ClinVar

Description

The p.R680P variant (also known as c.2039G>C), located in coding exon 13 of the MSH2 gene, results from a G to C substitution at nucleotide position 2039. The arginine at codon 680 is replaced by proline, an amino acid with dissimilar properties. This alteration has been previously identified in a family with suspected Lynch syndrome (Bonadona V et al. JAMA. 2011 Jun 8;305(22):2304-10), in families that met Amsterdam I/II criteria for Lynch syndrome, and in individuals whose tumors demonstrated high microsatellite stability and/or absent MSH2/MSH6 staining on immunohistochemistry (Ambry internal data; Grandval P et al. Database (Oxford), 2013 May;2013:bat036; Xu Y et al. Front Genet, 2020 Aug;11:991). Based on internal structural analysis, this variant is anticipated to result in a significant disruption in ATP binding (Gupta S et al. Nat. Struct. Mol. Biol., 2011 Dec;19:72-8). In a massively parallel cell-based functional assay testing susceptibility to a DNA damaging agent, 6-thioguanine (6-TG), this variant was reported to be functionally deleterious (Jia X et al. Am J Hum Genet, 2021 01;108:163-175). The yeast equivalent of this variant demonstrated an increased mutation rate in a multiplexed functional assay performed using Saccharomyces cerevisiae (Ollodart AR et al. Genetics, 2021 06;218:). This variant was not reported in population-based cohorts in the Genome Aggregation Database (gnomAD). This amino acid position is highly conserved in available vertebrate species. In addition, this alteration is predicted to be deleterious by in silico analysis. Based on the supporting evidence, this alteration is interpreted as a disease-causing mutation.