Variable expressivity of the clinical and biochemical phenotype associated with the apolipoprotein E p.Leu149del mutation

Splenomegaly with sea-blue histiocytes, thrombocytopenia and hypertriglyceridemia is a very rare association that has been described in only one report to date. The molecular defect in the two reported patients consists in a deletion of a leucine at position 149 in the receptor-binding region of the apoE molecule. Here, we report on another family in whom the proband and his brother were diagnosed with splenomegaly, thrombocytopenia and hypertriglyceridemia. An apoE p.Leu149del mutation was found in both subjects. A large beta band in the VLDL fraction and elevated VLDL cholesterol-to-plasma triglyceride ratio was observed in the proband only. Their mother, presenting with isolated hypertriglyceridemia, also carried the same p.Leu149del mutation. The coexistence of factors facilitating the development of hypertriglyceridemia and/or low HDL-cholesterol level could explain why the proband and his brother developed a splenomegaly with thrombocytopenia, whereas the mother did not. Moreover, the presence of an apoE2 allele in the proband likely explains the more severe phenotype we observed in this subject. In conclusion, the apoE p.Leu149del mutation results in a very striking phenotype including one or all symptoms among splenomegaly, thrombocytopenia and hypertriglyceridemia, and should be considered as a differential diagnosis of storage disorders in the causes of splenomegaly with sea-blue histiocytes.     

SSCP analysis of paraffin wax embedded tissues in a family with an atypical form of Fabry disease

To investigate the distribution of a single base pair mutation within a family with one known case of Fabry disease, DNA from paraffin wax embedded necropsy material was studied using single-strand conformation polymorphism (SSCP) analysis. The proband, who presented with an atypical form of Fabry disease, had a G to A transition in exon 6 of the α-galactosidase A gene. This patient had mainly cardiac symptoms and late onset disease. Further cases of coronary disorders occurred in this family, including the proband's brother who died at 42 years of age of a cardiac disorder. Formalin fixed, paraffin wax embedded material from the brother and two more distant relatives was available for analysis. SSCP analysis showed that the proband's brother also carried the G to A transition. Thus, the atypical form of Fabry disease and unrelated cardiac diseases with similar clinical symptoms occurred within a single family. The variant form is rare but may account for a few of the numerous cases of cardiac disease in men and should be considered when clusters of cases of cardiac disease occur within a single family.     

一个家族性异常白蛋白高甲状腺素血症的表型和基因型分析

目的报告一个家族性异常白蛋白高甲状腺素血症(familial dysalbuminaemic hyperthyroxinaemia，FDH)家系。方法测定家系4个成员(先证者、母亲、女儿和弟弟)血清甲状腺激素和促甲状腺激素，荧光标记甲状腺素(thyroxine，T4)和血清温育后进行蛋白电泳，白蛋白基因点突变检测。结果先证者、母亲和女儿的血清总甲状腺素升高，游离甲状腺素、总三碘甲腺原氨酸、游离三碘甲腺原氨酸和促甲状腺激素正常，蛋白电泳显示T4-白蛋白峰明显升高增宽，白蛋白基因DNA编码区653G→A。弟弟的甲状腺激素正常，T4结合蛋白电泳未见异常，白蛋白基因未见突变。结论首次报道国内一个FDH家系，白蛋白基因DNA编码区653G→A引起白蛋白和T4亲和性增加，导致血清T4测定假性升高。     

一个异染性脑白质营养不良家系ARSA基因突变分析

目的分析并确定一个异染性脑白质营养不良（metachromatic leukodystrophy，MLD）家系芳基硫酸酯酶A（arylsulftase A，ARSA）的基因（ARSA）突变及遗传特征。方法收集先证者及其家系成员临床资料，采用聚合酶链反应和DNA直接测序方法进行ARSA突变检测，确定基因突变的位点，分析基因型与表型的关系。结果该家系先证者的ARSA基因同时存在第2外显子G251A（R84Q）与G296T（G99V）两个杂合突变，具有相似表型的胞弟与先证者的测序结果完全一致，先证者之父母分别携带ARSA基因第2外显子G251A（R84Q）与G296T（G99V）的杂合突变，表型正常的先证者之姐未发现这些突变。结论该家系中两位患儿均为ARSA基因复合杂合突变致病，其G251A（R84Q）突变来自父亲，G296T（G99V）突变来自母亲，其父母均为表型正常的基因突变携带者。     

