rs267607850

Positions:

• chr3-37042336-G-A

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.1731+5G>A variant causes a splice region, intron change involving the alteration of a 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 Pathogenic (★★★).

• Frequency: Genomes: not found (cov: 32)
• Consequence: MLH1 NM_000249.4 splice_region, intron
• Scores: Splicing: ADA: 0.9999
• Clinical Significance: Pathogenic reviewed by expert panel P:5
• Conservation: PhyloP100: 8.93

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 11 ACMG points.

• PM2: Very rare variant in population databases, with high coverage
• PP3: Multiple lines of computational evidence support a deleterious effect 4: dbscSNV1_ADA, dbscSNV1_RF, max_spliceai, phyloP100way_vertebrate [when BayesDel_noAF, Cadd was below the threshold]
• PP5: Variant 3-37042336-G-A is Pathogenic according to our data. Variant chr3-37042336-G-A is described in ClinVar as [Pathogenic]. Clinvar id is 89854.Status of the report is reviewed_by_expert_panel, 3 stars. Variant chr3-37042336-G-A is described in Lovd as [Pathogenic]. Variant chr3-37042336-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.1731+5G>A		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.1731+5G>A		splice_region_variant, intron_variant		1	NM_000249.4	ENSP00000231790.3

Frequencies

GnomAD3 genomes Cov.: 32

GnomAD4 exome Cov.: 28

GnomAD4 genome Cov.: 32

ClinVar

Significance: Pathogenic

Submissions summary: Pathogenic:5

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 21, 2023

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

Lynch syndrome Pathogenic:1

Pathogenic, reviewed by expert panel

curation

International Society for Gastrointestinal Hereditary Tumours (InSiGHT)

Jun 21, 2019

Variant causes splicing aberration leading to truncated protein: complete inactivation of variant allele -

not provided Pathogenic:1

Likely pathogenic, criteria provided, single submitter

clinical testing

GeneDx

Feb 17, 2022

Not observed at significant frequency in large population cohorts (gnomAD); This variant is associated with the following publications: (PMID: 19685281, 18561205) -

Hereditary nonpolyposis colorectal neoplasms Pathogenic:1

Likely pathogenic, criteria provided, single submitter

clinical testing

Labcorp Genetics (formerly Invitae), Labcorp

Nov 14, 2019

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. Nucleotide substitutions within the consensus splice site are a relatively common cause of aberrant splicing (PMID: 17576681, 9536098). Experimental studies have shown that this variant disrupts mRNA splicing (PMID: 18561205, 19685281). This variant has been observed in individual(s) with clinical features of Lynch syndrome (PMID: 18561205, 19685281, Invitae). This variant is not present in population databases (ExAC no frequency). This sequence change falls in intron 15 of the MLH1 gene. It does not directly change the encoded amino acid sequence of the MLH1 protein, but it affects a nucleotide within the consensus splice site of the intron. -

Hereditary cancer-predisposing syndrome Pathogenic:1

Pathogenic, criteria provided, single submitter

clinical testing

Ambry Genetics

Sep 11, 2020

The c.1731+5G>A intronic pathogenic mutation results from a G to A substitution 5 nucleotides after coding exon 15 in the MLH1 gene. This alteration has been reported in an individual with colorectal cancer whose family history met Amsterdam criteria for Lynch syndrome (Naruse H et al. Fam. Cancer 2009 Aug;8(4):509-17). This alteration has also been identified in an individual whose uterine tumor displayed loss of both MLH1/PMS2 staining on immunohistochemistry (IHC) with absent MLH1 promoter hypermethylation and had a family history of Lynch syndrome-associated cancers (Ambry internal data). Furthermore, RNA functional studies demonstrated exon 15 skipping for this variant resulting in a truncated transcript subject to nonsense mediated decay (Tournier I et al. Hum. Mutat. 2008 Dec;29(12):1412-24; Naruse H et al. Fam. Cancer 2009 Aug;8(4):509-17). In silico splice site analysis predicts that this alteration will weaken the native splice donor site. Based on the supporting evidence, this alteration is interpreted as a disease-causing mutation. -

Computational scores

Source: dbNSFP v4.3

Name	Calibrated prediction	Score	Prediction
BayesDel_noAF	Benign	-0.17
CADD	Benign	21
DANN	Uncertain	0.97
RBP_binding_hub_radar		0.0
RBP_regulation_power_radar		1.1

Splicing

Name	Calibrated prediction	Score	Prediction
dbscSNV1_ADA	Pathogenic	1.0
dbscSNV1_RF	Pathogenic	0.95
SpliceAI score (max)		0.65		Details are displayed if max score is > 0.2
DS_DL_spliceai		0.65		Position offset: -5

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

Publications

LitVar

Other links and lift over

dbSNP: rs267607850; hg19: chr3-37083827;