Comparison of SSCP and DHPLC for the detection of LDLR mutations in a New Zealand cohort

Familial hypercholesterolaemia (FH) is a common inherited disorder, associated with premature vascular disease. FH may be caused by many different mutations in the low density lipoprotein receptor (LDLR) gene, about 700 mutations have been described, most of which occur rarely and often only in single families. Although particular mutations are prevalent in certain ethnic groups, countries with heterogeneous population bases (such as NZ) may carry a wide variety of mutations; making a gene screening approach the appropriate first step for a mutation detection programme. We have compared SSCP with DHPLC to assess their effectiveness as methods for LDLR mutation detection. Although five novel LDLR mutations were detected by SSCP in patients with FH, DHPLC was more sensitive, with eight novel mutations detected. Six of these mutations (T392M, R419G, Y421N, 1206-1207delCT, 1872delC, and 1943delC) were clustered in exons 9 and 13 of the EGF precursor homology domain, one (679-680delAC) in the ligand binding domain (exon 4) and the eighth (P774H) in the membrane-spanning domain (exon 16). Twenty five mutations were identified in 35 patients in total. Of these, we were able to detect only 64% of mutations by SSCP even though all variants were detected by DHPLC. All patients are heterozygous for the mutations, which is consistent with the clinical phenotypes.     

A method for exceptionally low noise single channel recordings

Summary We present a method whereby, with integrating electronics, quartz patch electrodes and a novel use of silicone oil, background noise levels as low as .083 pA RMS in a 5 kHz bandwidth (4-pole Butterworth filter) have been achieved in single channel patch clamp recordings. These approaches result in much higher signal to noise ratios for single channel recording than have previously been reported and should allow many investigators to significantly reduce noise at a constant bandwidth or to increase their recording bandwidths by several kHz.     

Broadening the phenotypic spectrum of Pearson syndrome: Five new cases and a review of the literature

Pearson syndrome (PS) is a multisystem mitochondrial respiratory chain disorder typically characterized by sideroblastic anemia and exocrine pancreatic insufficiency. PS is caused by a single large‐scale mitochondrial DNA (mtDNA) deletion. PS classically presents in the first year of life and may be fatal in infancy. Children who survive PS may progress to develop Kearns–Sayre syndrome later in life. The full phenotypic spectrum and prognosis of the condition continue to evolve. Here we report five new patients with PS with unique clinical presentations, including four patients with onset later than previously reported in the literature, and one patient with prenatal onset of symptoms. The timing and unique features of these presentations support an expanded phenotypic spectrum of single large‐scale mtDNA deletion syndromes (SLSMDS) and reinforce the importance of including SLSMDS in the differential for children with complex multisystem presentations.     

High-throughput single strand conformation polymorphism mutation detection by automated capillary array electrophoresis: validation of the method

Capillary array electrophoresis (CAE) is a novel technique, which allows for high throughput analysis of DNA fragments. When screening for mutations in whole populations or large patient groups it is necessary to have robust and well-characterized setups for high throughput analysis. For large-scale mutation screening, we have developed procedures for single strand conformation polymorphism (SSCP) assays using CAE (CAE-SSCP) whereby we may increase both the sensitivity and the throughput compared to conventional SSCP analysis. In this study we have validated CAE-SSCP by 1) comparing detection by slab-gel based SSCP with CAE-SSCP of mutations in the MYH7, MYL2, and MYL3 genes encoding sarcomere proteins from patients suffering from hypertrophic cardiomyopathy; and 2) by constructing a series of 185 mutants having substitution mutations, as well as insertion/deletion mutations, or some combinations of these, in different sequence contexts in four exons and different positions relative to the end of the amplicon (three from the KCNQ1 gene, encoding a cardiac potassium channel, and one from the TNNI3 gene encoding cardiac troponin I). The method identified 181 out of 185 mutations (98%), and the data suggest that the position of mutation in the fragment had no effect on the sensitivity. Analysis of the specificity of the method showed that only very few mutants could not be distinguished from each other and there were no false positives.     

