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Wang K, Hu T, Tai M, Shen Y, Chai H, Lin S, Chen X. LDLR c.415G > A causes familial hypercholesterolemia by weakening LDLR binding to LDL. Lipids Health Dis 2024; 23:85. [PMID: 38515137 PMCID: PMC10956282 DOI: 10.1186/s12944-024-02068-2] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/05/2024] [Accepted: 02/28/2024] [Indexed: 03/23/2024] Open
Abstract
BACKGROUND Familial hypercholesterolemia (FH) is a prevalent hereditary disease that can cause aberrant cholesterol metabolism. In this study, we confirmed that c.415G > A in low-density lipoprotein receptor (LDLR), an FH-related gene, is a pathogenic variant in FH by in silico analysis and functional experiments. METHODS The proband and his family were evaluated using the diagnostic criteria of the Dutch Lipid Clinic Network. Whole-exome and Sanger sequencing were used to explore and validate FH-related variants. In silico analyses were used to evaluate the pathogenicity of the candidate variant and its impact on protein stability. Molecular and biochemical methods were performed to examine the effects of the LDLR c.415G > A variant in vitro. RESULTS Four of six participants had a diagnosis of FH. It was estimated that the LDLR c.415G > A variant in this family was likely pathogenic. Western blotting and qPCR suggested that LDLR c.415G > A does not affect protein expression. Functional studies showed that this variant may lead to dyslipidemia by impairing the binding and absorption of LDLR to low-density lipoprotein ( LDL). CONCLUSION LDLR c.415G > A is a pathogenic variant in FH; it causes a significant reduction in LDLR's capacity to bind LDL, resulting in impaired LDL uptake. These findings expand the spectrum of variants associated with FH.
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Affiliation(s)
- Kaihan Wang
- Department of Cardiology, The First Affiliated Hospital of Ningbo University, Ningbo, Zhejiang, China
| | - Tingting Hu
- Department of Cardiology, The Quzhou Affiliated Hospital of Wenzhou Medical University, Quzhou People's Hospital, Quzhou, Zhejiang, China
| | - Mengmeng Tai
- Department of Cardiology, The First Affiliated Hospital of Ningbo University, Ningbo, Zhejiang, China
| | - Yan Shen
- Department of Cardiology, The First Affiliated Hospital of Ningbo University, Ningbo, Zhejiang, China
| | - Haocheng Chai
- Department of Gastroenterology, Ningbo Ninth Hospital, Ningbo, Zhejiang, China
| | - Shaoyi Lin
- Department of Cardiology, The First Affiliated Hospital of Ningbo University, Ningbo, Zhejiang, China.
| | - Xiaomin Chen
- Department of Cardiology, The First Affiliated Hospital of Ningbo University, Ningbo, Zhejiang, China.
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Awan Z, Batran A, Al-Allaf FA, Alharbi RS, Hegazy GA, Jamalalail B, Almansouri M, Bima AI, Almukadi H, Kutbi HI, Altayar AE, Banaganapalli B, Shaik NA. Identification and functional characterization of two rare LDLR stop gain variants (p.C231* and p.R744*) in Saudi familial hypercholesterolemia patients. Panminerva Med 2023; 65:479-490. [PMID: 35274909 DOI: 10.23736/s0031-0808.22.04612-2] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
Abstract
BACKGROUND Familial hypercholesterolemia (FH) is a globally underdiagnosed inherited metabolic disorder. Owing to limited published data from Arab world, this study was conducted with the aim of identifying the genetic and molecular basis of FH in highly consanguineous Saudi population. METHODS We performed clinical screening, biochemical profiling, whole exome sequencing and variant segregation analysis of two Saudi FH families. Additionally, 500 normolipic individuals were screened to ensure the absence of FH variant in general Saudi population. Functional characterization of FH variants on secondary structure characteristics of RNA and protein molecules was performed using different bioinformatics modelling approaches. RESULTS WES analysis identified two independent rare LDLR gene stop gain variants (p.C231* and p.R744*) consistent to the clinical presentation of FH patients from two different families. RNAfold analysis has shown that both variants were predicted to disturb the free energy dynamics of LDLR mRNA molecule and destabilize its folding pattern and function. PSIPRED based structural modelling analysis has suggested that both variants bring drastic changes disturbing the secondary structural elements of LDLR molecule. The p.C231* and p.R744* variants are responsible for partial or no protein product, thus they are class 1 variants causing loss of function (LoF) LDLR variants. CONCLUSIONS This study highlights the effectiveness of the WES, sanger sequencing, and computational analysis in expanding FH variant spectrum in culturally distinct populations like Saudi Arabia. Genetic testing of FH patients is very essential in better clinical diagnosis, screening, treatment, and management and prevention of cardiovascular disease burden in the society.
