Mouse Cancer Genetics Program, Center for Cancer Research, National Cancer Institute, Frederick, MD, 21702, USA.
J Hum Genet. 2020 Sep;65(9):805-809. doi: 10.1038/s10038-020-0768-0. Epub 2020 May 11.
A pathogenic mutation in BRCA2 significantly increases the risk of breast and ovarian cancers making it imperative to examine the functional consequences of variants of uncertain clinical significance. Variants that are predicted to result in a truncated protein are unambiguously classified as pathogenic. We have previously shown how a pathogenic splice site variant known to generate a premature termination codon (PTC) in exon 9 and a nonsense mutation at exon 7, can generate functional BRCA2 by skipping exons 4-7 and restoring the reading frame. Using a well-established mouse embryonic stem cell-based assay, we functionally characterize here one splice site mutation and 11 pathogenic BRCA2 variants that are either nonsense mutation or generate PTC in different exons ranging from exons 4 to 7. Our study shows that five variants can restore the open reading frame by exon skipping and generate a functional protein. This suggests further need to exercise prudence when classifying clearly pathogenic variants.
BRCA2 中的致病突变显著增加了乳腺癌和卵巢癌的风险,因此必须研究具有不确定临床意义的变异的功能后果。预测会导致截断蛋白的变异被明确归类为致病性变异。我们之前已经展示了一种已知会在第 9 外显子产生提前终止密码子 (PTC) 并在第 7 外显子产生无义突变的致病性剪接位点变异,如何通过跳过第 4-7 外显子并恢复阅读框来产生功能性 BRCA2。在这里,我们使用一种成熟的基于小鼠胚胎干细胞的测定法,对一个剪接位点突变和 11 种致病性 BRCA2 变异进行了功能表征,这些变异要么是无义突变,要么在从第 4 到第 7 外显子的不同外显子中产生 PTC。我们的研究表明,有五个变体可以通过外显子跳跃恢复开放阅读框并产生功能性蛋白质。这表明在分类明确的致病性变异时需要进一步谨慎行事。