多聚丙氨酸延展突变与人类遗传病

三核苷酸重复的延展突变是导致遗传病的重要机制之一。根据产生机制和遗传特点的不同，可将其分为2类：一类是引起多种神经系统遗传病的动态突变；另一类就是本文重点介绍的多聚丙氨酸延展（polyalanine expansion，PAE）突变。PAE是指编码多聚丙氨酸的不完全GCN（N为A、C、G或T中任意一种）三核苷酸重复的延展，其结果是蛋白中多聚丙氨酸链的氨基酸数增多。PAE突变能在世代间稳定传递，其产生机制可能为等位基因间的不等交换。迄今为止，已在9种遗传病中发现PAE突变。本文将对PAE突变及所致遗传病作一介绍。

Polyalanine expansion in human genetic diseases

Expansion of trinucleotide repeats represents an important type of pathogenic mutations.It can be further divided into two subtypes based on the mechanism leading to the expansion and the genetic features.One subtype is the dynamic mutation,which has been implicated in 17 neurodegenerative genetic diseases.The another subtype is polyalanine expansion(PAE),which will be reviewed in this paper.PAE refers to the duplication of the imperfect GCN (N=A or C or G or T) triplet repeats within the coding region of a gene,which leads to an expanded polyalanine tract in encoded protein.PAE is stable over generations and has been suggested to be caused by unequal crossing-over.So far,PAE has been identified in 9 human genetic diseases.In this review,we will introduce the features of PAE and the PAE-related genetic diseases.