NM_000249.4:c.1964T>C

Variant names:

Variant summary

Our verdict is Uncertain significance. Variant got 2 ACMG points: 2P and 0B. PM5

The NM_000249.4(MLH1):c.1964T>C(p.Ile655Thr) variant causes a missense change involving the alteration of a conserved nucleotide. The variant allele was found at a frequency of 0.0000552 in 1,613,532 control chromosomes in the GnomAD database, with no homozygous occurrence. 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. I655V) has been classified as Likely benign.

Frequency

Genomes: 𝑓 0.000092 ( 0 hom., cov: 31)

Exomes 𝑓: 0.000051 ( 0 hom. )

Consequence

MLH1
NM_000249.4 missense

Scores

Clinical Significance

Conflicting classifications of pathogenicity criteria provided, conflicting classifications U:7B:10

Conservation

PhyloP100: 7.70

Variant links:

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]

MLH1 links:

Genome browser will be placed here

ACMG classification

Classification made for transcript

Verdict is Uncertain_significance. Variant got 2 ACMG points.

PM5

Other missense variant is known to change same aminoacid residue: Variant chr3-37048583-A-G is described in Lovd as [Pathogenic].

Transcripts

RefSeq

Gene	Transcript	HGVSc	HGVSp	Effect	Exon rank	MANE	Protein	UniProt
MLH1	NM_000249.4 link	c.1964T>C	p.Ile655Thr	missense_variant	Exon 17 of 19	ENST00000231790.8	NP_000240.1	P40692-1

Ensembl

Gene	Transcript	HGVSc	HGVSp	Effect	Exon rank	TSL	MANE	Protein	Appris	UniProt
MLH1	ENST00000231790.8 link	c.1964T>C	p.Ile655Thr	missense_variant	Exon 17 of 19	1	NM_000249.4	ENSP00000231790.3		P40692-1

Frequencies

GnomAD3 genomes

AF:

0.0000921

AC:

AN:

152048

Hom.:

Cov.:

show subpopulations

Gnomad AFR

AF:

0.00

Gnomad AMI

AF:

0.00

Gnomad AMR

AF:

0.00

Gnomad ASJ

AF:

0.00

Gnomad EAS

AF:

0.00

Gnomad SAS

AF:

0.00

Gnomad FIN

AF:

0.0000944

Gnomad MID

AF:

0.00

Gnomad NFE

AF:

0.000191

Gnomad OTH

AF:

0.00

GnomAD3 exomes

AF:

0.0000756

AC:

AN:

251246

Hom.:

AF XY:

0.0000736

AC XY:

AN XY:

135778

show subpopulations

Gnomad AFR exome

AF:

0.00

Gnomad AMR exome

AF:

0.00

Gnomad ASJ exome

AF:

0.00

Gnomad EAS exome

AF:

0.00

Gnomad SAS exome

AF:

0.00

Gnomad FIN exome

AF:

0.000185

Gnomad NFE exome

AF:

0.000132

Gnomad OTH exome

AF:

0.00

GnomAD4 exome

AF:

0.0000513

AC:

AN:

1461484

Hom.:

Cov.:

AF XY:

0.0000523

AC XY:

AN XY:

727060

show subpopulations

Gnomad4 AFR exome

AF:

0.00

Gnomad4 AMR exome

AF:

0.00

Gnomad4 ASJ exome

AF:

0.00

Gnomad4 EAS exome

AF:

0.00

Gnomad4 SAS exome

AF:

0.00

Gnomad4 FIN exome

AF:

0.000169

Gnomad4 NFE exome

AF:

0.0000576

Gnomad4 OTH exome

AF:

0.0000166

GnomAD4 genome

AF:

0.0000921

AC:

AN:

152048

Hom.:

Cov.:

AF XY:

0.0000539

AC XY:

AN XY:

74240

show subpopulations

Gnomad4 AFR

AF:

0.00

Gnomad4 AMR

AF:

0.00

Gnomad4 ASJ

AF:

0.00

Gnomad4 EAS

AF:

0.00

Gnomad4 SAS

AF:

0.00

Gnomad4 FIN

AF:

0.0000944

Gnomad4 NFE

AF:

0.000191

Gnomad4 OTH

AF:

0.00

Alfa

AF:

0.0000747

Hom.:

Bravo

AF:

0.0000642

ESP6500AA

AF:

0.00

AC:

ESP6500EA

AF:

0.000233

AC:

ExAC

AF:

0.0000988

AC:

EpiCase

AF:

0.000109

EpiControl

AF:

