Genetic Variant MLH1:p.Asn222Ser (chr3-37012087-A-G) – ACMG Classification: Uncertain_significance (1 pts)

Variant summary

Our verdict is Uncertain significance. The variant received 1 ACMG points: 4P and 3B. PM1PM2BP4_ModerateBP6

The NM_000249.4(MLH1):c.665A>G(p.Asn222Ser) variant causes a missense change. The variant allele was found at a frequency of 0.0000131 in 152,190 control chromosomes in the GnomAD database, with no homozygous occurrence. In-silico tool predicts a benign outcome for this variant. 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. N222K) has been classified as Uncertain significance.

Frequency

Genomes: 𝑓 0.000013 ( 0 hom., cov: 32)

Exomes 𝑓: 0.0 ( 0 hom. )

Failed GnomAD Quality Control

Consequence

MLH1
NM_000249.4 missense

Scores

Clinical Significance

Conflicting classifications of pathogenicity criteria provided, conflicting classifications U:3B:1

Conservation

PhyloP100: 3.73

Publications

3 publications found

Variant links:

COSMIC-nc: COSV99212384

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

MLH1 links:

Genome browser will be placed here

ACMG classification

Classification was made for transcript

Our verdict: Uncertain_significance. The variant received 1 ACMG points.

PM1

In a hotspot region, there are 4 aminoacids with missense pathogenic changes in the window of +-8 aminoacids around while only 5 benign, 38 uncertain in NM_000249.4

PM2

Very rare variant in population databases, with high coverage;

BP4

Computational evidence support a benign effect (MetaRNN=0.15995392).

BP6

Variant 3-37012087-A-G is Benign according to our data. Variant chr3-37012087-A-G is described in ClinVar as Conflicting_classifications_of_pathogenicity. ClinVar VariationId is 483557.

Variant Effect in Transcripts

ACMG analysis was done for transcript: NM_000249.4. You can select a different transcript below to see updated ACMG assignments.

RefSeq Transcripts

Gene	Transcript	Tags	HGVSc	HGVSp	Effect	Exon Rank	Protein
MLH1	NM_000249.4	MANE Select	c.665A>G	p.Asn222Ser	missense	Exon 8 of 19	NP_000240.1
MLH1	NM_001354628.2		c.665A>G	p.Asn222Ser	missense	Exon 8 of 18	NP_001341557.1
MLH1	NM_001354629.2		c.566A>G	p.Asn189Ser	missense	Exon 7 of 18	NP_001341558.1

Ensembl Transcripts

Gene	Transcript	Tags	HGVSc	HGVSp	Effect	Exon Rank	Protein
MLH1	ENST00000231790.8	TSL:1 MANE Select	c.665A>G	p.Asn222Ser	missense	Exon 8 of 19	ENSP00000231790.3
MLH1	ENST00000456676.7	TSL:1	c.665A>G	p.Asn222Ser	missense	Exon 8 of 17	ENSP00000416687.3
MLH1	ENST00000413740.2	TSL:1	c.665A>G	p.Asn222Ser	missense	Exon 8 of 15	ENSP00000416476.2

Frequencies

GnomAD3 genomes

AF:

0.0000131

AC:

AN:

152190

Hom.:

Cov.:

show subpopulations

Gnomad AFR

AF:

0.0000483

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:

0.00

Gnomad MID

AF:

0.00

Gnomad NFE

AF:

0.00

Gnomad OTH

AF:

0.00

GnomAD2 exomes

AF:

0.00000398

AC:

AN:

251134

AF XY:

0.00

show subpopulations

Gnomad AFR exome

AF:

0.0000615

Gnomad AMR exome

AF:

0.00

Gnomad ASJ exome

AF:

0.00

Gnomad EAS exome

AF:

0.00

Gnomad FIN exome

AF:

0.00

Gnomad NFE exome

AF:

0.00

Gnomad OTH exome

AF:

0.00

GnomAD4 exome

Data not reliable, filtered out with message: AC0

AF:

0.00

AC:

AN:

1459714

Hom.:

Cov.:

AF XY:

0.00

AC XY:

AN XY:

726338

African (AFR)

AF:

0.00

AC:

AN:

33448

American (AMR)

AF:

0.00

AC:

AN:

44720

Ashkenazi Jewish (ASJ)

AF:

0.00

AC:

AN:

26122

East Asian (EAS)

AF:

0.00

AC:

AN:

39690

South Asian (SAS)

AF:

0.00

AC:

AN:

86238

European-Finnish (FIN)

AF:

0.00

AC:

AN:

53412

Middle Eastern (MID)

AF:

0.00

AC:

AN:

5766

European-Non Finnish (NFE)

AF:

0.00

AC:

AN:

1109984

Other (OTH)

AF:

0.00

AC:

AN:

60334

GnomAD4 genome

AF:

0.0000131

AC:

AN:

152190

Hom.:

Cov.:

AF XY:

0.00

AC XY:

AN XY:

74344

show subpopulations

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

African (AFR)

AF:

0.0000483

AC:

AN:

41432

American (AMR)

AF:

0.00

AC:

AN:

15274

Ashkenazi Jewish (ASJ)

AF:

0.00

AC:

AN:

3472

East Asian (EAS)

AF:

0.00

AC:

AN:

5204

South Asian (SAS)

AF:

0.00

AC:

AN:

4838

European-Finnish (FIN)

AF:

0.00

AC:

AN:

10606

Middle Eastern (MID)

AF:

0.00

AC:

AN:

316

European-Non Finnish (NFE)

AF:

0.00

AC:

AN:

68044

Other (OTH)

AF:

0.00

AC:

AN:

2092

⚠️ The allele balance in gnomAD version 4 Genomes is significantly skewed from the expected value of 0.5. (p-value = 0.00000000770867), which strongly suggests a high chance of mosaicism in these individuals.