Association of apolipoprotein ɛ4 allele with hypertriglyceridemia in obesity

Hypertriglyceridemia is the most frequent lipid abnormality associated with obesity. Genetic polymorphism of apolipoprotein E (apoE) has been demonstrated to influence lipid levels. We wanted to assess the role of apoE alleles in the hypertriglyceridemias of the obese population. The apoE phenotypes and lipid status were investigated in a population of 172 obese French subjects. The frequencies of phenotypes E4/3, E4/4 and E4/2 were 29.7%, 8.1% and 2.1%, respectively, in a subgroup with triglycerides greater than or equal to 200 mg/dl (n = 37) versus 14.2%, 2.7% and 0.9% in the normolipidemic subgroup (p less than 0.005). The odds ratio of hypertriglyceridemia was 3.15 for obese subjects with epsilon 4; 27.7% of hypertriglyceridemias could be attributed to epsilon 4 allele. It is concluded that the genetic polymorphism of apoE modulates the effects of obesity on lipids and lipoproteins and that allele epsilon 4 increases the risk of obesity-induced hypertriglyceridemia.     

Lack of association of apolipoprotein E polymorphism with plasma Lp(a) levels in the Chinese

Apolipoprotein E (apoE) polymorphism and its influence on plasma lipids, lipoproteins, lipoprotein (a) [Lp(a)] and apolipoproteins was studied in 536 (270 males and 266 females) healthy Chinese in Singapore. From analysis of variance with age and BMI as covariates, apoE genotype was found to exert a significant influence on plasma total cholesterol (TC), low-density lipoprotein cholesterol (LDL-C) and apoB in females. Its effect in males was marginally significant only on LDL-C. In both sexes, plasma TC, LDL-C and apoB were lower in those who were E2-3 than in those who were E3-3. There was no significant difference in log-transformed Lp(a) level between the apoE genotypes after adjusting for the confounding effect of LDL-C in addition to age and BMI. The percentage variance (R2times100) of the lipid traits explained by apoE polymorphism in the females was 4.94% for plasma TC, 5.85% for LDL-C and 4.25% for apoB. We conclude that: 1) ε2 allele had a lowering effect on plasma TC, LDL-C and apoB; 2) apoE polymorphism did not have any significant influence on Lp(a) concentration; and 3) the effect of apoE polymorphism on plasma TC, LDL-C and apoB was gender-specific, with a stronger influence in females than in males.     

Prediction of consanguinity using human DNA fingerprints.

DNA fingerprinting was performed to verify the pedigree structure of a family under investigation for an unusual case of beta thalassaemia. A higher than expected proportion of hypervariable bands was shared by the proband and his mother, leading to suspicion that the child had been the product of a consanguineous mating. Further analysis of the mother's brother showed that he was almost certainly the proband's father.     

The apolipoprotein C-II variant apoC-IILys19→Thr is not associated with dyslipidemia in an affected kindred

The rare apolipoprotein C-II (apoC-II) mutation, apoC-II_Lys19→Thr, also known as apoC-II-v, has been found previously in association with hyperlipoproteinemia. From a lipid clinic screening we identified three unrelated individuals who had the apoC-II_Lys19→Thr mutation. Among eight family members of one proband, we have found another four who were affected. None of the inviduals in this kindred is dyslipidemic and there is no difference in lipid levels between affected and unaffected family members. Therefore, we conclude that the presence of this apolipoprotein variant by itself has no effect on lipoprotein levels. In addition, the apolipoprotein E (apoE) isoform, apoE4 does not have a synergistic effect on lipoprotein levels in this kindred, in contrast to observations on the interaction of apoE4 with another apoC-II mutant (apoC-II_Toronto). The single nucleotide substitution that causes the apoC-II_Lys19→Thr variant introduces a previously unrecognized restriction site (for Mae III), that provides for easy screening.     

