ClinVar Genomic variation as it relates to human health

PVS1_STR, PS4_STR, PM2_SUP

This variant is considered likely pathogenic. This variant occurs within a consensus splice junction and is predicted to result in abnormal mRNA splicing of either an out-of-frame exon or an in-frame exon necessary for protein stability and/or normal function.

For these reasons, this variant has been classified as Pathogenic. Algorithms developed to predict the effect of sequence changes on RNA splicing suggest that this variant may disrupt the consensus splice site. ClinVar contains an entry for this variant (Variation ID: 1459392). Disruption of this splice site has been observed in individuals with a personal and/or family history of cancer or constitutional mismatch repair deficiency syndrome (PMID: 24763289, 26318770, 30013564). 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 sequence change affects an acceptor splice site in intron 11 of the PMS2 gene. It is expected to disrupt RNA splicing. Variants that disrupt the donor or acceptor splice site typically lead to a loss of protein function (PMID: 16199547), and loss-of-function variants in PMS2 are known to be pathogenic (PMID: 21376568, 24362816).

The c.2007-2A>G intronic pathogenic mutation results from an A to G substitution two nucleotides upstream from coding exon 12 in the PMS2 gene. Alterations that disrupt the canonical splice site are expected to result in aberrant splicing. In silico splice site analysis predicts that this alteration will weaken the native splice acceptor site and will result in the creation or strengthening of a novel splice acceptor site. The resulting transcript is predicted to be in-frame and is not expected to trigger nonsense-mediated mRNAdecay; however, direct evidence is unavailable. The exact functional effect of the altered amino acid sequence is unknown; however, a significant portion of the protein is affected (Ambry internal data). This alteration has been identified homozygous in multiple individuals with CMMRD clinical diagnosis (Lavoine N et al. J Med Genet, 2015 Nov;52:770-8). This alteration has been reported in a patient with CRC at 45 years old and first degree relative(s) with CRC and endometrial cancer (Tesch VK et al. Front Immunol, 2018 Jul;9:1506). (Wang Q et al. J Med Genet, 2020 07;57:487-499). Based on the supporting evidence, this alteration is interpreted as a disease-causing mutation.