Functional analysis of BRCA1 and BRCA2 splicing variants using a minigene assay

BRCA1 and BRCA2, known as tumor suppressor genes, have been shown to increase the risk of developing breast and ovarian cancer. Intronic variants that can result in aberrant splicing events are classified as Variant uncertain significance until the functional impact is clearly predicted or confirmed. Thus, the purpose of this study is to assist in the interpretation of splicing variants and to reclassify the clinical significance of non-coding region variants that are classified as VUS.

The variants BRCA1:c.80 + 3_80 + 5del, BRCA1:c.548-15G > A, BRCA2:c.8755-19 A > G, and BRCA2:c.317-10 A > G were ultimately chosen. Through the minigene assay, we can observe exon skipping in BRCA1:c.80 + 3_80 + 5del, intron retention in BRCA1:c.548-15G > A and BRCA2:c.8755-19 A > G. This study performed a minigene assay using the remaining samples from the patients tested at Seoul National University Hospital. Wild-type and mutant type minigene constructs were designed respectively for each variant sample.

Finally aberrant splicing patterns were found in three of the four variants: BRCA1:c.80 + 3_80 + 5del, BRCA1:c.548-15G > A, BRCA2:c.8755-19 A > G that were previously classified as VUS through experimental analysis. As a result, we reclassify BRCA1;c.80 + 3_80 + 5del as LP and we classify BRCA1;c.548-15G > A and BRCA2;c.8755-19 A > G as VUS.