GPNMB基因纯合变异导致色素异常性皮肤淀粉样变性一家系

目的:对1个色素异常性皮肤淀粉样变性家系的3例患者的 GPNMB基因进行变异分析,明确其致病原因。 方法:对先证者行高通量测序,采用生物信息学方法寻找致病基因变异,并通过Sanger测序对家系内成员是否携带变异进行验证。结果:先证者及其哥哥、妹妹 GPNMB基因的第5外显子均存在c.5...     

Reduction in amyloid A amyloid formation in apolipoprotein-E-deficient mice.

Apolipoproteins have been implicated in the formation of amyloid fibrils. Recent studies have demonstrated that apolipoprotein E (apoE), alone or in combination with apolipoprotein J (apoJ), and other lipoproteins appear to enhance deposition of amyloid fibrils both in systemic and cerebral amyloids, especially Alzheimer's disease (AD). ApoE enhanced the ability of the amyloid beta-protein (1-40) fragment (A beta) to form fibrils in vitro, with apoE4 promoting the greatest fibril formation. ApoE was found associated with both human and mouse amyloid A (AA) deposits. To define the role of apoE in vivo, we utilized mice lacking the apoE gene by gene targeting. We used the AA model in mice to characterize the function of the apoE protein in amyloid fibrillogenesis. ApoE-deficient mice exhibited a decrease in deposition of AA when compared with heterozygous mutant or wild-type animals. In addition, apoE-deficient mice that were injected with an adenovirus that expressed the human apoE3 gene had restored AA deposition and the apoE was associated with the AA fibrils. These results are agreement with the in vitro studies using the beta-peptide and suggest that apoE is not essential for amyloid fibrillogenesis but can promote the development of amyloid deposition.     

Electrophoretic screening for human apolipoprotein C-II variants: repeated identification of apolipoprotein C-II(K19T)

Screening for apolipoprotein (apo) C-II variants in the plasma of 400 students, 600 patients of a cardiological rehabilitation center, and 1200 patients of an outpatient lipid clinic by isoelectric focusing and subsequent anti-apo C-II immunoblotting led to the identification of four individuals whose plasma samples contained an apo C-II isoform with an abnormal isoelectric point. In all cases direct sequencing of PCR-amplified DNA assessed a heterozygous A to C transversion in codon 19 of the apo C-II gene which leads to the replacement of lysine with threonine. Two of the four index patients presented with moderate hypertriglyceridemia; one suffered from severe hyperlipidemia, with triglyceride levels ranging between 180 and 1900 mg/dl, depending on dietary changes. Sequencing of this proband's lipoprotein lipase gene showed no alteration compared to the wildtype sequence. A study in his family revealed that heterozygosity for apo C-II(K19T) is not associated with differences in mean lipid and lipoprotein concentrations. In conclusion, apo C-II(K19T) occurs in Germany at a frequency of approximately 1 in 550. Although this variant is not sufficient to cause hypertriglyceridemia, it may be possible that apo C-II(K19T) causes hypertriglyceridemia in the presence of additional as yet unidentified environmental and/or genetic factors.Abbreviations Apo Apolipoprotein - HDL High-density lipoprotein - HTGL Hepatic triglyceride lipase - IEF Isoelectric focusing - LPL Lipoprotein lipase - PCR Polymerase chain reaction - VLDL Very low density lipoproteins     

