脊髓小脑共济失调3型致病蛋白ataxin-3毒性损伤机制

脊髓小脑共济失调3型是我国常见的三核苷酸序列异常扩增导致的常染色体显性遗传疾病。其致病蛋白ataxin-3具有泛素结合蛋白功能,调节细胞蛋白质稳态;同时ataxin-3蛋白功能可能还与细胞骨架等相关。异常扩展突变的ataxin-3有聚集倾向,在细胞内募集多种蛋白成分形成蛋白聚集体或包涵体,导致基因转录异常、蛋白稳态失衡、能量代谢障碍、运输障碍等多种细胞功能损伤以致细胞凋亡,进而影响细胞功能而致病。结合目前对多聚谷氨酸异常扩展突变疾病的研究现状,此文就现有的脊髓小脑共济失调3型致病机制进行综述。     

脊髓小脑性共济失调3型发病机制的研究进展

脊髓小脑性共济失调3型/马查多-约瑟夫疾病（SCA3/MJD）是一种常染色体显性遗传的迟发性神经退行性疾病,其致残率、病死率高.该疾病严重威胁患者的身心健康和生活质量.对于该病的确切发病机制还未完全阐明,临床亦无有效的治疗方法.目前国内外的研究表明,该疾病与致病基因、致病蛋白、神经元内包涵体、泛素-蛋白酶体通路、自噬-溶酶体通路、基因转录、分子伴侣、线粒体氧化应激、细胞凋亡等多种因素相关.该文就该病发病机制的研究进展作一简要的综述.     

马查多-约瑟夫病的分子遗传学研究进展

迄今为止,至少已定位了常染色体显性遗传小脑件共济失调28种不同的基因型,已克隆18个致病基因,其中对不同种族和地域的研究表明,马查多-约瑟夫病(Machado-Joseph disease,MJD),即脊髓小脑性共济失调3型(spinoocerebellar ataxia type 3,SCA3),是世界上最常见的SCAs亚型.它是由位于致病基因MJD13'端的CAG三核苷酸重复扩增突变引起的一种具有明显的临床和遗传异质性的神经系统退行性疾病.作者就SCA3/MJD的分子遗传学方面的研究进展进行综述.     

原癌基因LMO3相互作用蛋白的筛选及鉴定

目的 通过筛选LMO3的相互作用蛋白,进一步了解LMO3的作用及可能机制.方法:酵母双杂交方法 筛选LMO3相互作用蛋白,并通过酵母结合试验、免疫共沉淀及荧光共定位等进行验证.结果:在初步获得相互作用蛋白CIB的基础上,在酵母中证实了LMO3与CIB的相互作用,并通过酵母结合试验确定了CIB与LMO3的相互作用位点,发...     

东北地区正常汉族人群 SCA1及 SCA3/MJD基因内CAG重复变异研究

目的　对东北地区 110名汉族正常人 SCA1及 SCA3/ MJD基因 (CAG) n拷贝进行检测 ,探讨其正常变异范围 ,并对临床诊断为遗传型脊髓小脑共济失调的 8个家系的 2 5例患者和 6个散发病例进行基因分型评价和症状前及产前诊断。方法　应用荧光 - PCR方法测定不同基因型片段长度 ,并进行 DNA序列分析。结果　 SCA3/ MJD基因 (CAG) n正常变异范围为 14～ 38个拷贝 ,集中于 14个拷贝 ,其等位基因频率为 39.5 5 % ,杂合频率为 78.18% ,共 13种等位基因。检出一个家系先证者携带有 (CAG) 6 8的 SCA3/ MJD基因 ,并对该家系成员进行了症状前诊断 ,没有发现 (CAG) n拷贝异常突变 ;SCA1基因内 (CAG) n正常变异范围 2 0～ 39拷贝 ,集中于 2 6及 2 7次 ,等位基因频率分别为 34.0 9%和 2 0 .91% ,杂合频率为 84 .5 5 % ,共 13种等位基因 ;散发病例未检出 CAG扩展性突变。结论　 SCA1及 SCA3/ MJD基因中 (CAG) n正常变异范围存在地区和种族差异 ,SCAs基因分型是该病症状前及产前诊断的首选策略。     

脊髓小脑性共济失调3型线粒体DNA突变的研究

目的 探索脊髓小脑性共济失调3型(spinocerebellar ataxia type 3,SCA3)与线粒体DNA(mitochondrial DNA,mtDNA)突变的关系.方法 采用测序方法对临床诊断为脊髓小脑性共济失调的患者及家系成员行MJD1基因CAG重复拷贝数检测,以基因水平确诊SCA3患者及症状前患者.然后采用聚合酶链反应、单链构象多态性分析、测序方法对基因确诊的43例SCA3患者及症状前患者和30名对照组的mtDNA片段进行分析.结果 发现SCA3组4名成员存在mtDNA位点8282.8290区域9个碱基缺失.结论 在SCA3患者及症状前患者中发现mtDNA缺失突变的现象.     

