In this study, most major outcomes of atherosclerosis, including myocardial infarction, myocardial ischemia, inter- mittent claudication, arterial surgery and stroke, were assessed. None of the analyzed polymorphisms in the WRN gene associated with these pathologies. Furthermore, dependent on the polymorphism, either higher or lower risk estimates for the different cardiovascular pathologies were observed. In contrast, a consistent risk profile over these various outcomes of atherosclerosis was expected. Therefore, we concluded that the i1-C/T, L1074F and C1367R polymorphisms do not contribute to the risk of developing cardiovascular pathologies. For the C1367R SNP, these results are in line with recent studies in Caucasians (Bohr et al., 2004; Castro et al., 2000), but at odds with findings in Japanese, where the carriers of the 1367R allele had lower risks for myocardial infarction (Morita et al., 1999; Ye et al., 1997). As already suggested by others (Bohr et al., 2004), the disparity in results might come from population differences, which is also supported by the fact that in the Japanese the minor allele frequency of the C1367R poly- morphism is more than three times lower than in Caucasians. In the Japanese the C1367R variation may also be in linkage disequilibrium with another, so far unidentified polymorphism that is not present in Caucasians.

In WS patients, the observed pathologies and decrease in lifespan are attributable to the loss of a functional WRN protein. Polymorphisms in the WRN gene may also affect the functionality of the protein. The i1-C/T SNP is located in the first intron of the WRN gene. An intronic SNP may influence the splicing process or the stability of the mRNA, and thereby the amount of functional protein synthesized. However, for the i1- C/T polymorphism the effect has still to be established. The L1074F polymorphism is in exon 26, and in the vicinity of the RecQ C-terminal (RQC) domain. The C1367R SNP is located

M. Kuningas et al./Mechanisms of Ageing and Development 127 (2006) 307–313

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Bendixen, M.H., Nexo, B.A., Bohr, V.A., Frederiksen, H., M

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in exon 34, near to the nuclear localization signal (Matsumoto et al., 1998). It has been shown that these polymorphisms result in subtle changes in the helicase/exonuclease activities of the WRN protein (Bohr et al., 2004; Kamath-Loeb et al., 2004). The localization to the nucleus of the protein carrying the C1367R polymorphism appeared to be unaffected (Bohr et al., 2004). It can be reasoned that the differential functional effects caused by the polymorphisms in the WRN gene, are not sufficient for causing pathologies or influence the lifespan. However another possibility is, that the polymorphisms alter the functionality of the WRN protein, but due to compensatory mechanisms no effects at phenotypic level are observed.

The first strength of this study is the elderly cohort, which is suitable for testing the effect of variations in the WRN gene on age-associated disease and mortality patterns in the population at large. The other strength is the possibility to estimate several phenotypes in one cohort, and the prospective analysis with a high number of events (deaths) during the follow-up. The latter results in a good power for the detection of effects on lifespan. The weakness of the study might be related to the selection of analyzed polymorphisms. The SNPs were selected based on their published associations, however there might be other, so far undetected functional polymorphisms in the WRN gene leading to changes in the pace of aging. An approach to overcome this is to analyze, either separately and/or in a combination of haplotypes, a larger set of evenly distributed SNPs in the WRN gene, and determine their influence on the prevalence of age-associated diseases and lifespan.

Erkkola, R., Panduro, A., Riestra, R., Piussan, C., Deeb, S.S., Wang, L., Edland,S.D., Martin,G.M., Oshima,J.,