Our verdict is Uncertain significance. Variant got 2 ACMG points: 2P and 0B. PP3_Moderate
The NM_000535.7(PMS2):c.2453T>C(p.Ile818Thr) variant causes a missense change involving the alteration of a conserved nucleotide. In-silico tool predicts a pathogenic outcome for this variant. Variant has been reported in ClinVar as Uncertain significance (★★).
PMS2 (HGNC:9122): (PMS1 homolog 2, mismatch repair system component) The protein encoded by this gene is a key component of the mismatch repair system that functions to correct DNA mismatches and small insertions and deletions that can occur during DNA replication and homologous recombination. This protein forms heterodimers with the gene product of the mutL homolog 1 (MLH1) gene to form the MutL-alpha heterodimer. The MutL-alpha heterodimer possesses an endonucleolytic activity that is activated following recognition of mismatches and insertion/deletion loops by the MutS-alpha and MutS-beta heterodimers, and is necessary for removal of the mismatched DNA. There is a DQHA(X)2E(X)4E motif found at the C-terminus of the protein encoded by this gene that forms part of the active site of the nuclease. Mutations in this gene have been associated with hereditary nonpolyposis colorectal cancer (HNPCC; also known as Lynch syndrome) and Turcot syndrome. [provided by RefSeq, Apr 2016]
Review Status: criteria provided, single submitter
Collection Method: clinical testing
This sequence change replaces isoleucine, which is neutral and non-polar, with threonine, which is neutral and polar, at codon 818 of the PMS2 protein (p.Ile818Thr). The frequency data for this variant in the population databases (gnomAD) is considered unreliable due to the presence of homologous sequence, such as pseudogenes or paralogs, in the genome. This missense change has been observed in individual(s) with pancreatic cancer (PMID: 28726808). ClinVar contains an entry for this variant (Variation ID: 186346). Invitae Evidence Modeling incorporating data from in vitro experimental studies (internal data) indicates that this missense variant is not expected to disrupt PMS2 function with a negative predictive value of 95%. In summary, the available evidence is currently insufficient to determine the role of this variant in disease. Therefore, it has been classified as a Variant of Uncertain Significance. -
Review Status: criteria provided, single submitter
Collection Method: clinical testing
The p.I818T variant (also known as c.2453T>C), located in coding exon 15 of the PMS2 gene, results from a T to C substitution at nucleotide position 2453. The isoleucine at codon 818 is replaced by threonine, an amino acid with similar properties. This alteration has been identified 1/302 individuals with pancreatic cancer and was classified as a variant of unknown significance (Chaffee KG et al. Genet Med, 2018 01;20:119-127). This amino acid position is highly conserved in available vertebrate species. In addition, this alteration is predicted to be deleterious by in silico analysis. Since supporting evidence is limited at this time, the clinical significance of this alteration remains unclear. -