0.00

ClinVar

Significance: Conflicting classifications of pathogenicity

Submissions summary: Uncertain:7Benign:10

Revision: criteria provided, conflicting classifications

LINK: link

Submissions by phenotype

not provided

Uncertain:2Benign:3

Nov 03, 2021

Institute for Clinical Genetics, University Hospital TU Dresden, University Hospital TU Dresden

Significance: Likely benign

Review Status: criteria provided, single submitter

Collection Method: clinical testing

- -

Sep 11, 2019

GeneDx

Significance: Likely benign

Review Status: criteria provided, single submitter

Collection Method: clinical testing

This variant is associated with the following publications: (PMID: 17510385, 22703879, 8938136, 17348456, 10970186, 18383312, 16341804, 11376800, 25637381, 27600092, 31159747, 31332305) -

Oct 10, 2024

Quest Diagnostics Nichols Institute San Juan Capistrano

Significance: Uncertain significance

Review Status: criteria provided, single submitter

Collection Method: clinical testing

The MLH1 c.1964T>C (p.Ile655Thr) variant has been reported in the published literature in individuals with hereditary non-polyposis colon cancer (HNPCC), also known as Lynch syndrome (PMID: 11376800 (2001), 10970186 (2000), 8938136 (1996)), including one individual who also carried a pathogenic MSH2 variant (PMID: 17348456 (2007)). Additionally, this variant has been reported in individuals with a personal and/or family history of breast and/or ovarian cancer, and at least one reportedly healthy individual (PMIDs: 33471991 (2021), 31159747 (2019), see also LOVD (https://databases.lovd.nl/shared)). Functional studies demonstrated that this variant was not damaging to protein function (PMID: 17510385 (2007)). The frequency of this variant in the general population, 0.00016 (4/25086 chromosomes (Genome Aggregation Database, http://gnomad.broadinstitute.org)), is uninformative in the assessment of its pathogenicity. Analysis of this variant using bioinformatics tools for the prediction of the effect of amino acid changes on protein structure and function yielded conflicting predictions that this variant is deleterious or benign. Based on the available information, we are unable to determine the clinical significance of this variant. -

Jul 13, 2012

Biesecker Lab/Clinical Genomics Section, National Institutes of Health

Significance: Uncertain significance

Review Status: no assertion criteria provided

Collection Method: research

- -

Nov 01, 2024

CeGaT Center for Human Genetics Tuebingen

Significance: Likely benign

Review Status: criteria provided, single submitter

Collection Method: clinical testing

MLH1: BS3:Supporting -

not specified

Uncertain:2Benign:1

Mar 04, 2025

Center for Genomic Medicine, Rigshospitalet, Copenhagen University Hospital

Significance: Uncertain significance

Review Status: criteria provided, single submitter

Collection Method: clinical testing

- -

Dec 11, 2023

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

Significance: Likely benign

Review Status: criteria provided, single submitter

Collection Method: clinical testing

Variant summary: MLH1 c.1964T>C (p.Ile655Thr) results in a non-conservative amino acid change located in the DNA mismatch repair protein Mlh1, C-terminal domain (IPR032189) of the encoded protein sequence. Three of five in-silico tools predict a benign effect of the variant on protein function. The variant allele was found at a frequency of 7.6e-05 in 251246 control chromosomes (gnomAD). This frequency is not significantly higher than expected for a pathogenic variant in MLH1 causing Lynch Syndrome (7.6e-05 vs 0.00071), allowing no conclusion about variant significance. c.1964T>C has been reported in the literature in individuals with a personal or family history of colorectal or other MLH1-related cancers, and at-least one instance of co-occurrence in a patient with hMLH1 promoter hypermethylation suggestive of a sporadic etiology has been ascertained (e.g., Irmejs_2007, Keller_1996, Potocnik_2001, Ravnik-Glavac_2000, Schubert_2019, Svensson_2022, Tsoaousis_2019). These report(s) do not provide unequivocal conclusions about association of the variant with Lynch syndrome. A co-occurrence with another pathogenic variant has been reported (MSH2 c.1786_1788del, p.Asn596del; Irmejs_2007), providing supporting evidence for a benign role. At least one publication reports experimental evidence evaluating an impact on protein function. The most pronounced variant effect results in 74% of normal activity in an in-vitro MMR assay and >75% relative MLH1 expression (Takahashi_2007). The following publications have been ascertained in the context of this evaluation (PMID: 31697235, 22290698, 25637381, 18383312, 11179758, 17348456, 22703879, 8938136, 27647783, 11376800, 10970186, 30426508, 35430768, 17510385, 31159747). Multiple submitters have cited clinical-significance assessments for this variant to ClinVar after 2014. Multiple submitters reported the variant with conflicting assessments (likely benign, n = 6; VUS, n = 6). Based on the evidence outlined above, the variant was classified as likely benign. -

