3-37004399-A-G

Variant names:

• chr3-37004399-A-G
• rs267607732
• NM_000249.4:c.307-2A>G

Variant summary

Our verdict is Pathogenic. The variant received 18 ACMG points: 18P and 0B. PVS1 PM2 PP5_Very_Strong

The NM_000249.4(MLH1):​c.307-2A>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: 33)
• Consequence: MLH1 NM_000249.4 splice_acceptor, intron
• Scores: Splicing: ADA: 1.000
• Clinical Significance: Pathogenic/Likely pathogenic criteria provided, multiple submitters, no conflicts P:5
• Conservation: PhyloP100: 8.56
• Publications: 7 publications found

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 Gene-Disease associations (from GenCC):

• Lynch syndrome

  Inheritance: AD Classification: DEFINITIVE, SUPPORTIVE Submitted by: G2P, ClinGen, Orphanet
• Lynch syndrome 2

  Inheritance: AD Classification: DEFINITIVE, STRONG Submitted by: Ambry Genetics, Genomics England PanelApp
• Muir-Torre syndrome

  Inheritance: AD Classification: DEFINITIVE, STRONG, MODERATE, SUPPORTIVE Submitted by: Genomics England PanelApp, Ambry Genetics, G2P, Orphanet
• mismatch repair cancer syndrome 1

  Inheritance: AR Classification: DEFINITIVE, STRONG, SUPPORTIVE Submitted by: Ambry Genetics, G2P, Labcorp Genetics (formerly Invitae), Orphanet, ClinGen
• Lynch syndrome 1

  Inheritance: AD Classification: STRONG Submitted by: Labcorp Genetics (formerly Invitae)
• ovarian cancer

  Inheritance: AD Classification: STRONG Submitted by: Genomics England PanelApp
• malignant pancreatic neoplasm

  Inheritance: AD Classification: MODERATE Submitted by: Genomics England PanelApp
• rhabdomyosarcoma

  Inheritance: AR Classification: MODERATE Submitted by: Genomics England PanelApp
• prostate cancer

  Inheritance: AD Classification: LIMITED Submitted by: Ambry Genetics
• breast cancer

  Inheritance: AD Classification: NO_KNOWN Submitted by: Ambry Genetics
• hereditary breast carcinoma

  Inheritance: AD Classification: NO_KNOWN Submitted by: ClinGen

ACMG classification

Our verdict: Pathogenic. The variant received 18 ACMG points.

• PVS1: Splicing +-2 bp (donor or acceptor) variant, LoF is a know mechanism of disease, Cryptic splice site detected, with MaxEntScore 4.2, offset of -22, new splice context is: gcagtgagtttttctttcAGtct. Cryptic site results in frameshift change. If cryptic site found is not functional and variant results in exon loss, it results in frameshift change.
• PM2: Very rare variant in population databases, with high coverage
• PP5: Variant 3-37004399-A-G is Pathogenic according to our data. Variant chr3-37004399-A-G is described in ClinVar as Pathogenic/Likely_pathogenic. ClinVar VariationId is 234719.Status of the report is criteria_provided_multiple_submitters_no_conflicts, 2 stars.

Variant Effect in Transcripts

ACMG analysis was done for transcript: NM_000249.4. You can select a different transcript below to see updated ACMG assignments.

RefSeq Transcripts

Selected	Gene	Transcript	Tags	HGVSc	HGVSp	Effect	Exon Rank	Protein	UniProt
	MLH1	NM_000249.4	MANE Select	c.307-2A>G		splice_acceptor intron	N/A	NP_000240.1
	MLH1	NM_001354628.2		c.307-2A>G		splice_acceptor intron	N/A	NP_001341557.1
	MLH1	NM_001354629.2		c.208-2A>G		splice_acceptor intron	N/A	NP_001341558.1

Ensembl Transcripts

Selected	Gene	Transcript	Tags	HGVSc	HGVSp	Effect	Exon Rank	Protein	UniProt
	MLH1	ENST00000231790.8	TSL:1 MANE Select	c.307-2A>G		splice_acceptor intron	N/A	ENSP00000231790.3
	MLH1	ENST00000456676.7	TSL:1	c.307-2A>G		splice_acceptor intron	N/A	ENSP00000416687.3
	MLH1	ENST00000413740.2	TSL:1	c.307-2A>G		splice_acceptor intron	N/A	ENSP00000416476.2