应用复合诱导突变分离PCR法检测mtDNA的单核苷酸多态性

目的应用复合诱导突变分离PCR(multiplexed mutagenically separated PCR,MS-PCR)技术、银染分型,建立线粒体DNA(mitochondrial DNA,mtDNA)编码区单核苷酸多态(single nucleotide polymorphism,SNP)分型系统,探讨其应用价值。并调查了成都汉族群体mtDNA编码区4个SNP基因座等位基因频率和单倍型分布情况。方法根据SNP基因座(C12705T、A8701G、G8584A、C10400T)设计两条片段相差4个碱基的等位基因特异性引物和一条公共引物,4个SNP基因座复合扩增,PCR产物经聚丙烯酰胺凝胶电泳、银染显带后确定样本的基因型。结果不同SNP基因座为长度不同的单一谱带,其分型结果与直接测序一致。在成都汉族160名无关个体中,4个SNP基因座C12705T、A8701G、G8584A、C10400T等位基因频率分别为0.3813/0.6187、0.4813/0·5187、0.8250/0.1750、0.4938/0.5062;共检出6种单倍型,单倍型的基因多样性为0.7137。结论建立的MMS-PCR银染分型系统是一种简单、快速、准确、有效的SNP分型方法,对建立mtDNA编码区SNP数据库,研究群体遗传学、进化学和进行法医学个人识别和亲子鉴定有重要意义。     

Surface markers of human natural killer cells as analyzed in a modified single cell cytotoxicity assay on poly-L-lysine coated cover slips

A modified single cell cytotoxicity assay using poly-L-lysine coated cover slips (PLL-SCCA) was employed to study the frequency and surface marker profile of human peripheral blood lymphocytes (PBL) with NK reactivity against K 562 target cells. When compared with the previously described agarose single cell cytotoxicity assay (A-SCCA) identical results were obtained. For 13 donors tested 18.1 +/- 4.4% of the PBL formed conjugates with K 562 and 2.7 +/- 1.6% displayed NK reactivity. In contrast to the A-SCCA, the PLL-modified assay permits direct identification of both conjugate forming (TBC) and cytolytic PBL (NK) by means of surface markers. Indirect immunofluorescence studies with monoclonal anti-PBL antibodies revealed that neither the plating procedures nor the incubation conditions employed affected the expression of the antigens recognized by these reagents. This method of directly identifying NK cells showed that OKM1+ cells were enriched among the NK cells as compared to PBL and TBC (55% vs. 23% and 43%, respectively). In contrast, the OKT3+ or Leu1+ fraction of the NK cells was reduced as compared to PBL and TBC. However, using this method of identification at the effector cell level, a substantial proportion of the NK cells were OKT3+ or Leu1+ (57% or 58% respectively, 7 donors). Approximately 25% of the NK cells were Leu2a+ and 30% were Leu3a+, respectively. However, the size of the Leu3a+ fraction varied considerably with individual donors and the size of this fraction appeared to be inversely related to that of the donors NK pool.     

Will the new cytogenetics replace the old cytogenetics?

With the advent of array-based comparative genomic hybridization technology, the analog cytogenetic analysis that has been used for the past 100 years could be replaced by the quantitative, microarray-based molecular analysis. Major advantages of the new array-based cytogenetic technologies are the high resolution and the high throughput. This technology is the first to offer an autonomous whole-chromosome analysis in one hybridization reaction for the detection of submicroscopic gains/losses. However, as with any new technology, it needs to be validated with regard to its performance in various applications (e.g. clinical genetic testing and cancer applications), comparative cost, and the data interpretation.     

