3-36996708-G-A

Variant names:

• chr3-36996708-G-A
• rs63751661
• NM_000249.4:c.206G>A

Variant summary

Our verdict is Uncertain significance. The variant received 5 ACMG points: 5P and 0B. PM1 PM2 PP3

The NM_000249.4(MLH1):​c.206G>A​(p.Arg69Lys) variant causes a missense, splice region change involving the alteration of a conserved nucleotide. The variant allele was found at a frequency of 0.00000137 in 1,458,384 control chromosomes in the GnomAD database, with no homozygous occurrence. In-silico tool predicts a pathogenic outcome for this variant. 2/3 splice prediction tools predict no significant impact on normal splicing. Variant has been reported in ClinVar as Uncertain significance (★★). Another variant affecting the same amino acid position, but resulting in a different missense (i.e. R69T) has been classified as Uncertain significance.

• Frequency:
  • Genomes: not found (cov: 32)
  • Exomes 𝑓: 0.0000014 (0 hom.)
• Consequence: MLH1 NM_000249.4 missense, splice_region
• Scores: Splicing: ADA: 0.9784
• Clinical Significance: Uncertain significance criteria provided, multiple submitters, no conflicts U:6
• Conservation: PhyloP100: 9.51
• Publications: 8 publications found

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 Gene-Disease associations (from GenCC):

• Lynch syndrome

  Inheritance: AD Classification: DEFINITIVE, SUPPORTIVE Submitted by: G2P, ClinGen, Orphanet
• Lynch syndrome 2

  Inheritance: AD Classification: DEFINITIVE, STRONG Submitted by: Ambry Genetics, Genomics England PanelApp
• Muir-Torre syndrome

  Inheritance: AD Classification: DEFINITIVE, STRONG, MODERATE, SUPPORTIVE Submitted by: Genomics England PanelApp, Ambry Genetics, G2P, Orphanet
• mismatch repair cancer syndrome 1

  Inheritance: AR Classification: DEFINITIVE, STRONG, SUPPORTIVE Submitted by: Ambry Genetics, G2P, Labcorp Genetics (formerly Invitae), Orphanet, ClinGen
• Lynch syndrome 1

  Inheritance: AD Classification: STRONG Submitted by: Labcorp Genetics (formerly Invitae)
• ovarian cancer

  Inheritance: AD Classification: STRONG Submitted by: Genomics England PanelApp
• malignant pancreatic neoplasm

  Inheritance: AD Classification: MODERATE Submitted by: Genomics England PanelApp
• rhabdomyosarcoma

  Inheritance: AR Classification: MODERATE Submitted by: Genomics England PanelApp
• prostate cancer

  Inheritance: AD Classification: LIMITED Submitted by: Ambry Genetics
• breast cancer

  Inheritance: AD Classification: NO_KNOWN Submitted by: Ambry Genetics
• hereditary breast carcinoma

  Inheritance: AD Classification: NO_KNOWN Submitted by: ClinGen

ACMG classification

Our verdict: Uncertain_significance. The variant received 5 ACMG points.

• PM1: In a hotspot region, there are 8 aminoacids with missense pathogenic changes in the window of +-8 aminoacids around while only 1 benign, 15 uncertain in NM_000249.4
• PM2: Very rare variant in population databases, with high coverage
• PP3: MetaRNN computational evidence supports a deleterious effect, 0.755

Transcripts

RefSeq

Gene	Transcript	HGVSc	HGVSp	Effect	Exon rank	MANE	Protein	UniProt
MLH1	NM_000249.4	c.206G>A	p.Arg69Lys	missense_variant, splice_region_variant	Exon 2 of 19	ENST00000231790.8	NP_000240.1

Ensembl

Gene	Transcript	HGVSc	HGVSp	Effect	Exon rank	TSL	MANE	Protein	Appris	UniProt
MLH1	ENST00000231790.8	c.206G>A	p.Arg69Lys	missense_variant, splice_region_variant	Exon 2 of 19	1	NM_000249.4	ENSP00000231790.3

Frequencies

GnomAD3 genomes Cov.: 32

GnomAD4 exome AF: 0.00000137 AC: 2 AN: 1458384 Hom.: 0 Cov.: 30 AF XY: 0.00 AC XY: 0 AN XY: 725852

⚠️ The allele balance in gnomAD version 4 Exomes is significantly skewed from the expected value of 0.5.

African (AFR) AF: 0.00 AC: 0 AN: 33404

American (AMR) AF: 0.00 AC: 0 AN: 44718

Ashkenazi Jewish (ASJ) AF: 0.00 AC: 0 AN: 26122

East Asian (EAS) AF: 0.00 AC: 0 AN: 39664

South Asian (SAS) AF: 0.00 AC: 0 AN: 86172

European-Finnish (FIN) AF: 0.00 AC: 0 AN: 53404

Middle Eastern (MID) AF: 0.00 AC: 0 AN: 5760

European-Non Finnish (NFE) AF: 0.00000180 AC: 2 AN: 1108856

Other (OTH) AF: 0.00 AC: 0 AN: 60284

⚠️ The allele balance in gnomAD4 Exomes is highly skewed from 0.5 (p-value = 0.038550), which strongly suggests a high chance of mosaicism in these individuals.