Aug 03, 2020

Genetic Services Laboratory, University of Chicago

Significance: Uncertain significance

Review Status: criteria provided, single submitter

Collection Method: clinical testing

DNA sequence analysis of the MLH1 gene demonstrated a sequence change, c.1964T>C, in exon 17 that results in an amino acid change, p.Ile655Thr. This sequence change has been described in the gnomAD database with a low frequency of 0.016% in the European sub-population (dbSNP rs63751225). The p.Ile655Thr change affects a poorly conserved amino acid residue located in a domain of the MLH1 protein that is not known to be functional. In-silico pathogenicity prediction tools (SIFT, PolyPhen2, Align GVGD, REVEL) provide contradictory results for the p.Ile655Thr substitution. The p.Ile655Thr change has previously been described in a family with gastric cancer (PMID: 8938136); however, functional studies have demonstrated mismatch repair activity similar to that of the wild type allele in the presence of this sequence change (PMID: 17510385). Due to these contrasting evidences, the clinical significance of the p.Ile655Thr change remains unknown at this time. -

Hereditary cancer-predisposing syndrome

Uncertain:1Benign:2

Jul 20, 2015

Color Diagnostics, LLC DBA Color Health

Significance: Likely benign

Review Status: criteria provided, single submitter

Collection Method: clinical testing

- -

Aug 01, 2018

GeneKor MSA

Significance: Uncertain significance

Review Status: criteria provided, single submitter

Collection Method: clinical testing

- -

Oct 29, 2018

Ambry Genetics

Significance: Likely benign

Review Status: criteria provided, single submitter

Collection Method: clinical testing

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. -

Colorectal cancer, hereditary nonpolyposis, type 2

Uncertain:1Benign:1

Apr 18, 2017

Counsyl

Significance: Uncertain significance

Review Status: criteria provided, single submitter

Collection Method: clinical testing

- -

Nov 27, 2024

Myriad Genetics, Inc.

Significance: Likely benign

Review Status: criteria provided, single submitter

Collection Method: clinical testing

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: 27363726]. -

Colorectal cancer, non-polyposis

Uncertain:1

Jun 01, 2014

CSER _CC_NCGL, University of Washington

Significance: Uncertain significance

Review Status: no assertion criteria provided

Collection Method: research

- -

Lynch syndrome

Benign:1

Sep 17, 2024

All of Us Research Program, National Institutes of Health

Significance: Likely benign

Review Status: criteria provided, single submitter

Collection Method: clinical testing

- -

MLH1-related disorder

Benign:1

Mar 03, 2020

PreventionGenetics, part of Exact Sciences

Significance: Likely benign

Review Status: no assertion criteria provided

Collection Method: clinical testing

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). -

Hereditary nonpolyposis colorectal neoplasms

Benign:1

Jan 30, 2025

Labcorp Genetics (formerly Invitae), Labcorp

Significance: Likely benign

Review Status: criteria provided, single submitter

Collection Method: clinical testing

- -

Computational scores

Source: dbNSFP v4.3

Name

Calibrated prediction

Score

Prediction

AlphaMissense

Benign

0.22

BayesDel_addAF

Uncertain

0.12

BayesDel_noAF

Pathogenic

0.25

CADD

Benign

DANN

Uncertain

0.99

DEOGEN2

Uncertain

0.66

D;.;.;.;.;.

Eigen

Benign

-0.069

Eigen_PC

Benign

0.18

FATHMM_MKL

Pathogenic

0.98

LIST_S2

Uncertain

0.94

D;D;.;.;.;D

M_CAP

Benign

0.052

MetaRNN

Uncertain

0.44

T;T;T;T;T;T

MetaSVM

Uncertain

-0.25

MutationAssessor

Benign

0.41

N;.;.;.;.;.

PrimateAI

Benign

0.47

PROVEAN

Benign

-1.5

N;N;N;N;N;N

REVEL

Uncertain

0.59

Sift

Benign

0.15

T;T;T;T;T;T

Sift4G

Benign

0.43

T;T;T;T;T;T

Polyphen

0.0080

B;.;.;.;.;.

Vest4

0.57

MVP

0.97

MPC

0.084

ClinPred

0.15

GERP RS

5.8

Varity_R

0.29

gMVP

0.47

Splicing

Name

Calibrated prediction

Score

Prediction

SpliceAI score (max)

0.0

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

Below is the list of publications found by LitVar. It may be empty.

Variant summary

Frequency

Consequence

Scores

Clinical Significance

Conservation

ACMG classification

Transcripts

RefSeq

Ensembl

Frequencies

ClinVar

Submissions by phenotype

Computational scores

Splicing

Publications

LitVar

Other links and lift over