Phenotypic characterization and predictive analysis of p.Asp47Asn LDL receptor mutation associated with Familial Hypercholesterolemia in a Chilean population

BackgroundFamilial hypercholesterolemia (FH) is an inherited disorder mainly caused by mutations in the LDL receptor (LDL-R) and characterized by elevation of low-density lipoprotein cholesterol (LDL-C) levels and premature cardiovascular disease.ObjectiveIn this study, we evaluated the clinical phenotype of the p.Asp47Asn, described as an uncertain pathogenic variant, and its effect on the structure of LDL-R and ligand interactions with apolipoproteins.Methods27 children and adolescents with suspected FH diagnosis were recruited from a pediatric endocrinology outpatient clinic. Blood samples were collected after 12 h fasting for lipid profile analysis. DNA sequencing was performed for six FH-related genes by Ion Torrent PGM platform and copy number variation by MLPA. For index cases, a familial cascade screening was done restricted to the same mutation found in the index case. In silico analysis were developed to evaluate the binding capacity of LDL-R to apolipoproteins B100 and E.ResultsLipid profile in children and adolescents demonstrated higher LDL-C levels in p.Asp47Asn carriers compared to the wild type genotype. In silico analysis predicted a reduction in the binding capacity of the ligand-binding modules LA1-2 of p.Asp47Asn LDL-R for ApoB100 and ApoE, which was not produced by local structural changes or folding defects but as a consequence of a decreased apparent affinity for both apolipoproteins.ConclusionThe clinical phenotype and the structural effects of p.Asp47Asn LDL-R mutation suggest that this variant associates to FH.     

Recall by genotype and cascade screening for familial hypercholesterolemia in a population-based biobank from Estonia

PurposeLarge-scale, population-based biobanks integrating health records and genomic profiles may provide a platform to identify individuals with disease-predisposing genetic variants. Here, we recall probands carrying familial hypercholesterolemia (FH)-associated variants, perform cascade screening of family members, and describe health outcomes affected by such a strategy.MethodsThe Estonian Biobank of Estonian Genome Center, University of Tartu, comprises 52,274 individuals. Among 4776 participants with exome or genome sequences, we identified 27 individuals who carried FH-associated variants in the LDLR, APOB, or PCSK9 genes. Cascade screening of 64 family members identified an additional 20 carriers of FH-associated variants.ResultsVia genetic counseling and clinical management of carriers, we were able to reclassify 51% of the study participants from having previously established nonspecific hypercholesterolemia to having FH and identify 32% who were completely unaware of harboring a high-risk disease-associated genetic variant. Imaging-based risk stratification targeted 86% of the variant carriers for statin treatment recommendations.ConclusionGenotype-guided recall of probands and subsequent cascade screening for familial hypercholesterolemia is feasible within a population-based biobank and may facilitate more appropriate clinical management.     

Genetic identification of familial hypercholesterolemia within whole genome sequences in 6820 newborns

Familial hypercholesterolemia (FH) is defined as a monogenic disease, characterized by elevated low-density lipoprotein cholesterol (LDL-C) levels. FH remains underdiagnosed and undertreated in Chinese. We whole-genome sequenced 6820 newborns from Qingdao of China to investigate the FH-related gene (LDLR, APOB, PCSK9) mutation types, carrier ratio and genotype–phenotype correlation. In this study, the prevalence of FH in Qingdao of China was 0.47% (95% CI: 0.32%–0.66%). The plasma lipid levels of FH-related gene mutation carriers begin to increase as early as infant. T-CHO and LDL-C of FH infants was higher by 48.1% (p < 0.001) and 42.9% (p < 0.001) relative to non-FH infants. A total of 22 FH infants and their parent participate in further studies. The results indicated that FH infant parent noncarriers have the normal plasma lipid level, while T-CHO and LDL-C increased in FH infants and FH infant parent carriers, but no difference between the groups. This highlights the importance of genetic factors. In conclusion, the spectrum of FH-causing mutations in the newborns of Qingdao, China was described for the first time. These data can serve as a considerable dataset for next-generation sequencing analysis of the Chinese population with FH and potentially helping reform regional policies for early detection and prevention of FH.     

