家族性高胆固醇血症患者低密度脂蛋白受体基因复合杂合突变分析

目的:对1例临床确诊为纯合型家族性高胆固醇血症(FH)先证者及其核心家系成员进行基因检测分析,探讨患儿发病的分子病理基础.方法:收集先证者及父母血标本及临床资料,酚氯仿法提取基因组DNA,DNA直接测序方法检测低密度脂蛋白受体(LDL-R)基因18个外显子和启动子及载脂蛋白B(ApoB100)R3500Q位点,核苷酸序列分析结果与Gen Bank比对寻找突变.结果:(1)先证者三尖瓣轻度关闭不全,先证者父母双侧颈总动脉内-中膜增厚,先证者母亲左侧颈内动脉起始处后壁多发混合回声斑块(2)该家系排除ApoB100基因R3500Q突变;(3)先证者LDL-R基因第13外显子发生A606T和D601Y复合杂合突变,前者第1879位G→A碱基置换,导致丙氨酸改变为苏氨酸,后者为1864位G>T碱基置换,导致天冬氨酸改变为酪氨酸,其父为携带A606T突变的杂合子,其母为携带D601Y突变的杂合子.结论:先证者LDL-R基因存在A606T和D601Y复合杂合突变,它们分别来源于父系及母系遗传.     

家族性高胆固醇血症患者低密度脂蛋白受体基因新突变位点的鉴定

家族性高胆固醇血症(hypercholesterolemia familial,FH)是由于低密度脂蛋白受体(low density lipoprotein receptor,LDLR)基因突变导致的常染色体显性遗传性疾病,临床上表现为多发黄色瘤、高水平血浆LDL、早发性冠心病及有阳性家族史。本研究通过临床症状结合血脂测定诊断出一个FH家系,其纯合子FH患者的血浆总胆固醇水平高达19．05mmol／L,LDL达17．06mmol／L,并有黄色瘤;而杂合子FH患者的血浆总胆固醇水平为7．96mmol／L,LDL为5．55mmol/L,并有心绞痛症状和黄色瘤。我们对该FH家系患者LDLR基因的PCR扩增DNA片段进行测序,发现纯合子FH患者LDLR基因Exon4区域内发生了GAG683GCG突变,即编码LDLR第683位的谷氨酸被丙氨酸替换,而杂合子FH患者该位点呈现杂合突变。此基因型与临床诊断遗传谱完全一致。同时,利用获得Epstein-Barr(EB)病毒转化型人永生淋巴细胞株(EBV-Ls)与荧光探针DiI标记的LDL结合反应,再通过流式细胞仪检测结果显示,具有功能性LDLR的EBV-Ls细胞比例,在纯合子FH患者(7．02％)和杂合子FH患者(62．64％)均比健康对照者(84．69％)低,纯合子FH患者LDLR活性仅为健康对照者的8．29％、而杂合子FH患者LDLR活性约为健康对照者的73．96％,前者呈现非常显著的降低。这些EBV-Ls细胞LDLR的功能变化分析,有力地支持了该FH家系的临床诊断和DNA测序结果。经查阅最新的UMD-LDLR完全版证实,本研究发现鉴定的GAG683GCG突变是人LDLR基因的新突变位点。     

中国人群家族性高胆固醇血症LDLR基因突变研究进展

家族性高胆固醇血症(Familial hypercholesterolemia,FH)主要是由于低密度脂蛋白受体(Low-density lipoprotein receptor,LDLR)基因突变导致的单基因显性遗传性疾病。FH患者LDLR基因突变导致细胞膜表面LDLR减少或缺如,机体代谢胆固醇能力降低,血浆胆固醇增高并沉积在不同的组织和器官,常伴有全身黄色瘤和早发冠心病,因此FH也是最常见的严重代谢性疾病。世界范围内对LDLR基因突变的报道总共有1741种,经整理我国目前报道的140例FH指示病例,包括108种LDLR基因突变类型。文章对已报道的中国FH患者LDLR基因突变特点进行系统分析和综述,旨在为FH诊断治疗提供参考依据。     

