Founder pathogenic variants in colorectal neoplasia susceptibility genes in Ashkenazi Jews undergoing colonoscopy

Colorectal neoplasia is one of the most common tumors affecting Western populations.

In this study we used a custom amplicon sequencing platform and an in-house bioinformatic pipeline to study constitutional DNA from two different case series of Ashkenazi Jews undergoing colonoscopy (n = 765). The first series all had pathologically confirmed colorectal adenomas and/or carcinoma. The second series consisted of persons who had undergone a colonoscopy within the five years prior to ascertainment, regardless of findings. Ninety-one percent of all patients were asymptomatic at the time of colonoscopy.

In the first group (n = 438), we identified 65 founder variants (56 in APC, 2 in GREM1, 3 in MSH2 and 4 in BLM). In the second group (n = 327), the findings were 30, nothing, 1 and 1, respectively, as well as 2 MSH6 variants.

Overall, we found that 10 to 15% of Ashkenazi Jewish persons undergoing colonoscopy harbor variants of interest in colorectal and/or polyposis predisposition. This includes pathogenic variants in MSH6, which is associated with colorectal cancer but not with polyposis. We identified no pathogenic variants in more recently discovered polyposis predisposition genes (POLE, POLD1 or NTHL1), rendering the presence of such founder variants rare.