新LPL基因复合杂合变异导致的一例新生儿脂蛋白脂肪酶缺乏症

目的明确1例脂蛋白脂肪酶缺乏症新生儿的遗传学病因。方法应用目标区域捕获测序技术对患儿进行遗传代谢疾病相关基因检测,并对可疑变异位点在患儿及其父母进行Sanger测序验证。结果基因检测结果显示患儿LPL基因存在c.347G>C(p.Argll6Pro)和c.472T>G(p.Tyrl58Asp)复合杂合变异,父亲携带c.347G〉C(p・Argll6Pro)杂合变异,母亲携带c.472T>G(p.Tyrl58Asp)杂合变异,因此患儿的变异分别来源于其父母。结论LPL基因c.347G>C(p.Argll6Pro)和c.472T>G(p.Tyrl58Asp)复合杂合变异可能是这例脂蛋白脂肪酶缺乏症新生儿的致病原因。     

Identification of two mutations in a compound heterozygous child with dihydrolipoamide dehydrogenase deficiency

An infant girl with elevated blood lactate, pyruvate, and plasma branched-chain amino acids was diagnosed with dihydrolipoamide dehydrogenase (E3; dihydrolipoamide: NAD+ oxidoreductase, EC 1.8.1.4) deficiency. Activities of the pyruvate dehydrogenase complex and E3 from patient were 26 and 2% of controls in blood lymphocytes, and 11 and 14% in cultured skin fibroblasts, respectively. Western blot analysis demonstrated that the amount of E3 protein in fibroblasts from the patient and her father was about half of controls, while Northern blot analysis showed normal amounts of E3 RNA. DNA sequencing of cloned full-length E3 cDNAs from the patient revealed two mutations in separate alleles. One is a single base insertion of an extra adenine in the last codon of the leader peptide sequence (TAC-->TAAC) leading to a nonsense mutation which results in the premature termination of the precursor E3 polypeptide (Y35X). The other is a missense mutation due to substitution of guanine for adenine, causing an Arg-->Gly substitution at amino acid 460 of the mature protein (R460G) which triggers the loss of E3 activity probably by structural change in the E3 dimer. DNA sequencing of E3 cDNAs from the parents demonstrated that the nonsense mutation was inherited from the father and the missense mutation was inherited from the mother.      

Severe hypertriglyceridemia in a patient heterozygous for a lipoprotein lipase gene allele with two novel missense variants

Rare monogenic hyperchylomicronemia is caused by loss-of-function mutations in genes involved in the catabolism of triglyceride-rich lipoproteins, including the lipoprotein lipase gene, LPL. Clinical hallmarks of this condition are eruptive xanthomas, recurrent pancreatitis and abdominal pain. Patients with LPL deficiency and severe or recurrent pancreatitis are eligible for the first gene therapy treatment approved by the European Union. Therefore the precise molecular diagnosis of familial hyperchylomicronemia may affect treatment decisions. We present a 57-year-old male patient with excessive hypertriglyceridemia despite intensive lipid-lowering therapy. Abdominal sonography showed signs of chronic pancreatitis. Direct DNA sequencing and cloning revealed two novel missense variants, c.1302A>T and c.1306G>A, in exon 8 of the LPL gene coexisting on the same allele. The variants result in the amino-acid exchanges p.(Lys434Asn) and p.(Gly436Arg). They are located in the carboxy-terminal domain of lipoprotein lipase that interacts with the glycosylphosphatidylinositol-anchored HDL-binding protein (GPIHBP1) and are likely of functional relevance. No further relevant mutations were found by direct sequencing of the genes for APOA5, APOC2, LMF1 and GPIHBP1. We conclude that heterozygosity for damaging mutations of LPL may be sufficient to produce severe hypertriglyceridemia and that chylomicronemia may be transmitted in a dominant manner, at least in some families.     

家族性脂蛋白脂酶缺乏症的基因分析

目的分析中国家族性脂蛋白脂酶（ｌｉｐｏｐｒｏｔｅｉｎｌｉｐａｓｅ,ＬＰＬ）缺乏症的基因突变。方法以基因组ＤＮＡ为模板,借助聚合酶链反应扩增产物,用双脱氧末端终止法,对患者ＬＰＬ的ＤＮＡ序列进行检测。结果对ＬＰＬ基因的９个外显子测序,发现在第６外显子中一碱基发生错义突变,即６Ｇ９７９→Ａ（Ｇｌｕ２４２→Ｌｙｓ）,这是一杂合子的等位基因突变。结论ＬＰＬ基因在该位置的突变可能是导致患者ＬＰＬ活性显著降低和血清甘油三酯增高的原因。该位点的基因突变系首次报道。同时也为研究动脉粥样硬化和高脂血症等多种代谢疾病的发病机理提供了重要证据。     

