背景:MRE11A-RAD50-Nibrin(MRN)复合物在修复DNA双链断裂方面发挥着重要作用。遗传不稳定性疾病的三个因素中的遗传突变和MRN基因与乳腺癌易感性有关。但是基础数据并不完全令人信服。这里,我们解决了两个相关的问题:(1)是一些罕见的MRN变异中危乳腺癌易感性等位基因,如果是这样(2),那么MRN基因遵循BRCA1/BRCA2模式,其中大多数易感性等位基因是蛋白质截短变体,还是遵循ATM/CHEK2模式,其中一半或更多的易感性等位基因是错义替换?
方法:使用高分辨率熔解曲线分析,然后进行Sanger测序,我们在1,313例早发性乳腺癌病例和1,123例人群对照中,对MRN基因的编码外显子和近端剪接连接区进行了突变筛选.使用类似于以前应用于ATM的生物信息学方法,汇集了三个基因中的罕见变体。BRCA1、BRCA2和CHEK2,然后通过逻辑回归进行评估。
结果:对我们的ATM进行重新分析,BRCA1和BRCA2突变筛查数据显示,这些基因没有致病性等位基因(除了中等风险的SNP),在高加索美国人中,次要等位基因频率>0.1%,非洲裔美国人,或者东亚人。将我们的MRN分析限制在等位基因频率<0.1%的变体,并结合蛋白质截断变体,可能是剪接变异,和关键功能域罕见错义替换,我们发现显著证据表明MRN基因确实是中危乳腺癌易感基因(比值比(OR)=2.88,P=0.0090).关键结构域错义置换比截短变体更频繁(24对12个观察),并且赋予略高的OR(3.07对2.61),具有较低的P值(0.029对0.14)。
结论:这些数据证明MRE11A,RAD50和NBN是中危乳腺癌易感基因。像ATM和CHEK2一样,它们的致病变体谱包括相对高比例的错义取代。然而,数据既不能确定是否在同一分析模型下对3种基因中的每一种变异进行了最佳评估,也不能对本研究中观察到的单个变异进行临床可操作的分类.
BACKGROUND: The MRE11A-RAD50-Nibrin (MRN) complex plays several critical roles related to repair of DNA double-strand breaks. Inherited mutations in the three components predispose to genetic instability disorders and the MRN genes have been implicated in breast cancer susceptibility, but the underlying data are not entirely convincing. Here, we address two related questions: (1) are some rare MRN variants intermediate-risk breast cancer susceptibility alleles, and if so (2) do the MRN genes follow a BRCA1/BRCA2 pattern wherein most susceptibility alleles are protein-truncating variants, or do they follow an ATM/CHEK2 pattern wherein half or more of the susceptibility alleles are missense substitutions?
METHODS: Using high-resolution melt curve analysis followed by Sanger sequencing, we mutation screened the coding exons and proximal splice junction regions of the MRN genes in 1,313 early-onset breast cancer cases and 1,123 population controls. Rare variants in the three genes were pooled using bioinformatics methods similar to those previously applied to ATM, BRCA1, BRCA2, and CHEK2, and then assessed by logistic regression.
RESULTS: Re-analysis of our ATM, BRCA1, and BRCA2 mutation screening data revealed that these genes do not harbor pathogenic alleles (other than modest-risk SNPs) with minor allele frequencies>0.1% in Caucasian Americans, African Americans, or East Asians. Limiting our MRN analyses to variants with allele frequencies of <0.1% and combining protein-truncating variants, likely spliceogenic variants, and key functional domain rare missense substitutions, we found significant evidence that the MRN genes are indeed intermediate-risk breast cancer susceptibility genes (odds ratio (OR)=2.88, P=0.0090). Key domain missense substitutions were more frequent than the truncating variants (24 versus 12 observations) and conferred a slightly higher OR (3.07 versus 2.61) with a lower P value (0.029 versus 0.14).
CONCLUSIONS: These data establish that MRE11A, RAD50, and NBN are intermediate-risk breast cancer susceptibility genes. Like ATM and CHEK2, their spectrum of pathogenic variants includes a relatively high proportion of missense substitutions. However, the data neither establish whether variants in each of the three genes are best evaluated under the same analysis model nor achieve clinically actionable classification of individual variants observed in this study.