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Affiliation(s)
- Zuhier Awan
- Department of Clinical Biochemistry, Faculty of Medicine, King Abdulaziz University, Jeddah, Saudi Arabia
| | - Alhanuf Batran
- Department of Clinical Biochemistry, Faculty of Medicine, King Abdulaziz University, Jeddah, Saudi Arabia
| | - Faisal A Al-Allaf
- Department of Medical Genetics, Faculty of Medicine, Umm Al-Qura University, Makkah, Saudi Arabia
| | - Raneem S Alharbi
- Department of Genetics, Al Borg Medical Laboratories, Jeddah, Saudi Arabia
| | - Gehan A Hegazy
- Department of Clinical Biochemistry, Faculty of Medicine, King Abdulaziz University, Jeddah, Saudi Arabia
| | - Bassam Jamalalail
- Department of Genetics, Al Borg Medical Laboratories, Jeddah, Saudi Arabia
- Department of Pharmacology and Toxicology, Faculty of Pharmacy, King Abdulaziz University, Jeddah, Saudi Arabia
| | - Majid Almansouri
- Department of Clinical Biochemistry, Faculty of Medicine, King Abdulaziz University, Jeddah, Saudi Arabia
| | - Abdulhadi I Bima
- Department of Clinical Biochemistry, Faculty of Medicine, King Abdulaziz University, Jeddah, Saudi Arabia
| | - Haifa Almukadi
- Department of Pharmacy Practice, Faculty of Pharmacy, King Abdulaiziz University, Jeddah, Saudi Arabia
| | - Hussam I Kutbi
- Department of Genetic Medicine, Faculty of Medicine, King Abdulaziz University, Jeddah, Saudi Arabia
| | - Ahmed E Altayar
- Department of Genetic Medicine, Faculty of Medicine, King Abdulaziz University, Jeddah, Saudi Arabia
| | - Babajan Banaganapalli
- Department of Pharmacology and Toxicology, Faculty of Pharmacy, King Abdulaziz University, Jeddah, Saudi Arabia
- Princess Al-Jawhara Center of Excellence in Research of Hereditary Disorders, King Abdulaziz University, Jeddah, Saudi Arabia
| | - Noor A Shaik
- Department of Pharmacology and Toxicology, Faculty of Pharmacy, King Abdulaziz University, Jeddah, Saudi Arabia -
- Princess Al-Jawhara Center of Excellence in Research of Hereditary Disorders, King Abdulaziz University, Jeddah, Saudi Arabia
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3
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Athar M, Toonsi M, Abduljaleel Z, Bouazzaoui A, Bogari NM, Dannoun A, Al-Allaf FA. Novel LDLR Variant in Familial Hypercholesterolemia: NGS-Based Identification, In Silico Characterization, and Pharmacogenetic Insights. Life (Basel) 2023; 13:1542. [PMID: 37511917 PMCID: PMC10381584 DOI: 10.3390/life13071542] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/20/2023] [Revised: 06/25/2023] [Accepted: 07/07/2023] [Indexed: 07/30/2023] Open
Abstract
BACKGROUND Familial Hypercholesterolemia (FH) is a hereditary condition that causes a rise in blood cholesterol throughout a person's life. FH can result in myocardial infarction and even sudden death if not treated. FH is thought to be caused mainly by variants in the gene for the low-density lipoprotein receptor (LDLR). This study aimed to investigate the genetic variants in FH patients, verify their pathogenicity, and comprehend the relationships between genotype and phenotype. Also, review studies assessed the relationship between the LDLR null variants and the reaction to lipid-lowering therapy. METHODS The study utilised high-throughput next-generation sequencing for genetic screening of FH-associated genes and capillary sequencing for cascade screening. Furthermore, bioinformatic analysis was employed to describe the pathogenic effects of the revealed novel variant on the structural features of the corresponding RNA molecule. RESULTS We studied the clinical signs of hypercholesterolemia in a Saudi family with three generations of FH. We discovered a novel frameshift variant (c.666_670dup, p.(Asp224Alafs*43) in the LDLR and a known single nucleotide variant (c.9835A > G, p.(Ser3279Gly) in the APOB gene. It is thought that the LDLR variant causes a protein to be prematurely truncated, likely through nonsense-mediated protein decay. The LDLR variant is strongly predicted to be pathogenic in accordance with ACMG guidelines and co-segregated with the FH clinical characteristics of the family. This LDLR variant exhibited severe clinical FH phenotypes and was restricted to the LDLR protein's ligand-binding domain. According to computational functional characterization, this LDLR variant was predicted to change the free energy dynamics of the RNA molecule, thereby affecting its stability. This frameshift variant is thought to eliminate important functional domains in LDLR that are required for receptor recycling and LDL particle binding. We provide insight into how FH patients with a null variant in the LDLR gene respond to lipid-lowering therapy. CONCLUSIONS The findings expand the range of FH variants and assist coronary artery disease preventive efforts by improving diagnosis, understanding the genotype-phenotype relationship, prognosis, and personalised therapy for patients with FH.
