NM_000249.4:c.326A>G

Variant names:

• chr3-37004420-A-G
• rs587779004
• NM_000249.4:c.326A>G

Variant summary

Our verdict is Pathogenic. Variant got 10 ACMG points: 10P and 0B. PM1 PM2 PM5 PP3_Strong

The NM_000249.4(MLH1):​c.326A>G​(p.His109Arg) variant causes a missense change involving the alteration of a conserved nucleotide. The variant allele was found at a frequency of 0.000000684 in 1,461,822 control chromosomes in the GnomAD database, with no homozygous occurrence. In-silico tool predicts a pathogenic outcome for this variant. 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. H109P) has been classified as Pathogenic.

• Frequency:
  • Genomes: not found (cov: 33)
  • Exomes 𝑓: 6.8e-7 (0 hom.)
• Consequence: MLH1 NM_000249.4 missense
• Clinical Significance: Uncertain significance criteria provided, multiple submitters, no conflicts U:2
• Conservation: PhyloP100: 8.56

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 Pathogenic. Variant got 10 ACMG points.

• PM1: In a helix (size 6) in uniprot entity MLH1_HUMAN there are 6 pathogenic changes around while only 1 benign (86%) in NM_000249.4
• PM2: Very rare variant in population databases, with high coverage
• PM5: Other missense variant is known to change same aminoacid residue: Variant chr3-37004420-A-C is described in Lovd as [Pathogenic].
• PP3: MetaRNN computational evidence supports a deleterious effect, 0.941

Transcripts

RefSeq

Gene	Transcript	HGVSc	HGVSp	Effect	Exon rank	MANE	Protein	UniProt
MLH1	NM_000249.4	c.326A>G	p.His109Arg	missense_variant	Exon 4 of 19	ENST00000231790.8	NP_000240.1

Ensembl

Gene	Transcript	HGVSc	HGVSp	Effect	Exon rank	TSL	MANE	Protein	Appris	UniProt
MLH1	ENST00000231790.8	c.326A>G	p.His109Arg	missense_variant	Exon 4 of 19	1	NM_000249.4	ENSP00000231790.3

Frequencies

GnomAD3 genomes Cov.: 33

GnomAD4 exome AF: 6.84e-7 AC: 1 AN: 1461822 Hom.: 0 Cov.: 30 AF XY: 0.00 AC XY: 0 AN XY: 727216

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: 0.00

Gnomad4 NFE exome AF: 8.99e-7

Gnomad4 OTH exome AF: 0.00

GnomAD4 genome Cov.: 33

ClinVar

Significance: Uncertain significance

Submissions summary: Uncertain:2

Revision: criteria provided, multiple submitters, no conflicts

Submissions by phenotype

Hereditary nonpolyposis colorectal neoplasms Uncertain:1

Jun 14, 2019

Labcorp Genetics (formerly Invitae), Labcorp

Significance: Uncertain significance

Review Status: criteria provided, single submitter

Collection Method: clinical testing

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. Algorithms developed to predict the effect of missense changes on protein structure and function (SIFT, PolyPhen-2, Align-GVGD) all suggest that this variant is likely to be disruptive, but these predictions have not been confirmed by published functional studies and their clinical significance is uncertain. This variant has not been reported in the literature in individuals with MLH1-related disease. This variant is not present in population databases (ExAC no frequency). This sequence change replaces histidine with arginine at codon 109 of the MLH1 protein (p.His109Arg). The histidine residue is highly conserved and there is a small physicochemical difference between histidine and arginine. -

Hereditary cancer-predisposing syndrome Uncertain:1

Jan 14, 2025

Ambry Genetics

Significance: Uncertain significance

Review Status: criteria provided, single submitter

Collection Method: clinical testing

The p.H109R variant (also known as c.326A>G), located in coding exon 4 of the MLH1 gene, results from an A to G substitution at nucleotide position 326. The histidine at codon 109 is replaced by arginine, an amino acid with highly similar properties. This amino acid position is highly conserved in available vertebrate species. In addition, this alteration is predicted to be deleterious by in silico analysis. Based on the available evidence, the clinical significance of this variant remains unclear. -

Computational scores

Source: dbNSFP v4.3

Name	Calibrated prediction	Score	Prediction
AlphaMissense	Pathogenic	0.90
BayesDel_addAF	Pathogenic	0.51	D
BayesDel_noAF	Pathogenic	0.49
CADD	Pathogenic	27
DANN	Uncertain	1.0
DEOGEN2	Pathogenic	0.83	D;.;T
Eigen	Uncertain	0.65
Eigen_PC	Pathogenic	0.69
FATHMM_MKL	Pathogenic	1.0	D
LIST_S2	Pathogenic	0.99	D;D;D
M_CAP	Uncertain	0.10	D
MetaRNN	Pathogenic	0.94	D;D;D
MetaSVM	Uncertain	0.33	D
MutationAssessor	Uncertain	2.8	M;.;.
PrimateAI	Pathogenic	0.81	D
PROVEAN	Pathogenic	-7.1	D;D;D
REVEL	Pathogenic	0.86
Sift	Benign	0.039	D;T;D
Sift4G	Uncertain	0.040	D;D;D
Polyphen		0.98	D;.;.
Vest4		0.87
MutPred		0.83		Gain of MoRF binding (P = 0.0287);.;.;
MVP		0.98
MPC		0.44
ClinPred		0.99	D
GERP RS		6.0
RBP_binding_hub_radar		0.0
RBP_regulation_power_radar		1.1
Varity_R		0.91
gMVP		0.91

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

Other links and lift over

dbSNP: rs587779004; hg19: chr3-37045911;