rs397514684

Positions:

• chr3-37000965-T-C
• chr3-37000965-T-G

Variant summary

Our verdict is Likely pathogenic. Variant got 7 ACMG points: 7P and 0B. PM2 PP3_Strong PP5

The NM_000249.4(MLH1):​c.218T>C​(p.Leu73Pro) variant causes a missense 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. 13/21 in silico tools predict a damaging outcome for this variant. Variant has been reported in ClinVar as Conflicting classifications of pathogenicity (no stars). Synonymous variant affecting the same amino acid position (i.e. L73L) has been classified as Pathogenic.

• Frequency: Genomes: not found (cov: 32)
• Consequence: MLH1 NM_000249.4 missense
• Clinical Significance: Conflicting classifications of pathogenicity criteria provided, conflicting classifications P:2 U:1
• Conservation: PhyloP100: 7.56

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 Likely_pathogenic. Variant got 7 ACMG points.

• PM2: Very rare variant in population databases, with high coverage
• PP3: MetaRNN computational evidence supports a deleterious effect, 0.987
• PP5: Variant 3-37000965-T-C is Pathogenic according to our data. Variant chr3-37000965-T-C is described in ClinVar as [Conflicting_classifications_of_pathogenicity]. Clinvar id is 1365656.We mark this variant Likely_pathogenic, oryginal submissions are: {Likely_pathogenic=2, Uncertain_significance=1}.

Transcripts

RefSeq

Gene	Transcript	HGVSc	HGVSp	Effect	#exon/exons	MANE	Protein	UniProt
MLH1	NM_000249.4	c.218T>C	p.Leu73Pro	missense_variant	3/19	ENST00000231790.8	NP_000240.1

Ensembl

Gene	Transcript	HGVSc	HGVSp	Effect	#exon/exons	TSL	MANE	Protein	Appris	UniProt
MLH1	ENST00000231790.8	c.218T>C	p.Leu73Pro	missense_variant	3/19	1	NM_000249.4	ENSP00000231790	P1

Frequencies

GnomAD3 genomes Cov.: 32

GnomAD4 exome Cov.: 28

GnomAD4 genome Cov.: 32

ClinVar

Significance: Conflicting classifications of pathogenicity

Submissions summary: Pathogenic:2 Uncertain:1

Revision: criteria provided, conflicting classifications

Submissions by phenotype

Colorectal cancer, hereditary nonpolyposis, type 2 Pathogenic:1

Likely pathogenic, criteria provided, single submitter

clinical testing

Myriad Genetics, Inc.

Jul 12, 2023

This variant is considered likely pathogenic. Functional studies indicate this variant impacts protein function [PMID:22736432]. This variant is expected to disrupt protein structure [Myriad internal data]. -

Hereditary cancer-predisposing syndrome Pathogenic:1

Likely pathogenic, criteria provided, single submitter

clinical testing

Ambry Genetics

Mar 31, 2023

The p.L73P variant (also known as c.218T>C), located in coding exon 3 of the MLH1 gene, results from a T to C substitution at nucleotide position 218. The leucine at codon 73 is replaced by proline, an amino acid with similar properties. This alteration was identified in an individual meeting Amsterdam II criteria whose tumor demonstrated high microsatellite instability and loss of MLH1 and PMS2 expression by immunohistochemistry (Ambry internal data). This alteration was also identified in an individual diagnosed with colorectal cancer at age 36 that demonstrated microsatellite instability (Borràs E et al. Hum. Mutat., 2012 Nov;33:1576-88). This alteration was detected in an individual with a personal and family history of colorectal cancer who was reported to have Lynch syndrome (Wang X et al. Carcinogenesis, 2018 05;39:708-718). In an in vitro complementation assay, this variant was reported to have deficient mismatch repair (MMR) activity relative to wild type MLH1 (Borràs E et al. Hum. Mutat., 2012 Nov;33:1576-88). In a functional genetic screen performed in yeast, this variant was identified and demonstrated an intermediate mutator phenotype indicating an approximate 34–66% decrease in MMR activity (Ellison AR et al. Nucleic Acids Res., 2004 Oct;32:5321-38). Based on an internal structural analysis, this variant is more disruptive than known nearby pathogenic variants (Wu H et al. Acta Crystallogr F Struct Biol Commun, 2015 Aug;71:981-5). This variant is considered to be rare based on population cohorts in the Genome Aggregation Database (gnomAD). This amino acid position is well conserved in available vertebrate species. In addition, this alteration is predicted to be deleterious by in silico analysis. Based on the majority of available evidence to date, this variant is likely to be pathogenic. -

Hereditary nonpolyposis colorectal neoplasms Uncertain:1

Uncertain significance, criteria provided, single submitter

clinical testing

Labcorp Genetics (formerly Invitae), Labcorp

Apr 17, 2021

Experimental studies have shown that this variant affects MLH1 protein function (PMID: 22736432, 15475387). In summary, the available evidence is currently insufficient to determine the role of this variant in disease. Therefore, it has been classified as a Variant of Uncertain Significance. Advanced modeling of protein sequence and biophysical properties (such as structural, functional, and spatial information, amino acid conservation, physicochemical variation, residue mobility, and thermodynamic stability) performed at Invitae indicates that this missense variant is expected to disrupt MLH1 protein function. This variant has been observed in individual(s) with clinical features of Lynch syndrome (PMID: 22736432). This variant is not present in population databases (ExAC no frequency). This sequence change replaces leucine with proline at codon 73 of the MLH1 protein (p.Leu73Pro). The leucine residue is moderately conserved and there is a moderate physicochemical difference between leucine and proline. -

Computational scores

Source: dbNSFP v4.3

Name	Calibrated prediction	Score	Prediction
AlphaMissense	Pathogenic	0.99
BayesDel_addAF	Pathogenic	0.56	D
BayesDel_noAF	Pathogenic	0.57
CADD	Pathogenic	29
DANN	Pathogenic	1.0
DEOGEN2	Pathogenic	0.95	D
Eigen	Pathogenic	0.74
Eigen_PC	Pathogenic	0.74
FATHMM_MKL	Pathogenic	0.98	D
LIST_S2	Pathogenic	0.98	D
M_CAP	Pathogenic	0.40	D
MetaRNN	Pathogenic	0.99	D
MetaSVM	Uncertain	0.65	D
MutationAssessor	Pathogenic	4.5	H
MutationTaster	Benign	1.0	D;D;D;D;D;D
PrimateAI	Pathogenic	0.81	D
PROVEAN	Pathogenic	-5.3	D
REVEL	Pathogenic	0.96
Sift	Uncertain	0.0010	D
Sift4G	Uncertain	0.0020	D
Polyphen		1.0	D
Vest4		0.98
MutPred		0.89		Gain of disorder (P = 0.0294);
MVP		1.0
MPC		0.50
ClinPred		1.0	D
GERP RS		6.0
RBP_binding_hub_radar		0.0
RBP_regulation_power_radar		1.7
Varity_R		0.99
gMVP		0.93

Splicing

Name	Calibrated prediction	Score	Prediction
SpliceAI score (max)		0.010		Details are displayed if max score is > 0.2

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

Publications

LitVar

Other links and lift over

dbSNP: rs397514684; hg19: chr3-37042456;