A frame-shift mutation of PMS2 is a widespread cause of Lynch syndrome

Mark Clendenning ¹, Leigha Senter ¹, Heather Hampel ¹, Kristina Lagerstedt Robinson ², Shuying Sun ¹, Daniel Buchanan ³, Michael D Walsh ³, Mef Nilbert ⁴, Jane S Green ⁵, John Potter ⁶, Annika Lindblom ² and Albert de la Chapelle ^1*

¹ The Ohio State University, United States
² Karolinska Institute, Sweden
³ Queensland Institute for Medical Research, Australia
⁴ Lund University, Sweden
⁵ Memorial University of Newfoundland, Canada
⁶ Fred Hutchinson Cancer Research Center, United States

^* To whom correspondence should be addressed. E-mail: albert.delachapelle{at}osumc.edu.

Accepted 17 December 2007

Abstract

Background: When compared to the other mismatch repair genes involved in Lynch syndrome, the identification of mutations within PMS2 has been limited (<2% of all identified mutations), yet the immunohistochemical analysis of tumour samples indicates that approximately 5% of Lynch syndrome cases are caused by PMS2. This disparity is primarily due to complications in the study of this gene caused by interference from pseudogene sequences.

Methods: Using a recently developed method for detecting PMS2 specific mutations, we have screened 99 patients who are likely candidates for PMS2 mutations based on immunohistochemical analysis.

Results: We have identified a frequently occurring frame-shift mutation (c.736_741del6ins11) in 12 ostensibly unrelated Lynch syndrome patients (20% of patients we have identified with a deleterious mutation in PMS2, n=61). These individuals all display the rare allele (population frequency < 0.05) at a SNP in exon 11, and have been shown to possess a short common haplotype; allowing us to calculate that the mutation arose around 1625 years ago (65 generations; 95% CI: [22, 120]).

Discussion: Ancestral analysis indicates that this mutation is enriched in individuals with British and Swedish ancestry. We estimate that there are >10,000 carriers of this mutation in the United States alone. The identification of both the mutation and the common haplotype in one Swedish control sample (n = 225), along with evidence that Lynch syndrome associated cancers are rarer than expected in the probands’ families would suggest that this is a prevalent mutation with reduced penetrance.

Keywords: Age calculation, Founder effect, Lynch syndrome, PMS2

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