ClinVar Genomic variation as it relates to human health

Multifactorial likelihood analysis posterior probability 0.001-0.049

This variant is considered likely benign. This variant is strongly associated with less severe personal and family histories of cancer, typical for individuals without pathogenic variants in this gene [PMID: 25085752].

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.

Variant summary: MLH1 c.974G>A (p.Arg325Gln) results in a conservative amino acid change located in the DNA mismatch repair protein, S5 domain 2-like of the encoded protein sequence. Four of five in-silico tools predict a benign effect of the variant on protein function. The variant allele was found at a frequency of 4.4e-05 in 251356 control chromosomes. This frequency is not significantly higher than estimated for a pathogenic variant in MLH1 causing Hereditary Nonpolyposis Colorectal Cancer (4.4e-05 vs 0.00071), allowing no conclusion about variant significance. c.974G>A has been reported in the literature in individuals affected with Lynch Syndrome, including two families in which the variant appears to segregate with disease (two affected patients per family carrying the variant; Borras_2012, Castillejo_2014). Additionally, the variant was reported in MSI-high cancers, without strong evidence for causality (Deihimi_2017, Li_2020). These reports do not provide unequivocal conclusions about association of the variant with Lynch Syndrome. Suggesting a benign impact, functional studies including splicing assay, MMR assay, MLH1 expression and PMS2 expression, and MLH1 and PMS2 subcellular localization show the variant to have function similar to WT (Borras_2012). These results showed no damaging effect of this variant. The following publications have been ascertained in the context of this evaluation (PMID: 22736432, 24953332, 28591715, 30306255, 31391288, 31784484). ClinVar contains an entry for this variant (Variation ID: 90456). Based on the evidence outlined above, the variant was classified as likely benign.

This variant is considered likely benign or benign based on one or more of the following criteria: it is a conservative change, it occurs at a poorly conserved position in the protein, it is predicted to be benign by multiple in silico algorithms, and/or has population frequency not consistent with disease.

This variant is classified as likely benign based on ACMG/AMP sequence variant interpretation guidelines (Richards et al. 2015 PMID: 25741868, with internal and published modifications).