3-37047517-A-G

Variant names:

• chr3-37047517-A-G
• rs267607852
• NM_000249.4:c.1732-2A>G

Variant summary

Our verdict is Pathogenic. Variant got 12 ACMG points: 12P and 0B. PVS1_Moderate PM2 PP5_Very_Strong

The NM_000249.4(MLH1):​c.1732-2A>G variant causes a splice acceptor, intron 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. 3/3 splice prediction tools predicting alterations to normal splicing. Variant has been reported in ClinVar as Likely pathogenic (★★★).

• Frequency: Genomes: not found (cov: 31)
• Consequence: MLH1 NM_000249.4 splice_acceptor, intron
• Scores: Splicing: ADA: 1.000
• Clinical Significance: Likely pathogenic reviewed by expert panel P:5
• Conservation: PhyloP100: 7.25

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 12 ACMG points.

• PVS1: Splicing +-2 bp (donor or acceptor) variant, product NOT destroyed by NMD, known LOF gene, truncates exone, which is 0.072655216 fraction of the gene. Cryptic splice site detected, with MaxEntScore 3.2, offset of -31, new splice context is: atttggatgctccgttaaAGctt. Cryptic site results in frameshift change. If cryptic site found is not functional and variant results in exon loss, it results in inframe change.
• PM2: Very rare variant in population databases, with high coverage
• PP5: Variant 3-37047517-A-G is Pathogenic according to our data. Variant chr3-37047517-A-G is described in ClinVar as [Likely_pathogenic]. Clinvar id is 89861.Status of the report is reviewed_by_expert_panel, 3 stars. Variant chr3-37047517-A-G is described in Lovd as [Likely_pathogenic]. Variant chr3-37047517-A-G is described in Lovd as [Pathogenic].

Transcripts

RefSeq

Gene	Transcript	HGVSc	HGVSp	Effect	Exon rank	MANE	Protein	UniProt
MLH1	NM_000249.4	c.1732-2A>G		splice_acceptor_variant, intron_variant	Intron 15 of 18	ENST00000231790.8	NP_000240.1

Ensembl

Gene	Transcript	HGVSc	HGVSp	Effect	Exon rank	TSL	MANE	Protein	Appris	UniProt
MLH1	ENST00000231790.8	c.1732-2A>G		splice_acceptor_variant, intron_variant	Intron 15 of 18	1	NM_000249.4	ENSP00000231790.3

Frequencies

GnomAD3 genomes Cov.: 31

GnomAD4 exome Cov.: 31

GnomAD4 genome Cov.: 31

ClinVar

Significance: Likely pathogenic

Submissions summary: Pathogenic:5

Revision: reviewed by expert panel

Submissions by phenotype

Colorectal cancer, hereditary nonpolyposis, type 2 Pathogenic:1

Jul 21, 2023

Myriad Genetics, Inc.

Significance: Likely pathogenic

Review Status: criteria provided, single submitter

Collection Method: clinical testing

This variant is considered likely pathogenic. This variant occurs within a consensus splice junction and is predicted to result in abnormal mRNA splicing of either an out-of-frame exon or an in-frame exon necessary for protein stability and/or normal function. -

Lynch syndrome Pathogenic:1

Jun 21, 2019

International Society for Gastrointestinal Hereditary Tumours (InSiGHT)

Significance: Likely pathogenic

Review Status: reviewed by expert panel

Collection Method: curation

Interrupts canonical donor splice site -

not provided Pathogenic:1

Jun 06, 2017

Quest Diagnostics Nichols Institute San Juan Capistrano

Significance: Likely pathogenic

Review Status: criteria provided, single submitter

Collection Method: clinical testing

- -

Hereditary nonpolyposis colorectal neoplasms Pathogenic:1

May 18, 2023

Labcorp Genetics (formerly Invitae), Labcorp

Significance: Pathogenic

Review Status: criteria provided, single submitter

Collection Method: clinical testing

This sequence change affects an acceptor splice site in intron 15 of the MLH1 gene. RNA analysis indicates that disruption of this splice site induces altered splicing and likely results in a shortened protein product. This variant is not present in population databases (gnomAD no frequency). Disruption of this splice site has been observed in individual(s) with Lynch syndrome (PMID: 8571956, 24090359; Invitae). It has also been observed to segregate with disease in related individuals. ClinVar contains an entry for this variant (Variation ID: 89861). Studies have shown that disruption of this splice site results in skipping of exon 16, but is expected to preserve the integrity of the reading-frame (PMID: 24090359). This variant disrupts a region of the MLH1 protein in which other variant(s) (p.Ala586Asp) have been determined to be pathogenic (PMID: 16395668, 30998989; Invitae). This suggests that this is a clinically significant region of the protein, and that variants that disrupt it are likely to be disease-causing. For these reasons, this variant has been classified as Pathogenic. -

Hereditary cancer-predisposing syndrome Pathogenic:1

Aug 07, 2020

Ambry Genetics

Significance: Pathogenic

Review Status: criteria provided, single submitter

Collection Method: clinical testing

The c.1732-2A>G intronic variant results from an A to G substitution two nucleotides upstream from coding exon 16 in the MLH1 gene. This variant has been identified in at least one proband whose Lynch syndrome-associated tumor demonstrated high microsatellite instability (MSI-H) and/or loss of both MLH1/PMS2 protein expression on immunohistochemistry (IHC) (Ambry internal data). This variant was not reported in population-based cohorts in the Genome Aggregation Database (gnomAD) (Lek M et al. Nature. 2016 08;536:285-91). This nucleotide position is highly conserved in available vertebrate species. In silico splice site analysis predicts that this alteration will weaken the native splice acceptor site and will result in the creation or strengthening of a novel splice acceptor site; however, direct evidence is insufficient at this time (Ambry internal data). Alterations that disrupt the canonical splice site are expected to cause aberrant splicing, resulting in an abnormal protein or a transcript that is subject to nonsense-mediated mRNA decay. Based on the supporting evidence, 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	0.24
CADD	Pathogenic	35
DANN	Uncertain	1.0
Eigen	Pathogenic	1.1
Eigen_PC	Pathogenic	0.89
FATHMM_MKL	Pathogenic	0.99	D
GERP RS		5.3

Splicing

Name	Calibrated prediction	Score	Prediction
dbscSNV1_ADA	Pathogenic	1.0
dbscSNV1_RF	Pathogenic	0.93
SpliceAI score (max)		1.0		Details are displayed if max score is > 0.2
DS_AG_spliceai		0.73		Position offset: 42
DS_AL_spliceai		1.0		Position offset: 2

Find out detailed SpliceAI scores and Pangolin per-transcript scores at spliceailookup.broadinstitute.org

Publications

LitVar

Other links and lift over

dbSNP: rs267607852; hg19: chr3-37089008;