Characterization of the unique Chinese W483X mutation in the low-density lipoprotein–receptor gene in young patients with homozygous familial hypercholesterolemia

Familial hypercholesterolemia in Chinese children and adolescents: a multicenter study

BACKGROUND

Familial hypercholesterolemia (FH) is an inherited disorder mainly marked by increased low-density lipoprotein cholesterol (LDL-C) concentrations and a heightened risk of early-onset arteriosclerotic cardiovascular disease (ASCVD). This study seeks to characterize the genetic spectrum and genotype‒phenotype correlations of FH in Chinese pediatric individuals.

METHODS

Data were gathered from individuals diagnosed with FH either clinically or genetically at multiple hospitals across mainland China from January 2016 to June 2024.

RESULTS

In total, 140 children and adolescents (mean age of 6.00 years) with clinically and genetically diagnosed FH were enrolled in the study, with 87 distinct variants identified in the LDLR, APOB and PCSK9 genes. Among the variants, 11 variants were newly identified worldwide, with 9 classified as "pathogenic" or "likely pathogenic", and 2 classified as "variants of uncertain significance". Additionally, the 5 most common variants in the study were c.1448G > A (p.W483*), c.1879G > A (p.A627T), c.1216C > A (p.R406R), and c.1747C > T (p.H583Y) in the LDLR gene, as well as c.10579C > T (p.R3527W) in the APOB gene, accounting for 49.29% (69/140) of all patients. These variants are primarily observed in the Asian or Chinese population and are distinct from those present in Caucasian groups. In this cohort, 105 patients were diagnosed with heterozygous FH (HeFH), while 35 were diagnosed with homozygous FH (HoFH). Finally, only 28.57% of the patients (40/140) were using lipid-lowering medications with 33.33% of HoFH patients initiating treatment after the age of 8. Additionally, only 3 compound heterozygous patients (2.14%) underwent liver transplantation because of significantly high lipid levels.

CONCLUSION

This study reveals the variable genotypes and phenotypes of children with FH in China and illustrates that the genotypes in the Chinese population differ from those in Caucasians, providing a valuable dataset for the clinical genetic screening of FH in China. Furthermore, the older age at diagnosis and treatment highlights the underdiagnosis and undertreatment of Chinese FH pediatric patients, suggesting that early identification should be improved through lipid or genetic screening, and that more timely and regular pharmacological treatments should be implemented.

Novel LDLR variants affecting low density lipoprotein metabolism identified in familial hypercholesterolemia

BACKGROUND

Familial hypercholesterolemia (FH) is an autosomal dominant disease of lipid metabolism mainly caused by mutations in the low-density lipoprotein receptor (LDLR) gene. Genetic detection of patients with FH help with precise diagnosis and treatment, thus reducing the risk of coronary heart disease (CHD) and other related diseases. The study aimed to identify the causative gene mutations in a Chinese FH family and reveal the pathogenicity and the mechanism of these mutations.

METHODS AND RESULTS

Whole exome sequencing was performed in a patient with severe lipid metabolism dysfunction seeking fertility guidance from a Chinese FH family. Two LDLR variants c.1875 C > G (p.N625K; novel variant) and c.1448G > A (p.W483*) were identified in the family. Wildtype and mutant LDLR constructs were established by the site-direct mutagenesis technique. Functional studies were carried out by cell transfection to evaluate the impact of detected variants on LDLR activity. The two variants were proven to affect LDL uptake and binding, resulting in cholesterol clearance reduction to different degrees. According to The American College of Medical Genetics and Genomics (ACMG) Standards and Guidelines, the W483* variant was classified as "Pathogenic", while the N625K variant as "VUS".

CONCLUSIONS

Our results provide novel experimental evidence of functional alteration by LDLR variants identified in our study and expand the mutational spectrum of LDLR mutation induced FH.

Screening and clinical characteristics analysis of familial hypercholesterolemia in a tertiary public hospital

Background and aims

Familial hypercholesterolemia (FH) is becoming a global burden. However, it remains underdiagnosed and undertreated worldwide. This study aimed to observe the screening rate of FH patients and department distribution among hospitalized patients using different diagnostic criteria.

