丙烯酰胺诱导小鼠淋巴瘤细胞tk基因突变谱的实验研究

目的为研究丙烯酰胺(AA)致基因突变的机制提供实验依据。方法挑选经AA诱导的小鼠淋巴瘤L5178Y3．2．7c-tk^ /-细胞tk基因突变子(tk-/-)，提取基因组DNA，用等位基因特异性聚合酶链反应(PCR)扩增、杂合性缺失(LOH)分析、序列分析等技术，分析其突变谱。结果AA诱导突变体tk基因LOH发生率为78．8％。LOH的发生率随AA剂量的增加呈上升趋势，染毒剂量越大，tk等位基因缺失的发生就越严重。在大集落(LC)中，AA低剂量组(150、300μg/m1)诱导LOH的发生率(25．0％、33．3％)与自发突变组和AA高剂量组(600、750μg/ml)LOH的发生率(66．7％、77．8％、85．7％)相比，差异均有统计学意义(P＜0．05)。序列分析证实，AA诱导的tk基因点突变主要为碱基置换以及1个移码，其中碱基置换主要的类型为T：G→G：T的颠换。结论AA诱导的tk基因突变谱是以功能性等位基因缺失为主的突变类型，其次是碱基置换，移码较少发生。

Mutational spectra in the tk gene of mouse lymphoma cells induced by acrylamide

OBJECTIVE: To investigate the mechanism of acrylamide (AA)-induced mutational spectra in the tk gene of mouse lymphoma cells. METHODS: L5178Y3.2.7c-tk(+/-) cells were treated with AA at different concentrations. Mutational spectra of tk locus were analyzed by the mouse lymphoma assay (microtiter procedure), and frequency of loss of heterozygosity (LOH) analysis with allele special PCR. Subsequently determined the DNA sequence of negative LOH's colonies induced by AA. RESULTS: The LOH of mutants derived from AA induction was 78.8%, and showed a good dose-response relationship in large colonies. The occurrence of LOH of large colonies at lower doses (150 microg/ml and 300 microg/ml) were 25.0% and 33.3% respectively which were significantly different from those of control (66.7%), and at higher doses (600 microg/ml and 750 microg/ml) were 77.8% and 85.7%. By Sequence analysis showed that AA-induced point mutations were mainly base substitutions, and most of them were T:G-->G:T transversions. CONCLUSION: Functional tk allele gene loss is major mutational event in both spontaneous and induced tk mutants. And point mutations were base substitution.