rs63750855

chr3-37028857-AC-Achr3-37028857-AC-ACC

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.1489del(p.Arg497GlyfsTer11) variant causes a frameshift change involving the alteration of a non-conserved nucleotide. The variant allele was found at a frequency of 0.000000684 in 1,461,844 control chromosomes in the GnomAD database, with no homozygous occurrence. Variant has been reported in ClinVar as Pathogenic (★★★). Synonymous variant affecting the same amino acid position (i.e. T495T) has been classified as Likely benign. Variant results in nonsense mediated mRNA decay.

• Frequency:
  • Genomes: not found (cov: 32)
  • Exomes 𝑓: 6.8e-7 (0 hom.)
• Consequence: MLH1 NM_000249.4 frameshift
• Clinical Significance: Pathogenic reviewed by expert panel P:5
• Conservation: PhyloP100: 0.659

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 3-37028857-AC-A is Pathogenic according to our data. Variant chr3-37028857-AC-A is described in ClinVar as [Pathogenic]. Clinvar id is 89752.Status of the report is reviewed_by_expert_panel, 3 stars. Variant chr3-37028857-AC-A is described in Lovd as [Likely_pathogenic]. Variant chr3-37028857-AC-A is described in Lovd as [Pathogenic]. Variant chr3-37028857-AC-A is described in Lovd as [Pathogenic]. Variant chr3-37028857-AC-A is described in Lovd as [Likely_pathogenic].

Transcripts

RefSeq

Gene	Transcript	HGVSc	HGVSp	Effect	#exon/exons	MANE	UniProt
MLH1	NM_000249.4	c.1489del	p.Arg497GlyfsTer11	frameshift_variant	13/19	ENST00000231790.8

Ensembl

Gene	Transcript	HGVSc	HGVSp	Effect	#exon/exons	TSL	MANE	Appris	UniProt
MLH1	ENST00000231790.8	c.1489del	p.Arg497GlyfsTer11	frameshift_variant	13/19	1	NM_000249.4	P1

Frequencies

GnomAD3 genomes Cov.: 32

GnomAD3 exomes AF: 0.00000398 AC: 1 AN: 251484 Hom.: 0 AF XY: 0.00000736 AC XY: 1 AN XY: 135912

Gnomad AFR exome AF: 0.00

Gnomad AMR exome AF: 0.00

Gnomad ASJ exome AF: 0.00

Gnomad EAS exome AF: 0.00

Gnomad SAS exome AF: 0.0000327

Gnomad FIN exome AF: 0.00

Gnomad NFE exome AF: 0.00

Gnomad OTH exome AF: 0.00

GnomAD4 exome AF: 6.84e-7 AC: 1 AN: 1461844 Hom.: 0 Cov.: 32 AF XY: 0.00000138 AC XY: 1 AN XY: 727224

Gnomad4 AFR exome AF: 0.00

Gnomad4 AMR exome AF: 0.00

Gnomad4 ASJ exome AF: 0.00

Gnomad4 EAS exome AF: 0.00

Gnomad4 SAS exome AF: 0.0000116

Gnomad4 FIN exome AF: 0.00

Gnomad4 NFE exome AF: 0.00

Gnomad4 OTH exome AF: 0.00

GnomAD4 genome Cov.: 32

ClinVar

Significance: Pathogenic

Submissions summary: Pathogenic:5

Revision: reviewed by expert panel

Submissions by phenotype

Colorectal cancer, hereditary nonpolyposis, type 2 Pathogenic:2

Pathogenic, criteria provided, single submitter	clinical testing	KCCC/NGS Laboratory, Kuwait Cancer Control Center	Jul 07, 2023	MLH1 (Arg497fs): This sequence change creates a premature translational stop signal (p.Arg497Glyfs*11) in the MLH1 gene. It is expected to result in an absent or disrupted protein product. The frequency data for this variant in the population databases is considered unreliable, as metrics indicate poor data quality at this position in the ExAC database. This variant has been reported in individuals affected with Lynch syndrome and Muir-Torre syndrome (PMID: 15872200, 18270343). ClinVar contains an entry for this variant (Variation ID: 89752) with 3 submissions, all pathogenic, 3 stars, no conflict, and reviewed by an expert panel. Loss-of-function variants in MLH1 are known to be pathogenic (PMID: 15713769, 24362816). Therefore, this variant has been classified as Pathogenic. . -
Pathogenic, criteria provided, single submitter	clinical testing	Myriad Genetics, Inc.	Jul 20, 2023	This variant is considered pathogenic. This variant creates a frameshift 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 -

Hereditary nonpolyposis colorectal neoplasms Pathogenic:1

Pathogenic, criteria provided, single submitter

clinical testing

Invitae

Dec 07, 2020

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 reported in individuals affected with Lynch syndrome and Muir-Torre syndrome (PMID: 15872200, 18270343). ClinVar contains an entry for this variant (Variation ID: 89752). The frequency data for this variant in the population databases is considered unreliable, as metrics indicate poor data quality at this position in the ExAC database. This sequence change creates a premature translational stop signal (p.Arg497Glyfs*11) 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

Dec 30, 2021

The c.1489delC pathogenic mutation, located in coding exon 13 of the MLH1 gene, results from a deletion of one nucleotide at nucleotide position 1489, causing a translational frameshift with a predicted alternate stop codon (p.R497Gfs*11). This mutation was identified in a patient with colorectal cancer at 46 and Muir-Torre phenotype (Hampel H et al. N. Engl. J. Med. 2005 May;352:1851-60; South CD et al. J. Natl. Cancer Inst. 2008 Feb;100:277-81). This mutation was also reported in a patient with endometrial cancer showing absent MLH1 and PMS2 protein expression by immunohistochemistry (Moline J et al. Gynecol. Oncol. 2013 Jul;130:121-6). 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

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: rs63750855; hg19: chr3-37070348;