一个常染色体显性智力低下1型家系的MBD5基因新变异

目的对1例智力、运动发育落后、语言发育严重受损、面部畸形合并癫痫的患儿及其家系成员进行基因变异分析。方法应用全外显子分析技术对先证者进行致病变异筛查,结合先证者的表型确定候选致病位点,应用Sanger测序对先证者、父母及其他家系成员进行变异位点验证。结果先证者携带MBD5基因c.2217delT(p.F739Lfs*6)框移变异,文献未见报道,来源于母亲,经家系验证,其兄携带相同变异且具有相似的表型,其母年幼时语言表达能力差,学习成绩差,可做家务,无抽搐病史。结论发现一个MBD5基因新的致病变异,丰富了MBD5基因变异谱,家系研究发现该基因变异存在表现度差异。本研究结果为该家系的病因诊断和产前诊断提供了依据。     

Hypoalphalipoproteinemia resembling fish eye disease

A 16-year-old boy presented with bilateral arcus cornealis and markedly decreased plasma high density lipoprotein cholesterol. The plasma lipoprotein abnormalities, as well as decreased mass and activity of lecithin:cholesterol acyltransferase (LCAT), were similar to those described in patients with fish eye disease. Increased number of target cells and decreased osmotic fragility of the proband's erythrocytes were noted. The proband's father and one of his brothers showed intermediate plasma lipoprotein and LCAT alterations. The father's erythrocytes also showed abnormal osmotic fragility. The mother of the propositus had normal plasma lipoproteins and erythrocyte osmotic fragility, but her LCAT activity was also low. Many of these features suggest a disorder similar to fish eye disease which is clinically and biochemically distinct from other hypoalphalipoproteinemias.     

Development of the HDL-C and LDL-C direct methods and the subsequent evolution

Today, more than a decade after the development of direct methods for determining HDL-cholesterol (HDL-C) and LDL-cholesterol (LDL-C) concentrations, there are calls to review the reagents in response to discrepancies in patient samples with increased levels of atypical lipoproteins, such as apoE-rich HDL, IDL, Lp-X, and Lp-Y. Seven direct HDL-C assays showed different reactions toward apoE-rich HDL in sera from patients with CETP deficiency and cholestasis. On the other hand, the reactivity of the direct LDL-C assays to serum samples with elevated levels of IDL, Lp-X, and Lp-Y varied considerably between assay kits from each manufacturer. We have also examined the anti-atherogenic functions of apoE-rich HDL from the serum of healthy individuals and patients with CETP deficiency and cholestasis. The ability of apoE-rich HDL to remove cholesterol from cholesterol-loaded macrophages showed that the apoE-rich HDL from CETP-deficient serum took up more cholesterol than apoE-poor HDL (p < 0.01), but no significant differences were observed for apoE-rich HDL from patients with cholestasis.     

Apolipoprotein E pathology in vascular dementia

Vascular dementia (VaD) is the second most common form of dementia and is currently defined as a cerebral vessel vascular disease leading to ischemic episodes. Apolipoprotein E (apoE) gene polymorphism has been proposed as a risk factor for VaD, however, to date there are few documented post-mortem studies on apoE pathology in the VaD brain. To investigate a potential role for the apoE protein, we analyzed seven confirmed cases of VaD by immunohistochemistry utilizing an antibody that specifically detects the amino-terminal fragment of apoE. Application of this antibody, termed N-terminal, apoE cleavage fragment (nApoECF) revealed consistent labeling within neurofibrillary tangles (NFTs), blood vessels, and reactive astrocytes. Labeling occurred in VaD cases that had confirmed APOE genotypes of 3/3, 3/4, and 4/4, with respect to NFTs, staining of the nApoECF co-localized with PHF-1 and was predominantly localized to large, stellate neurons in layer II of the entorhinal cortex. Quantitative analysis indicated that approximately 38.4% of all identified NFTs contained the amino-terminal fragment of apoE. Collectively, these data support a role for the proteolytic cleavage of apoE in the VaD and support previous reports that APOE polymorphism is significantly associated with susceptibility in this disease.     

