NM_000249.4:c.1A>T

Variant names:

• chr3-36993548-A-T
• NM_000249.4:c.1A>T

Variant summary

Our verdict is Pathogenic. Variant got 14 ACMG points: 14P and 0B. PVS1 PS1_Moderate PM2 PP5_Moderate

The NM_000249.4(MLH1):​c.1A>T​(p.Met1?) variant causes a initiator codon change involving the alteration of a non-conserved nucleotide. The variant was absent in control chromosomes in GnomAD project. In-silico tool predicts a pathogenic outcome for this variant. Variant has been reported in ClinVar as Pathogenic (★).

• Frequency: Genomes: not found (cov: 33)
• Consequence: MLH1 NM_000249.4 initiator_codon
• Clinical Significance: Pathogenic criteria provided, single submitter P:2
• Conservation: PhyloP100: 1.69

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 14 ACMG points.

• PVS1: Start lost variant, next in-frame start position is after 34 pathogenic variants. Next in-frame start position is after 35 codons. Genomic position: 36993650. Lost 0.045 part of the original CDS.
• PS1: Another start lost variant in NM_000249.4 (MLH1) was described as [Pathogenic] in Lovd
• PM2: Very rare variant in population databases, with high coverage
• PP5: Variant 3-36993548-A-T is Pathogenic according to our data. Variant chr3-36993548-A-T is described in ClinVar as [Pathogenic]. Clinvar id is 1255698.Status of the report is criteria_provided_single_submitter, 1 stars.

Transcripts

RefSeq

Gene	Transcript	HGVSc	HGVSp	Effect	Exon rank	MANE	Protein	UniProt
MLH1	NM_000249.4	c.1A>T	p.Met1?	initiator_codon_variant	Exon 1 of 19	ENST00000231790.8	NP_000240.1

Ensembl

Gene	Transcript	HGVSc	HGVSp	Effect	Exon rank	TSL	MANE	Protein	Appris	UniProt
MLH1	ENST00000231790.8	c.1A>T	p.Met1?	initiator_codon_variant	Exon 1 of 19	1	NM_000249.4	ENSP00000231790.3

Frequencies

GnomAD3 genomes Cov.: 33

GnomAD4 exome Cov.: 31

GnomAD4 genome Cov.: 33

ClinVar

Significance: Pathogenic

Submissions summary: Pathogenic:2

Revision: criteria provided, single submitter

Submissions by phenotype

Colonic neoplasm Pathogenic:1

Sep 11, 2021

Medical Genetics Laboratory, Umraniye Training and Research Hospital, University of Health Sciences

Significance: Pathogenic

Review Status: no assertion criteria provided

Collection Method: clinical testing

- -

Hereditary cancer-predisposing syndrome Pathogenic:1

Jun 07, 2022

Ambry Genetics

Significance: Pathogenic

Review Status: criteria provided, single submitter

Collection Method: clinical testing

The p.M1? pathogenic mutation (also known as c.1A>T), located in coding exon 1 of the MLH1 gene, results from an A to T substitution at nucleotide position 1. This alters the methionine residue at the initiation codon (ATG). This variant has been reported in an individual with colorectal cancer who underwent cancer multi-gene testing (Akcay IM et al. Int J Cancer, 2021 01;148:285-295). Another alteration affecting the initiation codon, p.M1? (c.3G>A), has been detected in multiple Lynch syndrome families meeting Amsterdam criteria (Guillem JG et al. Ann Surg. 2007 Apr;245(4):560-5; Ambry internal data). Sequence variations that modify the initiation codon are expected to result in either loss of translation initiation, N-terminal truncation, or cause a shift in the mRNA reading frame. Based on the supporting evidence, this alteration is interpreted as a disease-causing mutation. -

Computational scores

Source: dbNSFP v4.3

Name	Calibrated prediction	Score	Prediction
BayesDel_addAF	Pathogenic	0.29	D
BayesDel_noAF	Pathogenic	0.18
CADD	Uncertain	24
DANN	Benign	0.95
DEOGEN2	Benign	0.32	T
Eigen	Uncertain	0.43
Eigen_PC	Uncertain	0.49
FATHMM_MKL	Pathogenic	0.99	D
LIST_S2	Uncertain	0.90	D
M_CAP	Pathogenic	0.97	D
MetaRNN	Pathogenic	0.99	D
MetaSVM	Uncertain	0.64	D
PROVEAN	Benign	-0.40	N
REVEL	Uncertain	0.57
Sift	Pathogenic	0.0	D
Sift4G	Benign	0.53	T
Polyphen		0.73	P
Vest4		0.78
MutPred		0.99		Loss of MoRF binding (P = 0.0778);
MVP		0.97
ClinPred		0.99	D
GERP RS		5.9
Varity_R		0.93
gMVP		0.43

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

No publications associated with this variant yet.

Other links and lift over

hg19: chr3-37035039;