ClinVar Genomic variation as it relates to human health

This variant is denoted MSH2 c.128A>T at the cDNA level, p.Tyr43Phe (Y43F) at the protein level, and results in the change of a Tyrosine to a Phenylalanine (TAT>TTT). This variant has not, to our knowledge, been published in the literature as pathogenic or benign. MSH2 Tyr43Phe was not observed in approximately 6,500 individuals of European and African American ancestry in the NHLBI Exome Sequencing Project, suggesting it is not a common benign variant in these populations. Since Tyrosine and Phenylalanine differ in polarity, charge, size or other properties, this is considered a non-conservative amino acid substitution. MSH2 Tyr43Phe occurs at a position that is conserved across species and is located in the mismatch binding domain (Lützen 2008). In silico analyses predict that this variant is probably damaging to protein structure and function. Based on currently available evidence, it is unclear whether MSH2 Tyr43Phe is a pathogenic or benign variant. We consider it to be a variant of uncertain significance.

This missense variant replaces tyrosine with phenylalanine at codon 43 of the MSH2 protein. Computational prediction suggests that this variant may have deleterious impact on protein structure and function (internally defined REVEL score threshold >= 0.7, PMID: 27666373). This variant does not impact MSH2 function in a 6-thioguanine sensitivity assay in haploid human cells (internally defined LOF score threshold <= -1.32, PMID: 33357406). To our knowledge, this variant has not been reported in individuals affected with MSH2-related disorders in the literature. This variant has not been identified in the general population by the Genome Aggregation Database (gnomAD). The available evidence is insufficient to determine the role of this variant in disease conclusively. Therefore, this variant is classified as a Variant of Uncertain Significance.

This sequence change replaces tyrosine, which is neutral and polar, with phenylalanine, which is neutral and non-polar, at codon 43 of the MSH2 protein (p.Tyr43Phe). This variant is not present in population databases (gnomAD no frequency). This variant has not been reported in the literature in individuals affected with MSH2-related conditions. ClinVar contains an entry for this variant (Variation ID: 422056). Advanced modeling performed at Invitae incorporating data from internal and/or published experimental studies (PMID: 33357406) indicates that this missense variant is not expected to disrupt MSH2 function with a negative predictive value of 80%. 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.

This alteration is classified as likely benign based on a combination of the following: seen in unaffected individuals, population frequency, intact protein function, lack of segregation with disease, co-occurrence, RNA analysis, in silico models, amino acid conservation, lack of disease association in case-control studies, and/or the mechanism of disease or impacted region is inconsistent with a known cause of pathogenicity.

This missense variant replaces tyrosine with phenylalanine at codon 43 of the MSH2 protein. Computational prediction suggests that this variant may have deleterious impact on protein structure and function (internally defined REVEL score threshold >= 0.7, PMID: 27666373). This variant does not impact MSH2 function in a 6-thioguanine sensitivity assay in haploid human cells (internally defined LOF score threshold <= -1.32, PMID: 33357406). To our knowledge, this variant has not been reported in individuals affected with MSH2-related disorders in the literature. This variant has not been identified in the general population by the Genome Aggregation Database (gnomAD). The available evidence is insufficient to determine the role of this variant in disease conclusively. Therefore, this variant is classified as a Variant of Uncertain Significance.

The MSH2 p.Tyr43Phe variant was not identified in the literature nor was it identified in the following databases: dbSNP, COGR, Clinvitae, Cosmic, MutDB, UMD-LDSB, Insight Colon Cancer Gene Variant Database, Zhejiang Colon Cancer Database, Mismatch Repair Genes Variant Database, or the Insight Hereditary Tumours Database. The variant was identified in ClinVar as a variant of uncertain significance (2x by Ambry and GeneDx). The variant was not identified in the following control databases: the 1000 Genomes Project, the NHLBI GO Exome Sequencing Project, the Exome Aggregatin Consortium (August 8th 2016), or the Genome Aggregation Database (February 27, 2017). The p.Tyr43Phe residue is conserved in mammals and computational analyses (PolyPhen-2, SIFT, AlignGVGD, BLOSUM, MutationTaster) provide inconsistent predictions regarding the impact to the protein; this information is not very predictive of pathogenicity. The variant occurs outside of the splicing consensus sequence and in silico or computational prediction software programs do not predict an effect on splicing. A similar variant, MSH2 p.Tyr43Cys, at the same position is more common, and is considered a variant of uncertain significance by several sources on ClinVar (6x as uncertain significance and 1x as likely benign). In summary, based on the above information the clinical significance of this variant cannot be determined with certainty at this time. This variant is classified as a variant of uncertain significance.

Variant interpreted as Uncertain significance and reported on 09-19-2019 by Lab or GTR ID 506138. GenomeConnect assertions are reported exactly as they appear on the patient-provided report from the testing laboratory. GenomeConnect staff make no attempt to reinterpret the clinical significance of the variant.