与14-3-3ζ相互作用的蛋白Polo样激酶1的筛选与鉴定

目的:应用酵母双杂交系统筛选与14-3-3ζ相互作用的蛋白,进一步鉴定其与Polo样激酶1(Plk1)相互作用。方法:构建pGBKT7-14-3-3ζ诱饵表达载体,筛选HeLa细胞cDNA文库中与14-3-3ζ相互作用蛋白,进一步通过共转酵母、免疫荧光以及外源性和内源性的细胞免疫共沉淀实验验证两者的相互作用。结果:通过酵母双杂交系统筛选出的阳性相互作用蛋白中包括Plk1,进一步通过共转酵母,外源性和内源性的细胞免疫共沉淀实验证实两者的相互作用,免疫荧光实验证实两者共定位于有丝分裂过程中胞质分裂期的中体。结论:Plk1是高度保守的丝氨酸/苏氨酸蛋白激酶,在中体的成熟,有丝分裂期染色体的分离,胞质分裂以及DNA的损伤应答等环节发挥重要作用,其与14-3-3ζ的相互作用为14-3-3蛋白家族参与有丝分裂(M期)的调控提供了直接证据。     

Ataxin-3相互作用蛋白A3IP的克隆与细胞及组织定位的初步研究

目的 根据前期筛选到的与ataxin-3蛋白羧基端相互作用的A3IP部分序列,进行A3IP基因的克隆,并探讨其细胞及组织定位情况.方法 应用生物信息学及Northern印迹方法克隆A3IP基因并检测其转录本在人体组织和人脑不同部位的表达情况;应用Western印迹及免疫荧光方法检测A3IP蛋白在细胞中的表达及定位情况;应用免疫组织化学染色方法检测A3IP蛋白在人体各组织和人脑不同部位的表达及定位情况.结果 对A3IP基因序列全长阅读框进行了cDNA克隆及序列拼接;检测了A3IP的3个转录本(1 kb、1.35 kb、6 kb)在人体不同组织和人脑不同部位的表达谱;获得了A3IP-pEGFP在COS-7细胞和人大脑皮质、小脑、肌肉、周围神经、肝脏、肾脏的表达及定位情况.结论 所克隆的A3IP基因编码ataxin-3的一种相互作用蛋白A3IP,其3个剪切本在人体多种组织和人脑不同部位广泛表达,是一种细胞胞浆蛋白.     

Machado--Joseph的研究进展病基因检测及新突变位点

马查多-约瑟夫病（Machado—Josephdisease,MJD）也被称为脊髓小脑性共济失调3型（spinocerebellarataxia3,SCA3）,是最常见的遗传性脊髓小脑性共济失调亚型。发病机制尚不清楚,复杂的病情一直是临床工作者极大的挑战。得益于分子细胞遗传学迅猛发展,MJD症状前诊断及基因诊断成为现实并还在继续向前发展。逐步用于疾病诊断、鉴别诊断及治疗中,同时为遗传咨询提供科学依据。为寻求新突破,该文集中总结该疾病ATXN3突变致病机制及基因检测应用研究现状。更好地理解这些复杂的分子机制,探讨基因检测以及新基因突变位点的发现对这一致命性疾病的诊断及治疗意义。     

应用酵母双杂交系统筛选Foxp3△2相互作用蛋白

目的:应用酵母双杂交系统从人外周血白细胞cD-NA文库中筛选与转录因子Foxp3相互作用的蛋白,为进一步研究Foxp3的转录调控机制奠定基础。方法:首先构建pG-BKT7-Foxp3△2酵母双杂交诱饵载体,转化AH109酵母细胞,检测其毒性及自激活作用;然后将诱饵质粒与人外周血白细胞cDNA文库共转AH109酵母细胞,筛选了与Foxp3△2存在相互作用的蛋白。结果:成功构建了pGBKT7-Foxp3△2酵母表达载体,经转染AH109酵母细胞,无有毒性,无自激活作用。获得了40个阳性克隆,经生物信息学分析,其中9个具有开放读框。结论:应用酵母双杂交技术筛选出一组可与Foxp3△2相互作用的候选蛋白,为进一步研究Foxp3△2功能奠定了基础。     

