J Pathol Transl Med.  2022 Jul;56(4):212-216. 10.4132/jptm.2022.05.02.

Founder BRCA1 mutations in Nepalese population

• Mehta A
• Diwan H
• Gupta G
• Nathany S
• Agnihotri S
• Dhanda S

• KMID: 2531613
• DOI: http://doi.org/10.4132/jptm.2022.05.02

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 BRCA1 gene in the Nepalese people.
Methods
Germline BRCA 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 BRCA 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 BRCA1/2 variants. Twenty-seven of these 58 tested harbored pathogenic genetic alterations in BRCA1/2 genes, with 23 being BRCA1 mutant. Sixteen of 23 BRCA1 mutant cases shared one common pathogenic mutation c.2214_2215insT (p.Lys739Ter) (NM_007294.4). Additionally, a second highly recurrent mutation in BRCA1 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.

Keyword

Founder mutation; Nepal

Figure

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  Fig. 1 The commonly encountered BRCA1 mutations in the non-Nepalese population (A) and the Nepalese population (B) in the present study [19,20]. Note the dominance of just two genetic alterations in the Nepalese people and contrast to the widespread distribution of pathogenic mutation in the full-length BRCA1 gene in the non-Nepalese population.

Reference

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