3-37042331-G-T

Variant summary

Our verdict is Pathogenic. Variant got 11 ACMG points: 11P and 0B. PM2 PP3 PP5_Very_Strong

The NM_000249.4(MLH1):c.1731G>T(p.Ser577=) variant causes a splice region, synonymous change involving the alteration of a non-conserved nucleotide. The variant was absent in control chromosomes in GnomAD project. In-silico tool predicts a benign outcome for this variant. 3/3 splice prediction tools predicting alterations to normal splicing. Variant has been reported in ClinVar as Likely pathogenic (★★). Synonymous variant affecting the same amino acid position (i.e. S577S) has been classified as Pathogenic.

• Frequency:
  • Genomes: not found (cov: 32)
  • Exomes 𝑓: 0.0 (0 hom.)
  • Failed GnomAD Quality Control
• Consequence: MLH1 NM_000249.4 splice_region, synonymous
• Scores: Splicing: ADA: 0.9698
• Clinical Significance: Pathogenic/Likely pathogenic criteria provided, multiple submitters, no conflicts P:3
• Conservation: PhyloP100: 0.502

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 11 ACMG points.

• 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 3-37042331-G-T is Pathogenic according to our data. Variant chr3-37042331-G-T is described in ClinVar as [Likely_pathogenic]. Clinvar id is 525656.Status of the report is criteria_provided_multiple_submitters_no_conflicts, 2 stars.

Transcripts

RefSeq

Gene	Transcript	HGVSc	HGVSp	Effect	#exon/exons	MANE	UniProt
MLH1	NM_000249.4	c.1731G>T	p.Ser577=	splice_region_variant, synonymous_variant	15/19	ENST00000231790.8

Ensembl

Gene	Transcript	HGVSc	HGVSp	Effect	#exon/exons	TSL	MANE	Appris	UniProt
MLH1	ENST00000231790.8	c.1731G>T	p.Ser577=	splice_region_variant, synonymous_variant	15/19	1	NM_000249.4	P1

Frequencies

GnomAD3 genomes Cov.: 32

GnomAD4 exome Data not reliable, filtered out with message: AC0 AF: 0.00 AC: 0 AN: 1443522 Hom.: 0 Cov.: 29 AF XY: 0.00 AC XY: 0 AN XY: 719466

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/Likely pathogenic

Submissions summary: Pathogenic:3

Revision: criteria provided, multiple submitters, no conflicts

Submissions by phenotype

Colorectal cancer, hereditary nonpolyposis, type 2 Pathogenic:1

Pathogenic, criteria provided, single submitter

clinical testing

Myriad Genetics, Inc.

Jun 09, 2023

This variant is considered pathogenic. This variant is strongly associated with more severe personal and family histories of cancer, typical for individuals with pathogenic variants in this gene [PMID: 25085752, 27363726]. mRNA analysis has demonstrated abnormal mRNA splicing occurs [Myriad internal data]. -

Hereditary nonpolyposis colorectal neoplasms Pathogenic:1

Pathogenic, criteria provided, single submitter

clinical testing

Invitae

Jun 11, 2021

This sequence change affects codon 577 of the MLH1 mRNA. It is a 'silent' change, meaning that it does not change the encoded amino acid sequence of the MLH1 protein. This variant also falls at the last nucleotide of exon 15, which is part of the consensus splice site for this exon. This variant is not present in population databases (ExAC no frequency). For these reasons, this variant has been classified as Pathogenic. This variant disrupts the c.1731G nucleotide in the MLH1 gene. Other variant(s) that disrupt this nucleotide have been determined to be pathogenic (PMID: 16341550, 15849733, 20223024, 18561205, 16451135). This suggests that this nucleotide is clinically significant, and that variants that disrupt this position are likely to be disease-causing. Nucleotide substitutions within 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, but this prediction has not been confirmed by published transcriptional studies. This variant has been observed in individual(s) with clinical features of Lynch syndrome (PMID: 28135145, 25110875, Invitae). It has also been observed to segregate with disease in related individuals. ClinVar contains an entry for this variant (Variation ID: 525656). -

Hereditary cancer-predisposing syndrome Pathogenic:1

Likely pathogenic, criteria provided, single submitter

clinical testing

Ambry Genetics

Jun 24, 2020

The c.1731G>T variant (also known as p.S577S), located in coding exon 15 of the MLH1 gene, results from a G to T substitution at nucleotide position 1731. This nucleotide substitution does not change the amino acid at codon 577. However, this change occurs in the last base pair of coding exon 15, which makes it likely to have some effect on normal mRNA splicing. Another variant at the same nucleotide position, c.1731G>A, has been reported as pathogenic based on being identified in several probands who met Amsterdam criteria for Lynch syndrome and had loss of MLH1 expression on immunohistochemistry in their tumors (Pistorius SR et al. Int. J. Colorectal Dis. 2000 Nov;15(5-6):255-63; Mangold E et al. Int. J. Cancer. 2005 Sep;116(5):692-702; Jasperson KW et al. Fam. Cancer, 2010 Jun;9:99-107). In addition, splicing data reported in multiple studies demonstrate out-of-frame exon 15 skipping for the c.1731G>A variant (Kohonen-Corish M et al. Am. J. Hum. Genet. 1996 Oct;59(4):818-24; Auclair J et al. Hum. Mutat. 2006 Feb;27(2):145-54; Pagenstecher C et.al. Hum. Genet. 2006 Mar;119:9-22; Tournier I et al. Hum. Mutat. 2008 Dec;29(12):1412-24). This variant was not reported in population-based cohorts in the Genome Aggregation Database (gnomAD). This nucleotide position is highly conserved through mammals, but not in all available vertebrate species. Using the BDGP and ESEfinder splice site prediction tools, this alteration is predicted to weaken the efficiency of the native splice donor site; however, direct evidence is unavailable. 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_noAF	Benign	-0.36
Cadd	Benign	20
Dann	Benign	0.86
RBP_binding_hub_radar		0.0
RBP_regulation_power_radar		2.8

Splicing

Name	Calibrated prediction	Score	Prediction
dbscSNV1_ADA	Pathogenic	0.97
dbscSNV1_RF	Pathogenic	0.79
SpliceAI score (max)		0.64		Details are displayed if max score is > 0.2
DS_DL_spliceai		0.64		Position offset: 0

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

Publications

LitVar

Other links and lift over

dbSNP: rs63751657; hg19: chr3-37083822;