Clinical variant interpretation comparing two saturation genome editing-based functional studies for BRCA2

Background: using haploid human HAP1 cells and mouse embryonic stem cells, respectively, demonstrated contradictory functional results in 16.9% (1,052/6,208) of the variants. We performed clinical variant interpretation and tried to address the discordance by comparing two studies combined with 24 years of clinicopathological data collected at a single institution. Methods: guidelines and/or multifactorial likelihood analysis. For variants with concordant SGE functional results, either PS3 or BS3 was assigned. Major error rates were compared for variants with discordant results. Results: Among the 88 variants from 526 patients, 13, including three potentially hypomorphic variants, showed discordant results. Major error rates were lower for HAP1-SGE dataset, but without statistical significance. Among the 75 variants with concordant results, 28 and 47 were assigned PS3 and BS3, respectively. Consequently, 93.1% (27/29) of the variants of uncertain significance were reclassified as likely pathogenic (n = 3) or likely benign (n = 24). Conclusion: Concordant SGE results are clinically useful for variant reclassification. When discordant results are present, functional evidence should not be assigned, but HAP1-SGE dataset is suggested to be more consistent with patient-specific data. Further segregation analysis and long-term follow-up are needed to resolve discordant cases.