Methods

A total of 45,410 inpatients with LDL-C ≥3.5 mmol/L between 2008 and 2019 were included from The Second Affiliated Hospital of Nanchang University. Inpatients are diagnosed and divided into groups by Dutch Lipid Clinic Network (DLCN) criteria, Chinese-modified DLCN criteria and Chinese expert consensus (CEC) criteria.

Results

There were 172, 1,076 and 115 inpatients included in the DLCN group, Chinese-modified DLCN group and CEC group, respectively (screening rates: 0.38%, 2.37% and 0.25%). These FH patients had a very high risk of atherosclerotic cardiovascular disease (ASCVD) (55.7%-74.4%), especially in the DLCN group and CEC group (70.4%-74.4%). More than half of the patients were in the Department of Cardiology, and other high-risk departments included Neurology, Nephrology, Vascular Surgery, Otolaryngology & Head Neck Surgery and Traditional Chinese Medicine (24.35%-31.51%). Overall, hypertension, coronary heart disease, carotid arteriosclerosis, hepatic cyst, arrhythmia, and nonalcoholic fatty liver disease were common accompanying diseases with FH.

Conclusions

It is necessary to establish appropriate diagnostic criteria and more positive treatment strategies for the FH inpatient population. In addition, promoting awareness of FH among doctors from other departments is also necessary. Therefore, developing a comprehensive management strategy for FH disease is very important.

Expanding the genetic spectrum for Chinese familial hypercholesterolemia population with six genetic mutations identified using a next-generation sequencing-based laboratory-developed screening test

BACKGROUND

This study was to reveal the prevalence of definite familial hypercholesterolemia (FH) in the hospital-visiting population, determine the pathogenic mutation detection rate in clinically diagnosed definite FH patients, and expand the FH mutation spectrum in China.

METHODS

Blood lipid profiles of 41,803 patients visiting the hospital were investigated and 4967 patients with clinical diagnoses of other metabolic diseases were excluded. One hundred and seventy-three (0.41%) received a definite diagnosis of FH according to the Dutch Lipid Clinical Network Criteria-Chinese Revised Version (DLCN-CRV), and 18 patients subsequently agreed to undergo genetic testing. A next-generation sequencing (NGS)-based laboratory-developed test covering the exonic regions of 24 lipid metabolism-related genes was conducted alongside in silico analyses to identify possible FH mutations in 16 definite FH patients, according to the American College of Medical Genetics and Genomics (ACMG) criteria. Sanger sequencing was used to confirm mutations, and SWISS-MODEL was used to simulate the molecular structures of the confirmed protein-carrying mutations.

RESULTS

The FH prevalence was 0.41% for the 41,803 individuals (DLCN-CRV grade >8) and 25% of definite FH patients carried six FH pathogenic mutations (≥ACMG Class 4). All genetic variants were confirmed by Sanger sequencing. Five pathogenic variants on the LDLR gene (NM_000527: c.C1783T: p.R595W, c.T493G: p.W165G, c.G1879A: p.A627T, c.G682T: p.E228X, and exon10: c.G1432A: p.G478R) and one pathogenic variant on APOB (NM_000384: c.C10579T: p.R3527W) in 25% of the identified definite FH patients. Two pathogenic mutations, c.T493G (p.W165G) and c.C1783T (p.R595W), were added to the current genetic spectrum of FH in China.

CONCLUSION

This study contributes to improving the current FH detection rate and genetic screening strategies; it provides new directions for treatment, management, and drug development.

Proprotein convertase subtilisin/kexin type 9 inhibitor non responses in an adult with a history of coronary revascularization: A case report

BACKGROUND

Familial hypercholesterolemia (FH) is an autosomal dominant disorder that is characterized by severely increased low-density lipoprotein (LDL) cholesterol levels. At the same time, elevated LDL levels accelerated the development of coronary heart disease. Several classes of drugs are currently in use to treat FH. Proprotein convertase subtilisin/kexin type 9 inhibitor (PCSK9i) is novel one of these.

