用GT重复多态性诊断21三体患者中超数21号染色体减数分裂起源的研究

通过PCR扩增、PAG电泳和硝酸银显色,首次分析了人类21号染色体长臂上两个紧靠着丝粒的GT重复序列（D21S215和D21S120）在中国人中的多态性,并用于光天愚型患者中超数21号染色体减数分裂起源的诊断。D21S215和D21S120在中国人中分别有6和5个等位片段,杂合率观测值均为0.68,多态信息含量分别为0.67和0.65。用这两标记,在17例已知超数21号染色体双亲来源的患者中,检测出16例的减数分裂起源;其中来自母亲减数分裂Ⅰ和Ⅱ的分别有7和4例,属父亲减数分裂Ⅰ和Ⅱ不分离的分别为2和3例。对研究超数21号染色体起源的生物学意义等进行了讨论。     

冠状病毒核衣壳蛋白与延伸因子-1α的相互作用

目的:分析SARS冠状病毒(SARS-CoV)核衣壳蛋白(N蛋白)和229E冠状病毒(HCoV-229E)核衣壳蛋白与细胞延伸因子(EF)-1α的相互作用、翻译抑制效应及与多核细胞形成的关系。方法:构建、表达及纯化SARS-N蛋白和229E-N蛋白的GST融合蛋白,用GST-pull down方法分析其与过表达的EF-1α及内源EF-1α之间的相互作用;构建和表达SARS-N蛋白和229E-N蛋白的GFP融合表达载体,转染293T细胞,通过共聚焦显微镜分析SARS-N蛋白和229E-N蛋白的亚细胞定位及多核细胞的形成;在293T细胞中过表达SARS-N蛋白或229E-N蛋白,通过Co-IP分析其与EF-1α的相互作用。分别在细胞内和体外翻译系统中分析二者抑制报告基因翻译的程度。结果:SARS-N蛋白和229E-N蛋白都定位于细胞质,并不像其他冠状病毒的N蛋白那样定位到细胞核;二者都能诱导形成多核细胞,但229E-N蛋白导致细胞形成多核细胞的时间要晚;二者都能与EF-1α相互作用并且共定位于细胞质,二者都能导致EF-1α形成多聚体;二者在细胞内及细胞外对报告基因都有抑制翻译效应。结论:SARS冠状病毒和229E冠状病毒的核衣壳蛋白均定位于细胞胞质,可与EF-1α相互作用,导致EF-1α形成多聚体,抑制报告基因翻译及导致细胞形成多核。     

人类染色体8q24.1带特异性微小卫星DNA的筛选

本研究运用人类高分辨染色体显微切割、ＰＣＲ技术获得的８ｑ２４．１带特异性探针池,构建了该区带的ｐＵＣ１９文库,从中筛选出４８个含ＣＡ重复顺序的微小卫星ＤＮＡ的克隆,已完成１２个克隆的序列分析,发现了一个世界上至今未曾报道过的、在正常人群中已检出１１个等位片段的、杂合度在中国汉族人群和美国盎格鲁撤克逊族人群中分别达０．８４和０．８３的高度多态的微小卫星ＤＮＡ（编号：Ｄ８Ｓ７Ｆ）,经ＰＣＲ检测人鼠杂种细胞系列,证实其来源于人８号染色体。     

Molecular Cloning and Characterization of Galactosylceramide Expression Factor-1 (GEF-1)

A rat brain cDNA clone has been isolated using a eukaryotic cell transient expression system with anti-galactosylceramide (GalCer) monoclonal antibody (MAb), that induces GalCer expression in COS-7 cells. The protein was designated as GalCer expression factor-1 (GEF-1). The deduced amino acid sequences revealed a strikingly high homology to a mouse hepatocyte growth factor-regulated tyrosine kinase substrate (Hrs), but no homology to UDP-galactose: ceramide galactosyltransferase. COS-7 cells transfected with the cDNA clone showed dramatic morphological changes and cell growth suppression. Overexpression of GEF-1 in MDCK (MDCK/GEF-1) cells showed GalCer-derived sulfatide expression as well as morphological changes, but not cell growth suppression. The enzyme activity and the mRNA level of CGT increased significantly in MDCK/GEF-1 cells compared with control cells. Taking these results together, it is suggested that GEF-1 may play an important role in regulating GalCer and sulfatide expression in the epithelial cells as well as in the brain.     

