Founder <i>BRCA1</i> mutations in Nepalese population

Abstract

Background: Founder mutation is a heritable genetic alteration observed with high frequency in a geographically and culturally isolated population where one or more ancestors becomes the forebearer of the altered gene. The current study reports two founder mutations in the <i>BRCA1</i> gene in the Nepalese people.Methods: Germline <i>BRCA</i> testing in all surface epithelial ovarian cancers and the selected case of breast, prostate, and pancreatic cancers has been the standard practice from 2016 to 2021. One thousand one hundred thirtythree probands were screened for germline <i>BRCA</i> variants by next generation sequencing. The variants were classified as per the American Society of Medical Genetics and Genomics recommendations. Pathogenic (class V) and likely pathogenic (class IV) were considered clinically relevant and utilized for cascade screening.Results: Nepalese population made up a subcohort of 5.12% (58/1,133) of probands tested for germline <i>BRCA1/2</i> variants. Twenty-seven of these 58 tested harbored pathogenic genetic alterations in <i>BRCA1/2</i> genes, with 23 being <i>BRCA1</i> mutant. Sixteen of 23 <i>BRCA1</i> mutant cases shared one common pathogenic mutation c.2214_2215insT (p.Lys739Ter) (NM_007294.4). Additionally, a second highly recurrent mutation in <i>BRCA1</i> gene c.5068A>T (p.Lys1690Ter) (NM_007294.4) was noted in six patients from this population.Conclusions: The overwhelming abundance of the above two variants in a geographically confined population confers these two genetic alterations a status of founder mutations amongst the people of Nepal. A more extensive population-based study to reaffirm these findings will help establish a dual site-specific germline testing similar to the “Multisite-3-assay” in Ashkenazi Jews as the primary screening tool, especially in a resource-constrained environment.