3-37020451-G-A

Position:

• chr3-37020451-G-A

Variant summary

Our verdict is Pathogenic. Variant got 10 ACMG points: 10P and 0B. PVS1 PM2

The NM_001354621.2(MLH1):​c.3G>A​(p.Met1?) variant causes a start lost change involving the alteration of a non-conserved nucleotide. The variant was absent in control chromosomes in GnomAD project. In-silico tool predicts a benign outcome for this variant. Variant has been reported in ClinVar as Uncertain significance (★★).

• Frequency: Genomes: not found (cov: 33)
• Consequence: MLH1 NM_001354621.2 start_lost
• Clinical Significance: Uncertain significance criteria provided, multiple submitters, no conflicts U:3
• Conservation: PhyloP100: 0.843

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 (HGNC:):

ACMG classification

Verdict is Pathogenic. Variant got 10 ACMG points.

• PVS1: Start lost variant, no new inframe start found.
• PM2: Very rare variant in population databases, with high coverage

Transcripts

RefSeq

Gene	Transcript	HGVSc	HGVSp	Effect	#exon/exons	MANE	Protein	UniProt
MLH1	NM_000249.4	c.1026G>A	p.Met342Ile	missense_variant	11/19	ENST00000231790.8	NP_000240.1

Ensembl

Gene	Transcript	HGVSc	HGVSp	Effect	#exon/exons	TSL	MANE	Protein	Appris	UniProt
MLH1	ENST00000231790.8	c.1026G>A	p.Met342Ile	missense_variant	11/19	1	NM_000249.4	ENSP00000231790.3

Frequencies

GnomAD3 genomes Cov.: 33

GnomAD4 exome Cov.: 32

GnomAD4 genome Cov.: 33

ClinVar

Significance: Uncertain significance

Submissions summary: Uncertain:3

Revision: criteria provided, multiple submitters, no conflicts

Submissions by phenotype

Colorectal cancer, hereditary nonpolyposis, type 2 Uncertain:1

Uncertain significance, criteria provided, single submitter

clinical testing

Baylor Genetics

Jun 14, 2023

- -

Hereditary nonpolyposis colorectal neoplasms Uncertain:1

Uncertain significance, criteria provided, single submitter

clinical testing

Labcorp Genetics (formerly Invitae), Labcorp

Oct 12, 2016

This sequence change replaces methionine with isoleucine at codon 342 of the MLH1 protein (p.Met342Ile). The methionine residue is weakly conserved and there is a small physicochemical difference between methionine and isoleucine. This variant is not present in population databases (ExAC no frequency) and has not been reported in the literature in individuals with a MLH1-related disease. 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 tolerated, but these predictions have not been confirmed by published functional studies. In summary, this variant is a novel missense change that is not predicted to affect protein function. There is no indication that it causes disease, but the available evidence is currently insufficient to prove that conclusively. Therefore, it has been classified as a Variant of Uncertain Significance. -

Hereditary cancer-predisposing syndrome Uncertain:1

Uncertain significance, criteria provided, single submitter

clinical testing

Ambry Genetics

Jun 18, 2021

The p.M342I variant (also known as c.1026G>A), located in coding exon 11 of the MLH1 gene, results from a G to A substitution at nucleotide position 1026. The methionine at codon 342 is replaced by isoleucine, an amino acid with highly similar properties. This amino acid position is not 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. -

Computational scores

Source: dbNSFP v4.3

Name	Calibrated prediction	Score	Prediction
AlphaMissense	Uncertain	0.36
BayesDel_addAF	Pathogenic	0.17	D
BayesDel_noAF	Uncertain	0.0
CADD	Benign	16
DANN	Uncertain	0.99
DEOGEN2	Benign	0.33	T;.;.;.;.;.;.
Eigen	Benign	-0.42
Eigen_PC	Benign	-0.32
FATHMM_MKL	Uncertain	0.87	D
LIST_S2	Uncertain	0.93	D;D;.;.;.;D;D
M_CAP	Benign	0.038	D
MetaRNN	Benign	0.26	T;T;T;T;T;T;T
MetaSVM	Uncertain	-0.12	T
MutationAssessor	Benign	1.6	L;.;.;.;.;.;.
PrimateAI	Benign	0.31	T
PROVEAN	Benign	-0.51	N;N;N;N;N;N;N
REVEL	Uncertain	0.46
Sift	Benign	0.12	T;T;T;T;T;T;T
Sift4G	Benign	0.072	T;T;T;T;T;T;T
Polyphen		0.0	B;.;.;.;.;.;.
Vest4		0.44
MutPred		0.47		Loss of disorder (P = 0.0648);.;.;.;.;.;.;
MVP		0.98
MPC		0.073
ClinPred		0.33	T
GERP RS		-0.57
Varity_R		0.078
gMVP		0.26

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: rs1060500704; hg19: chr3-37061942;