3-37025823-C-T

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.1225C>T(p.Gln409Ter) variant causes a stop gained 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 (★★★). Synonymous variant affecting the same amino acid position (i.e. Q409Q) has been classified as Likely benign. Variant results in nonsense mediated mRNA decay.

• Frequency: Genomes: not found (cov: 31)
• Consequence: MLH1 NM_000249.4 stop_gained
• Clinical Significance: Pathogenic reviewed by expert panel P:5
• Conservation: PhyloP100: 0.633

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 3-37025823-C-T is Pathogenic according to our data. Variant chr3-37025823-C-T is described in ClinVar as [Pathogenic]. Clinvar id is 89683.Status of the report is reviewed_by_expert_panel, 3 stars. Variant chr3-37025823-C-T is described in Lovd as [Pathogenic].

Transcripts

RefSeq

Gene	Transcript	HGVSc	HGVSp	Effect	#exon/exons	MANE	UniProt
MLH1	NM_000249.4	c.1225C>T	p.Gln409Ter	stop_gained	12/19	ENST00000231790.8

Ensembl

Gene	Transcript	HGVSc	HGVSp	Effect	#exon/exons	TSL	MANE	Appris	UniProt
MLH1	ENST00000231790.8	c.1225C>T	p.Gln409Ter	stop_gained	12/19	1	NM_000249.4	P1

Frequencies

GnomAD3 genomes Cov.: 31

GnomAD4 exome Cov.: 34

GnomAD4 genome Cov.: 31

ClinVar

Significance: Pathogenic

Submissions summary: Pathogenic:5

Revision: reviewed by expert panel

Submissions by phenotype

Lynch syndrome Pathogenic:2

Pathogenic, criteria provided, single submitter	clinical testing	Women's Health and Genetics/Laboratory Corporation of America, LabCorp	May 11, 2018	Variant summary: MLH1 c.1225C>T (p.Gln409X) results in a premature termination codon, predicted to cause a truncation of the encoded protein or absence of the protein due to nonsense mediated decay, which are commonly known mechanisms for disease. Truncations downstream of this position have been classified as pathogenic by our laboratory (eg. c.1381A>T, p.Lys461X; c.1459C>T, p.Arg487X; c.1489dupC, p.Arg497fsX6). The variant was absent in 121402 control chromosomes. c.1225C>T has been reported in the literature in multiple individuals affected with Lynch Syndrome. These data indicate that the variant is very likely to be associated with disease. To our knowledge, no experimental evidence demonstrating an impact on protein function has been reported. One clinical diagnostic laboratory has submitted clinical-significance assessments for this variant to ClinVar after 2014 without evidence for independent evaluation and classified the variant as pathogenic. Based on the evidence outlined above, the variant was classified as pathogenic. -
Pathogenic, reviewed by expert panel	research	International Society for Gastrointestinal Hereditary Tumours (InSiGHT)	Sep 05, 2013	Coding sequence variation resulting in a stop codon -

Colorectal cancer, hereditary nonpolyposis, type 2 Pathogenic:1

Pathogenic, criteria provided, single submitter

clinical testing

Myriad Genetics, Inc.

Jul 19, 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

Invitae

Apr 25, 2022

This sequence change creates a premature translational stop signal (p.Gln409*) in the MLH1 gene. It is expected to result in an absent or disrupted protein product. Loss-of-function variants in MLH1 are known to be pathogenic (PMID: 15713769, 24362816). This variant is not present in population databases (gnomAD no frequency). This premature translational stop signal has been observed in individual(s) with Lynch syndrome (PMID: 12624141, 17312306, 27064304). ClinVar contains an entry for this variant (Variation ID: 89683). For these reasons, this variant has been classified as Pathogenic. -

Hereditary cancer-predisposing syndrome Pathogenic:1

Pathogenic, criteria provided, single submitter

clinical testing

Ambry Genetics

Mar 20, 2021

The p.Q409* pathogenic mutation (also known as c.1225C>T), located in coding exon 12 of the MLH1 gene, results from a C to T substitution at nucleotide position 1225. This changes the amino acid from a glutamine to a stop codon within coding exon 12. This variant has been detected in multiple families meeting Amsterdam criteria (Lagerstedt Robinson K et al. J Natl Cancer Inst. 2007 Feb;99:291-9; Overbeek LI et al. Br J Cancer. 2007 May;96:1605-12; Jasperson KW et al. Fam Cancer. 2010 Jun;9:99-107). This variant was not reported in population-based cohorts in the Genome Aggregation Database (gnomAD). 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. -

Computational scores

Source: dbNSFP v4.3

Name	Calibrated prediction	Score	Prediction
BayesDel_addAF	Pathogenic	0.63	D
BayesDel_noAF	Pathogenic	0.31
Cadd	Pathogenic	32
Dann	Uncertain	0.99
Eigen	Benign	0.15
Eigen_PC	Benign	-0.10
FATHMM_MKL	Benign	0.45	N
MutationTaster	Benign	1.0	A;A;A;A;A;A
Vest4		0.87
GERP RS		2.6
RBP_binding_hub_radar		0.0
RBP_regulation_power_radar		1.1

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: rs63751153; hg19: chr3-37067314; COSMIC: COSV51614273; COSMIC: COSV51614273;