Allele Balance Distribution

Red line indicates average allele balance

Average allele balance: 0.400

Heterozygous variant carriers

0.00

0.20

0.40

0.60

0.80

0.95

Allele balance

Age Distribution

Genome Het

Variant carriers

<30

30-35

35-40

40-45

45-50

50-55

55-60

60-65

65-70

70-75

75-80

>80

Age

Alfa

AF:

0.00

Hom.:

Bravo

AF:

0.00000378

ExAC

AF:

0.00000824

AC:

ClinVar

Significance: Conflicting classifications of pathogenicity

Submissions summary: Uncertain:3Benign:1

Revision: criteria provided, conflicting classifications

LINK: link

Submissions by phenotype

Hereditary cancer-predisposing syndrome

Uncertain:2

Aug 04, 2025

Ambry Genetics

Significance:Uncertain significance

Review Status:criteria provided, single submitter

Collection Method:clinical testing

The p.N222S variant (also known as c.665A>G), located in coding exon 8 of the MLH1 gene, results from an A to G substitution at nucleotide position 665. The asparagine at codon 222 is replaced by serine, an amino acid with highly similar properties. This amino acid position is well conserved in available vertebrate species. In addition, the in silico prediction for this alteration is inconclusive. Since supporting evidence is limited at this time, the clinical significance of this alteration remains unclear.

Nov 26, 2019

Color Diagnostics, LLC DBA Color Health

Significance:Uncertain significance

Review Status:criteria provided, single submitter

Collection Method:clinical testing

This missense variant replaces asparagine with serine at codon 222 of the MLH1 protein. Computational prediction suggests that this variant may not impact protein structure and function (internally defined REVEL score threshold <= 0.5, PMID: 27666373). Splice site prediction tools suggest that this variant may not impact RNA splicing. To our knowledge, functional studies have not been performed for this variant. This variant has not been reported in individuals affected with hereditary cancer in the literature. This variant has been identified in 2/282540 chromosomes 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.

not provided

Uncertain:1

Feb 15, 2022

GeneDx

Significance:Uncertain significance

Review Status:criteria provided, single submitter

Collection Method:clinical testing

Not observed at significant frequency in large population cohorts (gnomAD); In silico analysis supports that this missense variant does not alter protein structure/function; Has not been previously published as a pathogenic or benign germline variant to our knowledge; This variant is associated with the following publications: (PMID: 26960396, 22753075, 32957448)

Hereditary nonpolyposis colorectal neoplasms

Benign:1

Mar 25, 2024

Labcorp Genetics (formerly Invitae), Labcorp

Significance:Benign

Review Status:criteria provided, single submitter

Collection Method:clinical testing

Computational scores

Source: dbNSFP v4.9

Name

Calibrated prediction

Score

Prediction

AlphaMissense

Benign

0.062

BayesDel_addAF

Uncertain

0.089

BayesDel_noAF

Benign

-0.11

CADD

Benign

(source)

DANN

Benign

0.79

DEOGEN2

Benign

0.37

Eigen

Benign

-0.44

Eigen_PC

Benign

-0.15

FATHMM_MKL

Uncertain

0.92

LIST_S2

Uncertain

0.87

M_CAP

Benign

0.055

MetaRNN

Benign

0.16

MetaSVM

Benign

-0.59

MutationAssessor

Benign

-1.1

PhyloP100

3.7

PrimateAI

Uncertain

0.51

PROVEAN

Benign

-0.88

REVEL

Uncertain

0.33

Sift

Benign

0.55

Sift4G

Benign

0.83

Polyphen

0.0

Vest4

0.31

MutPred

0.36

Gain of phosphorylation at S225 (P = 0.1787)

MVP

0.90

MPC

0.057

ClinPred

0.68

GERP RS

4.6

RBP_binding_hub_radar

0.0

RBP_regulation_power_radar

1.7

Varity_R

0.11

gMVP

0.42

Mutation Taster

=56/44

polymorphism

(source)

Splicing

Name

Calibrated prediction

Score

Prediction

SpliceAI score (max)

0.020

Details are displayed if max score is > 0.2

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

Publications

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Variant summary

Frequency

Consequence

Scores

Clinical Significance

Conservation

Publications

ACMG classification

Variant Effect in Transcripts

RefSeq Transcripts

Ensembl Transcripts

Frequencies

Age Distribution

ClinVar

Submissions by phenotype

Computational scores

Splicing

Publications

Other links and lift over