rs63750906

Variant names:

• chr3-37004439-TA-T
• rs63750906
• NM_000249.4:c.346delA

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.346delA​(p.Thr116GlnfsTer20) variant causes a frameshift change involving the alteration of a 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: 33)
• Consequence: MLH1 NM_000249.4 frameshift
• Clinical Significance: Pathogenic reviewed by expert panel P:2
• Conservation: PhyloP100: 8.94

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 3-37004439-TA-T is Pathogenic according to our data. Variant chr3-37004439-TA-T is described in ClinVar as [Pathogenic]. Clinvar id is 90174.Status of the report is reviewed_by_expert_panel, 3 stars. Variant chr3-37004439-TA-T is described in Lovd as [Pathogenic]. Variant chr3-37004439-TA-T is described in Lovd as [Pathogenic].

Transcripts

RefSeq

Gene	Transcript	HGVSc	HGVSp	Effect	Exon rank	MANE	Protein	UniProt
MLH1	NM_000249.4	c.346delA	p.Thr116GlnfsTer20	frameshift_variant	Exon 4 of 19	ENST00000231790.8	NP_000240.1

Ensembl

Gene	Transcript	HGVSc	HGVSp	Effect	Exon rank	TSL	MANE	Protein	Appris	UniProt
MLH1	ENST00000231790.8	c.346delA	p.Thr116GlnfsTer20	frameshift_variant	Exon 4 of 19	1	NM_000249.4	ENSP00000231790.3

Frequencies

GnomAD3 genomes Cov.: 33

GnomAD4 exome Cov.: 30

GnomAD4 genome Cov.: 33

ClinVar

Significance: Pathogenic

Submissions summary: Pathogenic:2

Revision: reviewed by expert panel

Submissions by phenotype

Carcinoma of colon Pathogenic:1

-

Department of Pathology and Laboratory Medicine, Sinai Health System

Significance: Pathogenic

Review Status: no assertion criteria provided

Collection Method: clinical testing

The p.Thr116GlnfsX20 variant has been reported in the literature in 8/1418 proband chromosomes with HNPCC. However, no control chromosomes were tested to establish the frequency of the variant in the general population (Casey 2005, Choi 2009). In one of these studies, the patient with the variant met the Amsterdam criteria and also showed loss of MLH1 protein expression (Casey 2005). The variant is listed in the dbSNP database as coming from a "clinical source" (ID#:rs63750906), but no frequency information was provided, and so the prevalence of this variant in the population is not known. This variant is predicted to cause a frameshift, which alters the protein's amino acid sequence beginning at codon 116 and leads to a premature stop codon, 20 codons downstream. This alteration is then predicted to lead to a truncated or absent protein and loss of function. Loss of function variants are an established mechanism of disease for the MLH1 gene and is the type of alteration expected to cause the disorder. In summary, based on the above information, this variant is classified as pathogenic. -

Lynch syndrome Pathogenic:1

Sep 05, 2013

International Society for Gastrointestinal Hereditary Tumours (InSiGHT)

Significance: Pathogenic

Review Status: reviewed by expert panel

Collection Method: research

Coding variation introducing premature termination codon -

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: rs63750906; hg19: chr3-37045930;