A randomized controlled trial of genetic testing and cascade screening in familial hypercholesterolemia

PurposeFamily-based cascade screening from index probands is considered an effective way of identifying undiagnosed individuals with familial hypercholesterolemia (FH). The role of genetic testing of the proband in the success of cascade screening for FH is unknown.MethodsWe randomized 240 individuals with a clinical diagnosis of FH to genetic testing for FH (n = 160) or usual care with lipid testing alone (n = 80). The primary study endpoint was the proportion of probands with at least one relative enrolled in the study within one year after the notification of results.ResultsProband median age was 59 (47–67) and 71% were female. Only 28 (12%) probands succeeded in enrolling a relative. While the genetic testing group had a higher proportion of probands with relatives enrolled (13.1%) compared with the usual care group (8.8%), this difference was not significant (p = 0.40). In subgroup analyses, enrollment of a relative was higher in the pathogenic variant group (22.7%) compared to the no pathogenic variant (9.5%) and usual care groups (8.8%) (p = 0.04).ConclusionWe observed a low rate of family participation in cascade screening despite repeated recommendations to probands. Compared to usual care, genetic testing did not improve family participation in cascade screening for FH.Clinical trial numberNCT04526457     

A novel LDLR mutation, H190Y, in a Utah kindred with familial Hypercholesterolemia

Heterozygous familial hypercholesterolemia (FH) is a serious disorder causing twice normal low-density lipoprotein (LDL) cholesterol levels early in childhood and very early coronary disease in both men and women. Treatment with multiple medications together with diet can normalize cholesterol levels in many persons with FH and prevent or delay the development of coronary atherosclerosis. Previously published blood cholesterol criteria greatly under-diagnosed new cases of FH among members of known families with FH and over-diagnosed FH among participants of general population screening. Thus, there is a need for accurate and genetically validated criteria for the early diagnosis of heterozygous FH. In the course of investigations of coronary artery disease in Utah, we identified a family whose proband showed elevated plasma levels of LDL cholesterol. To carry out molecular genetic diagnosis of the disease, we screened DNA samples for mutations in all 18 exons and the exon-intron boundaries of the LDL receptor gene (LDLR). Novel point mutations were identified in the proband: a C-to-T transversion at nucleotide position 631, causing substitution of tyrosine for histidine at codon 190 in exon 4 of the LDLR gene. The mutant allele-specific amplification method was used to examine 12 members of the family recruited for the diagnosis. This method helped to unequivocally diagnose 7 individuals as heterozygous for this particular LDLR mutation, while excluding the remaining 5 individuals from carrier status with FH. Received: March 29, 1999 / Accepted: June 18, 1999     

A pragmatic clinical trial of cascade testing for familial hypercholesterolemia

PurposeWe compared new cases detected per index case in familial hypercholesterolemia (FH) families with or without an identifiable monogenic etiology.MethodsWe enrolled 52 FH probands with a pathogenic variant (FH^g+) in LDLR, APOB, or PCSK9 and 73 probands without such a variant (FH^g–). After direct contact by the study team, family members (FMs) of FH^g+ probands could opt-in for genetic testing and FMs of FH^g– probands were asked to provide a lipid profile. New cases were defined as presence of a pathogenic variant in FH^g+ families and as low-density lipoprotein cholesterol ≥155 mg/dL in FH^g– families.ResultsOf 71 FH^g+ probands seen by a genetic counselor, 52 consented and identified 253 FMs (111 consented and were tested, yielding 48 new cases). Of 101 FH^g– probands who received counseling, 73 consented and identified 295 FMs (63 consented and were tested, yielding 17 new cases). New case detection per index case was significantly greater in FH^g+ than in FH^g– families (0.92 vs 0.23), a result of higher cascade testing uptake (43.9 vs 21.4%) and yield (43.2 vs 27.0%) in the former.ConclusionNew case detection rate was significantly higher in FH families with a monogenic etiology than in those without such an etiology owing to greater uptake and yield of cascade testing.     

