3-37008857-TAA-TA

Position:

• chr3-37008857-TAA-TA

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.503delA​(p.Asn168fs) variant causes a frameshift change involving the alteration of a non-conserved nucleotide. The variant was absent in control chromosomes in GnomAD project. Variant has been reported in ClinVar as Pathogenic (★★). Variant results in nonsense mediated mRNA decay.

• Frequency: Genomes: not found (cov: 32)
• Consequence: MLH1 NM_000249.4 frameshift
• Clinical Significance: Pathogenic criteria provided, multiple submitters, no conflicts P:4
• Conservation: PhyloP100: 1.50

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]

MLH1 (HGNC:):

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 3-37008857-TA-T is Pathogenic according to our data. Variant chr3-37008857-TA-T is described in ClinVar as [Pathogenic]. Clinvar id is 630044.Status of the report is criteria_provided_multiple_submitters_no_conflicts, 2 stars. Variant chr3-37008857-TA-T is described in Lovd as [Pathogenic]. Variant chr3-37008857-TA-T is described in Lovd as [Pathogenic].

Transcripts

RefSeq

Gene	Transcript	HGVSc	HGVSp	Effect	#exon/exons	MANE	Protein	UniProt
MLH1	NM_000249.4	c.503delA	p.Asn168fs	frameshift_variant	6/19	ENST00000231790.8	NP_000240.1

Ensembl

Gene	Transcript	HGVSc	HGVSp	Effect	#exon/exons	TSL	MANE	Protein	Appris	UniProt
MLH1	ENST00000231790.8	c.503delA	p.Asn168fs	frameshift_variant	6/19	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:4

Revision: criteria provided, multiple submitters, no conflicts

Submissions by phenotype

Hereditary cancer-predisposing syndrome Pathogenic:2

Pathogenic, criteria provided, single submitter	clinical testing	Ambry Genetics	Jun 08, 2022	The c.503delA pathogenic mutation, located in coding exon 6 of the MLH1 gene, results from a deletion of one nucleotide at nucleotide position 503, causing a translational frameshift with a predicted alternate stop codon (p.N168Ifs*34). This mutation was identified in one Brazilian patient with Lynch syndrome meeting Amsterdam or Bethesda guidelines (Dominguez-Valentin M et al. Hered. Cancer Clin. Pract. 2013 Dec;11:18). One study also demonstrated reduced MLH1 expression in an HNPCC patient with this mutation (designated c.498delA), indicating the effect of nonsense mediated decay (Tournier I et al. Hum. Mutat. 2004 Apr;23:379-84). 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. -
Pathogenic, criteria provided, single submitter	clinical testing	Color Diagnostics, LLC DBA Color Health	Apr 05, 2022	This variant deletes 1 nucleotide in exon 6 of the MLH1 gene, creating a frameshift and premature translation stop signal. This variant is expected to result in an absent or non-functional protein product. This variant has been reported in individuals affected with Lynch syndrome or colorectal cancer with clinical features of Lynch syndrome (PMID: 33253688; DOI: 10.1186/s13053-019-0115-7). This variant has not been identified in the general population by the Genome Aggregation Database (gnomAD). Loss of MLH1 function is a known mechanism of disease (clinicalgenome.org). Based on the available evidence, this variant is classified as Pathogenic. -

Colorectal cancer, hereditary nonpolyposis, type 2 Pathogenic:1

Pathogenic, criteria provided, single submitter

clinical testing

Myriad Genetics, Inc.

Jul 14, 2023

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

not provided Pathogenic:1

Pathogenic, criteria provided, single submitter

clinical testing

Center for Genomic Medicine, Rigshospitalet, Copenhagen University Hospital

Jul 31, 2024

- -

Computational scores

Source: dbNSFP v4.3

Splicing

Name	Calibrated prediction	Score	Prediction
SpliceAI score (max)		0.020		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: rs63749959; hg19: chr3-37050348;