垂直变性梯度凝胶电泳在大肠癌APEX基因变异检测中的应用

目的探讨变性梯度凝胶电泳(denaturinggradientgelelectrophoresis,DGGE)在大肠癌APEX基因单核苷酸多态性(singlenucleotidepolymorphism,SNP)或基因突变筛选中的应用价值。方法对散发性大肠癌APEX基因5个外显子进行DGGE检测及DNA测序,分析DGGE带型和测序结果之间的关系。结果根据DGGE原理及实验观察结果,发现无论何种碱基改变,在DGGE胶上通常只可能呈现4种带型中的一种,本研究发现其中的3种。杂合子的特征是在变性胶的泳道上出现不同水平的4条带,纯合子呈单一条带;带有错配的DNA分子在凝胶上的位置总是落后于没有错配的分子;当碱基改变为A/T→G/C时,突变DNA分子泳动较快,其条带位于野生型分子之前,当碱基改变为G/C→A/T时,结果相反。结论对于一已知的SNP,利用DGGE带型可以判断SNP的基因型和等位基因频率而免去进一步测序工作;对突变检测而言,DGGE可预测碱基改变的类型,有利于对测序结果判读的准确性。

Application of DGGE in detection for genetic variations of APEX gene in colorectal cancers

Objective To evaluate denaturing gradient gel electrophoresis (DGGE) in detection of single nucleotide polymorphisms or mutations of APEX gene in colorectal cancers.Method Five exons of APEX gene in colorectal cancers were screened by DGGE following sequencing.The relationship between the band mobility patterns of DGGE and results of DNA sequencing were studied and the related literatures were reviewed.Results According to the principles of DGGE as well as the experimental findings,it was observed that whatever the bases were changed,only one of four patterns of DNA bands presented on DGGE and three of these patterns were identified on denaturing gradient gels in this research.Heterozygotes were characterized by four bands at different levels on a lane of denatured gels and homozygotes just presented one band.Each band represented one type of DNA molecules.The DNA molecules with a mismatch were always got behind those molecules without mismatch on gels.When the base mutated from A/T to G/C,the mutant DNA molecules moved faster and was located in front of the wild-type molecules ongels.When the base mutated from G/C to A/T,the results of electrophoresis was contrary.Conclusions For a known SNP,the genotypes and allele frequencies can be determined by the patterns of DNA bands on denaturing gradient gels with exemption of sequencing,while for the mutant DGGE may be helpful to predict the changes of base mutations,which will be favorable to correctly analyze the results of sequencing.