CASE SUMMARY

This manuscript reports a case of FH that responded modestly after treatment with PCSK9i and statin drugs. Of even more concern is that the patient frequently admitted to the hospital during a 12-year follow-up period. Subsequently, we identified a heterozygous mutation, 1448G>A (W483X) of the LDL receptor (LDLR) in this patient. The serum levels of PCSK9 (proprotein convertase subtilisin/kexin type 9) in the patient was 71.30 ± 26.66 ng/mL, which is close the average level reported in the literature. This LDLR mutation affects LDLR metabolism or structure, which may make it unsuitable for use of PCSK9i.

CONCLUSION

Our outcome demonstrates that LDLR-W483X represents a partial loss-of-function LDLR and may contribute to PCSK9i ineffective. In the meanwhile, additional measures are therefore required (particularly with gene sequencing or change the treatment plan) must be initiated as early as possible. Genetic testing for clinically challenging cases who do not respond to PCSK9i therapy is very helpful.

Development of an Optimized Tetra-Amplification Refractory Mutation System PCR for Detection of 12 Pathogenic Familial Hypercholesterolemia Variants in the Asian Population

Early detection of genetic diseases such as familial hypercholesterolemia (FH), and the confirmation of related pathogenic variants, are crucial in reducing the risk for premature coronary artery disease. Currently, next-generation sequencing is used for detecting FH-related candidate genes but is expensive and time-consuming. There is a lack of kits suitable for the detection of the common FH-related variants in the Asia-Pacific region. Thus, this study addressed that need with the development of an optimized tetra-amplification mutation system (T-ARMS) PCR-based assay for the detection of 12 pathogenic variants of FH in the Asian population. The two important parameters for T-ARMS PCR assay performance-annealing temperature and the ratio of outer/inner primer concentrations-were optimized in this study. The optimal annealing temperature of all 12 T-ARMS PCR reactions was 64.6°C. The ideal ratios of outer/inner primer concentrations with each pathogenic variant were: A1, 1:2; A2, 1:4; L1, 1:10; L2, 1:1; L3, 1:2; L4, 1:8; L5, 1:1; L6, 1:2; L7, 1:8; L8, 1:8; L9, 1:2; and L10, 1:8. The lowest limit of detection using DNA extracted from patients was 0.1 ng. The present article highlights the beneficial findings on T-ARMS PCR as part of the development of a PCR-based detection kit for use in detecting FH in economically developing countries in Asia with a greater prevalence of FH.

Integrated analysis of microRNA and mRNA expression profiles in homozygous familial hypercholesterolemia patients and validation of atherosclerosis associated critical regulatory network

Homozygous familial hypercholesterolemia (HoFH) is a rare, life-threatening genetic disorder characterized by an extremely elevated serum level of low-density lipoprotein cholesterol (LDL-C) and accelerated premature atherosclerotic cardiovascular diseases (ASCVD). However, the detailed mechanism of how the pathogenic mutations of HoFH trigger the acceleration of ASCVD is not well understood. Therefore, we performed high-throughput RNA and small RNA sequencing on the peripheral blood RNA samples of six HoFH patients and three healthy controls. The gene and miRNA expression differences were analyzed, and seven miRNAs and six corresponding genes were screened out through regulatory network analysis. Validation through quantitative PCR of genes and miRNAs from 52 HoFH patients and 20 healthy controls revealed that the expression levels of hsa-miR-486-3p, hsa-miR-941, and BIRC5 were significantly upregulated in HoFH, while ID1, PLA2G4C, and CACNA2D2 were downregulated. Spearman correlation analysis found that the levels of ID1, hsa-miR-941, and hsa-miR-486-3p were significantly correlated with additional ASCVD risk factors in HoFH patients. This study represents the first integrated analysis of transcriptome and miRNA expression profiles in patients with HoFH, a rare disease, and as a result, six differentially expressed miRNAs/genes that may be related to atherosclerosis in HoFH are reported. The miRNA-mRNA regulatory network may be the critical regulation mechanism by which ASCVD is accelerated in HoFH.