Phenotypic and genotypic characterization of familial hypercholesterolemia in French adult and pediatric populations

BackgroundFamilial hypercholesterolemia (FH) is the most common genetic disorder associated with a high risk for premature atherosclerotic cardiovascular disease attributable to increased levels of LDL-cholesterol (LDL-C) from birth. FH is both underdiagnosed and undertreated.ObjectiveWe describe the clinical, biological, and genetic characteristics of 147 patients in France with clinical FH (including a group of 26 subjects aged < 20 years); we explore how best to detect patients with monogenic FH.MethodsWe retrospectively reviewed all available data on patients undergoing genetic tests for FH from 2009 to 2019. FH diagnoses were based on the Dutch Lipid Clinics Network (DLCN) scores of adults, and elevated LDL-C levels in subjects < 20 years of age. We evaluated LDLR, APOB, and PCSK9 status.ResultsThe mutations of adults (in 25.6% of all adults) were associated with DLCN scores indicating “possible FH,” "probable FH, and “definitive FH” at rates of 4%, 16%, and 53%, respectively. The areas under the ROC curves of the DLCN score and the maximum LDL-C level did not differ (p = 0.32). We found that the pediatric group evidenced more monogenic etiologies (77%, increasing to 91% when an elevated LDL-C level was combined with a family history of hypercholesterolemia and/or premature coronary artery disease).ConclusionDiagnosis of monogenic FH may be optimized by screening children in terms of their LDL-C levels, associated with reverse-cascade screening of relatives when the children serve as index cases.     

Failure of cosegregation between a rare STAP1 missense variant and hypercholesterolemia

Autosomal dominant familial hypercholesterolemia (FH) is characterized by elevated low-density lipoprotein cholesterol levels and an increased risk for atherosclerotic cardiovascular disease. Although rare pathogenic variants in genes encoding the low-density lipoprotein receptor, apolipoprotein B, proprotein convertase subtilisin/kexin 9 are found in more than 80% of molecularly defined patients with FH, a few rare minor causative genes have been proposed, including the gene encoding signal-transducing adaptor family member 1 (STAP1). Here, we describe a patient with hypercholesterolemia and the rare heterozygous missense variant p.D207N in STAP1. However, extending the pedigree showed failure of the variant to cosegregate with hypercholesterolemia, as both his sons were carriers of the variant and both were also normolipidemic. The findings add to the evidence against STAP1 as a genetic locus for FH.     

Preferences for opt-in and opt-out enrollment and consent models in biobank research: a national survey of Veterans Administration patients

PurposeIn 2006, the Department of Veterans Affairs launched the Genomic Medicine Program with the goal of using genomic information to personalize and improve health care for veterans. A step toward this goal is the Million Veteran Program, which aims to enroll a million veterans in a longitudinal cohort study and establish a database with genomic, lifestyle, military-exposure, and health information. Before the launch of the Million Veteran Program, a survey of Department of Veterans Affairs patients was conducted to measure preferences for opt-in and opt-out models of enrollment and consent.MethodsAn online survey was conducted with a random sample of 451 veterans. The survey described the proposed Million Veteran Program database and asked respondents about the acceptability of opt-in and opt-out models of enrollment. The study examined differences in responses among demographic groups and relationships between beliefs about each model and willingness to participate.ResultsMost respondents were willing to participate under both opt-in (80%) and opt-out (69%) models. Nearly 80% said they would be comfortable providing access to residual clinical samples for research. At least half of respondents did not strongly favor one model over the other; of those who expressed a preference, significantly more people said they would participate in a study using opt-in methods. Stronger preferences for the opt-in approach were expressed among younger patients and Hispanic patients.ConclusionSupport for the study and willingness to participate were high for both enrollment models. The use of an opt-out model could impede recruitment of certain demographic groups, including Hispanic patients and patients under the age of 55 years.Genet Med 2012:14(9):787–794.     