Somatic mosaicism of the CAG repeat expansion in spinocerebellar ataxia type 3/Machado-Joseph disease

An expanded and unstable CAG repeat in the coding region of the MJD1 gene is the mutation responsible for spinocerebellar ataxia 3/Machado-Joseph disease. In order to determine whether there was a higher degree of instability in affected regions, the size of the expanded CAG repeat was analyzed in different regions of the central nervous system, in two unrelated SCA3/MJD patients. The degree of somatic mosaicism was quantified and compared to that in a SCA1 patient. Instability of the expanded CAG repeat was observed in peripheral tissues as well as in CNS of the three patients, but there was no correlation between the degree of mosaicism and the selective vulnerability of CNS structures. As in the other diseases caused by expanded CAG repeats, a lower degree of mosaicism was found in the cerebellar cortex of both SCA1 and SCA3/MJD patients, probably reflecting specific properties of this structure. In SCA3/MJD, the degree of mosaicism seemed to correlate with age at death rather than with the size of the expanded CAG repeat. Finally, somatic instability was more pronounced in SCA1 than in SCA3/MJD patients. Hum Mutat 11:23–27, 1998. © 1998 Wiley-Liss, Inc.     

Autosomal dominant cerebellar ataxias in the Kinki area of Japan

Summary The autosomal dominant cerebellar ataxias are a heterogeneous group of neurodegenerative disorders characterized by slowly progressive cerebellar ataxia. Recently, among the ataxias, spinocerebellar ataxia type 1 (SCA1), Machado-Joseph disease (MJD) and dentatorubral-pallidoluysian atrophy have been found to be caused by expansion of a CAG trinucleotide repeat in the coding region of the disease genes. We have analyzed the CAG repeats of 67 patients from 47 families with dominantly inherited ataxia who lived in the Kinki area of Japan. The following results were obtained. First, 31 patients from 22 families were found to be positive for the MJD repeat expansion, indicating that MJD is the most common dominantly inherited ataxia in the Kinki area of Japan. Second, no SCA1 repeat expansion was found among the families studied. This presents a striking contrast to the fact that there are many families with SCA1 in Hokkaido and the Tohoku area of Japan. These findings suggest geographic variation in autosomal dominant cerebellar ataxias in Japan.     

Intranuclear immunolocalization of 14-3-3 protein isoforms in brains with spinocerebellar ataxia type 1

Immunolocalization of 14-3-3 protein isoforms, one of the interacters with ataxin 1, was investigated in spinocerebellar ataxia type 1 (SCA 1) brains using isoform-specific antibodies. Samples from the pons and from the cerebellum of four SCA1 cases and three controls were studied. The intensity of the immunoreactivity (IR) and its subcellular topography were analyzed. In control subjects, granular immunoreactivity for an epitope common to all known isoforms of 14-3-3 proteins (14-3-3 COM) found in the cytoplasm of some pontine and dentate nucleus neurons was weak. It was observed in some Purkinje cells, while its intensity varied. Many nuclei of those neurons and Purkinje cells of SCA1 were intensely immunopositive for 14-3-3 COM, while it was less in their cytoplasm. Expanded polyglutamine epitope was colocalized to 14-3-3 COM epitope in some pontine neurons, sometimes accumulated in intranuclear inclusion-like structures. This findings support previous reports that 14-3-3 proteins stabilize mutant ataxin 1 in nucleus and possibly lead to neurodegeneration. However, nuclear localization of 14-3-3 proteins in SCA1 brains was dependent on its isoforms, i.e. pontine neurons intensely positive for beta, Purkinje cells for tau and dentate nucleus neurons for both, while all of those neurons were consistently positive for zeta isoform, although sigma isoform tended to be located in the cytoplasm. Nuclear accumulation and isoform- and region-dependent subcellular localizations of 14-3-3 proteins may be related to SCA1 pathology, which exhibits marked regional variability.     