Comprehensive (apo)lipoprotein profiling in patients with genetic hypertriglyceridemia using LC-MS and NMR spectroscopy

BackgroundMutations in genes encoding lipoprotein lipase (LPL) or its regulators can cause severe hypertriglyceridemia (HTG). Thus far, the effect of genetic HTG on the lipid profile has been mainly determined via conventional techniques.ObjectiveTo show detailed differences in the (apo)lipoprotein profile of patients with genetic HTG by combining LC-MS and NMR techniques.MethodsFasted serum from 7 patients with genetic HTG and 10 normolipidemic controls was used to measure the concentration of a spectrum of apolipoproteins by LC-MS, and to estimate the concentration and size of lipoprotein subclasses and class-specific lipid composition using NMR spectroscopy.ResultsPatients with genetic HTG compared to normolipidemic controls had higher levels of apoB48 (fold change [FC] 11.3, P<0.001), apoC-I (FC 1.5, P<0.001), apoC-II (FC 4.3, P=0.007), apoC-III (FC 3.4, P<0.001), and apoE (FC 4.3, P<0.001), without altered apoB100. In addition, patients with genetic HTG had higher concentrations of TG-rich lipoproteins (i.e., chylomicrons and very low-density lipoproteins [VLDL]; FC 3.0, P<0.001), but lower LDL (FC 0.4, P=0.001), of which medium and small-sized LDL particles appeared even absent. While the correlation coefficient between NMR and enzymatic analysis in normolipidemic controls was high, it was considerably reduced in patients with genetic HTG.ConclusionThe lipoprotein profile of patients with genetic HTG is predominated with large lipoproteins (i.e., chylomicrons, VLDL), explaining high levels of apoC-I, apoC-II, apoC-III and apoE, whereas small atherogenic LDL particles are absent. The presence of chylomicrons in patients with HTG weakens the accuracy of the NMR-based model as it was designed for normolipidemic fasted individuals.     

Effects of apoE gene polymorphism on Lp(a) concentrations depend on the size of apo(a): a study of 466 white men

 Polymorphisms in the genes for the low-density lipoprotein (LDL) receptor ligands, apolipoprotein E (apoE), and apolipoprotein B (apoB) are associated with variation in plasma levels of LDL cholesterol. Lp(a) lipoprotein(a) [Lp(a)] is LDL in which apoB is attached to a glycoprotein called apolipoprotein(a) [apo(a)]. Apo(a) has several genetically determined isoforms differing in molecular weight, which are inversely correlated with Lp(a) concentrations in blood. The interaction of apo(a) with triglyceride-rich lipoproteins differs with the size of apo(a), and therefore the effects of apoE gene polymorphism on Lp(a) levels could also depend on apo(a) size. We have investigated the possible effect of genetic variation in the apoE and apoB genes on plasma Lp(a) concentrations in 466 white men with different apo(a) phenotypes. Overall there was no significant association between the common apoE polymorphism and Lp(a), but in the subgroup with apo(a)-S4, concentrations of Lp(a) differed significantly among the apoE genotypes (P=0.05). Lp(a) was highest in the apoE genotypes ɛ₂ɛ₃ and ɛ₃ɛ₃ and lowest in genotype ɛ₃ɛ₄, and the apoE polymorphism was estimated to account for about 2.4% of the variation in Lp(a). In contrast, in the subgroup with apo(a)-S2 Lp(a) was significantly lower (P=0.04) in apoE genotype ɛ₂ɛ₃ than in genotype ɛ₃ɛ₃. Lp(a) concentrations did not differ among the XbaI (P=0.65) or SP 24/27 (P=0.26) polymorphisms of the apoB gene. The expected effects of both apoE and apoB polymorphism on LDL levels were significant in the whole population sample and in subjects with large-sized apo(a) isoforms (P<0.01), whereas no effect was seen in those with low molecular weight apo(a) isoforms. We conclude that the influence of apoE genotypes on Lp(a) concentrations depends on the size of the apo(a) molecule in Lp(a), possibly because both apo(a)-S4 and apoE4 have high affinity for triglyceride-rich lipoproteins and may be taken up and degraded rapidly by remnant receptors. Received: 12 January 1995 / Accepted: 12 July 1996     

