3-37020312-T-G

Variant summary

Our verdict is Pathogenic. Variant got 18 ACMG points: 18P and 0B. PVS1 PM2 PP5_Very_Strong

The NM_000249.4(MLH1):c.887T>G(p.Leu296Ter) variant causes a stop gained, splice region 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. 1/1 splice prediction tools predict no significant impact on normal splicing. Variant has been reported in ClinVar as Pathogenic (★★★). Synonymous variant affecting the same amino acid position (i.e. L296L) has been classified as Likely benign. Variant results in nonsense mediated mRNA decay.

• Frequency: Genomes: not found (cov: 32)
• Consequence: MLH1 NM_000249.4 stop_gained, splice_region
• Clinical Significance: Pathogenic reviewed by expert panel P:6
• Conservation: PhyloP100: 7.64

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 18 ACMG points.

• PVS1: Loss of function variant, product undergoes nonsense mediated mRNA decay. LoF is a known mechanism of disease.
• PM2: Very rare variant in population databases, with high coverage
• PP5: Variant 3-37020312-T-G is Pathogenic according to our data. Variant chr3-37020312-T-G is described in ClinVar as [Pathogenic]. Clinvar id is 90430.Status of the report is reviewed_by_expert_panel, 3 stars. Variant chr3-37020312-T-G is described in Lovd as [Pathogenic].

Transcripts

RefSeq

Gene	Transcript	HGVSc	HGVSp	Effect	#exon/exons	MANE	UniProt
MLH1	NM_000249.4	c.887T>G	p.Leu296Ter	stop_gained, splice_region_variant	11/19	ENST00000231790.8

Ensembl

Gene	Transcript	HGVSc	HGVSp	Effect	#exon/exons	TSL	MANE	Appris	UniProt
MLH1	ENST00000231790.8	c.887T>G	p.Leu296Ter	stop_gained, splice_region_variant	11/19	1	NM_000249.4	P1

Frequencies

GnomAD3 genomes Cov.: 32

GnomAD4 exome Cov.: 31

GnomAD4 genome Cov.: 32

ClinVar

Significance: Pathogenic

Submissions summary: Pathogenic:6

Revision: reviewed by expert panel

Submissions by phenotype

Colorectal cancer, hereditary nonpolyposis, type 2 Pathogenic:1

Pathogenic, criteria provided, single submitter

clinical testing

Myriad Genetics, Inc.

Jul 18, 2023

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

Lynch syndrome Pathogenic:1

Pathogenic, reviewed by expert panel

research

International Society for Gastrointestinal Hereditary Tumours (InSiGHT)

Sep 05, 2013

Coding sequence variation resulting in a stop codon -

not provided Pathogenic:1

Pathogenic, criteria provided, single submitter

clinical testing

GeneDx

Oct 11, 2016

This variant is denoted MLH1 c.887T>G at the cDNA level and p.Leu296Ter (L296X) at the protein level. The substitution creates a nonsense variant, which changes a Leucine to a premature stop codon (TTA>TGA), and is predicted to cause loss of normal protein function through either protein truncation or nonsense-mediated mRNA decay. The International Society for Gastrointestinal Hereditary Tumours Incorporated (InSiGHT) classifies this variant as pathogenic (Thompson 2014). MLH1 Leu296Ter has been reported in at least one individual with Lynch syndrome (Lee 2005). We consider this variant to be pathogenic. -

Hereditary nonpolyposis colorectal neoplasms Pathogenic:1

Pathogenic, criteria provided, single submitter

clinical testing

Invitae

Jan 15, 2021

For these reasons, this variant has been classified as Pathogenic. Loss-of-function variants in MLH1 are known to be pathogenic (PMID: 15713769, 24362816). This variant has been observed in individuals affected with Lynch syndrome and colorectal cancer (PMID: 15996210, 28445943). ClinVar contains an entry for this variant (Variation ID: 90430). This variant is not present in population databases (ExAC no frequency). This sequence change creates a premature translational stop signal (p.Leu296*) in the MLH1 gene. It is expected to result in an absent or disrupted protein product. -

Hereditary cancer-predisposing syndrome Pathogenic:1

Pathogenic, criteria provided, single submitter

clinical testing

Ambry Genetics

Jun 15, 2023

The p.L296* pathogenic mutation (also known as c.887T>G), located in coding exon 11 of the MLH1 gene, results from a T to G substitution at nucleotide position 887. This changes the amino acid from a leucine to a stop codon within coding exon 11. This mutation has been reported in multiple individuals who meet Amsterdam II criteria and/or have mismatch repair deficient colorectal cancer (Zhang J et al. Oncotarget, 2017 Apr;8:24533-24547; Yang M et al. Ther Adv Med Oncol, 2021 Jun;13:17588359211023290; Jiang W et al. Int J Cancer, 2019 May;144:2161-2168; Lee SC et al. Clin Genet, 2005 Aug;68:137-45). In addition to the clinical data presented in the literature, this alteration is expected to result in loss of function by premature protein truncation or nonsense-mediated mRNA decay. As such, this alteration is interpreted as a disease-causing mutation. -

Colon cancer Pathogenic:1

Pathogenic, no assertion criteria provided

clinical testing

3DMed Clinical Laboratory Inc

Mar 08, 2018

- -

Computational scores

Source: dbNSFP v4.3

Name	Calibrated prediction	Score	Prediction
BayesDel_addAF	Pathogenic	0.63	D
BayesDel_noAF	Pathogenic	0.65
Cadd	Pathogenic	39
Dann	Uncertain	0.99
Eigen	Pathogenic	1.2
Eigen_PC	Pathogenic	1.0
FATHMM_MKL	Pathogenic	0.99	D
MutationTaster	Benign	1.0	A;A;A;A;A;A
Vest4		0.96
GERP RS		5.8
RBP_binding_hub_radar		0.0
RBP_regulation_power_radar		1.0

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: rs63750547; hg19: chr3-37061803;