【作者】 刘平；

【导师】 王擎； 刘木根； 刘静宇；

【作者基本信息】 华中科技大学 ， 生物化学与分子生物学， 2008， 博士

【摘要】 遗传性皮肤病和非综合征型神经性耳聋(Nonsyndromic hearing impairment,NSHI)是两大类比较重要的常染色体显性遗传病。本课题对这两类遗传疾病进行了分子遗传学研究,涉及家系鉴定,致病基因的定位和基因突变分析。第一部分内容是有关遗传性皮肤病的。我们研究了播散性浅表光化性汗孔角化症(DSAP)和寻常型鱼鳞病(IV)。目前为止,DSAP的基因克隆目前还未完成,其病理发生机制也仅限于推测。而寻常型鱼鳞病(IV)发病率很高,有报道称其发病率仅次于感冒,是目前遗传性皮肤病中的研究热点。本论文以我们实验室采集并鉴定的一个DSAP大家系和二个IV家系为基础,对这两种遗传性皮肤病进行了分子遗传学研究。⑴我们鉴定了一个患有DSAP的中国家系,通过全基因组扫描和连锁分析,首先排除了该家系与已知位点或候选基因的连锁,然后在染色体上1p31.3-p31.1区域,发现了一个新的DSAP连锁位点,在D1S2897获得最大两点LOD值5.09。单倍型分析将该位点精细定位于D1S438和D1S464之间8.2cM,或11.9Mb的范围内。这一结果是迄今为止世界上报道的有关DSAP的第三个遗传位点,对该家系在该位点中的基因进行系统的检测,将有可能发现一个新的DSAP致病基因。对这一课题的进一步研究将有助于阐明DSAP的病理发生机制。⑵我们鉴定了二个患有IV的中国家系。首先排除了这两个家系与FLG基因和其它鱼鳞病亚型相关疾病致病基因的连锁。通过对其中一个大家系的全基因组扫描和连锁分析,在染色体上10q22.3-q24.2区域得到了最大两点LOD值3.19。单倍型分析将该位点精细定位于D10S569和D10S1709之间20.7cM或20.3Mb的范围内。第二个家系也与该位点连锁,最大LOD值达到3.95。两个独立家系都与该位点连锁的结果,强有力地表明了这一位点内存在一个新的IV致病基因,这是已报道的第二个IV遗传位点,我们的研究为找到新的IV致病基因提供了可能。鉴于目前只有一个IV致病基因被发现,找到一个新的IV致病基因将极大地促进IV的发病机理研究。第二部分内容是有关遗传性皮肤病的。耳聋严重影响患者的生活,而且发病率很高。非综合征型神经性耳聋(NSHI)是人类最常见的听觉损伤,有很高的遗传异质性,其中15～20%为常染色体显性遗传(DFNA)。ACTG1基因突变可以导致DFNA,它编码的蛋白产物γ-肌动蛋白是一种细胞质的非肌肉肌动蛋白,是耳蜗听觉毛细胞主要的细胞骨架蛋白。在一个患DFNA的中国人家系中,我们发现致病基因与微卫星多态标记D17S928连锁,进一步的单倍型分析将其定位D17S928和D17S784之间。对该区域内ACTG1基因测序,发现了一新的突变,第122位氨基酸由异亮氨酸变为缬氨酸(c.364A>G;p.I122V)。该突变在家系中与疾病共分离,同时对150个正常对照的RFLP分析也没有发现该突变。鉴于以往有关DFNA研究的家系都来自于欧洲和美洲,我们的结果在一定程度上说明ACTG1基因突变也是导致中国人DFNA的一个重要因素。更多还原

【Abstract】 Inherited skin disease and nonsyndromic hearing impairment are two important autosomal dominant diseases. In the present study, we have employed the molecular genetic technology, including clinical characterization of large families, linkage mapping of the chromosomal location of the disease causing genes, and mutational analysis, to study the two types of diseases.The first part of the thesis focuses on inherited skin diseases. We studied disseminated superficial actinic porokeratosis (DSAP) and ichthyosis vulgaris (IV). To date, no specific genes for DSAP have bene definitvely identified, however, there are two genes that have been mapped to chromosomes 12 and 15. In this study, I mapped the third genetic locus for DSAP to chromosome 1. IV has a high prevalence rate, which is ranked the second only after influenza. For IV, there is only one gene, FLG, that has been identified. In this study, I mapped the second genetic locus for IV.⑴A Chinese DSAP family with autosomal dominant inheritance was identified and clinically characterized. Genome-wide linkage analysis was performed and the known loci or candidate genes were excluded. Further analysis identified a new DSAP locus on chromosome 1p31.3-p31.1 with a maximum two-point LOD score of 5.09 with marker D1S2897. The disease gene was defined within an 8.2 cM or 11.9 Mb region between markers D1S438 and D1S464. This is the third locus identified for DSAP (DSAP3). Further mutational analysis of the candidate genes in the region will identify the specific gene for DSAP, which will provide insights into the pathogenesis of DSAP.⑵Two Chinese families with autosomal dominant IV were clinically and genetically characterized. The FLG gene and other ichthyosis associated genes were first excluded as the disease-causing gene in the two families. The larger family was then characterized by genome-wide linkage analysis to identify a new genetic locus for IV. Significant linkage was identified with markers on chromosome 10q22.3-q24.2 with a maximum LOD score of 3.19. Fine mapping defined the new genetic locus within a 20.7 cM region between markers D10S569 and D10S1709. The second family also showed positive linkage to the same region. The combined maximum LOD score in the two families was 3.95. Identification of linkage in two independent families provides strong genetic evidence that a novel gene for IV is located on chromosome 10q22.3-24.2. Future studies of the candidate genes at the 10q IV locus will identify a specific gene, which will provide insights into the pathogenesis of IV.The second part of the thesis focuses on genetics of hearing loss. Hearing loss severely affects the quality of life, and has a high prevalence rate. Non-syndromic hearing impairment (NSHI) is the most common sensory defect in humans and is genetically heterogeneous with 15～20% of cases being autosomal dominant (DFNA). DFNA can be caused by mutations in the ACTG1 gene, which encodesγ-actin. Theγ-actin is a cytoplasmic nonmuscle actin, which is a major cytoskeletal protein of the sensory hair cells of the cochlea. A Chinese family with DFNA was identified and characterized. After excluding known genes and genetic loci, linkage was identified with marker D17S928 with a maximum LOD score of 2.17. Haplotype analysis defined the causative gene between D17S928 and D17S784. A novel missense mutation (c.364A>G; p.I122V) was identified in the ACTG1 gene. The mutation co-segregated with the affected individuals in the family and did not exist in unaffected family members and 150 unrelated normal controls. As the families used in previous research were all from Europe and USA, our study partly indicated that the mutations in ACTG1 was a cause of autosomal dominant DFNA in the Chinese family.更多还原