On the distribution of intranuclear and cytoplasmic aggregates in the brainstem of patients with spinocerebellar ataxia type 2 and 3

The polyglutamine (polyQ) diseases are a group of genetically and clinically heterogeneous neurodegenerative diseases, characterized by the expansion of polyQ sequences in unrelated disease proteins, which form different types of neuronal aggregates. The aim of this study was to characterize the aggregation pathology in the brainstem of spinocerebellar ataxia type 2 (SCA2) and 3 (SCA3) patients. For good recognition of neurodegeneration and rare aggregates, we employed 100 µm PEG embedded brainstem sections, which were immunostained with the 1C2 antibody, targeted at polyQ expansions, or with an antibody against p62, a reliable marker of protein aggregates. Brainstem areas were scored semiquantitatively for neurodegeneration, severity of granular cytoplasmic staining (GCS) and frequency of neuronal nuclear inclusions (NNI). SCA2 and SCA3 tissue exhibited the same aggregate types and similar staining patterns. Several brainstem areas showed statistically significant differences between disease groups, whereby SCA2 showed more severe GCS and SCA3 showed more numerous NNI. We observed a positive correlation between GCS severity and neurodegeneration in SCA2 and SCA3 and an inverse correlation between the frequency of NNI and neurodegeneration in SCA3. Although their respective disease proteins are unrelated, SCA2 and SCA3 showed the same aggregate types. Apparently, the polyQ sequence alone is sufficient as a driver of protein aggregation. This is then modified by protein context and intrinsic properties of neuronal populations. The severity of GCS was the best predictor of neurodegeneration in both disorders, while the inverse correlation of neurodegeneration and NNI in SCA3 tissue implies a protective role of these aggregates.     

The repeat expansion detection method in the analysis of diseases with CAG/CTG repeat expansion: Usefulness and limitations

The repeat expansion detection (RED) method was described to detect expansions of trinucleotide repeats of unknown chromosomal location. We have improved the RED method by the use of 8-mer oligonucleotides and assessed its usefulness in 30 samples from patients with spinocerebellar ataxia type 1 (SCA1), Huntington's disease (HD), and Machado Joseph's disease (MJD), for which the number of CAG/CTG repeats was determined by sequencing. There was a good correlation between the number of repeats detected by sequencing and those identified by RED. However, in 17% of samples, the RED gave additional fragments for ligation products of different size than the CAG/CTG repeat expansion detected in the sample by sequencing. The same was observed in a group of control subjects (n = 78) without known clinical abnormalities in which products of more than 40 repeats were detected in 27% of them, indicating that CAG/CTG repeat expansions are common in the general population. Wether this corresponds to unidentified loci with expansions deserves further investigation. Hum Mutat 10:486–488, 1997. © 1997 Wiley-Liss, Inc.     

甲型H3N2流感病毒截短型PB1-F2蛋白与宿主蛋白的相互作用的初步研究

目的利用酵母双杂交技术研究甲型H3N2流感病毒截短型PB1-F2蛋白与人类宿主蛋白的相互作用,为该病毒蛋白的功能研究和致病机制提供理论依据。方法以本实验室分离和鉴定的甲型H3N2流感病毒A／Guangdong／7028／2010为模版,构建pGBKT7-PB1-F2重组载体,利用Y2HGold酵母双杂交系统,从人类通用cDNA文库中筛选与其相互作用的蛋白。结果成功构建含诱饵蛋白基因的pGBKT7-PB1-F2重组载体,转化酵母自激活和毒性实验显示为阴性：酵母双杂交实验显示Y2HGold和Y187酵母的结合率为5．22％,符合实验要求;经筛选和验证后,得到3个与截短型PB1-F2蛋白有相互作用的阳性克隆,分别为钾／钠ATP酶B1亚基、热休克蛋白40和白介素-2受体1亚基。结论初步推断截短型H3N2流感病毒PB1-F2蛋白可能影响流感病毒在宿主细胞中的复制功能和凋亡调控。     

人sCR1转化克隆菌的快速筛选和鉴定

目的 用G418快速筛选及鉴定重组人可溶性补体受体1型（sCR1）高拷贝转化克隆菌。方法 采用的sCR1重组质粒,经电转化将其克隆入SMD1168细胞中,利用G418的抗性,快速筛选转化克隆菌,并对克隆菌株提取基因组DNA进行聚合酶链反应（PCR）鉴定;该克隆菌经甲醇诱导培养后,对其表达产物进行十二烷基磺酸钠-聚丙烯酰胺凝胶电泳（SDS-PAGE）及Western blot鉴定分析。结果 从G418快速筛选的酵母克隆菌株中提取的基因组DNA进行PCR鉴定,获得了高拷贝整合的重组酵母克隆菌株,经诱导培养后,对其表达产物进行SDS-PAGE及Western blot鉴定分析,该表达蛋白在SDS-PAGE上表现为相对分子质量大于30 000的蛋白区带,在Western blot分析中可被sCR1的CD35单克隆抗体（mAb）识别,成功获得高拷贝整合的重组酵母细胞株,可表达出重组人sCR1融合蛋白。结论 经高浓度G418药物快速筛选的高拷贝SMD1168细胞株,用于表达人sCR1融合蛋白。