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Affiliation(s)
- Mohammad Athar
- Department of Medical Genetics, Faculty of Medicine, Umm Al-Qura University, Makkah 21955, Saudi Arabia
- Science and Technology Unit, Umm Al-Qura University, Makkah 21955, Saudi Arabia
| | - Mawaddah Toonsi
- Department of Pediatrics, Umm Al-Qura University, Makkah 21955, Saudi Arabia
| | - Zainularifeen Abduljaleel
- Department of Medical Genetics, Faculty of Medicine, Umm Al-Qura University, Makkah 21955, Saudi Arabia
- Science and Technology Unit, Umm Al-Qura University, Makkah 21955, Saudi Arabia
| | - Abdellatif Bouazzaoui
- Department of Medical Genetics, Faculty of Medicine, Umm Al-Qura University, Makkah 21955, Saudi Arabia
- Science and Technology Unit, Umm Al-Qura University, Makkah 21955, Saudi Arabia
| | - Neda M Bogari
- Department of Medical Genetics, Faculty of Medicine, Umm Al-Qura University, Makkah 21955, Saudi Arabia
| | - Anas Dannoun
- Department of Medical Genetics, Faculty of Medicine, Umm Al-Qura University, Makkah 21955, Saudi Arabia
| | - Faisal A Al-Allaf
- Department of Medical Genetics, Faculty of Medicine, Umm Al-Qura University, Makkah 21955, Saudi Arabia
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Alaifan MA, Abusharifah O, Bokhary RY, Banaganapalli B, Shaik NA, Kamal NM, Saadah OI. Granulomatous hepatitis in a Saudi child with IL2RA defect: a case report and literature review. Ther Adv Chronic Dis 2022; 13:20406223221116798. [PMID: 35968218 PMCID: PMC9373126 DOI: 10.1177/20406223221116798] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/18/2021] [Accepted: 06/30/2022] [Indexed: 11/17/2022] Open
Abstract
Interleukin-2 receptor alpha (IL2RA) defect (OMIM- # 606367) is an immune disease where affected patients are vulnerable to developing recurrent microbial infections in addition to lymphadenopathy and dermatological manifestations. This condition is known to be caused by pathogenic variants in the IL2RA gene, which are inherited in an autosomal recessive fashion. In this case report, we present a patient with IL2RA defect from Saudi Arabia who presented with chronic diarrhea, poor weight gain, mild villous atrophy, malnutrition, hepatomegaly, nonspecific inflammation, and an eczematous skin rash. His genetic analysis revealed a novel, homozygous, and likely pathogenic variant, that is, c.504 C>A (Cys168Ter), located in the exon 4of the IL2RA gene, which was inherited from his parents in an autosomal recessive mode of inheritance. This variant produces a 272-amino-acid shorter IL2RA protein chain, which most likely becomes degraded in the cytosol. Thus, we assume that the c.504 C>A is a null allele that abolishes the synthesis of IL2RA, malforms the IL-2 receptor complex, and eventually causes immunodeficiency manifestations. To our knowledge, this is the first time a person with IL2RA defect has shown signs of granulomatous hepatitis on a liver biopsy.
