Characterizing BRCA1 Variants Using Multiplex Functional Assays

Individuals with deleterious germline mutations in the tumor suppressor gene BRCA1 are at an increased risk for breast and ovarian cancers that are associated with poor disease outcomes. While cancer screenings have helped identify BRCA1 variants in patients, there is not enough information on many of these variants to determine if they are deleterious and thus link them with disease predisposition. To infer the cancer risk of these variants of uncertain significance (VUS), many functional assays have been developed to characterize variant BRCA1 protein functions. In this review, we will discuss the assays that have been used to examine the function of variant BRCA1 proteins and how functional assays are increasing throughput from methods that test one variant at a time to multiplexed formats. Multiplex assays utilizing homology-directed repair (HDR) and saturation genome editing (SGE), among others, have been able to evaluate more thoroughly BRCA1 variants and functional regions. Based on these new developments in BRCA1 functional assays, we will also discuss the need for more multiplexed assays to increase confidence in functional interpretation and other potential approaches for better classifying BRCA1 VUS.