Hsa-miRNA-23a-3p promotes atherogenesis in a novel mouse model of atherosclerosis

Of the known regulators of atherosclerosis, miRNAs have been demonstrated to play critical roles in lipoprotein homeostasis and plaque formation. Here, we generated a novel animal model of atherosclerosis by knocking in LDLRW483X in C57BL/6 mice, as the W483X mutation in LDLR is considered the most common newly identified pathogenic mutation in Chinese familial hypercholesterolemia (FH) individuals. Using the new in vivo mouse model combined with a well-established atherosclerotic in vitro human cell model, we identified a novel atherosclerosis-related miRNA, miR-23a-3p, by microarray analysis of mouse aortic tissue specimens and human aortic endothelial cells (HAECs). miR-23a-3p was consistently downregulated in both models, which was confirmed by qPCR. Bioinformatics analysis and further validation experiments revealed that the TNFα-induced protein 3 (TNFAIP3) gene was the key target of miR-23a-3p. The miR-23a-3p-related functional pathways were then analyzed in HAECs. Collectively, the present results suggest that miR-23a-3p regulates inflammatory and apoptotic pathways in atherogenesis by targeting TNFAIP3 through the NF-κB and p38/MAPK signaling pathways.

Targeted Genetic Analysis in a Chinese Cohort of 208 Patients Related to Familial Hypercholesterolemia

AIM

Familial hypercholesterolemia (FH) is the most commonly encountered genetic condition that predisposes individuals to severe autosomal dominant lipid metabolism dysfunction. Although more than 75% of the European population has been scrutinized for FH-causing mutations, the genetic diagnosis proportion among Chinese people remains very low (less than 0.5%). The aim of this study was to identify genetic mutations and help make a precise diagnosis in Chinese FH patients.

METHODS

We designed a gene panel containing 20 genes responsible for FH and tested 208 unrelated Chinese possible/probable or definite FH probands. In addition, we called LDLR copy number variation (CNVs) with the panel data by panelcn.MOPS, and multiple ligation-dependent probe amplification (MLPA) was used to search for CNVs in LDLR, APOB, and PCSK9.

RESULTS

A total of 79 probands (38.0%) tested positive for a (likely) pathogenic mutation, most of which were LDLR mutations, and three LDLR CNVs called from the panel data were all successfully confirmed by MLPA analysis. In total, 48 different mutations were identified, including 45 LDLR mutations, 1 APOB mutation, 1 ABCG5 mutation, and 1 APOE mutation. Among them, the five most frequent mutations (LDLR c.1879G＞A, c.1747C＞T, c.313＋1G＞A, c.400T＞C, and APOB c.10579C＞T) were detected. Moreover, we also found that patients with LDLR variants of CNVs and splicing and nonsense had increased low-density lipoprotein cholesterol levels when compared with those who carried missense variants.

CONCLUSIONS

The spectrum of FH-causing mutations in the Chinese population is refined and expanded. Analyses of FH causal genes have been a great help in clinical diagnosis and have deep implications in disease treatment. These data can serve as a considerable dataset for next-generation sequencing analysis of the Chinese population with FH and contribute to the genetic diagnosis and counseling of FH patients.

Nano-MOF@defected film C3N4 Z-scheme composite for visible-light photocatalytic nitrogen fixation

Photocatalytic nitrogen fixation has attracted extensive attention in recent years.