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Affiliation(s)
- Meshari A Alaifan
- Department of Pediatrics, Faculty of Medicine, King Abdulaziz University, Jeddah, Saudi Arabia
| | - Ohood Abusharifah
- Department of Pediatrics, Maternity and Children Hospital Abha, Abha, Saudi Arabia
| | - Rana Yagoub Bokhary
- Department of Pathology, Faculty of Medicine, King Abdulaziz University, Jeddah, Saudi Arabia
| | - Babajan Banaganapalli
- Princess Al-Jawhara Center of Excellence in Research of Hereditary Disorders, King Abdulaziz University, Jeddah, Saudi Arabia
| | - Noor Ahmad Shaik
- Princess Al-Jawhara Center of Excellence in Research of Hereditary Disorders, King Abdulaziz University, Jeddah, Saudi Arabia
| | - Naglaa M Kamal
- Department of Pediatrics, Kasr Alainy Faculty of Medicine, Cairo University, Cairo, Egypt
| | - Omar I Saadah
- Department of Pediatrics, Faculty of Medicine, King Abdulaziz University, P.O. Box 80205, Jeddah 21589, Saudi Arabia
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5
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Awan ZA, Rashidi OM, Al-Shehri BA, Jamil K, Elango R, Al-Aama JY, Hegele RA, Banaganapalli B, Shaik NA. Saudi Familial Hypercholesterolemia Patients With Rare LDLR Stop Gain Variant Showed Variable Clinical Phenotype and Resistance to Multiple Drug Regimen. Front Med (Lausanne) 2021; 8:694668. [PMID: 34249980 PMCID: PMC8267156 DOI: 10.3389/fmed.2021.694668] [Citation(s) in RCA: 7] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/13/2021] [Accepted: 05/31/2021] [Indexed: 12/16/2022] Open
Abstract
Familial hypercholesterolemia (FH), a well-known lipid disease caused by inherited genetic defects in cholesterol uptake and metabolism is underdiagnosed in many countries including Saudi Arabia. The present study aims to identify the molecular basis of severe clinical manifestations of FH patients from unrelated Saudi consanguineous families. Two Saudi families with multiple FH patients fulfilling the combined FH diagnostic criteria of Simon Broome Register, and the Dutch Lipid Clinic Network (DLCN) were recruited. LipidSeq, a targeted resequencing panel for monogenic dyslipidemias, was used to identify causative pathogenic mutation in these two families and in 92 unrelated FH cases. Twelve FH patients from two unrelated families were sharing a very rare, pathogenic and founder LDLR stop gain mutation i.e., c.2027delG (p.Gly676Alafs*33) in both the homozygous or heterozygous states, but not in unrelated patients. Based on the variant zygosity, a marked phenotypic heterogeneity in terms of LDL-C levels, clinical presentations and resistance to anti-lipid treatment regimen (ACE inhibitors, β-blockers, ezetimibe, statins) of the FH patients was observed. This loss-of-function mutation is predicted to alter the free energy dynamics of the transcribed RNA, leading to its instability. Protein structural mapping has predicted that this non-sense mutation eliminates key functional domains in LDLR, which are essential for the receptor recycling and LDL particle binding. In conclusion, by combining genetics and structural bioinformatics approaches, this study identified and characterized a very rare FH causative LDLR pathogenic variant determining both clinical presentation and resistance to anti-lipid drug treatment.