Discerning non-disjunction in Down syndrome patients by means of GluK1-(AGAT)n and D21S2055-(GATA)n microsatellites on chromosome 21

INTRODUCTION:

Down syndrome (DS), the leading genetic cause of mental retardation, stems from non-disjunction of chromosome 21.

AIM:

Our aim was to discern non-disjunction in DS patients by genotyping GluK1-(AGAT)_n and D21S2055-(GATA)_n microsatellites on chromosome 21 using a family-based study design.

MATERIALS AND METHODS:

We have used a PCR and automated DNA sequencing followed by appropriate statistical analysis of genotype data for the present study

RESULTS AND DISCUSSION:

We show that a high power of discrimination and a low probability of matching indicate that both markers may be used to distinguish between two unrelated individuals. That the D21S2055-(GATA)_n allele distribution is evenly balanced, is indicated by a high power of exclusion [PE=0.280]. The estimated values of observed heterozygosity and polymorphism information content reveal that relative to GluK1-(AGAT)_n[H_obs=0.286], the D21S2055- (GATA)_n[H_obs=0.791] marker, is more informative. Though allele frequencies for both polymorphisms do not conform to Hardy-Weinberg equilibrium proportions, we were able to discern the parental origin of non-disjunction and also garnered evidence for triallelic (1:1:1) inheritance. The estimated proportion of meiosis-I to meiosis-II errors is 2:1 in maternal and 4:1 in paternal cases for GluK1-(AGAT)_n, whereas for D21S2055-(GATA)_n, the ratio is 2:1 in both maternal and paternal cases. Results underscore a need to systematically evaluate additional chromosome 21-specific markers in the context of non-disjunction DS.     

Identification and Characterization of a Mycobacterial (2R,3R)-2,3-Butanediol Dehydrogenase

Bacterial strain B-009, capable of using racemic 1,2-propanediol (PD), was identified as a rapid-growing member of the genus Mycobacterium. The strain is phylogenetically related to M. gilvum, but has slightly different physiological characteristics. An NAD⁺-dependent enantioselective alcohol dehydrogenase, which acts on R-PD, was purified from the strain. The enzyme was a homodimer of a peptide coded by a 1047-bp gene (mbd1). A highly conserved sequence for medium-chain dehydrogenase/reductases with a preference for secondary alcohols was found in the gene. Hydroxyacetone was produced from R-PD by an enzymatic reaction, indicating that position 2 of the substrate was oxidized. The enzyme activity was highest for (2R,3R)-2,3-butanediol (R,R-BD), enabling the enzyme to be identified as (2R,3R)-2,3-butanediol dehydrogenase (R,R-BD-DH). A homology search revealed M. gilvum, M. vanbaalenii, and M. semegmatis to have ORFs similar to mbd1, suggesting the widespread distribution of genes encoding R,R-BD-DH among mycobacterial strains.     

CD44 cross-linking induces integrin-mediated adhesion and transendothelial migration in breast cancer cell line by up-regulation of LFA-1 (alpha L beta2) and VLA-4 (alpha4beta1)

