findings provide the foundation to develop a broader biological understanding of lipoprotein metabolism and to identify new therapeutic opportunities for the prevention of CAD.

The prevalence of molecularly defined hoADH is much higher and the clinical phenotype is more variable than previously assumed. In light of the fact that novel therapies are, or will be registered for the treatment of hoADH patients, an uniform definition of hoADH either as a phenotypic or molecular entity is warranted in order to identify patients who are considered to be eligible for these novel agents.

Mutations in the low-density lipoprotein (LDL) receptor gene are responsible for familial hypercholesterolemia (FH). At present, more than 600 mutations in this gene are known to underlie FH. However, the array of mutations varies considerably in different populations. Therefore, the delineation of essentially all LDL-receptor gene mutations in a population is a prerequisite for the implementation of nation-wide genetic testing for FH. In the Netherlands, mutation analysis by denaturing gradient gel electrophoresis and sequencing in 1641 clinically diagnosed FH patients resulted in the characterization of 159 different LDL-receptor gene defects. The nine most common mutations were responsible for 66.5% of our FH index cases. Of these, four mutations occurred with relatively high frequencies in specific parts of the Netherlands. The remaining mutations were only encountered in single FH patients, comprising 22.2% of the patient cohort analyzed. Subsequent genetic testing of relatives of the index cases within the national FH screening program resulted in the identification of 5,531 FH patients in total. The analysis for LDL-receptor mutations is a continuing effort to update the LDL-receptor mutation catalogue. Subsequently, with the newly generated index cases, the screening program can be extended and continued to identify and treat FH patients as early as possible and reduce cardiovascular morbidity and mortality in these patients at high risk.

Rationale: Autosomal-dominant hypercholesterolemia (ADH) is characterized by elevated low-density lipoprotein cholesterol levels and increased risk for coronary vascular disease. ADH is caused by mutations in the low-density lipoprotein receptor, apolipoprotein B, or proprotein convertase subtilisin/kexin 9. A number of patients, however, suffer from familial hypercholesterolemia 4 (FH4), defined as ADH in absence of mutations in these genes and thereafter use the abbreviation FH4. Objective: To identify a fourth locus associated with ADH. Methods and Results: Parametric linkage analysis combined with exome sequencing in a FH4 family resulted in the identification of the variant p.Glu97Asp in signal transducing adaptor family member 1 ( STAP1 ), encoding signal transducing adaptor family member 1. Sanger sequencing of STAP1 in 400 additional unrelated FH4 probands identified a second p.Glu97Asp carrier and 3 additional missense variants, p.Leu69Ser, p.Ile71Thr, and p.Asp207Asn. STAP1 carriers (n=40) showed significantly higher plasma total cholesterol and low-density lipoprotein cholesterol levels compared with nonaffected relatives (n=91). Conclusions: We mapped a novel ADH locus at 4p13 and identified 4 variants in STAP1 that associate with ADH.

Autosomal-dominant hypercholesterolemia (ADH) has been identified as a major risk factor for coronary vascular disease (CVD) and is associated with mutations in the low-density lipoprotein receptor (LDLR) and the apolipoprotein B (APOB) gene. Since 1991 DNA samples from clinically diagnosed ADH patients have been routinely analyzed for the presence of LDLR and APOB gene mutations. As of 2001, 1,641 index patients (164 index patients per year) had been identified, while from 2001 onward a more sensitive, high-throughput system was used, resulting in the identification of 1,177 new index patients (average=294 index patients per year). Of these 1,177 index cases, 131 different causative genetic variants in the LDLR gene and six different causative mutations in the APOB gene were new for the Dutch population. Of these 131 mutations, 83 LDLR and four APOB gene mutations had not been reported before. The inclusion of all 2,818 index cases into the national screening program for familial hypercholesterolemia (FH) resulted in the identification of 7,079 relatives who carried a mutation that causes ADH. Screening of the LDLR and APOB genes in clinically diagnosed FH patients resulted in approximately 77% of the patients being identified as carriers of a causative mutation. The population of patients with ADH was divided into three genetically distinct groups: carriers of an LDLR mutation (FH), carriers of an APOB mutation (FDB), and non-LDLR/non-APOB patients (FH3). No differences were found with regard to untreated cholesterol levels, response to therapy, and onset of CVD. However, all groups were at an increased risk for CVD. Therefore, to ultimately identify all individuals with ADH, the identification of new genes and mutations in the genes that cause ADH is of crucial importance for the ongoing national program to identify patients with ADH by genetic cascade screening.

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Autosomal dominant hypercholesterolaemia (ADH) is a major risk factor for coronary artery disease. This disorder is caused by mutations in the genes coding for the low-density lipoprotein receptor (LDLR), apolipoprotein B (APOB), and proprotein convertase subtilisin/kexin 9 (PCSK9). However, in 41% of the cases, we cannot find mutations in these genes. In this study, new genetic approaches were used for the identification and validation of new variants that cause ADH. Methods and results Using exome sequencing, we unexpectedly identified a novel APOB mutation, p.R3059C, in a small-sized ADH family. Since this mutation was located outside the regularly screened APOB region, we extended our routine sequencing strategy and identified another novel APOB mutation (p.K3394N) in a second family. In vitro analyses show that both mutations attenuate binding to the LDLR significantly. Despite this, both mutations were not always associated with ADH in both families, which prompted us to validate causality through using a novel genetic approach. Conclusion This study shows that advances in genetics help increasing our understanding of the causes of ADH. We identified two novel functional APOB mutations located outside the routinely analysed APOB region, suggesting that screening for mutations causing ADH should encompass the entire APOB coding sequence involved in LDL binding to help identifying and treating patients at increased cardiovascular risk.

The penultimate step in carnitine biosynthesis is mediated by ␥-trimethylaminobutyraldehyde dehydrogenase (EC 1.2.1.47), a cytosolic NAD ؉ -dependent aldehyde dehydrogenase that converts ␥-trimethylaminobutyraldehyde into ␥-butyrobetaine. This enzyme was purified from rat liver, and two internal peptide fragments were sequenced by Edman degradation. The peptide sequences were used to search the Expressed Sequence Tag data base, which led to the identification of a rat cDNA containing an open reading frame of 1485 base pairs encoding a polypeptide of 494 amino acids with a calculated molecular mass of 55 kDa. Expression of the coding sequence in Escherichia coli confirmed that the cDNA encodes ␥-trimethylaminobutyraldehyde dehydrogenase. The previously identified human aldehyde dehydrogenase 9 (EC 1.2.1.19) has 92% identity with rat trimethylaminobutyraldehyde dehydrogenase and has been reported to convert substrates that resemble ␥-trimethylaminobutyraldehyde. When aldehyde dehydrogenase 9 was expressed in E. coli, it exhibited high trimethylaminobutyraldehyde dehydrogenase activity. Furthermore, comparison of the enzymatic characteristics of the heterologously expressed human and rat dehydrogenases with those of purified rat liver trimethylaminobutyraldehyde dehydrogenase revealed that the three enzymes have highly similar substrate specificities. In addition, the highest V max /K m values were obtained with ␥-trimethylaminobutyraldehyde as substrate. This indicates that human aldehyde dehydrogenase 9 is the ␥-trimethylaminobutyraldehyde dehydrogenase, which functions in carnitine biosynthesis.