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Affiliation(s)
- Zuhier Ahmed Awan
- Department of Clinical Biochemistry, Faculty of Medicine, King Abdulaziz University, Jeddah, Saudi Arabia.,Department of Genetics, Al Borg Medical Laboratories, Jeddah, Saudi Arabia
| | - Omran M Rashidi
- Department of Clinical Biochemistry, Faculty of Medicine, King Abdulaziz University, Jeddah, Saudi Arabia.,Department of Genetic Medicine, Faculty of Medicine, King Abdulaziz University, Jeddah, Saudi Arabia.,Princess Al-Jawhara Center of Excellence in Research of Hereditary Disorders, King Abdulaziz University, Jeddah, Saudi Arabia
| | - Bandar Ali Al-Shehri
- Department of Genetic Medicine, Faculty of Medicine, King Abdulaziz University, Jeddah, Saudi Arabia.,Princess Al-Jawhara Center of Excellence in Research of Hereditary Disorders, King Abdulaziz University, Jeddah, Saudi Arabia
| | - Kaiser Jamil
- Department of Genetics, Bhagwan Mahavir Medical Research Center (BMMRC), Hyderabad, India
| | - Ramu Elango
- Department of Genetic Medicine, Faculty of Medicine, King Abdulaziz University, Jeddah, Saudi Arabia.,Princess Al-Jawhara Center of Excellence in Research of Hereditary Disorders, King Abdulaziz University, Jeddah, Saudi Arabia
| | - Jumana Y Al-Aama
- Department of Genetic Medicine, Faculty of Medicine, King Abdulaziz University, Jeddah, Saudi Arabia.,Princess Al-Jawhara Center of Excellence in Research of Hereditary Disorders, King Abdulaziz University, Jeddah, Saudi Arabia
| | - Robert A Hegele
- Departments of Medicine and Biochemistry, Schulich School of Medicine and Dentistry, Robarts Research Institute, Western University, London, ON, Canada
| | - Babajan Banaganapalli
- Department of Genetic Medicine, Faculty of Medicine, King Abdulaziz University, Jeddah, Saudi Arabia.,Princess Al-Jawhara Center of Excellence in Research of Hereditary Disorders, King Abdulaziz University, Jeddah, Saudi Arabia
| | - Noor A Shaik
- Department of Genetic Medicine, Faculty of Medicine, King Abdulaziz University, Jeddah, Saudi Arabia.,Princess Al-Jawhara Center of Excellence in Research of Hereditary Disorders, King Abdulaziz University, Jeddah, Saudi Arabia
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6
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Pirazzi C, Håkansson L, Gustafsson C, Omerovic E, Wiklund O, Mancina RM. High prevalence of genetic determined familial hypercholesterolemia in premature coronary artery disease. APPLICATION OF CLINICAL GENETICS 2019; 12:71-78. [PMID: 31213876 PMCID: PMC6538839 DOI: 10.2147/tacg.s202942] [Citation(s) in RCA: 13] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 01/26/2019] [Accepted: 03/14/2019] [Indexed: 02/02/2023]
Abstract
Background: Premature coronary artery disease (CAD) is a major cause of mortality and morbidity. Increased low-density lipoprotein-cholesterol (LDL-C) level is a major risk factor for CAD and thus the main target for its prevention. Familial Hypercholesterolemia (FH) is a genetic inherited disorder characterized by high LDL-C, and subsequent premature CAD development. Early drug treatment with lipid-lowering medications in FH prevents cardiovascular disease onset. The FH prevalence in the Northern European general population is 0.3%, and it is estimated that it explains 20% of premature CAD cases in individuals with familial clustering. Despite the wide number of papers showing the prevalence of clinical FH in cardiovascular disease, the prevalence of genetic FH in individuals with premature CAD is not yet well known. Here, we examined the prevalence of genetically determined FH in individuals with premature CAD. Patients and methods: 66 patients who underwent coronary angiography with suspected premature acute coronary syndrome (age <50 years for men and <55 years for women) underwent genetic screening to identify FH-causing mutations. All patients underwent physical and clinical examinations. Information about family and personal history, drug therapy and habits were also collected. Results: We found FH-causative mutations in 3/66 (4.5%) screened individuals with premature CAD. When considering individuals with confirmed CAD after coronary angiography, the FH mutation prevalence was 6.1% (3/49). After excluding individuals with classical risk factors for CAD other than hypercholesterolemia, the FH mutation prevalence raised to 15.8% (3/19). Conclusion: In conclusion, we found that individuals with premature CAD have a more than 15-fold increased prevalence of FH mutations compared to the general population.
