rs267607778

Positions:

• chr3-37012100-G-A
• chr3-37012100-G-C
• chr3-37012100-G-T

Variant summary

Our verdict is Pathogenic. Variant got 22 ACMG points: 22P and 0B. PVS1 PM2 PP3_Strong PP5_Very_Strong

The NM_000249.4(MLH1):​c.677+1G>A variant causes a splice donor change involving the alteration of a conserved nucleotide. The variant allele was found at a frequency of 0.000000689 in 1,451,290 control chromosomes in the GnomAD database, with no homozygous occurrence. 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)
  • Exomes 𝑓: 6.9e-7 (0 hom.)
• Consequence: MLH1 NM_000249.4 splice_donor
• Scores: Splicing: ADA: 1.000
• Clinical Significance: Likely pathogenic reviewed by expert panel P:6
• Conservation: PhyloP100: 7.32

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]

ACMG classification

Verdict is Pathogenic. Variant got 22 ACMG points.

• PVS1: Splicing +-2 bp (donor or acceptor) variant, LoF is a know mechanism of disease, No cryptic splice site detected. Exon removal results in frameshift change.
• PM2: Very rare variant in population databases, with high coverage
• PP3: Splicing scoreres supports a deletorius effect: Scorers claiming Pathogenic: dbscSNV1_ADA, dbscSNV1_RF, max_spliceai. No scorers claiming Uncertain. No scorers claiming Benign.
• PP5: Variant 3-37012100-G-A is Pathogenic according to our data. Variant chr3-37012100-G-A is described in ClinVar as [Likely_pathogenic]. Clinvar id is 90311.Status of the report is reviewed_by_expert_panel, 3 stars. Variant chr3-37012100-G-A is described in Lovd as [Likely_pathogenic]. Variant chr3-37012100-G-A is described in Lovd as [Pathogenic].

Transcripts

RefSeq

Gene	Transcript	HGVSc	HGVSp	Effect	#exon/exons	MANE	UniProt
MLH1	NM_000249.4	c.677+1G>A		splice_donor_variant		ENST00000231790.8

Ensembl

Gene	Transcript	HGVSc	HGVSp	Effect	#exon/exons	TSL	MANE	Appris	UniProt
MLH1	ENST00000231790.8	c.677+1G>A		splice_donor_variant		1	NM_000249.4	P1

Frequencies

GnomAD3 genomes Cov.: 32

GnomAD4 exome AF: 6.89e-7 AC: 1 AN: 1451290 Hom.: 0 Cov.: 30 AF XY: 0.00 AC XY: 0 AN XY: 722580

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: 9.07e-7

Gnomad4 OTH exome AF: 0.00

GnomAD4 genome Cov.: 32

ClinVar

Significance: Likely pathogenic

Submissions summary: Pathogenic:6

Revision: reviewed by expert panel

Submissions by phenotype

Colorectal cancer, hereditary nonpolyposis, type 2 Pathogenic:2

Pathogenic, criteria provided, single submitter	clinical testing	Myriad Genetics, Inc.	Mar 15, 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. Functional studies indicate this variant impacts protein function [PMID 12655562]. -
Likely pathogenic, criteria provided, single submitter	clinical testing	Counsyl	Jun 04, 2018	- -

Hereditary cancer-predisposing syndrome Pathogenic:2

Pathogenic, criteria provided, single submitter	clinical testing	Ambry Genetics	Nov 04, 2020	The c.677+1G>A intronic pathogenic mutation results from a G to A substitution one nucleotide after coding exon 8 of the MLH1 gene. This variant has been reported in multiple Lynch syndrome families (Palicio M et al. J Med Genet, 2002 Jun;39:E29; Rossi BM et al. BMC Cancer, 2017 Sep;17:623; Schneider NB et al. Cancer Med, 2018 05;7:2078-2088). This alteration was detected in 1/132 unrelated individuals and met Amsterdam I/II criteria for Lynch syndrome and their tumor testing results demonstrated high microsatellite instability was present (De Lellis L et al. PLoS One, 2013 Nov;8:e81194). Another alteration impacting the same donor site (c.677+1G>T) has also been reported in multiple Lynch syndrome families (Domingo E et al. J Med Genet. 2004 Sep;41(9):664-8; Lagerstedt Robinson K et al. J Natl Cancer Inst. 2007 Feb 21;99(4):291-9) and has been detected in a family meeting Amsterdam criteria with an MSI-H colon tumor exhibiting loss of MLH1 expression on IHC (Ambry internal data). 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 and may result in the creation or strengthening of a novel splice donor site. 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. -
Likely pathogenic, criteria provided, single submitter	clinical testing	Color Diagnostics, LLC DBA Color Health	Dec 18, 2018	- -

Lynch syndrome Pathogenic:1

Likely pathogenic, reviewed by expert panel

curation

International Society for Gastrointestinal Hereditary Tumours (InSiGHT)

Jun 21, 2019

Interrupts canonical donor splice site -

Hereditary nonpolyposis colorectal neoplasms Pathogenic:1

Pathogenic, criteria provided, single submitter

clinical testing

Labcorp Genetics (formerly Invitae), Labcorp

Jan 13, 2021

For these reasons, this variant has been classified as Pathogenic. A different variant affecting this nucleotide (c.677+1G>T) has been determined to be pathogenic (PMID: 27601186, 12624141, 15342696, 17312306). This suggests that this nucleotide is important for normal RNA splicing, and that other variants at this position may also be pathogenic. Loss-of-function variants in MLH1 are known to be pathogenic. This particular variant has been reported in the literature in a family affected with Lynch syndrome (PMID: 12070261). This sequence change affects a donor splice site in intron 8 of the MLH1 gene. It is expected to disrupt RNA splicing and likely results in an absent or disrupted protein product. -

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
MutationTaster	Benign	1.0	D;D;D;D;D;D
GERP RS		5.5
RBP_binding_hub_radar		0.0
RBP_regulation_power_radar		1.7

Splicing

Name	Calibrated prediction	Score	Prediction
dbscSNV1_ADA	Pathogenic	1.0
dbscSNV1_RF	Pathogenic	0.94
SpliceAI score (max)		0.99		Details are displayed if max score is > 0.2
DS_DG_spliceai		0.41		Position offset: -9
DS_DL_spliceai		0.99		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: rs267607778; hg19: chr3-37053591; COSMIC: COSV99212286; COSMIC: COSV99212286;