Brothers with novel compound heterozygous mutations in COL27A1 causing dental and genital abnormalities

COL27A1 encodes a collagen type XXVII alpha 1 chain. It is the product of this gene that provides the structural support of connective tissue and is reported to be the causative gene of Steel syndrome (OMIM #615155). The primary symptoms of patients with this defect are consistent with systemic bone disease; however, recent reports note findings of intellectual disability and hearing loss. In this study, we identified novel COL27A1 compound heterozygous variants in two brothers with rhizomelia and congenital hip dislocation as well as dental and genital abnormalities that have not yet been reported in Steel syndrome. This variant, of maternal origin, caused an amino acid substitution of arginine for glycine, c.2026G>C or p.G676R, in the collagen helix domain, which is assumed to damage the structure of the helix. The paternally transmitted variant, c.2367G>A, is located at the 3′ end of exon 12, and cDNA analysis revealed a splicing alteration. These novel, compound heterozygous COL27A1 variants might indicate an association of the gene with tooth and genital abnormalities.     

复合杂合性蛋白C基因突变导致的遗传性蛋白C缺陷症家系分析

目的 对1个遗传性蛋白C(proteinC,PC)缺陷症家系进行蛋白 C基因(protein C gene,PROC)突变检测,探讨其分子发病机制.方法 通过检测先证者及其家系成员(共4代15人)血浆蛋白C活性(protein C activity,PC∶A)、蛋白C抗原含量(protein C antigen,PC∶Ag)及其他凝血指标进行表型分析;用PCR法扩增先证者PROC的9个外显子及其侧翼序列,PCR产物纯化后测序,发现突变位点则反向测序予以证实;针对先证者的突变位点,对其家系成员进行相应基因突变检测.结果 先证者PC∶ A和PC∶Ag明显降低,分别为26％和18.60％,家系中其他成员中有7人PC∶A降低,6人PC∶Ag降低.先证者的PROC第7外显子存在g.6128T＞G杂合错义突变导致p.Phe139Val,第9外显子存在g.8478G＞C杂合错义突变导致p.Asp255His;其祖母、父亲、三姑和四姑均存在g.6128T＞G杂合突变,母亲、二舅、妹妹和儿子均存在g.8478G＞C杂合突变.存在g.8478G＞C突变的成员PC∶A下降明显.结论 先证者PROCg.6128T＞G和g.8478G＞C突变分别来自其父系家族和母系家族,该复合杂合错义突变是导致遗传性PC缺陷症的分子基础.     

Plasma lipoprotein abnormalities in a case of primary high-density-lipoprotein (HDL) deficiency

A 53-year-old patient with primary HDL-deficiency is reported. About 2% of the normal concentration of alpha1 HDL was present in his plasma. The alpha1-high-density-lipoproteins separated into two fast-moving components in polyacrylamide gel electrophoresis. The Apo HDL contained both the main apolipoproteins, Apo A-I and Apo A-II, but in disproportionally reduced amounts, the concentration of Apo A-I being reduced about 360-fold, and that of Apo A-II about 14-fold. Concomitantly, the amount of the Apo C polypeptides in the HDL-fractions was decreased to about 5.5% and the activity of the enzyme lecithin cholesterol acyltransferase (EC 2.3.1.4.3) in plasma was found to be only 40% of normal. Apoprotein D was present in the LDL in association with Apo B, forming an abnormal, fast-moving LDL-complex. Apo A-I and Apo A-II were both of normal size as determined by SDS-PAGE, and reduction with thiols resulted in the shift of the M.W. of Apo A-II from 17,000 daltons to about 8,500 daltons. Both proteins were found in the same position as their normal counterparts in analytical isoelectric focusing. The most likely explanation for the multiple lipoprotein abnormalities seems to be that a defect in the regulation or structure of Apo A-I is the basis of the HDL-deficeincy.     

