全外显子组捕获测序技术在单基因遗传病研究和诊断中的意义

Whole exome sequencing in the researches and diagnosis of monogenic disorders

外显子组(exome)即一个个体的基因组DNA上所有蛋白质编码序列(外显子)的总和。人类外显子组序列仅占人类整个基因组序列的1%,约为30 Mb,包括18万个左右的外显子,估计85%的人类致病突变都位于这1%的蛋白质编码序列上。在单基因病的致病基因定位和克隆研究中,通常采用的家系连锁分析法及定位克隆技术是最有效、最准确的方法之一。但是,如果患病亲属的人数有限,或不外显、外显不全,或基因突变是自发产生的,则连锁分析多半失效。这是单基因疾病分子遗传学研究中常常难以克服的"瓶颈"。然而,对各种遗传病患者的外显子组进行测序分析,所针对的是与疾病最相关的"蛋白质编码序列"区域,捕捉的是疾病的大部分致病突变信息,具有所需样本数量少、低费用、高通量的优势和特点,故可以大大加快鉴定人类疾病基因的进程。另外,对于外显子数目庞大的致病基因(如DMD、FBN1、PKD1等),用全外显子组测序技术进行基因诊断,则比传统的PCR+Sanger测序法更为经济。

Exome is the collection of all exons, i. e. the protein - coding sequencing, within the genomic DNA of an individual. Exome constitutes around 1% of the entire human genome or 30 megabases （Mb）, split across approximately 180, 000 exons. It esti- mated that about 85% variants located on these protein -coding regions. Traditionally, the family linkage analysis and positional cloning methods are used to identify the disease - causing gene for Mendelian disorders. However, because of the difficulty in collection of an adequate number of affected individuals and families for a statistically powerful study, or incomplete/non - penetrance of the dis- ease, or de novo mutations for sporadic cases, these approaches are not applicable. Thus, the whole exome -capture sequencing （WES） represents a cost -effective, reproducible and robust strategy for the sensitive and specific identification of variants in protein -coding changes in individual human genomes. In addition, during the gene testing for larger gene of monogenic defects such as DMD, FBN1, PKD1, WES is more cost- effective than PCR followed by Sanger sequencing technique.