有氧运动对高胆固醇血症大鼠肝脏低密度脂蛋白受体活性调节…

本文研究了实验性在醇血症大鼠肝脏低密度脂蛋白受体（ＬＤＬ－Ｒ）活性变化及有氧运动时ＬＤＬ－Ｒ活性调节的影响,发现,高脂（ＨＣ）组肝组织匀浆ＬＤＬ－ＲＩ自古以来生较正常对照（ＮＣ）组降低３７％（Ｐ〈０．０５）,同时血清大醇（ＴＣ）、低密度脂收白胆固醇（ＬＤＬ－Ｃ）及血清栽脂蛋白Ｂ（ＡｐｏＢ）均显著高于ＮＣ组（Ｐ〈０．０１）;高脂＋运动（ＨＥ）组ＴＣ、ＬＤＬ－Ｃ及ＡｐｏＢ均明显低于ＨＣ组,而ＬＤＬ－Ｒ     

有氧运动对高胆固醇血症大鼠肝脏低密度脂蛋白受体活性调节的影响

本文研究了实验性高胆固醇血症大鼠肝脏低密度脂蛋白受体（ＬＤＬＲ）活性变化及有氧运动时ＬＤＬＲ活性调节的影响。发现,高脂（ＨＣ）组肝组织匀浆ＬＤＬＲ活性较正常对照（ＮＣ）组降低３７％（Ｐ＜０．０５）,同时血清总胆固醇（ＴＣ）、低密度脂蛋白胆固醇（ＬＤＬＣ）及血清载脂蛋白Ｂ（ＡｐｏＢ）均显著高于ＮＣ组（Ｐ＜０．０１）;高脂＋运动（ＨＥ）组ＴＣ、ＬＤＬＣ及ＡｐｏＢ均明显低于ＨＣ组,而ＬＤＬＲ活性则较ＨＣ组增高２６％（Ｐ＜０．０５）。结果提示：（１）高胆固醇负荷时细胞可通过下行调节影响ＬＤＬＲ活性;（２）运动可能通过增加对细胞内胆固醇利用和降解,反馈作用于下行调节过程影响ＬＤＬＲ的合成,增加对ＬＤＬＣ摄取而显著改善血脂水平。     

家族性高胆固醇血症样表型遗传异质性的分子基础

家族性高胆固醇血症(FH)是由于低密度脂蛋白受体(LDL—R)基因突变,致使细胞表面LDL-R蛋白功能缺陷,导致血浆低密度脂蛋白(LDL)大幅度增高,并可导致早发冠心病。“FH”已经成为携带LDL-R基因突变患者的同意词,但日益增多的研究证实,其他6种基因突变也可通过不同机制导致FH样表型。这些致病基因的发现．促进胆固醇代谢的研究进入新领域,有助于深入探讨胆固醇代谢的调节机制,并将为FH样表型的诊断和治疗提供新的理论依据。文章就有关FH样表型遗传异质性的分子基础研究的近况作一简要综述．以引起人们的关注。     

PCR—单链构象多态性分析对p53基因点突变检测的研究进展

单链构象多态性（ＳＳＣＰ）对分析基因的突变是一种有效的手段,并具有其独特的优点。ＰＣＲ与ＳＳＣＰ结合后检测灵敏度更高,而在许多类型的肿瘤都存在有ｐ５３抑癌基因的突变,章综述了ＰＣＲ－ＳＳＣＰ分析技术检测ｐ５３基因突变的进展。     

腺病毒相关病毒携带低密度脂蛋白受体基因对实验性高胆固醇血症的治疗作用

低密度脂蛋白受体 (LDL- R)对于血清胆固醇的清除和预防动脉粥样硬化的发生起重要作用 .用构建了含有LDL- R基因的重组腺病毒相关病毒 ,通过腺病毒包被蛋白脂质体 (Adenosome) ,转移至食饵性高脂血症家兔的肝脏内 ,证明可以降低血浆胆固醇水平 ,为高胆固醇血症的基因治疗提供一条新途径     