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Affiliation(s)
- Carlo Pirazzi
- Department of Cardiology, Sahlgrenska University Hospital, Gothenburg, Sweden
| | - Lina Håkansson
- Department of Cardiology, Sahlgrenska University Hospital, Gothenburg, Sweden
| | - Carola Gustafsson
- Department of Cardiology, Sahlgrenska University Hospital, Gothenburg, Sweden
| | - Elmir Omerovic
- Department of Cardiology, Sahlgrenska University Hospital, Gothenburg, Sweden.,Department of Molecular and Clinical Medicine, Institute of Medicine, Sahlgrenska Academy, Wallenberg Laboratory, University of Gothenburg, Gothenburg, Sweden
| | - Olov Wiklund
- Department of Molecular and Clinical Medicine, Institute of Medicine, Sahlgrenska Academy, Wallenberg Laboratory, University of Gothenburg, Gothenburg, Sweden
| | - Rosellina Margherita Mancina
- Department of Molecular and Clinical Medicine, Institute of Medicine, Sahlgrenska Academy, Wallenberg Laboratory, University of Gothenburg, Gothenburg, Sweden
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7
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Benito-Vicente A, Uribe KB, Jebari S, Galicia-Garcia U, Ostolaza H, Martin C. Familial Hypercholesterolemia: The Most Frequent Cholesterol Metabolism Disorder Caused Disease. Int J Mol Sci 2018; 19:ijms19113426. [PMID: 30388787 PMCID: PMC6275065 DOI: 10.3390/ijms19113426] [Citation(s) in RCA: 70] [Impact Index Per Article: 11.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/29/2018] [Revised: 10/21/2018] [Accepted: 10/29/2018] [Indexed: 12/18/2022] Open
Abstract
Cholesterol is an essential component of cell barrier formation and signaling transduction involved in many essential physiologic processes. For this reason, cholesterol metabolism must be tightly controlled. Cell cholesterol is mainly acquired from two sources: Dietary cholesterol, which is absorbed in the intestine and, intracellularly synthesized cholesterol that is mainly synthesized in the liver. Once acquired, both are delivered to peripheral tissues in a lipoprotein dependent mechanism. Malfunctioning of cholesterol metabolism is caused by multiple hereditary diseases, including Familial Hypercholesterolemia, Sitosterolemia Type C and Niemann-Pick Type C1. Of these, familial hypercholesterolemia (FH) is a common inherited autosomal co-dominant disorder characterized by high plasma cholesterol levels. Its frequency is estimated to be 1:200 and, if untreated, increases the risk of premature cardiovascular disease. This review aims to summarize the current knowledge on cholesterol metabolism and the relation of FH to cholesterol homeostasis with special focus on the genetics, diagnosis and treatment.
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Affiliation(s)
- Asier Benito-Vicente
- Departamento de Bioquímica, Instituto Biofisika (UPV/EHU, CSIC), Universidad del País Vasco, Apdo.644, 48080 Bilbao, Spain.
| | - Kepa B Uribe
- Departamento de Bioquímica, Instituto Biofisika (UPV/EHU, CSIC), Universidad del País Vasco, Apdo.644, 48080 Bilbao, Spain.
| | - Shifa Jebari
- Departamento de Bioquímica, Instituto Biofisika (UPV/EHU, CSIC), Universidad del País Vasco, Apdo.644, 48080 Bilbao, Spain.
| | - Unai Galicia-Garcia
- Departamento de Bioquímica, Instituto Biofisika (UPV/EHU, CSIC), Universidad del País Vasco, Apdo.644, 48080 Bilbao, Spain.
| | - Helena Ostolaza
- Departamento de Bioquímica, Instituto Biofisika (UPV/EHU, CSIC), Universidad del País Vasco, Apdo.644, 48080 Bilbao, Spain.
| | - Cesar Martin
- Departamento de Bioquímica, Instituto Biofisika (UPV/EHU, CSIC), Universidad del País Vasco, Apdo.644, 48080 Bilbao, Spain.
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8
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Etxebarria A, Benito-Vicente A, Palacios L, Stef M, Cenarro A, Civeira F, Ostolaza H, Martin C. Functional Characterization and Classification of Frequent Low-Density Lipoprotein Receptor Variants. Hum Mutat 2014; 36:129-41. [DOI: 10.1002/humu.22721] [Citation(s) in RCA: 36] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/20/2014] [Accepted: 10/24/2014] [Indexed: 11/07/2022]
Affiliation(s)
- Aitor Etxebarria
- Unidad de Biofísica (CSIC, UPV/EHU) and Departamento de Bioquímica; Universidad del País Vasco; Bilbao 48080 Spain
| | - Asier Benito-Vicente
- Unidad de Biofísica (CSIC, UPV/EHU) and Departamento de Bioquímica; Universidad del País Vasco; Bilbao 48080 Spain
| | | | | | - Ana Cenarro
- Unidad de Lípidos and Laboratorio de Investigación Molecular; Hospital Universitario Miguel Servet; Instituto Aragonés de Ciencias de la Salud (IACS); Zaragoza Spain
| | - Fernando Civeira
