Shared BRCA1 founder variant identified in Rwandan women with breast cancer
A preprint reports that 4% of Rwandan breast cancer cases in a 175-woman cohort carry a single recurrent BRCA1 frameshift variant tracing to a common ancestral haplotype of around 581 kb.
A preprint deposited on bioRxiv describes the identification of a shared pathogenic founder variant in BRCA1 among Rwandan women diagnosed with breast cancer. In a cohort of 175 Rwandan women with breast cancer, seven unrelated carriers — representing approximately 4% of cases and 22% of all pathogenic variant carriers identified — harboured the same BRCA1 frameshift variant, designated c.4065_4068del (p.Asn1355Lysfs*10).
The variant is extremely rare in the gnomAD population reference dataset but has been observed recurrently in European, Asian, and Middle Eastern cohorts. Whole-exome sequencing and haplotype analysis of all seven carriers revealed a shared ancestral haplotype block of approximately 581 kilobases surrounding the variant, consistent with a common founder event rather than independent mutational origins.
The finding adds to a growing but still limited body of germline data from African populations, which remain substantially under-represented in global breast cancer genetics databases. The authors argue that population-specific founder variants are likely present across sub-Saharan Africa at frequencies that current reference datasets cannot reliably capture.
This work has not yet undergone peer review. The authors note that the cohort size limits statistical precision and that further studies in larger Rwandan and East African populations will be needed to characterise the full spectrum of pathogenic BRCA1/2 variants in the region.
Plain-language version
For patients, families, and general readers. Educational only — not medical advice.
Scientists studying breast cancer genetics in Rwanda have found that a number of unrelated women with breast cancer share an identical fault in a gene called BRCA1. When the same genetic fault appears repeatedly in people from the same population, it is called a founder variant — meaning it likely descended from a single ancestor rather than arising independently many times.
This matters because populations in Africa have historically been under-represented in genetics research, meaning important inherited cancer risks specific to those communities may have been missed. This study, which has not yet been formally reviewed by other scientists, is a step towards filling that gap.
The researchers say larger studies will be needed to understand how common this variant is across Rwanda and neighbouring countries.
This is an educational summary, not medical advice. If anything here raises questions for you, please speak with your GP or a clinical professional.
Sources
Read the original reporting — these are the public sources this summary draws from.
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Primary sourcePreprint bioRxiv (Cold Spring Harbor Laboratory) · 2026-05-29A Common Pathogenic Founder Variant in Rwandan Breast Cancer Cases