Familial defective apolipoprotein B-100: A review

Familial defective apolipoprotein B-100 (FDB) is an autosomal dominant genetic disorder of lipid metabolism associated with hyperlipidemia and elevated risk for atherosclerosis. FDB is caused by mutations in APOB reducing the binding affinity between apolipoprotein B-100 and the low-density lipoprotein receptor. Population studies suggest that approximately 0.1% of Northern Europeans and US Caucasians carries the R3500Q variant in APOB most commonly associated with FDB; in addition, the APOB R3500 W variant is known to make a significant contribution to familial hypercholesterolemia (FH) among East Asians. However, the elevation of plasma low-density lipoprotein cholesterol observed in FDB is frequently milder than that of FH due to mutations in LDLR, and FDB is subsequently underdiagnosed according to standard FH diagnostic criteria.     

Mutation spectrum and polygenic score in German patients with familial hypercholesterolemia

Autosomal-dominant familial hypercholesterolemia (FH) is characterized by increased plasma concentrations of low-density lipoprotein cholesterol (LDL-C) and a substantial risk to develop cardiovascular disease. Causative mutations in three major genes are known: the LDL receptor gene (LDLR), the apolipoprotein B gene (APOB) and the proprotein convertase subtilisin/kexin 9 gene (PCSK9). We clinically characterized 336 patients suspected to have FH and screened them for disease causing mutations in LDLR, APOB, and PCSK9. We genotyped six single nucleotide polymorphisms (SNPs) to calculate a polygenic risk score for the patients and 1985 controls. The 117 patients had a causative variant in one of the analyzed genes. Most variants were found in the LDLR gene (84.9%) with 11 novel mutations. The mean polygenic risk score was significantly higher in FH mutation negative subjects than in FH mutation positive patients (P < .05) and healthy controls (P < .001), whereas the score of the two latter groups did not differ significantly. However, the score explained only about 3% of the baseline LDL-C variance. We verified the previously described clinical and genetic variability of FH for German hypercholesterolemic patients. Evaluation of a six-SNP polygenic score recently proposed for clinical use suggests that it is not a reliable tool to classify hypercholesterolemic patients.     

Homozygous familial hypercholesterolemia: The c.1055G>A mutation in the LDLR gene and clinical heterogeneity

Familial hypercholesterolemia (FH) is a world public health issue because of its high frequency, morbidity, and mortality. FH is characterized by elevated plasma low-density lipoprotein cholesterol (LDL-C) levels and a high risk for premature cardiovascular disease. We report an 8-year-old male with homozygous familial hypercholesterolemia. The clinical and biochemical characteristics of this case were bilateral corneal arcus, xanthomas in several body parts, severe stenosis of the left carotid artery and serum total cholesterol levels of 782.0 mg/dL and 715.0 mg/dL LDL-C. The initial treatment was atorvastatin (40 mg) and ezetimibe (20 mg), with no satisfactory response. LDLR gene was analyzed and homozygosity for c.1055G>A mutation was observed, resulting in an amino acid change from cysteine to tyrosine in codon 352 (p.Cys352Tyr). This mutation is known as Mexico 2 and has only been observed in the Mexican population. Both parents and siblings were carriers of the same mutation, but the paternal grandmother and the father of the index case showed the phenomenon of incomplete penetrance. With the analysis 5 polymorphisms (rs1003723C>T, rs5930A>G, rs688C>T, rs5929T>C and rs5927A>G), a common ancestor for the mutation can be suggested and linkage to TGTCG haplotype.     

Sex‐related differences in premature cardiovascular disease in familial hypercholesterolemia

