ADAR1突变诱发遗传性对称性色素异常症的分子机制研究

The adenosine-to-inosine (A-to-I) RNA edited by ADARs is a post-transcriptional process that alters the RNA sequences by base modifications, thereby enhancing the diversity of gene products. Dyschromatosis symmetrica hereditaria (DSH) is an autosomal dominant genodermatosis and caused by heterozygous mutation of ADAR1 gene, an important member of the ADARs family. Since the pathogenesis of DSH is not completely understood yet, we hypothesize that the deficiency of ADAR1 editing may be associated with the pigmentary disorders. ADAR1 gene is known to give rise to two protein isoforms (p150 and p110) that differ by N-terminal 295 amino acids, and the haploinsufficiency of the p150 isoform is the determinant of DSH. First, whole transcriptome data and whole genome sequence will be obtained from the skin tissues of DSH patients and controls. Several algorithms will be utilized to detect genes in editing/base substitution events,splicing and expression are different between the DSH patients and controls. Next，these aberrant genes associated with p150 isoform will be identified by using a keratinocyte melanocyte coculture model and will be used as the potential candidate genes responsible for DSH. Last, the functions of these candidate genes will be clarified on the transportation, distribution and synthesis of melanosomes, so as to identify the key genes involved in DSH. This project will provide useful information to investigate the underlying pathophysiological mechanisms of pigmentation disorders, and will set up a good model for studying ADARs in the future.

RNA腺苷脱氨酶(ADARs)能够催化RNA的腺嘌呤(A)脱氨基生成次黄嘌呤(I)，从而改变密码子编码和产生可变剪接，增加基因产物的多样性，对基因转录后调控起重要作用。DSH是常染色体显性遗传性色素异常性疾病，它的致病基因ADAR1是ADARs家族的重要成员，很可能与ADAR1突变引起的靶基因编辑异常有关，其确切发病机制仍不清楚。ADAR1的编码产物有p150和p110两种，其中p150是DSH发病的关键诱因。本课题将通过比较转录组序列和基因组序列，首先筛选出DSH患者皮肤组织内存在的异常编辑、异常剪接和差异表达基因，并进一步采用细胞学模型筛选出与p150有关且在DSH皮肤组织中存在异常的基因，作为进一步进行功能验证的候选基因。通过研究这些异常编辑对色素合成、分布和转运的影响，识别介导DSH的关键基因。该研究不仅有助于揭示色素代谢的调控机制，也可为研究RNA的转录后修饰提供很好的疾病模型。

RNA腺苷脱氨酶(ADARs)主要功能是介导RNA编辑，它能够催化RNA的腺嘌呤(A)脱氨基生成次黄嘌呤(I)，从而改变密码子编码和产生可变剪接，进而增加基因产物的多样性，对基因转录后调控起重要作用。ADAR1作为ADARs的重要一员，它还参与了miRNA的加工过程。遗传性对称性色素异常症是一种常染色体显性遗传的色素异常性疾病，尽管已知ADAR1是其致病基因，但其确切发病机制仍不清楚。鉴于ADAR1的主要功能是RNA编辑，因此，我们提出假说，DSH发病机制可能与ADAR1突变引起的靶基因编辑异常有关。本课题主要开展了以下几个方面的工作：1) 对DSH患者皮肤组织进行了转录组测序，对相关差异表达基因及差异编辑位点进行了研究，共在DSH患者皮肤中检测到198个编辑水平降低的编辑位点；2) 对ADAR1上调表达和ADAR1下调表达的人黑素细胞的mRNA、miRNA进行了测序，进一步在细胞水平识别相关差异编辑位点和差异表达基因，共检测到902个差异编辑位点；3) 结合前面所获得的数据进一步分析，筛选出了潜在的重要候选基因，包括EDNRB、TBX15、MCHR1等；4) 对候选基因进行功能验证。该研究结果识别了ADAR1调控色素代谢的潜在相关基因，这为揭示ADAR1在色素代谢调控过程中的具体作用机制提供了重要证据，为色素异常性疾病的干预提供了潜在靶点，也为研究RNA的转录后修饰提供了很好的疾病模型。