3-37049020-A-G

Position:

• chr3-37049020-A-G

Variant summary

Our verdict is Pathogenic. Variant got 10 ACMG points: 10P and 0B. PM2 PP5_Very_Strong

The NM_000249.4(MLH1):​c.2103+3A>G variant causes a splice region, intron change. The variant was absent in control chromosomes in GnomAD project. In-silico tool predicts a benign outcome for this variant. 2/3 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_region, intron
• Scores: Splicing: ADA: 0.9981
• Clinical Significance: Pathogenic/Likely pathogenic criteria provided, multiple submitters, no conflicts P:6
• Conservation: PhyloP100: 5.28

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 10 ACMG points.

• PM2: Very rare variant in population databases, with high coverage
• PP5: Variant 3-37049020-A-G is Pathogenic according to our data. Variant chr3-37049020-A-G is described in ClinVar as [Likely_pathogenic]. Clinvar id is 90047.Status of the report is criteria_provided_multiple_submitters_no_conflicts, 2 stars. Variant chr3-37049020-A-G is described in Lovd as [Pathogenic].

Transcripts

RefSeq

Gene	Transcript	HGVSc	HGVSp	Effect	#exon/exons	MANE	Protein	UniProt
MLH1	NM_000249.4	c.2103+3A>G		splice_region_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.2103+3A>G		splice_region_variant, intron_variant		1	NM_000249.4	ENSP00000231790.3

Frequencies

GnomAD3 genomes Cov.: 32

GnomAD4 exome Cov.: 29

GnomAD4 genome Cov.: 32

ClinVar

Significance: Pathogenic/Likely pathogenic

Submissions summary: Pathogenic:6

Revision: criteria provided, multiple submitters, no conflicts

Submissions by phenotype

Colorectal cancer, hereditary nonpolyposis, type 2 Pathogenic:2

Likely pathogenic, criteria provided, single submitter	clinical testing	Baylor Genetics	Jun 08, 2023	- -
Likely pathogenic, criteria provided, single submitter	clinical testing	Myriad Genetics, Inc.	Feb 09, 2024	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. mRNA analysis has demonstrated abnormal mRNA splicing occurs [PMID: 32133419, 31641931, 38311346]. This variant has been reported in multiple individuals with clinical features of gene-specific disease [PMID: 21642682; Myriad internal data]. -

Hereditary cancer-predisposing syndrome Pathogenic:2

Pathogenic, criteria provided, single submitter	clinical testing	Ambry Genetics	Jul 26, 2021	The c.2103+3A>G intronic pathogenic mutation results from an A to G substitution 3 nucleotides after coding exon 18 in the MLH1 gene. This alteration was identified in individuals with a family history that met Amsterdam I criteria for Lynch syndrome and/or showed loss of MLH1 and PMS2 protein expression by immunohistochemistry in their colorectal tumors (Ambry internal data). This alteration was also identified in a French family suspected of having Lynch syndrome; however, the clinical phenotype and tumor characteristics were not provided (Bonadona, V et al. JAMA. 2011 Jun 8;305(22):2304-10). This nucleotide position is highly conserved in available vertebrate species. In silico splice site analysis predicts that this alteration may weaken the native splice donor site. RNA studies have demonstrated this alteration results in abnormal splicing in the set of samples tested (Ambry internal data). Based on the supporting evidence, this alteration is interpreted as a disease-causing mutation. -
Likely pathogenic, criteria provided, single submitter	clinical testing	Color Diagnostics, LLC DBA Color Health	Nov 07, 2022	This variant causes an A>G nucleotide substitution at the +3 position of intron 18 of the MLH1 RNA. Computational splicing tools predict that this variant may have a significant impact on RNA splicing. The Universal Mutation Database (UMD) reported the skipping of exon 18 as detected in the RT-PCR analysis of carrier RNA (http://www.umd.be/MLH1/4DACTION/Web_D_splice/53). This variant has been reported in a French family suspected of having Lynch syndrome (PMID: 21642682) and in individuals with a family history that met Amsterdam I criteria for Lynch syndrome and/or showed loss of MLH1 and PMS2 protein expression by immunohistochemistry in their colorectal tumors (ClinVar SCV000276974.5, communication with external laboratory). This variant has not been identified in the general population by the Genome Aggregation Database (gnomAD). Based on the available evidence, this variant is classified as Likely Pathogenic. -

not provided Pathogenic:1

Likely pathogenic, criteria provided, single submitter

clinical testing

Quest Diagnostics Nichols Institute San Juan Capistrano

Sep 01, 2023

The MLH1 c.2103+3A>G variant has been reported in the published literature in an individual with Lynch Syndrome (PMID: 21642682 (2011)). This variant was also determined to result in aberrant MLH1 splicing (PMID: 31642931 (2019)). In addition, internal laboratory data indicates that this variant was observed in an individual with colorectal cancer. This variant has not been reported in large, multi-ethnic general populations (Genome Aggregation Database, http://gnomad.broadinstitute.org). Analysis of this variant using software algorithms for the prediction of the effect of nucleotide changes on splicing yielded predictions that this variant may affect proper MLH1 mRNA splicing. Based on the available information, this variant is classified as likely pathogenic. -

Hereditary nonpolyposis colorectal neoplasms Pathogenic:1

Likely pathogenic, criteria provided, single submitter

clinical testing

Labcorp Genetics (formerly Invitae), Labcorp

May 27, 2022

In summary, the currently available evidence indicates that the variant is pathogenic, but additional data are needed to prove that conclusively. Therefore, this variant has been classified as Likely Pathogenic. This sequence change falls in intron 18 of the MLH1 gene. It does not directly change the encoded amino acid sequence of the MLH1 protein. It affects a nucleotide within the consensus splice site. This variant is not present in population databases (gnomAD no frequency). This variant has been observed in individuals with Lynch syndrome (Invitae; external communication). ClinVar contains an entry for this variant (Variation ID: 90047). Variants that disrupt the consensus splice site are a relatively common cause of aberrant splicing (PMID: 17576681, 9536098). Algorithms developed to predict the effect of sequence changes on RNA splicing suggest that this variant may disrupt the consensus splice site. -

Computational scores

Source: dbNSFP v4.3

Name	Calibrated prediction	Score	Prediction
BayesDel_noAF	Benign	-0.33
CADD	Benign	23
DANN	Benign	0.96

Splicing

Name	Calibrated prediction	Score	Prediction
dbscSNV1_ADA	Pathogenic	1.0
dbscSNV1_RF	Pathogenic	0.92
SpliceAI score (max)		0.42		Details are displayed if max score is > 0.2
DS_DL_spliceai		0.42		Position offset: -3

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

Publications

LitVar

Other links and lift over

dbSNP: rs587778976; hg19: chr3-37090511;