- Unidad de Lípidos and Laboratorio de Investigación Molecular; Hospital Universitario Miguel Servet; Instituto Aragonés de Ciencias de la Salud (IACS); Zaragoza Spain
| | - Helena Ostolaza
- Unidad de Biofísica (CSIC, UPV/EHU) and Departamento de Bioquímica; Universidad del País Vasco; Bilbao 48080 Spain
| | - Cesar Martin
- Unidad de Biofísica (CSIC, UPV/EHU) and Departamento de Bioquímica; Universidad del País Vasco; Bilbao 48080 Spain
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9
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Gao F, Ihn HE, Medina MW, Krauss RM. A common polymorphism in the LDL receptor gene has multiple effects on LDL receptor function. Hum Mol Genet 2013; 22:1424-31. [PMID: 23297366 DOI: 10.1093/hmg/dds559] [Citation(s) in RCA: 28] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022] Open
Abstract
A common synonymous single nucleotide polymorphism in exon 12 of the low-density lipoprotein receptor (LDLR) gene, rs688, has been associated with increased plasma total and LDL cholesterol in several populations. Using immortalized lymphoblastoid cell lines from a healthy study population, we confirmed an earlier report that the minor allele of rs688 is associated with increased exon 12 alternative splicing (P < 0.05) and showed that this triggered nonsense-mediated decay (NMD) of the alternatively spliced LDLR mRNA. However, since synonymous single nucleotide polymorphisms may influence structure and function of the encoded proteins by co-translational effects, we sought to test whether rs688 was also functional in the full-length mRNA. In HepG2 cells expressing LDLR cDNA constructs engineered to contain the major or minor allele of rs688, the latter was associated with a smaller amount of LDLR protein at the cell surface (-21.8 ± 0.6%, P = 0.012), a higher amount in the lysosome fraction (+25.7 ± 0.3%, P = 0.037) and reduced uptake of fluorescently labeled LDL (-24.3 ± 0.7%, P < 0.01). Moreover, in the presence of exogenous proprotein convertase subtilisin/kexin type 9 (PCSK9), a protein that reduces cellular LDL uptake by promoting lysosomal degradation of LDLR, the minor allele resulted in reduced capacity of a PCSK9 monoclonal antibody to increase LDL uptake. These findings are consistent with the hypothesis that rs688, which is located in the β-propeller region of LDLR, has effects on LDLR activity beyond its role in alternative splicing due to impairment of LDLR endosomal recycling and/or PCSK9 binding, processes in which the β-propeller is critically involved.
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Affiliation(s)
- Feng Gao
- Children’s Hospital Oakland Research Institute, 5700 Martin Luther King Jr. Way, Oakland, CA 94609, USA
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10
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Shawar SM, Al-Drees MA, Ramadan AR, Ali NH, Alfadhli SM. The Arabic allele: a single base pair substitution activates a 10-base downstream cryptic splice acceptor site in exon 12 of LDLR and severely decreases LDLR expression in two unrelated Arab families with familial hypercholesterolemia. Atherosclerosis 2011; 220:429-36. [PMID: 22129472 DOI: 10.1016/j.atherosclerosis.2011.10.045] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 08/23/2011] [Revised: 10/14/2011] [Accepted: 10/30/2011] [Indexed: 10/15/2022]
Abstract
Familial hypercholesterolemia (FH) is a monogenic autosomal dominant disorder caused by defects in LDLR. Few reports describe FH mutations among Arabs. We describe a mutation in LDLR of two unrelated Arab families. We investigated 19 patients using DNA sequencing, RFLP, and real-time (RT) PCR. DNA sequencing showed a base pair substitution (c.1706-2 A>T) in the splice acceptor site of LDLR intron 11. Our results were confirmed by RFLP on 2% agarose gel. In silico analysis predicted a new cryptic splice site downstream of the original position generating a 10-base deletion from the beginning of exon 12; (c.1706-1715del.ATCTCCTCAG). cDNA sequencing of exon 12 confirmed the computational analysis. The deletion was visualized on 4% agarose gel. The deletion generates a frameshift and a premature termination codon (c.1991-1993; p.(Asp569Valfs*93). RT-PCR revealed that LDLR mRNA is 9.3%±6.5 and 17.9%±8.0 for FH homozygote and heterozygote individuals respectively, compared to a healthy family control. We predict a class II LDLR mutation that leads to a truncated receptor missing exons 14-18. We called this mutation "the Arabic allele". We expect a significant contribution of this mutation to the prevalence of FH among Arabs. Also, we propose that the severe down regulation of LDLR mRNA expression is due to nonsense-mediated-decay.
