rs863224636

chr3-37048555-C-Achr3-37048555-C-Gchr3-37048555-C-T

Variant summary

Our verdict is Uncertain significance. Variant got 3 ACMG points: 4P and 1B. PM1 PM2 BP4

The NM_000249.4(MLH1):c.1935C>A(p.Asn645Lys) variant causes a missense 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. 13/21 in silico tools predict a benign outcome for this variant. Variant has been reported in ClinVar as Uncertain significance (★★). Another nucleotide change resulting in same amino acid change has been previously reported as Uncertain significancein ClinVar. Another variant affecting the same amino acid position, but resulting in a different missense (i.e. N645S) has been classified as Uncertain significance.

• Frequency: Genomes: not found (cov: 31)
• Consequence: MLH1 NM_000249.4 missense
• Clinical Significance: Uncertain significance criteria provided, multiple submitters, no conflicts U:2
• Conservation: PhyloP100: 0.781

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 Uncertain_significance. Variant got 3 ACMG points.

• PM1: In a hotspot region, there are 6 aminoacids with missense pathogenic changes in the window of +-8 aminoacids around while only 2 benign, 14 uncertain in NM_000249.4
• PM2: Very rare variant in population databases, with high coverage
• BP4: Computational evidence support a benign effect (MetaRNN=0.42145002).

Transcripts

RefSeq

Gene	Transcript	HGVSc	HGVSp	Effect	#exon/exons	MANE	UniProt
MLH1	NM_000249.4	c.1935C>A	p.Asn645Lys	missense_variant	17/19	ENST00000231790.8

Ensembl

Gene	Transcript	HGVSc	HGVSp	Effect	#exon/exons	TSL	MANE	Appris	UniProt
MLH1	ENST00000231790.8	c.1935C>A	p.Asn645Lys	missense_variant	17/19	1	NM_000249.4	P1

Frequencies

GnomAD3 genomes Cov.: 31

GnomAD4 exome Cov.: 31

GnomAD4 genome Cov.: 31

ClinVar

Significance: Uncertain significance

Submissions summary: Uncertain:2

Revision: criteria provided, multiple submitters, no conflicts

Submissions by phenotype

Hereditary nonpolyposis colorectal neoplasms Uncertain:1

Uncertain significance, criteria provided, single submitter

clinical testing

Invitae

Jun 21, 2023

This sequence change replaces asparagine, which is neutral and polar, with lysine, which is basic and polar, at codon 645 of the MLH1 protein (p.Asn645Lys). This variant is not present in population databases (gnomAD no frequency). This variant has not been reported in the literature in individuals affected with MLH1-related conditions. ClinVar contains an entry for this variant (Variation ID: 233213). 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 not expected to disrupt MLH1 protein function. 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. -

Hereditary cancer-predisposing syndrome Uncertain:1

Uncertain significance, criteria provided, single submitter

clinical testing

Ambry Genetics

Aug 05, 2015

The p.N645K variant (also known as c.1935C>A), located in coding exon 17 of the MLH1 gene, results from a C to A substitution at nucleotide position 1935. The asparagine at codon 645 is replaced by lysine, an amino acid with similar properties. This variant was not reported in population based cohorts in the following databases: Database of Single Nucleotide Polymorphisms (dbSNP), NHLBI Exome Sequencing Project (ESP), and 1000 Genomes Project. In the ESP, this variant was not observed in 6503 samples (13006 alleles) with coverage at this position. To date, this alteration has been detected with an allele frequency of approximately 0.002% (greater than 115000 alleles tested) in our clinical cohort. This amino acid position is well conserved in available vertebrate species. In addition, the in silico prediction for this alteration is inconclusive. In addition, this alteration is predicted to be benign by MAPP-MMR in silico analyses (Chao E et al. Hum Mutat. 2008 Jun;29(6):852-60). Since supporting evidence is limited at this time, the clinical significance of p.N645K remains unclear. -

Computational scores

Source: dbNSFP v4.3

Name	Calibrated prediction	Score	Prediction
AlphaMissense	Benign	0.19
BayesDel_addAF	Uncertain	0.054	T
BayesDel_noAF	Benign	-0.16
Cadd	Benign	16
Dann	Benign	0.93
DEOGEN2	Uncertain	0.74	D;.;.;.;.;.
Eigen	Benign	-0.52
Eigen_PC	Benign	-0.36
FATHMM_MKL	Uncertain	0.88	D
LIST_S2	Uncertain	0.89	D;D;.;.;.;D
M_CAP	Benign	0.036	D
MetaRNN	Benign	0.42	T;T;T;T;T;T
MetaSVM	Benign	-0.56	T
MutationAssessor	Benign	1.2	L;.;.;.;.;.
MutationTaster	Benign	1.0	D;D;D;D;D;D
PrimateAI	Uncertain	0.57	T
PROVEAN	Benign	-2.0	N;N;N;N;N;N
REVEL	Uncertain	0.36
Sift	Benign	0.83	T;T;T;T;T;T
Sift4G	Benign	1.0	T;T;T;T;T;T
Polyphen		0.0030	B;.;.;.;.;.
Vest4		0.57
MutPred		0.56		Gain of methylation at N645 (P = 0.018);.;.;.;.;.;
MVP		0.87
MPC		0.077
ClinPred		0.27	T
GERP RS		2.1
Varity_R		0.43
gMVP		0.46

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: rs863224636; hg19: chr3-37090046;