LDL受体基因内含子15结构分析及其在家族性高胆固醇血症基因诊断中的应用

为了解人类ＬＤＬ受体基因内含子１５的遗传背景,利用长链ＰＣＲ和锚定ＰＣＲ分离了ＬＤＬ受体基因外显子１５－内含子１５－外显子１６和内含子１５的３‘末端片段。利用Ｄｙｎａｌｂｅａｄｓ固相单链分离ＰＣＲ产物直接测序法测定了内含子１５ ３’末端１２２２个碱基序列。序列显示：３‘末端含有由１６个碱基组成的典型３’末端剪接位点;３‘端上游第３１个碱基处含有经典分支位点,除了经典分支位点外,在３’末端上游第２０     

家族性高胆固醇血症HDL-miRNAs调节血单核细胞功能机制

本研究通过生物信息学方法分析家族性高胆固醇血症患者外周血单核细胞差异表达基因、HDL载体差异表达miRNA及其生物学功能,研究差异HDL-miRNA与单核细胞差异基因的相关性,探讨HDL-miRNA调控外周血单核细胞功能机制,寻找动脉粥样硬化防治新靶点。运用R语言分析GEO数据库共享平台家族性高胆固醇血症外周血单核细胞基因及HDL-miRNA探针芯片得到差异基因及差异miRNA,利用miRwalk2. 0预测miRNA靶基因,并利用STRING进行蛋白互作分析,构建差异miRNA与差异基因之间的调控网络。运用GO及KEGG分析研究基因功能。利用GEO数据(GSE6054)筛选出834个差异表达基因,利用GEO数据(GSE25108)筛选出HDL上差异miRNA28个。交叉匹配得到由19个差异miRNA和56个差异基因组配对的74对miRNA-靶基因。GO富集分析56个差异基因主要富集于肾上腺素受体信号等分子功能。KEGG分析56个差异基因主要富集于造血谱系通路上。家族性高胆固醇血症差异HDL-miRNA与外周血单核细胞差异mRNA具有相关性,HDL-miRNA有通过调控血单核细胞功能的可能性,可能参与高胆固醇血症导致动脉粥样硬化过程。     

A combined LDL receptor/LDL receptor adaptor protein 1 mutation as the cause for severe familial hypercholesterolemia

Familial hypercholesterolemia (FH) results from impaired catabolism of plasma low density lipoproteins (LDL), thus leading to high cholesterol, atherosclerosis, and a high risk of premature myocardial infarction. FH is commonly caused by defects of the LDL receptor or its main ligand apoB, together mediating cellular uptake and clearance of plasma LDL. In some cases FH is inherited by mutations in the genes of PCSK9 and LDLRAP1 (ARH) in a dominant or recessive trait. The encoded proteins are required for LDL receptor stability and internalization within the LDLR pathway. To detect the underlying genetic defect in a family of Turkish descent showing unregular inheritance of severe FH, we screened the four candidate genes by denaturing gradient gel electrophoresis (DGGE) mutation analysis. We identified different combinatory mixtures of LDLR- and LDLRAP1-gene defects as the cause for severe familial hypercholesterolemia in this family. We also show for the first time that a heterozygous LDLR mutation combined with a homozygous LDLRAP1 mutation produces a more severe hypercholesterolemia phenotype in the same family than a homozygous LDLR mutation alone.     

Novel and recurrent mutations of the LDL receptor gene in Korean patients with familial hypercholesterolemia

