rs267607734

Positions:

• chr3-37001054-G-A
• chr3-37001054-G-C

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.306+1G>A 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 Pathogenic (★★★).

• Frequency:
  • Genomes: not found (cov: 32)
  • Exomes 𝑓: 0.0 (0 hom.)
  • Failed GnomAD Quality Control
• Consequence: MLH1 NM_000249.4 splice_donor, intron
• Scores: Splicing: ADA: 1.000
• Clinical Significance: Pathogenic reviewed by expert panel P:6
• Conservation: PhyloP100: 9.32

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 12 ACMG points.

• PVS1: Splicing +-2 bp (donor or acceptor) variant, product NOT destroyed by NMD, known LOF gene, truncates exone, which is 0.043152798 fraction of the gene. Cryptic splice site detected, with MaxEntScore 7.7, offset of -5, new splice context is: gagGTgaga. 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 3-37001054-G-A is Pathogenic according to our data. Variant chr3-37001054-G-A is described in ClinVar as [Pathogenic]. Clinvar id is 90142.Status of the report is reviewed_by_expert_panel, 3 stars. Variant chr3-37001054-G-A is described in Lovd as [Pathogenic]. Variant chr3-37001054-G-A is described in Lovd as [Likely_pathogenic].

Transcripts

RefSeq

Gene	Transcript	HGVSc	HGVSp	Effect	#exon/exons	MANE	Protein	UniProt
MLH1	NM_000249.4	c.306+1G>A		splice_donor_variant, intron_variant		ENST00000231790.8	NP_000240.1

Ensembl

Gene	Transcript	HGVSc	HGVSp	Effect	#exon/exons	TSL	MANE	Protein	Appris	UniProt
MLH1	ENST00000231790.8	c.306+1G>A		splice_donor_variant, intron_variant		1	NM_000249.4	ENSP00000231790.3

Frequencies

GnomAD3 genomes Cov.: 32

GnomAD4 exome Data not reliable, filtered out with message: AC0 AF: 0.00 AC: 0 AN: 1419572 Hom.: 0 Cov.: 25 AF XY: 0.00 AC XY: 0 AN XY: 708766

Gnomad4 AFR exome AF: 0.00

Gnomad4 AMR exome AF: 0.00

Gnomad4 ASJ exome AF: 0.00

Gnomad4 EAS exome AF: 0.00

Gnomad4 SAS exome AF: 0.00

Gnomad4 FIN exome AF: 0.00

Gnomad4 NFE exome AF: 0.00

Gnomad4 OTH exome AF: 0.00

GnomAD4 genome Cov.: 32

ClinVar

Significance: Pathogenic

Submissions summary: Pathogenic:6

Revision: reviewed by expert panel

Submissions by phenotype

Colorectal cancer, hereditary nonpolyposis, type 2 Pathogenic:1

Pathogenic, criteria provided, single submitter

clinical testing

Myriad Genetics, Inc.

Jul 12, 2023

This variant is considered 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. mRNA analysis has demonstrated abnormal mRNA splicing occurs [PMID: 12183410, 16341550]. -

Lynch syndrome 1 Pathogenic:1

Pathogenic, reviewed by expert panel

research

International Society for Gastrointestinal Hereditary Tumours (InSiGHT)

Nov 24, 2015

- -

Gastric cancer Pathogenic:1

Pathogenic, no assertion criteria provided

research

Laboratory for Genotyping Development, RIKEN

Jul 01, 2021

- -

not provided Pathogenic:1

Pathogenic, criteria provided, single submitter

clinical testing

Institute for Clinical Genetics, University Hospital TU Dresden, University Hospital TU Dresden

Nov 03, 2021

- -

Hereditary nonpolyposis colorectal neoplasms Pathogenic:1

Pathogenic, criteria provided, single submitter

clinical testing

Labcorp Genetics (formerly Invitae), Labcorp

Jul 19, 2017

For these reasons, this variant has been classified as Pathogenic. Donor and acceptor splice site variants typically lead to a loss of protein function (PMID: 16199547), and loss-of-function variants in MLH1 are known to be pathogenic (PMID: 15713769, 24362816). Algorithms developed to predict the effect of sequence changes on RNA splicing suggest that this variant may disrupt the consensus splice site, but this prediction has not been confirmed by published transcriptional studies. This variant has been reported in several individuals affected with Lynch syndrome (PMID: 10471527, 11151427, 15849733, 27601186). ClinVar contains an entry for this variant (Variation ID: 90142). This variant is not present in population databases (ExAC no frequency). This sequence change affects a donor splice site in intron 3 of the MLH1 gene. It is expected to disrupt RNA splicing and likely results in an absent or disrupted protein product. -

Hereditary cancer-predisposing syndrome Pathogenic:1

Pathogenic, criteria provided, single submitter

clinical testing

Ambry Genetics

Sep 03, 2024

The c.306+1G>A intronic pathogenic mutation results from a G to A substitution one nucleotide after coding exon 3 of the MLH1 gene. This mutation has been described in multiple unrelated Lynch syndrome families, including an Iranian family in which the proband was affected with colon cancer at 49 years and had a family history of colon and endometrial cancers (Planck M et al. Int. J. Cancer 1999 Oct;83(2):197-202), and a German family meeting Amsterdam Criteria, in which the proband's tumor was MSI-high (Pistorius SR et al. Int. J. Colorectal Dis. 2000 Nov;15(5-6):255-63). This alteration has also been shown to lead to aberrant splicing (Xiong HY et al. Science 2015 Jan;347(6218):1254806). This variant is considered to be rare based on population cohorts in the Genome Aggregation Database (gnomAD). This nucleotide position is highly conserved in available vertebrate species. In silico splice site analysis predicts that this alteration will weaken the native splice donor site. 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. As such, this alteration is classified 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	0.43
CADD	Pathogenic	34
DANN	Uncertain	0.99
Eigen	Pathogenic	1.2
Eigen_PC	Pathogenic	1.1
FATHMM_MKL	Pathogenic	1.0	D
GERP RS		5.6
RBP_binding_hub_radar		0.0
RBP_regulation_power_radar		2.8

Splicing

Name	Calibrated prediction	Score	Prediction
dbscSNV1_ADA	Pathogenic	1.0
dbscSNV1_RF	Pathogenic	0.94
SpliceAI score (max)		0.96		Details are displayed if max score is > 0.2
DS_DL_spliceai		0.96		Position offset: -1

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

Publications

LitVar

Other links and lift over

dbSNP: rs267607734; hg19: chr3-37042545; COSMIC: COSV51623336;