rs63749906

Positions:

• chr3-36993651-T-A
• chr3-36993651-T-G

Variant summary

Our verdict is Pathogenic. Variant got 15 ACMG points: 15P and 0B. PS1 PM1 PM2 PM5 PP3_Strong PP5

The NM_000249.4(MLH1):​c.104T>A​(p.Met35Lys) 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. Variant has been reported in ClinVar as Conflicting classifications of pathogenicity (no stars). Another nucleotide change resulting in the same amino acid substitution has been previously reported as Pathogenic in Lovd. Another variant affecting the same amino acid position, but resulting in a different missense (i.e. M35N) has been classified as Likely pathogenic.

• Frequency: Genomes: not found (cov: 33)
• Consequence: MLH1 NM_000249.4 missense
• Clinical Significance: Conflicting classifications of pathogenicity criteria provided, conflicting classifications P:1 U:1
• Conservation: PhyloP100: 7.62

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 15 ACMG points.

• PS1: Transcript NM_000249.4 (MLH1) is affected with MISSENSE_VARIANT having same AA change as one Pathogenic present in Lovd
• PM1: In a helix (size 13) in uniprot entity MLH1_HUMAN there are 19 pathogenic changes around while only 8 benign (70%) in NM_000249.4
• PM2: Very rare variant in population databases, with high coverage
• PM5: Other missense variant is known to change same aminoacid residue: Variant chrnull-null-null-null is described in UniProt as null.
• PP3: MetaRNN computational evidence supports a deleterious effect, 0.991
• PP5: Variant 3-36993651-T-A is Pathogenic according to our data. Variant chr3-36993651-T-A is described in ClinVar as [Conflicting_classifications_of_pathogenicity]. Clinvar id is 974958.We mark this variant Likely_pathogenic, oryginal submissions are: {Uncertain_significance=1, Likely_pathogenic=1}.

Transcripts

RefSeq

Gene	Transcript	HGVSc	HGVSp	Effect	#exon/exons	MANE	Protein	UniProt
MLH1	NM_000249.4	c.104T>A	p.Met35Lys	missense_variant	1/19	ENST00000231790.8	NP_000240.1

Ensembl

Gene	Transcript	HGVSc	HGVSp	Effect	#exon/exons	TSL	MANE	Protein	Appris	UniProt
MLH1	ENST00000231790.8	c.104T>A	p.Met35Lys	missense_variant	1/19	1	NM_000249.4	ENSP00000231790.3

Frequencies

GnomAD3 genomes Cov.: 33

GnomAD4 exome Cov.: 31

GnomAD4 genome Cov.: 33

ClinVar

Significance: Conflicting classifications of pathogenicity

Submissions summary: Pathogenic:1 Uncertain:1

Revision: criteria provided, conflicting classifications

Submissions by phenotype

Hereditary nonpolyposis colorectal neoplasms Pathogenic:1

Likely pathogenic, criteria provided, single submitter

clinical testing

Labcorp Genetics (formerly Invitae), Labcorp

Mar 24, 2023

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 variant disrupts the p.Met35 amino acid residue in MLH1. Other variant(s) that disrupt this residue have been determined to be pathogenic (PMID: 8521398, 9697702, 10082584, 12810663, 17510385, 24362816). This suggests that this residue is clinically significant, and that variants that disrupt this residue are likely to be disease-causing. 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) has been performed at Invitae for this missense variant, however the output from this modeling did not meet the statistical confidence thresholds required to predict the impact of this variant on MLH1 protein function. ClinVar contains an entry for this variant (Variation ID: 974958). This missense change has been observed in individual(s) with clinical features of Lynch syndrome (PMID: 16451135, 21520333, 34178123). This variant is not present in population databases (gnomAD no frequency). This sequence change replaces methionine, which is neutral and non-polar, with lysine, which is basic and polar, at codon 35 of the MLH1 protein (p.Met35Lys). -

not specified Uncertain:1

Uncertain significance, criteria provided, single submitter

clinical testing

Women's Health and Genetics/Laboratory Corporation of America, LabCorp

Jul 22, 2020

Variant summary: MLH1 c.104T>A (p.Met35Lys) results in a non-conservative amino acid change located in the DNA mismatch repair protein family, N-terminal domain of the encoded protein sequence. Five of five in-silico tools predict a damaging effect of the variant on protein function. The variant was absent in 250776 control chromosomes. The available data on variant occurrences in the general population are insufficient to allow any conclusion about variant significance. c.104T>A has been reported in the literature in at least one individual with Lynch Syndrome or suspected Lynch Syndrome (Kurzawski_2006). This report does not provide unequivocal conclusions about association of the variant with Lynch Syndrome. To our knowledge, no experimental evidence demonstrating an impact on protein function has been reported. No clinical diagnostic laboratories have submitted clinical-significance assessments for this variant to ClinVar after 2014. Based on the evidence outlined above, the variant was classified as uncertain significance. -

Computational scores

Source: dbNSFP v4.3

Name	Calibrated prediction	Score	Prediction
AlphaMissense	Pathogenic	0.99
BayesDel_addAF	Pathogenic	0.46	D
BayesDel_noAF	Pathogenic	0.43
CADD	Pathogenic	32
DANN	Uncertain	0.99
DEOGEN2	Pathogenic	0.88	D
Eigen	Uncertain	0.58
Eigen_PC	Uncertain	0.63
FATHMM_MKL	Pathogenic	0.97	D
LIST_S2	Pathogenic	0.98	D
M_CAP	Pathogenic	0.39	D
MetaRNN	Pathogenic	0.99	D
MetaSVM	Uncertain	0.045	D
MutationAssessor	Uncertain	2.7	M
PrimateAI	Pathogenic	0.84	D
PROVEAN	Uncertain	-4.0	D
REVEL	Pathogenic	0.90
Sift	Uncertain	0.0010	D
Sift4G	Uncertain	0.0030	D
Polyphen		0.96	D
Vest4		0.98
MutPred		0.95		Gain of ubiquitination at M35 (P = 0.03);
MVP		0.99
MPC		0.44
ClinPred		1.0	D
GERP RS		6.0
RBP_binding_hub_radar		0.0
RBP_regulation_power_radar		1.6
Varity_R		0.99
gMVP		0.97

Splicing

Name	Calibrated prediction	Score	Prediction
SpliceAI score (max)		0.0		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: rs63749906; hg19: chr3-37035142;