3-37017508-C-G

Position:

• chr3-37017508-C-G

Variant summary

Our verdict is Likely pathogenic. Variant got 9 ACMG points: 9P and 0B. PM2 PM5 PP3_Strong PP5

The NM_000249.4(MLH1):​c.793C>G​(p.Arg265Gly) variant causes a missense, splice region change involving the alteration of a conserved nucleotide. The variant was absent in control chromosomes in GnomAD project. In-silico tool predicts a pathogenic outcome for this variant. 1/1 splice prediction tools predict no significant impact on normal splicing. Variant has been reported in ClinVar as Conflicting classifications of pathogenicity (no stars). Another variant affecting the same amino acid position, but resulting in a different missense (i.e. R265C) has been classified as Pathogenic.

• Frequency: Genomes: not found (cov: 32)
• Consequence: MLH1 NM_000249.4 missense, splice_region
• Clinical Significance: Conflicting classifications of pathogenicity criteria provided, conflicting classifications P:2 U:3
• Conservation: PhyloP100: 7.28

Genes affected

MLH1 (HGNC:7127): (mutL homolog 1) The protein encoded by this gene can heterodimerize with mismatch repair endonuclease PMS2 to form MutL alpha, part of the DNA mismatch repair system. When MutL alpha is bound by MutS beta and some accessory proteins, the PMS2 subunit of MutL alpha introduces a single-strand break near DNA mismatches, providing an entry point for exonuclease degradation. The encoded protein is also involved in DNA damage signaling and can heterodimerize with DNA mismatch repair protein MLH3 to form MutL gamma, which is involved in meiosis. This gene was identified as a locus frequently mutated in hereditary nonpolyposis colon cancer (HNPCC). [provided by RefSeq, Aug 2017]

ACMG classification

Verdict is Likely_pathogenic. Variant got 9 ACMG points.

• PM2: Very rare variant in population databases, with high coverage
• PM5: Other missense variant is known to change same aminoacid residue: Variant chr3-37017508-C-T is described in Lovd as [Pathogenic].
• PP3: MetaRNN computational evidence supports a deleterious effect, 0.957
• PP5: Variant 3-37017508-C-G is Pathogenic according to our data. Variant chr3-37017508-C-G is described in ClinVar as [Conflicting_classifications_of_pathogenicity]. Clinvar id is 801205.We mark this variant Likely_pathogenic, oryginal submissions are: {Uncertain_significance=3, Pathogenic=1, Likely_pathogenic=1}.

Transcripts

RefSeq

Gene	Transcript	HGVSc	HGVSp	Effect	#exon/exons	MANE	Protein	UniProt
MLH1	NM_000249.4	c.793C>G	p.Arg265Gly	missense_variant, splice_region_variant	10/19	ENST00000231790.8	NP_000240.1

Ensembl

Gene	Transcript	HGVSc	HGVSp	Effect	#exon/exons	TSL	MANE	Protein	Appris	UniProt
MLH1	ENST00000231790.8	c.793C>G	p.Arg265Gly	missense_variant, splice_region_variant	10/19	1	NM_000249.4	ENSP00000231790.3

Frequencies

GnomAD3 genomes Cov.: 32

GnomAD4 exome Cov.: 31

GnomAD4 genome Cov.: 32

ClinVar

Significance: Conflicting classifications of pathogenicity

Submissions summary: Pathogenic:2 Uncertain:3

Revision: criteria provided, conflicting classifications

Submissions by phenotype

Colorectal cancer, hereditary nonpolyposis, type 2 Pathogenic:1

Likely pathogenic, criteria provided, single submitter

clinical testing

Myriad Genetics, Inc.

Jul 18, 2023

This variant is considered likely pathogenic. Functional studies indicate this variant impacts protein function [Myriad internal data]. This variant is expected to disrupt protein structure [Myriad internal data]. -

Hereditary cancer-predisposing syndrome Pathogenic:1

Pathogenic, criteria provided, single submitter

clinical testing

Ambry Genetics

Dec 29, 2021

The p.R265G pathogenic mutation (also known as c.793C>G), located in coding exon 10 of the MLH1 gene, results from a C to G substitution at nucleotide position 793. The arginine at codon 265 is replaced by glycine, an amino acid with dissimilar properties. This variant has been identified in multiple families diagnosed with Lynch syndrome (Mork ME et al. Cancer Genet. 2019 06;235-236:77-83; Ambry internal data).This variant has been identified in a proband(s) whose Lynch syndrome-associated tumor demonstrated loss of MLH1 and PMS2 expression by immunohistochemistry (Ambry internal data). Another alteration at the same codon, p.R265S (c.793C>A), has been identified in multiple individuals with Lynch/HNPCC-related cancers (Zavodna K et al. Neoplasma. 2006;53:269-76; Alemayehu A et al. Genes Chromosomes Cancer. 2008 Oct;47:906-14; Hardt K et al. Fam. Cancer. 2011 Jun;10:273-84; Ferguson SE et al. Cancer. 2014 Dec;120:3932-9), and has been shown to be deleterious in several functional assays (Wanat JJ et al. Hum. Mol. Genet. 2007 Feb;16:445-52; Drost M et al. Hum. Mutat. 2010 Mar;31:247-53; van der Klift HM et al. Mol Genet Genomic Med. 2015 Jul;3:327-45; Soukarieh O et al. PLoS Genet. 2016 Jan;12:e1005756). The p.R265G variant is considered to be rare based on population cohorts in the Genome Aggregation Database (gnomAD). This amino acid position is highly conserved in available vertebrate species. This alteration is predicted to be deleterious by in silico analysis. Based on the supporting evidence, this alteration is interpreted as a disease-causing mutation. -