We have identified 16 different mutations of the low-density lipoprotein receptor (LDLR) gene in 25 unrelated Korean patients with heterozygous familial hypercholesterolemia (FH), including five novel mutations, C83Y, 661del17, 1705insCTAG, C675X, and 941-1G>A. The 1705insCTAG mutation in which the four 3 cent -terminal nucleotides of exon 11 are duplicated was found to prevent splicing of exon 11 and would therefore generate a truncated polypeptide. The in-frame 36-bp deletion (1591del36) in exon 11, which had been reported only in one Korean FH patient, was also found. We showed that this change affects transport of the LDL receptor from the endoplasmic reticulum to the cell surface. In addition, we found 8 mutations (-136C>T, E119K, E207K, E207X, F382L, R574Q, 1846-1G>A, and P664L) that had been described in other ethnic groups but not in Koreans, and 2 mutations (R94H and D200N) that had been described in Koreans as well as other ethnic groups. 5 mutations (1591del36, E119K, E207X, E207K, and P664L) were found more than once in the Korean FH samples. Identification of the novel and recurring LDLR mutations in Korean FH patients should facilitate prenatal and early diagnosis in families at high risk of FH.     

Increased production of VLDL apoB-100 in subjects with familial hypercholesterolemia carrying the same null LDL receptor gene mutation

Early radiokinetic studies revealed that the classical metabolic defect in patients with familial hypercholesterolemia (FH) is hypocatabolism of LDL due to decreased LDL receptor activity. However, recent studies have suggested that hepatic oversecretion of apolipoprotein B-100 (apoB-100)-containing lipoproteins could also contribute to the markedly elevated plasma concentrations of LDL-cholesterol found in FH. The aim of this study was to examine the kinetics of apoB-100 labeled with a stable isotope (l-[5,5,5-D(3)] leucine) in five normolipidemic controls and in seven well-characterized FH subjects that included six FH heterozygotes and one FH homozygote carrying the same null LDL receptor gene mutation. As compared with controls, the VLDL apoB-100 production rate was increased by 50% in the FH heterozygotes and by 109% in the FH homozygote. Furthermore, FH subjects had significantly higher LDL apoB-100 pool size and lower LDL apoB-100 fractional catabolic rate than controls. These results indicate that the elevation of plasma LDL-cholesterol found in FH is attributable to both decreased clearance of LDL and increased hepatic production of apoB-100-containing lipoproteins.     

A nonsense mutation in the LDL receptor gene leads to familial hypercholesterolemia in the Druze sect.

Familial hypercholesterolemia (FH) is an autosomal dominant disease caused by mutations in the LDL receptor gene. Here we characterize an LDL receptor mutation that is associated with a distinct haplotype and causes FH in the Druze, a small Middle Eastern Islamic sect with a high degree of inbreeding. The mutation was found in FH families from two distinct Druze villages from the Golan Heights (northern Israel). It was not found neither in another Druze FH family residing in a different geographical area nor in eight Arab and four Jewish FH heterozygote index cases whose hypercholesterolemia cosegregates with an identical LDL receptor gene haplotype. The mutation, a single-base substitution, results in a termination codon in exon 4 of the LDL receptor gene that encodes for the fourth repeat of the binding domain of the mature receptor. It can be diagnosed by allele-specific oligonucleotide hybridization of PCR-amplified DNA from FH patients.     

A double mutant LDL receptor allele in a Cypriot family with heterozygous familial hypercholesterolemia

Two novel mutations Q363X and D365E were identified in the low-density lipoprotein receptor gene in a Cypriot patient with heterozygous familial hypercholesterolemia. Restriction enzyme analysis of the index case and seven of her family members, by using AvaII and PvuII respectively, demonstrated that the two exon 8 mutations are transmitted in cis within the family. The disease phenotype is probably caused by the stop-363 mutation; this would result in a truncated protein that would probably be rapidly degraded in the extracellular space. Received: 15 August 1996 / Accepted: 10 February 1997     

Screening for known mutations in the LDL receptor gene causing familial hypercholesterolemia

Familial hypercholesterolemia (FH) is caused by defective low density lipoprotein (LDL) receptors and is characterized by hypercholesterolemia and premature coronary heart disease. Two strategies can be used to identify the mutation in the LDL receptor gene underlying FH. One strategy is to search for novel mutations by DNA sequencing with or without prior mutation screening. The other strategy is to screen for known mutations. In this study we employed the latter strategy to screen 75 unrelated, Norwegian FH subjects for 38 known mutations. Three of the 38 mutations were detected in our group of FH subjects. Two subjects had FH-Padova, one had FH-Cincinnati-2 and one had FH-Gujerat. When additional unrelated FH heterozygotes were screened for the three mutations, the gene frequencies were 1.3%, 1.0% and 3.0%, respectively. In addition to identifying known mutations we also detected a novel stop codon in codon 541 (S541X). We conclude that screening for known mutations in the LDL receptor gene should be used as a complementary strategy to screening for novel mutations in order to understand the molecular genetics of FH.     

