Functional and structural analysis of C-terminal BRCA1 missense variants

Area of Science:

• Genetics
• Molecular Biology
• Cancer Research

Background:

• Germline mutations in BRCA1 and BRCA2 genes cause Hereditary Breast and Ovarian Cancer Syndrome (HBOCS).
• Genetic testing identifies variants of uncertain significance (VUS) in approximately 15% of cases, complicating diagnosis and counseling.
• Accurate classification of VUS is essential for patient management and risk assessment.

Purpose of the Study:

• To functionally assess seven missense variants of uncertain significance (VUS) in the C-terminal region of the BRCA1 gene.
• To determine the pathogenicity of these variants using a combination of in silico, structural, and functional assays.
• To improve the genetic diagnosis and counseling for HBOCS.

Main Methods:

• Utilized in silico prediction tools and structural analysis to evaluate seven BRCA1 missense VUS (Q1409L, S1473P, E1586G, R1589H, Y1703S, W1718L, G1770V).
• Performed a transcription activation (TA) assay to assess the functional impact of these variants on BRCA1 activity.
• Analyzed structural alterations in BRCT domains for variants Y1703S, W1718L, and G1770V.

Main Results:

• In silico prediction tools provided discrepant results, hindering interpretation.
• Structural analysis revealed significant alterations in BRCT domains for variants Y1703S, W1718L, and G1770V.
• The TA assay demonstrated that Y1703S, W1718L, and G1770V dramatically compromise BRCA1 transcriptional activity, while Q1409L, S1473P, E1586G, and R1589H function similarly to wild-type BRCA1.

Conclusions:

• Variants Y1703S, W1718L, and G1770V significantly impair BRCA1 function.
• These three variants can be classified as likely pathogenic BRCA1 mutations.
• The findings aid in the accurate genetic diagnosis and counseling for patients with HBOCS.