Description
The MSH2 p.Asn127Ser variant was identified in the literature in black, white and Hispanic populations with functional studies suggesting that the p.Asn127Ser variant, in isolation, does not compromise MMR. However in 2 studies, this variant was identified together with other missense substitutions (especially p.Ala328Pro), and demonstrated significantly decreased repair deficiency (Kantelinen 2012, Ollila 2008, Samowitz 2001). The variant was also identified in dbSNP (ID: rs17217772) “With benign, uncertain significance allele” and is listed in the 1000 Genomes Project in 124 of 5000 chromosomes (frequency: 0.0248). The variant is also identified in the NHLBI Exome Sequencing Project (ESP) in 4 of 8600 European American (frequency: 00005) and in 339 of 4406 African American alleles (frequency: 0.077). The variant is listed in the Exome Aggregation Consortium (ExAC) database (released Mar 14, 2016) and identified in 848 of 121398 chromosomes of which 27 were homozygous (frequency: 0.007) or 791 of 10402 Africans (frequency: 0.076), 20 of 11578 Latino (frequency: 0.002), 29 of 66732 European (Non-Finish) (frequency: 0.0004), 4 of 16510 South Asian (frequency: 0.0002) and 4 in 908 (frequency: 0.004) in other, increasing the likelihood this could be a low frequency benign variant. The variant is listed in GeneInsight - COGR (1x as benign by LMM and 2x as benign by ARUP); ClinVar (listed as benign by InSIGHT, Laboratory for Molecular Medicine, Emory Genetics, Ambry Genetics, Mayo Clinic, Pathway Genomics LabCorp and by TMI with no clinical significance given); in Clinvitae (by EmyClass 1x as benign) and InSiGHT Colon Cancer Gene Variant Databases (LOVD) 34x as Class 1 - not pathogenic. In UMD, the variant was identified 23x as neutral with a co-occurring pathogenic MLH1 p.Pro649LeufsX12, increasing the likelihood that the p.Asn127Ser variant does not have clinical significance. The p.Asn127 residue is conserved across mammals and other organisms, and four out of five computational analyses (PolyPhen-2, SIFT, AlignGVGD, BLOSUM, MutationTaster) suggest that the p.Asn127Ser variant may impact the protein; however, this information is not predictive enough to assume pathogenicity. The variant occurs outside of the splicing consensus sequence and in silico or computational prediction software programs (SpliceSiteFinder, MaxEntScan, NNSPLICE, GeneSplicer, HumanSpliceFinder) do not predict the abolishment of the consensus splice site; however, HumanSpliceFinder and MaxEntScan predict an altered 3' splice site in this region and we cannot eliminate the possibility of a novel cryptic splice site. In summary, based on the above information the clinical significance of this variant cannot be determined with certainty at this time although we would lean towards a more benign role for this variant. This variant is classified as likely benign.
| # | Sample | Method | Observation |
|---|
| Origin | Affected | Number tested | Tissue | Purpose | Method | Individuals | Allele frequency | Families | Co-occurrences |
|---|
| 1 | unknown | yes | not provided | not provided | not provided | | 17 | not provided | not provided | not provided |