Frequencies

GnomAD3 genomes Cov.: 33

GnomAD4 exome Cov.: 30

GnomAD4 genome Cov.: 33

ClinVar

Significance: Pathogenic/Likely pathogenic

Submissions summary: Pathogenic:5

Revision: criteria provided, multiple submitters, no conflicts

Submissions by phenotype

Colorectal cancer, hereditary nonpolyposis, type 2 Pathogenic:1

Jul 12, 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.

not provided Pathogenic:1

Dec 29, 2015

GeneDx

Significance: Likely pathogenic

Review Status: criteria provided, single submitter

Collection Method: clinical testing

This variant is denoted MLH1 c.307-2A>G or IVS3-2A>G and consists of an A>G nucleotide substitution at the -2 position of intron 3 of the MLH1 gene. This variant destroys a canonical splice acceptor site and is predicted to cause abnormal gene splicing, leading to either an abnormal message that is subject to nonsense-mediated mRNA decay or to an abnormal protein product. This variant has not, to our knowledge, been published in the literature. However, a different nucleotide substitution at this position, MLH1 c.307-2A>C, has been observed in an individual with a personal and family history of colon cancer whose tumor demonstrated microsatellite instability and loss of MLH1 protein expression as well as in another individual with a personal or family history suspicious for Lynch syndrome (Bartosova 2003, Goldberg 2015), and is classified as likely pathogenic by the International Society for Gastrointestinal Hereditary Tumours Incorporated (InSiGHT). Based on the currently available information, we consider MLH1 c.307-2A>G to be a likely pathogenic variant.

Hereditary nonpolyposis colorectal neoplasms Pathogenic:1

Dec 24, 2024

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 3 of the MLH1 gene. RNA analysis indicates that disruption of this splice site induces altered splicing and may result in an absent or altered protein product. This variant is not present in population databases (gnomAD no frequency). Disruption of this splice site has been observed in individuals with clinical features of Lynch syndrome (PMID: 26485756, 28449805, 28874130; internal data). Invitae Evidence Modeling of clinical and family history, age, sex, and reported ancestry of multiple individuals with this MLH1 variant has been performed. This variant is expected to be pathogenic with a positive predictive value of at least 99%. This is a validated machine learning model that incorporates the clinical features of 1,370,736 individuals referred to our laboratory for MLH1 testing. ClinVar contains an entry for this variant (Variation ID: 234719). Studies have shown that disruption of this splice site results in skipping of exon 4, and produces a non-functional protein and/or introduces a premature termination codon (internal data). For these reasons, this variant has been classified as Pathogenic.

Hereditary cancer-predisposing syndrome Pathogenic:1

May 14, 2024

Ambry Genetics

Significance: Pathogenic

Review Status: criteria provided, single submitter

Collection Method: clinical testing

The c.307-2A>G intronic pathogenic mutation results from an A to G substitution two nucleotides upstream from coding exon 4 in the MLH1 gene. This alteration has been detected in multiple individuals who meet either Bethesda or Amsterdam criteria (Maccaroni E et al. Oncotarget, 2015 Nov;6:38737-48; Sunga AY et al. Cancer Genet, 2017 Apr;212-213:1-7; Rossi BM et al. BMC Cancer, 2017 Sep;17:623), and a pediatric Lynch syndrome patient (Scollon S et al. Pediatr Blood Cancer, 2022 Nov;69:e29859). 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. RNA studies have demonstrated that this alteration results in abnormal splicing in the set of samples tested (Ambry internal data). In addition to the clinical data presented in the literature, 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 variant is interpreted as a disease-causing mutation.

Hereditary breast ovarian cancer syndrome Pathogenic:1

Mar 27, 2023

Cancer Genomics Group, Japanese Foundation For Cancer Research

Significance: Pathogenic

Review Status: criteria provided, single submitter

Collection Method: research

Computational scores

Source: dbNSFP v4.9

Name	Calibrated prediction	Score	Prediction
BayesDel_addAF	Pathogenic	0.63	D
BayesDel_noAF	Pathogenic	0.38
CADD	Pathogenic	32
DANN	Uncertain	0.99
Eigen	Pathogenic	1.2
Eigen_PC	Pathogenic	1.0
FATHMM_MKL	Pathogenic	1.0	D
PhyloP100		8.6
GERP RS		6.0
Mutation Taster		=0/100	disease causing (ClinVar)

Splicing

Name	Calibrated prediction	Score	Prediction
dbscSNV1_ADA	Pathogenic	1.0
dbscSNV1_RF	Pathogenic	0.93
SpliceAI score (max)		0.99		Details are displayed if max score is > 0.2
DS_AL_spliceai		0.99		Position offset: 2

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

Other links and lift over

dbSNP: rs267607732; hg19: chr3-37045890;