Posttranslational processing of the LDL receptor and its genetic disruption in familial hypercholesterolemia

Synthesis of the low density lipoprotein (LDL) receptor was studied by incubation of cultured human fibroblasts with 35S-methionine followed by immunoprecipitation with a monoclonal antireceptor antibody. The receptor was synthesized as a precursor with an apparent molecular weight of 120 kilodaltons (kd) that was converted to a mature form of 160 kd. This novel form of processing occurred 15-30 min after synthesis and did not appear to be due to the simple addition of N-linked oligosaccharide chains. Fibroblasts from a child with the phenotype of homozygous familial hypercholesterolemia showed a disruption in receptor processing. This child has two different mutant alleles at the LDL receptor locus. One allele, inherited from his heterozygous mother, produces an abnormal 120 kd protein that cannot be processed to the mature 160 kd form. The other allele, inherited from his heterozygous father, produces a receptor that is synthesized as an elongated 170 kd precursor which undergoes a 40 kd increase in molecular weight to form an abnormally large receptor of 210 kd.     

Screening for mutations in exon 4 of the LDL receptor gene in a German population with severe hypercholesterolemia

A group of 218 patients with severe hypercholesterolemia (LDL cholesterol >260 mg/dl) living in the Cologne area were screened for mutations in the 3 half of exon 4 of the low density lipoprotein (LDL) receptor gene by the single-strand conformation polymorphism (SSCP) method. The analysed fragment was 242 bp in length and comprised approximately 6% of the coding region. In 11 patients an abnormal SSCP pattern was observed. Two of the abnormal fragment patterns were identical. The results of the SSCP screening could be confirmed by direct DNA sequencing. Three of the ten different mutations were previously described (3 bp deletion: codon 197; Asp₂₀₀Gly; Glu₂₀₇stop). Of the newly identified mutations there were two deletions, two insertions, one combined insertion and deletion mutation and two single base pair substitutions [1 bp deletion: G in codon 197; 37 bp deletion: T in codon 196–208 or AT in 196–207 and GA in codon 208; 18 bp insertion: codon 201–206; 8 bp insertion: codon 155–156 and GA in codon 157; 6 bp insertion (codon 196–197) and 5 bp deletion (codon 199, C in codon 198 and G in codon 198 or 200); Asp₂₀₀Tyr; Asp₂₀₃Val]. The 8-bp insertion was detected in a second unrelated individual. The analysis of the functional consequences of the mutations indicates that all mutations were causative of the LDL cholesterol elevation.     

Recurrent and novel LDL receptor gene mutations causing heterozygous familial hypercholesterolemia in La Habana

The molecular basis of familial hypercholesterolemia (FH) in three families of Spanish descent from La Habana was investigated by the candidate gene approach. The Arg3500Gln mutation of apolipoprotein B-100 was not found. Identification of low density lipoprotein receptor (LDLR) gene haplotypes segregating with FH guided the characterisation of three point mutations by automated sequencing. One, a Val408Met missense mutation, a founder mutation in Afrikaner FH patients, was recurrent, being associated with a distinct DNA haplotype. The other two, Glu256Lys and Val776Met missense mutations, were novel and modified highly conserved residues. These mutations were absent in normolipidemic subjects and were associated in heterozygous carriers with twice the cholesterol levels observed in noncarriers. Noticeably, cardiovascular complications were rarely observed in older heterozygotes, even in those with the Afrikaner FH-2 mutation. These findings confirm the molecular heterogeneity of LDLR gene mutations causing FH and the variability of their expression across different populations.