An incomplete form of familial lipoprotein lipase deficiency presenting with type I hyperlipoproteinemia

The author reports the case of a patient with an incomplete form of familial lipoprotein lipase deficiency associated with type I hyperlipoproteinemia manifesting an autosomal recessive pattern of inheritance. The patient presented with hepatosplenomegaly, abdominal pain, and fasting chylomicronemia. A Western diet elicited a steep increase in plasma triglyceride concentration and the appearance of floating chylomicrons over a clear infranatant in fasting plasma. Postheparin lipoprotein lipase activity was moderately reduced to 38% of control values. Adipose tissue lipoprotein lipase activity was 10% of normal, whereas his muscle enzyme activity was within the reference range. Two-dimensional electrophoresis of plasma apolipoproteins revealed the presence of normal activator (apolipoprotein C-II). These results confirm the importance of the adipose tissue enzyme for the clearance of diet-derived plasma triglycerides.     

Lipoprotein lipase activity in patients with combined hyperlipidaemia

The aetiology of familial combined hyperlipidaemia remains obscure, with both genetic and environmental factors contributing to the phenotype, which is frequently associated with premature coronary heart disease. We have studied lipoprotein lipase (LPL) activity and hepatic lipase (HL) activity in patients with coronary heart disease to determine whether variation in lipase activities contributes to this phenotype. Forty-one patients (mean age 50 years; 30 male) were selected on the basis of cholesterol levels above 6.5 mmol/l and triglyceride levels above 2.2 mmol/1, with apoprotein B values over the 90th percentile. There was a family history of premature coronary heart disease in 78% and a personal history in 64%, at mean age 44, the patient group therefore predominantly corresponded to the common definition of familial combined hyperlipidaemia, appropriate in the absence of molecular markers. None of the patients was diabetic; hypertension and smoking were not over represented. Blood samples were taken following intravenous administration of heparin (100IU/kg body wt), and LPL and HL activities were measured. Mean post-heparin LPL was significantly lower in patients than controls 10 min after heparin administration (2.98 ± 1.04 and 3.86 ± 0.93 mol ml^-1 h^-1, respectively, P = 0.001), and 37% patients had values below the 10th percentile of controls. Both male and female patients had significantly higher HL activities than their respective controls at 5, 10, 20 and 30 minutes postheparin. As expected, both female patients and controls had lower HL activities than males, although this sex difference did not reach statistical significance in the patient group. Mean lipid and lipoprotein results were: cholesterol 8.2 mmol/1; triglycerides 4.2 mmol/l; high-density lipoprotein cholesterol 0.90 mmol/1; apoprotein Al 122 mg/dl; apoprotein B 171 mg/dl; lipoprotein (a) 23 mg/dl (median 10 mg/dl). High-density lipoprotein cholesterol and triglycerides were negatively correlated (r = -0.26, P = 0.05). HL was significantly related to body mass index at all time points whereas the negative correlation between post-heparin LPL and body mass index was significant only 30 min after heparin administration. Post-heparin LPL was only weakly correlated with triglycerides 10 and 20 min after heparin administration. These lipid and lipoprotein results are clearly potentially atherogenic as indicated by the extent of premature coronary heart disease in the group described. A decrease in LPL activity may contribute to this pattern.Abbreviations FCHL familial combined hyperlipidaemia - CHD coronary heart disease - LPL lipoprotein lipase - HL hepatic lipase - HDL high-density lipoprotein - VLDL very low density lipoprotein; - apo apoprotein - TG triglyceride - BMI body mass index Correspondence to: M. Seed     

我国首例家族性脂蛋白脂酶缺乏症的临床研究

本文报道了我国首例家庭性脂蛋白脂酶缺乏症。患者有反复发作的急性胰腺炎病史，空腹血清呈乳糜状，为典型的Ｉ型高脂蛋白血症表型。肝素化合的血浆脂蛋白酶活性低于正常的１／１０，载脂蛋白Ｃ－Ⅱ含量增高。肝酯酶活性正常。服用多种降脂药物无效。外源性肝素化合血浆输入短时间和低血清甘油三酯浓度。     

CEDNIK syndrome in a Brazilian patient with compound heterozygous pathogenic variants

CEDNIK (Cerebral Dysgenesis, Neuropathy, Ichthyosis, and Keratoderma) syndrome is a neuro ichthyotic syndrome characterized by a clinical constellation of features including severe developmental delay, microcephaly, and facial dysmorphism. Here, we report the clinical and molecular characterization of a patient with CEDNIK syndrome harboring two compound heterozygous variants in the SNAP29 gene. The patient presents a combination of a loss-of-function SNAP29 mutation and a ～370 kb 22q11.2 deletion, each of these genetic variants inherited from one of the parents. This report provides detailed data of a patient with unprecedented genetic events leading to the CEDNIK phenotype and may contribute to the elucidation of this rare condition.