3-37048944-G-C

Variant summary

Our verdict is Uncertain significance. Variant got 4 ACMG points: 4P and 0B. PM1 PM2

The NM_000249.4(MLH1):c.2030G>C(p.Ser677Thr) variant causes a missense change involving the alteration of a conserved nucleotide. The variant was absent in control chromosomes in GnomAD project. Variant has been reported in ClinVar as Uncertain significance (★). Another variant affecting the same amino acid position, but resulting in a different missense (i.e. S677C) has been classified as Uncertain significance.

• Frequency: Genomes: not found (cov: 32)
• Consequence: MLH1 NM_000249.4 missense
• Clinical Significance: Uncertain significance criteria provided, single submitter U:1
• Conservation: PhyloP100: 7.37

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 4 ACMG points.

• PM1: In a hotspot region, there are 5 aminoacids with missense pathogenic changes in the window of +-8 aminoacids around while only 1 benign, 16 uncertain in NM_000249.4
• PM2: Very rare variant in population databases, with high coverage

Transcripts

RefSeq

Gene	Transcript	HGVSc	HGVSp	Effect	#exon/exons	MANE	UniProt
MLH1	NM_000249.4	c.2030G>C	p.Ser677Thr	missense_variant	18/19	ENST00000231790.8

Ensembl

Gene	Transcript	HGVSc	HGVSp	Effect	#exon/exons	TSL	MANE	Appris	UniProt
MLH1	ENST00000231790.8	c.2030G>C	p.Ser677Thr	missense_variant	18/19	1	NM_000249.4	P1

Frequencies

GnomAD3 genomes Cov.: 32

GnomAD4 exome Cov.: 31

GnomAD4 genome Cov.: 32

ClinVar

Significance: Uncertain significance

Submissions summary: Uncertain:1

Revision: criteria provided, single submitter

Submissions by phenotype

Hereditary nonpolyposis colorectal neoplasms Uncertain:1

Uncertain significance, criteria provided, single submitter

clinical testing

Invitae

Aug 17, 2021

This sequence change replaces serine with threonine at codon 677 of the MLH1 protein (p.Ser677Thr). The serine residue is moderately conserved and there is a small physicochemical difference between serine and threonine. This variant is not present in population databases (ExAC no frequency). This variant has not been reported in the literature in individuals affected with MLH1-related conditions. 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. -

Computational scores

Source: dbNSFP v4.3

Name	Calibrated prediction	Score	Prediction
AlphaMissense	Benign	0.22
BayesDel_addAF	Pathogenic	0.30	D
BayesDel_noAF	Pathogenic	0.19
Cadd	Uncertain	25
Dann	Uncertain	0.99
DEOGEN2	Uncertain	0.61	D;.;.;.;.;.
Eigen	Uncertain	0.52
Eigen_PC	Uncertain	0.62
FATHMM_MKL	Pathogenic	0.97	D
LIST_S2	Benign	0.83	T;T;.;.;.;T
M_CAP	Uncertain	0.13	D
MetaRNN	Uncertain	0.63	D;D;D;D;D;D
MetaSVM	Uncertain	0.54	D
MutationAssessor	Uncertain	2.2	M;.;.;.;.;.
MutationTaster	Benign	1.0	D;D;D;D;D;D
PrimateAI	Uncertain	0.62	T
PROVEAN	Benign	-0.80	N;N;N;N;N;N
REVEL	Uncertain	0.54
Sift	Uncertain	0.022	D;T;T;T;T;T
Sift4G	Uncertain	0.051	T;D;D;D;D;D
Polyphen		0.63	P;.;.;.;.;.
Vest4		0.59
MutPred		0.43		Loss of ubiquitination at K678 (P = 0.0787);.;.;.;.;.;
MVP		0.93
MPC		0.068
ClinPred		0.86	D
GERP RS		5.9
Varity_R		0.77
gMVP		0.72

Splicing

Name	Calibrated prediction	Score	Prediction
SpliceAI score (max)		0.030		Details are displayed if max score is > 0.2

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

Publications

No publications associated with this variant yet.

Other links and lift over

hg19: chr3-37090435;