GnomAD4 genome Cov.: 32

ClinVar

Significance: Uncertain significance

Submissions summary: Uncertain:6

Revision: criteria provided, multiple submitters, no conflicts

Submissions by phenotype

Hereditary cancer-predisposing syndrome Uncertain:3

Jul 18, 2022

Ambry Genetics

Significance: Uncertain significance

Review Status: criteria provided, single submitter

Collection Method: clinical testing

The p.R69K variant (also known as c.206G>A), located in coding exon 2 of the MLH1 gene, results from a G to A substitution at nucleotide position 206. The arginine at codon 69 is replaced by lysine, an amino acid with highly similar properties. This variant has demonstrated reduced mismatch repair activity in two separate studies (Ellison AR et al. Hum. Mol. Genet., 2001 Sep;10:1889-900; Takahashi M et al. Cancer Res., 2007 May;67:4595-604). This alteration was detected in a patient with colon cancer who had at least two family members with colorectal and/or endometrial cancer in two generations (Stojcev Z et al. Acta Biochim Pol, 2013 Jun;60:195-8). This amino acid position is highly conserved in available vertebrate species. In addition, this alteration is predicted to be deleterious by in silico analysis. Since supporting evidence is limited at this time, the clinical significance of this alteration remains unclear. -

Jan 26, 2025

Molecular Diagnostics Laboratory, Catalan Institute of Oncology

Significance: Uncertain significance

Review Status: criteria provided, single submitter

Collection Method: clinical testing

PM2_Supporting c.206G>A located in exon 2 of the MLH1 gene, is predicted to result in the substitution of arginine by lysine at codon 69, p.(Arg69Lys). It is not present in the population database gnomAD v2.1.1, non cancer dataset (PM2_Supporting). Computational tools for this variant suggests no significant impact on splicing but the effect of the variant on protein function is indeterminate (MAPP+PolyPhen-2 prior probability for pathogenicity: 0.124). The variant has been functionally characterized and shown to proficient or intermediate MMR activity and expression (PMID: 17510385 and 11555625). This variant has been reported in the ClinVar database (4x uncertain significance) and in the LOVD database (4x benign, 1x uncertain significance, 5x not classified) but is not present in Insight database. Based on currently available information, the variant c.206G>A is classified as an uncertain significance variant according to to ClinGen-MMR Guidelines Draft v3.1. -

Mar 08, 2023

Color Diagnostics, LLC DBA Color Health

Significance: Uncertain significance

Review Status: criteria provided, single submitter

Collection Method: clinical testing

This missense variant replaces arginine with lysine at codon 69 of the MLH1 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). Functional studies have shown that the mutant protein exhibits normal expression levels and normal mismatch repair activity (PMID: 17510385, 31697235). To our knowledge, this variant has not been reported in individuals affected with MLH1-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. -

Muir-Torré syndrome;C1333991:Colorectal cancer, hereditary nonpolyposis, type 2 Uncertain:1

Sep 12, 2022

Department of Pathology and Laboratory Medicine, Sinai Health System

Significance: Uncertain significance

Review Status: criteria provided, single submitter

Collection Method: clinical testing

- -

Lynch syndrome Uncertain:1

Nov 30, 2023

All of Us Research Program, National Institutes of Health

Significance: Uncertain significance

Review Status: criteria provided, single submitter

Collection Method: clinical testing

This missense variant replaces arginine with lysine at codon 69 of the MLH1 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). Functional studies have shown that the mutant protein exhibits normal expression levels and normal mismatch repair activity (PMID: 17510385, 31697235). To our knowledge, this variant has not been reported in individuals affected with MLH1-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. -

Hereditary nonpolyposis colorectal neoplasms Uncertain:1

Oct 29, 2024

Labcorp Genetics (formerly Invitae), Labcorp

Significance: Uncertain significance

Review Status: criteria provided, single submitter

Collection Method: clinical testing

This sequence change replaces arginine, which is basic and polar, with lysine, which is basic and polar, at codon 69 of the MLH1 protein (p.Arg69Lys). This variant is not present in population databases (gnomAD no frequency). This missense change has been observed in individual(s) with clinical features of MLH1-related conditions (PMID: 21520333). ClinVar contains an entry for this variant (Variation ID: 489896). Invitae Evidence Modeling incorporating data from in vitro experimental studies (internal data) indicates that this missense variant is not expected to disrupt MLH1 function with a negative predictive value of 80%. Experimental studies are conflicting or provide insufficient evidence to determine the effect of this variant on MLH1 function (PMID: 11555625, 17510385, 31697235). 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. -

Computational scores

Source: dbNSFP v4.3

Name	Calibrated prediction	Score	Prediction
AlphaMissense	Benign	0.27
BayesDel_addAF	Pathogenic	0.29	D
BayesDel_noAF	Pathogenic	0.18
CADD	Pathogenic	30
DANN	Uncertain	1.0
DEOGEN2	Uncertain	0.61	D
Eigen	Pathogenic	0.69
Eigen_PC	Pathogenic	0.74
FATHMM_MKL	Pathogenic	1.0	D
LIST_S2	Uncertain	0.97	D
M_CAP	Uncertain	0.10	D
MetaRNN	Pathogenic	0.75	D
MetaSVM	Uncertain	0.54	D
MutationAssessor	Benign	1.4	L
PhyloP100		9.5
PrimateAI	Pathogenic	0.79	T
PROVEAN	Benign	-1.9	N
REVEL	Pathogenic	0.72
Sift	Benign	0.048	D
Sift4G	Benign	0.10	T
Polyphen		0.91	P
Vest4		0.65
MutPred		0.40		Gain of ubiquitination at R69 (P = 0.017);
MVP		0.96
MPC		0.25
ClinPred		0.92	D
GERP RS		5.5
RBP_binding_hub_radar		0.0
RBP_regulation_power_radar		2.8
Varity_R		0.72
gMVP		0.75
Mutation Taster		=40/60	disease causing

Splicing

Name	Calibrated prediction	Score	Prediction
dbscSNV1_ADA	Pathogenic	0.98
dbscSNV1_RF	Benign	0.70
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

Other links and lift over

dbSNP: rs63751661; hg19: chr3-37038199; COSMIC: COSV51617395;