BackgroundFamilial hypercholesterolemia (FH) is associated with an increased prevalence of premature atherosclerotic cardiovascular disease (ASCVD), however, little is known about sex-specific differences in premature ASCVD and its risk factors.ObjectiveThe present study seeks to assess the burden and risk factors for premature ASCVD among men and women with FH.MethodsIn this study we retrospectively examined sex-specific differences in ASCVD prevalence, risk factor burdens, and lipid treatment outcomes in 782 individuals with clinically or genetically confirmed FH treated in 5 U.S. lipid and genetics clinics. A generalized linear model using Binomial distribution with random study site effect and sex-stratified analysis was used to determine the strongest predictors of premature ASCVD, and lipid treatment outcomes. Covariates included age, sex, diabetes mellitus (DM), hypertension, and current smoking.ResultsAmong the cohort, 98/280 men (35%) and 89/502 women (18%) had premature ASCVD (defined as <55 years in men and <65 years in women). Women with premature ASCVD had higher mean treated total cholesterol (216 vs. 179 mg/dl, p=<0.001) and LDL-C (135 vs. 109 mg/dl, p= 0.005).ConclusionThese data confirm that high percentages of women and men with FH develop premature ASCVD, and suggest that FH may narrow the observed sex difference in premature ASCVD onset. These data support more aggressive prevention and treatment strategies in FH, including in women, to reduce non-lipid risk factors and residual hypercholesterolemia.     

Impact of variants of uncertain significance of LDL receptor on phenotypes of familial hypercholesterolemia

BackgroundData on the effect of variants of uncertain significance (VUS) of LDL receptor (LDLR) on familial hypercholesterolemia (FH) phenotype is limited.ObjectiveTo investigate the associations between genotypes and phenotypes, including low-density lipoprotein (LDL) cholesterol level and occurrence of major adverse cardiac events (MACEs), in FH patients (N = 1050, male/female = 490/560).MethodsWe retrospectively assessed the data of patients with FH admitted at Kanazawa University Hospital between 1990 and 2020. Based on genotype, the patients were divided into patients without variants, with VUS of LDLR, and with pathogenic variants. Cox proportional hazard model was used to identify the factors associated with MACEs.ResultsThe median follow-up duration was 12.6 years (interquartile range: 9.5–17.9 years). Altogether, 777 patients had FH mutation and 273 had pathogenic mutation, with 92 having VUS. Over the follow-up duration, 175 MACEs were observed. LDL cholesterol level was found to be significantly higher in patients with pathogenic variants (251 mg/dL) than in patients with VUS (225 mg/dL) and without variants (203 mg/dL). Pathogenic variants and VUS are significantly associated with MACEs (hazard ratio [HR] = 1.52, 95% confidence interval [CI] = 1.02–2.02, P = 0.033 and HR = 3.18, 95% CI = 2.00–4.36, P = 1.9 × 10^?5, relative to patients without any variants, respectively), independent of classical risk factors.ConclusionVUS of LDLR was significantly associated with poor outcomes in FH patients. Genetic testing is useful for the diagnosis and risk stratification of FH patients.     

A cautionary tale: Is this APOB whole-gene duplication actually pathogenic?

A 22-year-old woman presented with elevated low-density lipoprotein (LDL) cholesterol and clinically suspected familial hypercholesterolemia. Initial genetic analysis by Sanger sequencing found no causal variants in LDLR or other familial hypercholesterolemia genes. More than a decade later, her 9-year-old daughter was also found to have elevated LDL cholesterol. Re-analysis using current genetic methodology detected a novel whole-gene duplication of APOB in both individuals, which was tentatively assumed to explain their elevated LDL cholesterol based mainly on biological plausibility. However, on further assessment with cascade screening and cosegregation analysis involving multiple family members, the APOB duplication was eventually discounted as being causative. This case illustrates the risk of assuming pathogenicity of a novel genetic variant without undertaking corroborative diagnostic measures. It further highlights the time and skill required for accurate variant analysis and emphasizes the challenges faced by clinicians who are increasingly expected to rapidly interpret such results without sufficient time or resources to pursue supportive or corroborating evidence.     

Homozygous familial hypercholesterolemia in China: Genetic and clinical characteristics from a real-world,multi-center,cohort study