Independent Severe Cases of Heterozygous Familial Hypercholesterolemia Caused by the W483X and Novel W483G Mutations in the Low-Density Lipoprotein Receptor Gene That Were Clinically Diagnosed as Homozygous Cases

Background and Aims: The genetic spectrum underlying familial hypercholesterolemia (FH) remains unclear, especially in northeastern China. The aim of this study was to delineate the FH genetic spectrum and identify specific characteristics of FH patients in this region. Materials and Methods: The family history, personal medical history, and lifestyle habits of two unrelated patients clinically diagnosed with homozygous FH were recorded. DNA samples of the patients and their relatives were subjected to a newly designed next-generation sequencing panel using an Illumina Miseq platform. Detected variants were annotated and functionally predicted with in silico algorithms, and protein structures were modeled. Results: The patients' cholesterol levels were effectively reduced to 33.8% and 17.2% of the original level under conventional ezetimibe and statin treatment. Two pathogenic mutations, W483X and the novel mutation W483G, in the low-density lipoprotein receptor (LDLR) gene were identified. Both patients were heterozygous for the respective mutations. Under a high cholesterol/carbohydrate diet, these mutations could trigger a severe FH phenotype, but both patients responded well to regular medical treatments and dietary control. The W483X mutation results in a premature stop codon, leading to incomplete protein formation. Although the W483G mutation results in translation of the complete protein with no apparent structural difference, it still led to a severe FH phenotype similar to W483X. Conclusions: Identification of the novel W483G mutation expands the genetic spectrum of FH. Both mutations cause a severe FH phenotype under certain conditions, suggesting that W483 is important for LDLR function, highlighting potential targets for genetic screening or drug development.

The genetic spectrum of familial hypercholesterolemia in the central south region of China

BACKGROUND AND AIMS

Familial hypercholesterolemia (FH) is the most common and severe autosomal dominant lipid metabolism dysfunction, which causes xanthoma, atherosclerosis and coronary heart disease. Earlier studies showed that mutations in LDLR, APOB and PCSK9 cause FH. Although more than 75% of the population in Europe has been scrutinized for FH-causing mutations, the genetic diagnosis proportion among Chinese people remains very low (less than 0.5%). The aim of this study was to perform a survey and mutation detection among the Chinese population.

METHODS

219 FH patients from the central south region of China were enrolled. After extracting DNA from circulating lymphocytes, we used direct DNA sequencing to screen each exon of LDLR, APOB and PCSK9. All detected variants were predicted by Mutationtaster, Polyphen-2 and SIFT to assess their effects.

RESULTS

In total, 43 mutations were identified from 158 FH patients. Among them, 11 novel mutations were found, including seven LDLR mutations, two APOB mutations and two PCSK9 mutations. Moreover, five common mutations in LDLR were detected. We geographically marked their distributions on the map of China.

CONCLUSIONS

The spectrum of FH-causing mutations in the Chinese population is refined and expanded. Along with future studies, our study provides the necessary data as the foundation for the characterization of the allele frequency distribution in the Chinese population. The identification of more LDLR, APOB and PCSK9 novel mutations may expand the spectrum of FH-causing mutations and contribute to the genetic diagnosis and counseling of FH patients.

The use of targeted exome sequencing in genetic diagnosis of young patients with severe hypercholesterolemia

Familial hypercholesterolemia (FH) is an autosomal dominant disorder. Although genetic testing is an important tool for detecting FH-causing mutations in patients, diagnostic methods for young patients with severe hypercholesterolemia are understudied. This study compares the target exome sequencing (TES) technique with the DNA resequencing array technique on young patients with severe hypercholesterolemia. A total of 20 unrelated patients (mean age 14.8 years) with total cholesterol > 10 mmol/L were included. 12 patient samples were processed by DNA resequencing array, 14 patient samples were processed by TES, and 6 patient samples were processed by both methods. Functional characterization of novel mutations was performed by flow cytometry. The mutation detection rate (MDR) of DNA resequencing array was 75%, while the MDR of TES was 100%. A total of 27 different mutations in the LDLR were identified, including 3 novel mutations and 8 mutations with previously unknown pathogenicity. Functional characterization of c.673delA, c.1363delC, p.Leu575Phe and p.Leu582Phe variants found that all of them are pathogenic. Additionally, 7 patients were diagnosed with Heterozygous FH (HeFH) in which lipid levels were significantly higher than common HeFH patients. This data indicates that TES is a very efficient tool for genetic diagnosis in young patients with severe hypercholesterolemia.