CD44, a widely expressed cell surface glycoprotein, plays a major role in cell-cell adhesion, cell-substrate interaction, lymphocyte homing, and tumor metastasis. For tumor metastasis to occur through the blood vessel and lymphatic vessel pathway, the tumor cells must first adhere to endothelial cells. Recent studies have shown that high expression of CD44 in certain types of tumors is associated with the hematogenic spread of cancer cells. However, the functional relevance of CD44 to tumor cell metastasis remains unknown. In this study, we investigated the mechanisms of CD44 cross-linking-induced adhesion and transendothelial migration of tumor cells using MDA-MB-435S breast cancer cell line. Breast cancer cells were found to express high levels of CD44. Using flow cytometric analysis and immunofluorescence staining, we demonstrated that cross-linking of CD44 resulted in a marked induction of the expression of lymphocyte function-associated antigen-1 (LFA-1) and very late antigen-4 (VLA-4) by exocytosis. These results were also observed with the Hs578T breast cancer cell line. Furthermore, LFA-1- and VLA-4-mediated adhesion and transendothelial cancer cell migration were also studied. Anti-LFA-1 mAb or anti-VLA-4 mAb alone had no effect on adhesion or transendothelial cancer cell migration, but were able to inhibit both of these functions when added together. This shows that CD44 cross-linking induces LFA-1 and VLA-4 expression in MDA-MB-435S cells and increases integrin-mediated adhesion to endothelial cells, resulting in the transendothelial migration of breast cancer cells. These observations provide direct evidence of a new function for CD44 that is involved in the induction of LFA-1 and VLA-4 expression by exocytosis in MDA-MB-435S cells. Because these induced integrins promote tumor cell migration into the target tissue, it may be possible to suppress this by pharmacological means, and thus potentially cause a reduction in invasive capability and metastasis.     

脊髓性肌萎缩症SMN1基因2+0基因型携带者的家系研究

脊髓性肌萎缩症(spinal muscular atrophy, SMA)是一种儿童时期较为常见的神经肌肉病,属于常染色体隐性遗传。绝大多数SMA由运动神经元存活基因1 (survival motor neuron 1, SMN1)的纯合缺失突变所致。而SMN1的2+0基因型个体作为一种特殊的SMA携带者,给携带者筛查以及家系的遗传咨询带来了巨大的挑战。已有研究表明,g.27134T>G和g.27706₂7707delAT多态位点变异对于Ashkenazi犹太人群中的2+0基因型个体具有提示作用。为进一步探究这两个多态位点是否在中国人群也具有特异性,本研究纳入了44例家系成员和204例已知SMN1基因拷贝数的对照样本。44例家系成员来自于9个无关的SMN1基因纯合缺失的SMA家系,先证者双亲之一疑似为2+0基因型携带者。利用多重连接探针扩增(multiplex ligation-dependent probe amplification,MLPA)和短串联重复(short tandem repeat, STR)连锁分析进行基因型的鉴定以及多态位点的筛查,最终...     

基因重组胰高血糖素样肽-1衍生多肽的表达和产物纯化与鉴定

为研究利用基因重组方法生产人胰高血糖素样肽-1（GLP-1）衍生多肽的最佳表达及纯化条件,选用大肠杆菌偏爱密码子,以含人GLP-1的质粒为模板,用PCR方法合成全长人GLP-1衍生多肽基因,并定向插入到高效表达载体pMFH中,用大肠杆菌BL21进行表达,融合蛋白经Ni-NTA柱纯化后,用C18 Sep-Pak 反相柱脱盐,然后融合蛋白经甲酸水解,水解产物经Ni-NTA柱和高效液相色谱（HPLC）纯化制备后,目的肽由质谱鉴定。 实验结果表明：利用载体pMFH在BL21中,GLP-1衍生物的最佳诱导表达温度为37℃、诱导剂异丙基-β-D-硫代半乳糖苷（IPTG）的最佳浓度为0.6mmol/L,最佳诱导表达时间为6h;HPLC分析和制备GLP-1衍生物最佳条件为：流动相A(10% CNCH3∶90% H2O,0.1％TFA),流动相B(100% CNCH3,0.1% TFA),流速1ml／min,30 min线性梯度洗脱,B相至70%,检测波长280nm;质谱鉴定GLP-1衍生物的分子量为5.492kDa,与理论值相符合。在最佳表达及纯化条件下可得GLP-1衍生多肽的产量可达到11.6mg/L发酵产物,纯度≥98%。     

Metabolism of 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP) in mouse liver preparations

Using a mouse liver microsomal preparation, it was found that the heterocyclic ring system of MPTP underwent an initial α-oxidation to give chemically reactive metabolites that may be associated with the induction of Parkinsonism by MPTP. Subsequent oxidative metabolic transformations of these intermediates were found to give a lactam metabolite and a pyridone metabolite that potentially may interact with the neurotransmitter system.