BackgroundThere is a lack of large-scale data on the clinical and genotype characteristics of homozygous familial hypercholesterolemia (HoFH) patients in Asia.ObjectiveTo define the characteristics of phenotypic and genetic HoFH probands from mainland China.MethodsWe collected data from patients with suspected HoFH from ten clinical hospitals across mainland China from 2003 to 2019. Clinical data and DNA testing were obtained in all patients. The Kaplan-Meier method was used to generate survival curves, and the groups were compared with the log-rank test.ResultsA total of 108 unrelated probands with suspected HoFH (mean age 14.9 years) were included. The three most common variants were W483X (c.1448 G>A), A627T (c.1879 G>A), H583Y (c.1747 C>T). The majority (64.8%) were compound heterozygotes (n = 70), 23 (21.3%) were true HoFH patients. True HoFH showed higher LDL-C levels compared to compound HoFH (16.8±3.6 mmol/L vs. 15.0±3.1 mmol/L, P = 0.022). During follow-up, only 21.2% patients exhibited an LDL-C reduction of more than 50%. Kaplan-Meier analysis showed that the true HoFH probands had significantly worse survival rates compared to other genotype probands (13-year survival; 20.3% vs. 76.7%, respectively; P = 0.016). In addition, true HoFH shows that 2.8-fold (P = 0.022) increase any death and 3.0-fold (P = 0.023) increase cardiovascular death risk in relative to other FH.ConclusionsThis report shows that HoFH has devastating consequences, and that patients are often only diagnosed after they have been exposed to severely elevated LDL-C for years. Systematic screening and early intensive treatment are an absolute requirement for these young individuals with HoFH.     

Prognostic impact of cascade screening for familial hypercholesterolemia on cardiovascular events

BackgroundFamilial hypercholesterolemia (FH) is an autosomal dominant disorder mainly caused by mutations in the low-density lipoprotein (LDL) receptor or associated genes, resulting in elevated serum cholesterol levels and an increased risk of premature atherosclerotic cardiovascular disease (ASCVD).ObjectiveWe aimed to evaluate the prognostic impact of cascade screening for FH.MethodsWe retrospectively investigated the health records of 1050 patients with clinically diagnosed FH, including probands and their relatives who were cascade-screened, who were referred to our institute. We used Cox models that were adjusted for established ASCVD risk factors to assess the association between cascade screening and major adverse cardiac events (MACE). The median period of follow-up evaluating MACE was 12.3 years (interquartile ranges [IQR] = 9.1–17.5 years), and MACE included death associated with ASCVD, or acute coronary syndrome.ResultsDuring the observation period, 113 participants experienced MACE. The mean age of patients identified through cascade screening was 18-years younger than that of the probands (38.7 yr vs. 57.0 yr, P < 0.0001), with a lower proportion of ASCVD risk factors. Interestingly, patients identified through cascade screening under milder lipid-lowering therapies were at reduced risk for MACE (hazard ratio [HR] = 0.67; 95%CI = 0.44 to 0.90; P = 0.0044) when compared with the probands, even after adjusting for those known risk factors, including age, and prior ASCVD.ConclusionsThe identification of patients with FH via cascade screening appeared to result in better prognosis.     

Breast cancer risk stratification using genetic and non-genetic risk assessment tools for 246,142 women in the UK Biobank

PurposeThe benefit of using individual risk prediction tools to identify high-risk individuals for breast cancer (BC) screening is uncertain, despite the personalized approach of risk-based screening.MethodsWe studied the overlap of predicted high-risk individuals among 246,142 women enrolled in the UK Biobank. Risk predictors assessed include the Gail model (Gail), BC family history (FH, binary), BC polygenic risk score (PRS), and presence of loss-of-function (LoF) variants in BC predisposition genes. Youden J-index was used to select optimal thresholds for defining high-risk.ResultsIn total, 147,399 were considered at high risk for developing BC within the next 2 years by at least 1 of the 4 risk prediction tools examined (Gail_2-year > 0.5%: 47%, PRS_2-yea r > 0.7%: 30%, FH: 6%, and LoF: 1%); 92,851 (38%) were flagged by only 1 risk predictor. The overlap between individuals flagged as high-risk because of genetic (PRS) and Gail model risk factors was 30%. The best-performing combinatorial model comprises a union of high-risk women identified by PRS, FH, and, LoF (AUC_2-year [95% CI]: 62.2 [60.8 to 63.6]). Assigning individual weights to each risk prediction tool increased discriminatory ability.ConclusionRisk-based BC screening may require a multipronged approach that includes PRS, predisposition genes, FH, and other recognized risk factors.