TY - JOUR T1 - Functional analysis of <em>MSH2</em> unclassified variants found in suspected Lynch syndrome patients reveals pathogenicity due to attenuated mismatch repair JF - Journal of Medical Genetics JO - J Med Genet SP - 245 LP - 253 DO - 10.1136/jmedgenet-2013-101987 VL - 51 IS - 4 AU - Eva AL Wielders AU - Jan Hettinger AU - Rob Dekker AU - C Marleen Kets AU - Marjolijn J Ligtenberg AU - Arjen R Mensenkamp AU - Ans MW van den Ouweland AU - Judith Prins AU - Anja Wagner AU - Winand NM Dinjens AU - Hendrikus Jan Dubbink AU - Liselotte P van Hest AU - Fred Menko AU - Frans Hogervorst AU - Senno Verhoef AU - Hein te Riele Y1 - 2014/04/01 UR - http://jmg.bmj.com/content/51/4/245.abstract N2 - Background Lynch syndrome, an autosomal-dominant disorder characterised by high colorectal and endometrial cancer risks, is caused by inherited mutations in DNA mismatch repair (MMR) genes. Mutations fully abrogating gene function are unambiguously disease causing. However, missense mutations often have unknown functional implications, hampering genetic counselling. We have applied a novel approach to study three MSH2 unclassified variants (UVs) found in Dutch families with suspected Lynch syndrome. Methods The three mutations were recreated in the endogenous Msh2 gene in mouse embryonic stem cells by oligonucleotide-directed gene modification. The effect of the UVs on MMR activity was then tested using a set of functional assays interrogating the main MMR functions. Results We recreated and functionally tested three MSH2 UVs: MSH2-Y165D (c.493T&gt;G), MSH2-Q690E (c.2068C&gt;G) and MSH2-M813V (c.2437A&gt;G). We observed reduced levels of MSH2-Y165D and MSH2-Q690E but not MSH2-M813V proteins. MSH2-M813V was able to support all MMR functions similar to wild-type MSH2, whereas MSH2-Y165D and MSH2-Q690E showed partial defects. Conclusions Based on the results from our functional assays, we conclude that the MSH2-M813V variant is not disease causing. The MSH2-Y165D and MSH2-Q690E variants affect MMR function and are therefore likely the underlying cause of familial cancer predisposition. Since the MMR defect is partial, these variants may represent low penetrance alleles. ER -