Journal
JOURNAL OF MEDICAL GENETICS
Volume 37, Issue 9, Pages 646-652Publisher
BMJ PUBLISHING GROUP
DOI: 10.1136/jmg.37.9.646
Keywords
MSH2; recurrent mutation; splice donor site of exon 5; founder mutation
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Funding
- NCI NIH HHS [CA67941, P30CA16058] Funding Source: Medline
- NIGMS NIH HHS [GM58934] Funding Source: Medline
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Introduction-An intronic germline mutation in the MSH2 gene, A-->T at nt942+3, interferes with the exon 5 donor splicing mechanism leading to a mRNA lacking exon 5. This mutation causes typical hereditary non-polyposis colorectal cancer (HNPCC) and has been observed in numerous probands and families world wide. Recurrent mutations either arise repeatedly de novo or emanate from ancestral founding mutational events. The A-->T mutation had previously been shown to be enriched in the population of Newfoundland where most families shared a founder mutation. In contrast, in England, haplotypes failed to suggest a founder effect. If the absence of a founder effect could be proven world wide, the frequent de novo occurrence of the mutation would constitute an unexplored predisposition. Methods-We studied 10 families from England, Italy, Hong Kong, and Japan with a battery of intragenic and flanking polymorphic single nucleotide and rnicrosatellite markers. Results-Haplotype sharing was not apparent, even within the European and Asian kindreds. Our marker panel was sufficient to detect a major mutation arising within the past several thousand generations. Discussion-As a more ancient founder is implausible, we conclude that the A-->T mutation at nt942+3 of MSH2 occurs de novo with a relatively high frequency. We hypothesise that it arises as a consequence of misalignment at replication or recombination caused by a repeat of 26 adenines, of which the mutated A is the first. It is by far the most common recurrent de novo germline mutation yet to be detected in a human mismatch repair gene, accounting for 11% of all known pathogenic MSN2 mutations.
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