not specified Uncertain:1

Uncertain significance, criteria provided, single submitter

clinical testing

Women's Health and Genetics/Laboratory Corporation of America, LabCorp

May 01, 2019

Variant summary: MLH1 c.793C>G (p.Arg265Gly) results in a non-conservative amino acid change located in the N-terminal domain (IPR002099) of the encoded protein sequence. Five of five in-silico tools predict a damaging effect of the variant on protein function. Computational tools predict some impact on normal splicing: two predict the variant weakens a 3' acceptor site. However, these predictions have yet to be confirmed by functional studies. The variant was absent in 251460 control chromosomes (gnomAD). The available data on variant occurrences in the general population are insufficient to allow any conclusion about variant significance. The variant, c.793C>G has been reported in the literature in a young adult affected with colorectal cancer, who had a microsatellite instable tumor (Mork 2019), however promoter methylation status was not specified and the family did not meet the Amsterdam criteria II. Therefore, these data do not allow unequivocal conclusions about association of the variant with Hereditary Non-Polyposis Colon Cancer. Two other variants affecting the same nucleotide (c.793C>A and c.793C>T) are reported in numerous patients and classified as pathogenic by an expert panel, partly based on functional studies reporting aberrant splicing (InSiGHT). However, to our knowledge, no experimental evidence demonstrating an impact on splicing or protein function has been reported for the variant of interest. No clinical diagnostic laboratories have submitted clinical-significance assessments for this variant to ClinVar after 2014. Based on the evidence outlined above, the variant was classified as VUS-possibly pathogenic. -

not provided Uncertain:1

Uncertain significance, criteria provided, single submitter

clinical testing

Quest Diagnostics Nichols Institute San Juan Capistrano

Jan 31, 2019

- -

Hereditary nonpolyposis colorectal neoplasms Uncertain:1

Uncertain significance, criteria provided, single submitter

clinical testing

Labcorp Genetics (formerly Invitae), Labcorp

Jun 07, 2023

This variant is not present in population databases (gnomAD no frequency). This sequence change replaces arginine, which is basic and polar, with glycine, which is neutral and non-polar, at codon 265 of the MLH1 protein (p.Arg265Gly). This missense change has been observed in individual(s) with colorectal cancer (PMID: 31101557). 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 variant disrupts the p.Arg265 amino acid residue in MLH1. Other variant(s) that disrupt this residue have been determined to be pathogenic (PMID: 19423266, 29520894). This suggests that this residue is clinically significant, and that variants that disrupt this residue are likely to be disease-causing. An algorithm developed to predict the effect of missense changes on protein structure and function (PolyPhen-2) suggests that this variant is likely to be disruptive. ClinVar contains an entry for this variant (Variation ID: 801205). -

Computational scores

Source: dbNSFP v4.3

Name	Calibrated prediction	Score	Prediction
AlphaMissense	Pathogenic	1.0
BayesDel_addAF	Pathogenic	0.57	D
BayesDel_noAF	Pathogenic	0.59
CADD	Pathogenic	31
DANN	Uncertain	1.0
DEOGEN2	Pathogenic	0.90	D;.;.;.;.;.;.
Eigen	Pathogenic	1.1
Eigen_PC	Pathogenic	1.0
FATHMM_MKL	Pathogenic	1.0	D
LIST_S2	Pathogenic	0.99	D;D;.;.;.;D;D
M_CAP	Pathogenic	0.79	D
MetaRNN	Pathogenic	0.96	D;D;D;D;D;D;D
MetaSVM	Pathogenic	0.94	D
MutationAssessor	Pathogenic	4.8	H;.;.;.;.;.;.
PrimateAI	Uncertain	0.65	T
PROVEAN	Pathogenic	-7.0	D;D;D;D;D;D;D
REVEL	Pathogenic	0.96
Sift	Pathogenic	0.0	D;D;D;D;D;D;D
Sift4G	Pathogenic	0.0	D;D;D;D;D;D;D
Polyphen		1.0	D;.;.;.;.;.;.
Vest4		0.98
MutPred		0.76		Loss of stability (P = 0.0428);.;.;.;.;.;.;
MVP		0.99
MPC		0.45
ClinPred		1.0	D
GERP RS		5.7
Varity_R		0.99
gMVP		0.93

Splicing

Name	Calibrated prediction	Score	Prediction
SpliceAI score (max)		0.16		Details are displayed if max score is > 0.2

Find out detailed SpliceAI scores and Pangolin per-transcript scores at spliceailookup.broadinstitute.org

Publications

LitVar

Other links and lift over

dbSNP: rs63751194; hg19: chr3-37058999;