Kousseff syndrome caused by deletion of chromosome 22q11-13

Kousseff syndrome was originally described by Boris Kousseff in 1984: Pediatrics 74:395-398 in three siblings whose main features were conotruncal heart defects, neural tube defects, and dysmorphic features. The proband is a white male who has spina bifida, shunted hydrocephalus, cleft palate, short stature, cognitive impairment, and the typical craniofacial features of velo-cardio-facial syndrome (VCFS), including low-set and dysplastic ears, broad base of the nose, narrow alae nasi, and retrognathia. The family history is significant for a brother who died at 2 weeks of age with myelomeningocele, hydrocephalus, transposition of the great vessels, and unilateral renal agenesis, and a sister who died at 11 days of age with myelomeningocele, truncus arteriosus, hypocalcemia, and autopsy findings of absent thymus and parathyroid glands, consistent with DiGeorge anomaly. Given the clinical findings, family history, and recent knowledge that open neural tube defects can occur in VCFS/DiGeorge anomaly, FISH analysis for 22q11-13 deletion was performed on the proband. A deletion was detected in him and subsequently confirmed in his father. Molecular analysis on autopsy material confirmed the deletion in the proband's deceased brother. We suggest that individuals with neural tube defects associated with other anomalies such as congenital heart defects or cleft palate be evaluated for 22q deletions.     

Homozygous missense mutation p. Val298Met of F10 gene causing hereditary coagulation factor X deficiency in a Chinese pedigree北大核心CSCD

Objective: To identify potential mutation underlying congenital factor X (FX) deficiency in a consanguineous Chinese pedigree. Methods: Prothrombin time(PT), activated partial thromboplastin time(APTT), fibrinogen, FX activity(FX:C) and other coagulant parameters were determined with a one-stage clotting assay. The FX antigen(FX:Ag) was determined with an ELISA assay. All coding exons and exon-intron boundaries of the F10 gene were amplified with PCR and subjected to direct sequencing. Suspected mutation was confirmed by reverse sequencing and analyzed with CLC Genomics Workbench 7.5 software. Results: The PT and APTT in the proband were prolonged to 67.2 s and 102.9 s, respectively. Further study showed that her FX:C and FX:Ag were reduced by 1% and 8%, respectively. The PT of her father, mother, and little brother were slightly prolonged to 14.5 s, 14.4 s and 14.4 s, respectively. The FX:C and FX:Ag in her father, mother and little brother were all slightly reduced. Genetic analysis of the proband has revealed a homozygous G>A change at nucleotide 27881 in exon 8 of the F10 gene, which predicted a p. Val298Met substitution. The proband's father, mother, and little brother were all heterozygous for the p. Val298Met mutation. The proband has inherited the homozygous mutation from her parents by consanguineous marriage. Other family members were all normal. Bioinformatics analysis has indicated that this mutation may result in changes in the secondary structure of the FX protein. Conclusion: A homozygous mutation g.27881G>A(p. Val298Met) of the F10 gene has been identified, which probably accounts for the low FX concentrations in this pedigree. © 2016, West China University of Medical Sciences. All rights reserved.     

A novel mutation in exon b (R259C) of the MTM1 gene is associated with a mild myotubular myopathy. Mutation in brief no. 125. Online

The genetic basis of the relatively mild myopathic symptoms exhibited in a male was investigated. Mutation screening of a candidate gene, MTM1, represented a chance of establishing the molecular defect and the mode of inheritance. SSCA detected variation of the exon b PCR products from the proband and his mother, compared to that observed upon analysis of the PCR products from other members of the family and 159 unrelated X chromosomes. Sequencing revealed a C775 to T transition, in the proband and his mother, but not in his unaffected brother. To confirm the presence of a base change in this region, a Cfol site was introduced into the PCR product of the wildtype allele by using the forward primer 5'-AGAAAATAAGACGGTCATTGcG-3' (mismatch base in small font) with the exon b reverse primer as used by Laporte et al (1996). Analysis of DNA from other members of the family using this method revealed that this is a new mutation in the proband's mother. This mutation would result in a Arg259->Cys substitution.