3-37050606-C-T

Position:

• chr3-37050606-C-T

Variant summary

Our verdict is Pathogenic. Variant got 14 ACMG points: 14P and 0B. PVS1_Strong PM2 PP5_Very_Strong

The NM_000249.4(MLH1):​c.2224C>T​(p.Gln742*) variant causes a stop gained change involving the alteration of a 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: 32)
• Consequence: MLH1 NM_000249.4 stop_gained
• Clinical Significance: Pathogenic reviewed by expert panel P:5
• Conservation: PhyloP100: 7.70

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: Loss of function variant, product does not undergo nonsense mediated mRNA decay. Variant is located in the 3'-most exon, not predicted to undergo nonsense mediated mRNA decay. There are 8 pathogenic variants in the truncated region.
• PM2: Very rare variant in population databases, with high coverage
• PP5: Variant 3-37050606-C-T is Pathogenic according to our data. Variant chr3-37050606-C-T is described in ClinVar as [Pathogenic]. Clinvar id is 90094.Status of the report is reviewed_by_expert_panel, 3 stars. Variant chr3-37050606-C-T is described in Lovd as [Pathogenic].

Transcripts

RefSeq

Gene	Transcript	HGVSc	HGVSp	Effect	#exon/exons	MANE	Protein	UniProt
MLH1	NM_000249.4	c.2224C>T	p.Gln742*	stop_gained	19/19	ENST00000231790.8	NP_000240.1

Ensembl

Gene	Transcript	HGVSc	HGVSp	Effect	#exon/exons	TSL	MANE	Protein	Appris	UniProt
MLH1	ENST00000231790.8	c.2224C>T	p.Gln742*	stop_gained	19/19	1	NM_000249.4	ENSP00000231790.3

Frequencies

GnomAD3 genomes Cov.: 32

GnomAD4 exome Cov.: 31

GnomAD4 genome Cov.: 32

ClinVar

Significance: Pathogenic

Submissions summary: Pathogenic:5

Revision: reviewed by expert panel

Submissions by phenotype

Lynch syndrome Pathogenic:2

Pathogenic, reviewed by expert panel	research	International Society for Gastrointestinal Hereditary Tumours (InSiGHT)	Sep 05, 2013	Coding sequence variation resulting in a stop codon within functional domain in last exon -
Pathogenic, criteria provided, single submitter	research	A.C.Camargo Cancer Center / LGBM, A.C.Camargo Cancer Center	Jan 30, 2019	- -

Colorectal cancer, hereditary nonpolyposis, type 2 Pathogenic:1

Pathogenic, criteria provided, single submitter

clinical testing

Myriad Genetics, Inc.

Jul 25, 2023

This variant is considered pathogenic. This variant creates a termination codon and is predicted to result in premature protein truncation. -

Hereditary nonpolyposis colorectal neoplasms Pathogenic:1

Pathogenic, criteria provided, single submitter

clinical testing

Labcorp Genetics (formerly Invitae), Labcorp

May 23, 2020

For these reasons, this variant has been classified as Pathogenic. This variant disrupts the highly conserved C-terminal domain responsible for MLH1 constitutive dimerization with PMS2 (PMID: 12799449, 16338176, 20533529). A different truncating variant downstream of this variant (p.Lys751Serfs*3) has been reported in individuals affected with Lynch syndrome and has been determined to be pathogenic (PMID: 24802709, 8797773, 27295708, 18566915, 18931482). This suggests that variants that disrupt this region of the protein are likely to be causative of disease. This variant has been observed in an individual affected with colon cancer (PMID: 21681552). ClinVar contains an entry for this variant (Variation ID: 90094). This variant is not present in population databases (ExAC no frequency). This sequence change results in a premature translational stop signal in the MLH1 gene (p.Gln742*). While this is not anticipated to result in nonsense mediated decay, it is expected to disrupt the last 15 amino acids of the MLH1 protein. -

Hereditary cancer-predisposing syndrome Pathogenic:1

Pathogenic, criteria provided, single submitter

clinical testing

Ambry Genetics

Feb 14, 2022

The p.Q742* pathogenic mutation (also known as c.2224C>T), located in coding exon 19 of the MLH1 gene, results from a C to T substitution at nucleotide position 2224. This changes the amino acid from a glutamine to a stop codon within coding exon 19. This alteration occurs at the 3' terminus of theMLH1 gene, is not expected to trigger nonsense-mediated mRNA decay, and only impacts the last 15 amino acids of the protein. However, premature stop codons are typically deleterious in nature and the impacted region is critical for protein function based on an internal structural analysis which suggests that this variant perturbs a known functional domain responsible for binding to as well as stabilizing PMS2 and removes a terminal cysteine residue shown to be involved in metal binding as part of a functional domain in PMS2 (Ambry internal data; Mohd AB et al. DNA Repair (Amst.) 2006 Mar;5(3):347-61; Smith CE et al. PLoS Genet. 2013 Oct;9:e1003869). This mutation has been reported in a family who met either Amsterdam or Bethesda criteria (Valentin et al. Fam Cancer. 2011 Dec;10(4):641-7), as well as in an individual with endometrial cancer at age 50 whose tumor demonstrated loss of MLH1 and PMS2 staining by immunohistochemistry (IHC) (Adar T et al. Cancer, 2018 08;124:3145-3153). This variant is considered to be rare based on population cohorts in the Genome Aggregation Database (gnomAD). 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	0.57	D
BayesDel_noAF	Pathogenic	0.58
CADD	Pathogenic	39
DANN	Uncertain	1.0
Eigen	Pathogenic	1.2
Eigen_PC	Pathogenic	1.0
FATHMM_MKL	Uncertain	0.96	D
Vest4		0.84
GERP RS		5.4
RBP_binding_hub_radar		0.0
RBP_regulation_power_radar		1.7

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: rs587778992; hg19: chr3-37092097; COSMIC: COSV51622450; COSMIC: COSV51622450;