3-37001055-T-G

Variant names:

• chr3-37001055-T-G
• rs1553640340
• NM_000249.4:c.306+2T>G

Variant summary

Our verdict is Likely pathogenic. The variant received 6 ACMG points: 6P and 0B. PVS1_Moderate PM2 PP5_Moderate

The NM_000249.4(MLH1):​c.306+2T>G variant causes a splice donor, 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: 32)
• Consequence: MLH1 NM_000249.4 splice_donor, intron
• Scores: Splicing: ADA: 1.000
• Clinical Significance: Likely pathogenic criteria provided, single submitter P:2
• Conservation: PhyloP100: 7.48
• Publications: 0 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: Likely_pathogenic. The variant received 6 ACMG points.

• PVS1: Splicing +-2 bp (donor or acceptor) variant, product NOT destroyed by NMD, known LOF gene, truncates exone, which is 0.04359313 fraction of the gene. Cryptic splice site detected, with MaxEntScore 8.4, offset of -5, new splice context is: gagGTgagg. 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 3-37001055-T-G is Pathogenic according to our data. Variant chr3-37001055-T-G is described in ClinVar as Likely_pathogenic. ClinVar VariationId is 433849.Status of the report is criteria_provided_single_submitter, 1 stars.

Transcripts

RefSeq

Gene	Transcript	HGVSc	HGVSp	Effect	Exon rank	MANE	Protein	UniProt
MLH1	NM_000249.4	c.306+2T>G		splice_donor_variant, intron_variant	Intron 3 of 18	ENST00000231790.8	NP_000240.1

Ensembl

Gene	Transcript	HGVSc	HGVSp	Effect	Exon rank	TSL	MANE	Protein	Appris	UniProt
MLH1	ENST00000231790.8	c.306+2T>G		splice_donor_variant, intron_variant	Intron 3 of 18	1	NM_000249.4	ENSP00000231790.3

Frequencies

GnomAD3 genomes Cov.: 32

GnomAD4 exome Cov.: 25

GnomAD4 genome Cov.: 32

ClinVar

Significance: Likely pathogenic

Submissions summary: Pathogenic:2

Revision: criteria provided, single submitter

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 c.306+2T>G variant has not been previously reported in the literature. The variant is located in the 5' splice region, and is predicted to cause abnormal splicing because the nucleotide substitution occurs in the invariant +1 and +2 positions of the splice consensus sequence. Consensus splice site variants of the MLH1 gene are a known disease mechanism and is expected to cause Lynch syndrome. In summary, based on above information, this variant is classified as pathogenic. -

Hereditary cancer-predisposing syndrome Pathogenic:1

Oct 29, 2020

Ambry Genetics

Significance: Likely pathogenic

Review Status: criteria provided, single submitter

Collection Method: clinical testing

The c.306+2T>G intronic variant results from a T to G substitution two nucleotides after coding exon 3 in the MLH1 gene. Alterations that disrupt the canonical splice site are expected to result in aberrant splicing. In silico splice site analysis predicts that this alteration will weaken the native splice donor site. The resulting transcript is predicted to be in-frame and is not expected to trigger nonsense-mediated mRNAdecay; however, direct evidence is unavailable. The exact functional effect of the missing amino acids is unknown; however, the impacted region is critical for protein function (Ambry internal data). This variant was not reported in population-based cohorts in the Genome Aggregation Database (gnomAD). This nucleotide position is highly conserved in available vertebrate species. Based on the majority of available evidence to date, this variant is likely to be pathogenic. -

Computational scores

Source: dbNSFP v4.3

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	1.1
Eigen_PC	Pathogenic	0.97
FATHMM_MKL	Pathogenic	0.99	D
PhyloP100		7.5
GERP RS		5.6
RBP_binding_hub_radar		0.0
RBP_regulation_power_radar		1.1
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)		0.96		Details are displayed if max score is > 0.2
DS_DL_spliceai		0.96		Position offset: -2

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

Other links and lift over

dbSNP: rs1553640340; hg19: chr3-37042546; COSMIC: COSV106341054;