Heritability and Expression of C-Reactive Protein in Type 2 Diabetes in the Diabetes Heart Study

Elevated C-reactive protein (CRP) levels are associated with both prevalent and incident cardiovascular disease. In this study, familial aggregation was estimated, and we tested for association between serum CRP levels and polymorphisms within the CRP and APOE genes in sib-ships with type 2 diabetes mellitus, a population at increased risk for cardiovascular disease. CRP levels were determined in 461 diabetes-affected subjects from 224 sibships from the Diabetes Heart Study (DHS). Heritability estimates of CRP levels were obtained using variance component models. Genetic influence on serum CRP levels by single nucleotide polymorphisms (SNPs) in the CRP and APOE genes was evaluated by association analysis using mixed models. Subjects were Caucasian American (84%) and African-American (16%), 53% female, and had an average age of 62.2 ± 9.2 years. The median CRP level was 3.3 mg/L (range 0 to 59.3 mg/L), and estimated heritability for CRP was approximately 40%. Estimates of heritability were significantly greater than zero (P < 0.0001) and relatively constant, despite adjustments for important modifiers (age, sex, ethnicity, diabetes duration, statin-use and anti-inflammatory use) of CRP. There was no significant evidence for association of CRP levels with CRP gene SNPs; however, consistent with previous reports, there was significant evidence of association of CRP levels with polymorphisms within the APOE gene. These data indicate CRP levels are significantly influenced by genetic (and/or environmental) factors that are shared within DHS families. While the APOE locus shows evidence of contributing to CRP levels, no evidence of CRP gene polymorphism association with CRP levels was observed.     

The haplotype block, NFKBIL1-ATP6V1G2-BAT1-MICB-MICA, within the class III-class I boundary region of the human major histocompatibility complex may control susceptibility to hepatitis C virus-associated dilated cardiomyopathy

Cardiomyopathy is a heart muscle disease with impaired stretch response that can result in severe heart failure and sudden death. A small proportion of hepatitis C virus (HCV)-infected patients may be predisposed to develop dilated cardiomyopathy (DCM) and hypertrophic cardiomyopathy (HCM). The molecular mechanisms involved in the predisposition remain unknown due in part to the lack of information on their genetic background. Because the human leukocyte antigen (HLA) region has a pivotal role in controlling the susceptibility to HCV-induced liver disease, we hypothesized that particular HLA alleles and/or non-HLA gene alleles within the human major histocompatibility complex (MHC) genomic region might control the predisposition to HCV-associated DCM (HCV-DCM) and/or HCV-associated HCM (HCV-HCM). Here, we present mapping results of the MHC-related susceptibility gene locus for HCV-associated cardiomyopathy by analyzing microsatellite and single nucleotide polymorphism markers. To delineate the susceptibility locus, we genotyped 44 polymorphic markers scattered across the entire MHC region in a total of 59 patients (21 HCV-DCM and 38 HCV-HCM) and 120 controls. We mapped HCV-DCM susceptibility to a non-HLA gene locus spanning from NFKBIL1 to MICA gene loci within the MHC class III-class I boundary region. Our results showed that HCV-DCM was more strongly associated with alleles of the non-HLA genes rather than the HLA genes themselves. In addition, no significant association was found between the MHC markers and HCV-HCM. This marked difference in the MHC-related disease susceptibility for HCV- associated cardiomyopathy strongly suggests that the development of HCV- DCM and HCV-HCM is under the control of different pathogenic mechanisms.     

Propene Polymerisation with rac‐[Me2Si(2‐Me‐4‐(α‐naphthyl)‐1‐Ind)2]ZrCl2 as a Highly Active Catalyst: Influence of Monomer Concentration,Polymerisation Temperature and a Heterogenising Support

Propene was polymerised at high temperatures (up to 90 °C) using rac‐[Me₂Si(2‐Me‐4‐(α‐naphthyl)‐1‐Ind)₂]ZrCl₂/MAO as the catalytic system. The increasing deactivation reaction rate of the catalyst for polymerisations above 60 °C was less for a silica supported catalyst compared with the homogeneous one. The isotacticity of polypropene decreases from 99 to 96%. Also the morphology changes with different temperatures.

Increasing of the thermal stability for the rac‐[Me₂Si(2‐Me‐4‐(α‐naphthyl)‐1‐Ind)₂]ZrCl₂/MAO/SiO₂ with respect of the rac‐[Me₂Si(2‐Me‐4‐(α‐naphthyl)‐1‐Ind)₂]ZrCl₂/MAO system.