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Affiliation(s)
- Said M Shawar
- Biotechnology Program, Arabian Gulf University, Manama, Bahrain.
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Etxebarria A, Palacios L, Stef M, Tejedor D, Uribe KB, Oleaga A, Irigoyen L, Torres B, Ostolaza H, Martin C. Functional characterization of splicing and ligand-binding domain variants in the LDL receptor. Hum Mutat 2011; 33:232-43. [PMID: 21990180 DOI: 10.1002/humu.21630] [Citation(s) in RCA: 32] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/09/2011] [Accepted: 09/26/2011] [Indexed: 12/11/2022]
Abstract
Familial hypercholesterolemia (FH) is an autosomal dominant disorder mostly caused by mutations in the LDLR gene. Although the detection of functional mutations in the LDLR gene provides an unequivocal diagnosis of the FH condition, there are many variants whose pathogenicity is still unknown. The aims of this study were to set up a rapid method to determine the effect of LDLR mutations, thereby providing an accurate diagnosis of FH, and to functionally characterize six LDLR mutations detected at high frequency by the LIPOchip(®) platform (Progenika Biopharma, Spain) in the Spanish population. LDLR expression and activity were analyzed by one-single-step flow cytometry assay and confocal microscopy. Splicing effects were determined by sequencing reverse transcription polymerase chain reaction products. The analysis of three heterozygous variants with a single point mutation within the low-density lipoprotein binding domain allowed us to classify the c.806G>A variant as nonpathogenic, and c.862G>A and c.895G>A variants as causative of FH. The results obtained for three variants affecting donor splice sites of the LDLR mRNA, c.313+2dupT, c.1186+5G>A, and c.1845+1G>C, demonstrated that these mutations are pathogenic. These results expand our knowledge of mutations responsible for FH, providing an accurate diagnosis and leading to early treatment to reduce the risk of premature cardiovascular events.
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Affiliation(s)
- Aitor Etxebarria
- Unidad de Biofísica (Centro Mixto CSIC-UPV/EHU) and Departamento de Bioquímica, Universidad del País Vasco, Apdo. 644, 48080 Bilbao, Spain
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Vaca G, Vàzquez A, Magaña MT, Ramìrez ML, Dàvalos IP, Martìnez E, Marìn B, Carrillo G. Mutational analysis of the LDL receptor and APOB genes in Mexican individuals with autosomal dominant hypercholesterolemia. Atherosclerosis 2011; 218:391-6. [PMID: 21722902 DOI: 10.1016/j.atherosclerosis.2011.06.006] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 01/05/2011] [Revised: 06/03/2011] [Accepted: 06/03/2011] [Indexed: 11/30/2022]
Abstract
The goal of this project was to identify families with autosomal dominant hypercholesterolemia (ADH) to facilitate early detection and treatment and to provide genetic counselling as well as to approximate the mutational diversity of ADH in Mexico. Mutational analysis of the LDLR and APOB genes in 62 index cases with a clinical and/or biochemical diagnosis of ADH was performed. Twenty-five mutations (24 LDLR, 1 APOB) were identified in 38 index cases. A total of 162 individuals with ADH were identified using familial segregation analysis performed in 269 relatives of the index cases. In addition, a novel PCSK9 mutation, c.1850 C>A (p.Ala617Asp), was detected. The LDLR mutations showed the following characteristics: (1) four mutations are novel: c.695 -1G>T, c.1034_1035insA, c.1586 G>A, c.2264_2273del; (2) the most common mutations were c.682 G>A (FH-Mexico), c.1055 G>A (FH-Mexico 2), and c.1090 T>C (FH-Mexico 3); (3) five mutations were identified in 3 or more apparently unrelated probands; (4) three mutations were observed in a true homozygous state; and (5) four index cases were compound heterozygous, and one was a carrier of two mutations in the same allele. These results suggest that, in Mexico, ADH exhibits allelic heterogeneity with 5 relatively common LDLR mutations and that mutations in the APOB gene are not a common cause of ADH. This knowledge is important for the genotype-phenotype correlation and for optimising both cholesterol lowering therapies and mutational analysis protocols. In addition, these data contribute to the understanding of the molecular basis of ADH in Mexico.
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Affiliation(s)
- Gerardo Vaca
- Divisiòn de Genètica, Centro de Investigaciòn Biomèdica de Occidente, IMSS, Guadalajara, Jalisco, Mexico.
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