rs587778970

chr3-37048944-G-Achr3-37048944-G-Cchr3-37048944-G-T

Variant summary

Our verdict is Uncertain significance. Variant got 5 ACMG points: 5P and 0B. PM1 PM2 PP3

The NM_000249.4(MLH1):c.2030G>A(p.Ser677Asn) 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 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, multiple submitters, no conflicts U:3
• 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 5 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
• PP3: MetaRNN computational evidence supports a deleterious effect, 0.755

Transcripts

RefSeq

Gene	Transcript	HGVSc	HGVSp	Effect	#exon/exons	MANE	UniProt
MLH1	NM_000249.4	c.2030G>A	p.Ser677Asn	missense_variant	18/19	ENST00000231790.8

Ensembl

Gene	Transcript	HGVSc	HGVSp	Effect	#exon/exons	TSL	MANE	Appris	UniProt
MLH1	ENST00000231790.8	c.2030G>A	p.Ser677Asn	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:3

Revision: criteria provided, multiple submitters, no conflicts

Submissions by phenotype

not provided Uncertain:1

Uncertain significance, criteria provided, single submitter

clinical testing

GeneDx

Jan 07, 2014

This variant is denoted MLH1 c.2030G>A at the cDNA level, p.Ser677Asn (S677N) at the protein level, and results in the change of a Serine to an Asparagine (AGT>AAT). This variant has been observed in a patient with colorectal cancer <50 years of age (Hardt 2011). MLH1 Ser677Asn was not observed in approximately 6,500 individuals of European and African American ancestry in the NHLBI Exome Sequencing Project. This variant is a conservative substitution of one neutral polar amino acid for another, altering a position that is well conserved throughout evolution and is not located in a known functional domain. Multiple in silico algorithms predict that this variant may be damaging to protein structure and function. Based on the currently available information, we consider MLH1 Ser677Asn to be a variant of uncertain significance. -

Hereditary nonpolyposis colorectal neoplasms Uncertain:1

Uncertain significance, criteria provided, single submitter

clinical testing

Invitae

Sep 04, 2021

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. Algorithms developed to predict the effect of missense changes on protein structure and function are either unavailable or do not agree on the potential impact of this missense change (SIFT: "Deleterious"; PolyPhen-2: "Benign"; Align-GVGD: "Class C0"). This missense change has been observed in individual(s) with colorectal cancer (PMID: 21404117). This variant is not present in population databases (ExAC no frequency). This sequence change replaces serine with asparagine at codon 677 of the MLH1 protein (p.Ser677Asn). The serine residue is moderately conserved and there is a small physicochemical difference between serine and asparagine. -

Hereditary cancer-predisposing syndrome Uncertain:1

Uncertain significance, criteria provided, single submitter

clinical testing

Color Diagnostics, LLC DBA Color Health

Nov 15, 2022

This missense variant replaces serine with asparagine at codon 677 of the MLH1 protein. Computational prediction is inconclusive regarding the impact of this variant on protein structure and function (internally defined REVEL score threshold 0.5 < inconclusive < 0.7, PMID: 27666373). To our knowledge, functional studies have not been reported for this variant. This variant has been reported in an individual affected with colorectal cancer (PMID: 21404117). This variant has not been identified in the general population by the Genome Aggregation Database (gnomAD). The available evidence is insufficient to determine the role of this variant in disease conclusively. Therefore, this variant is classified as a Variant of Uncertain Significance. -

Computational scores

Source: dbNSFP v4.3

Name	Calibrated prediction	Score	Prediction
AlphaMissense	Pathogenic	0.73
BayesDel_addAF	Pathogenic	0.21	D
BayesDel_noAF	Uncertain	0.070
Cadd	Uncertain	25
Dann	Uncertain	1.0
DEOGEN2	Pathogenic	0.82	D;.;.;.;.;.
Eigen	Pathogenic	0.76
Eigen_PC	Pathogenic	0.79
FATHMM_MKL	Uncertain	0.97	D
LIST_S2	Uncertain	0.87	D;D;.;.;.;D
M_CAP	Uncertain	0.19	D
MetaRNN	Pathogenic	0.76	D;D;D;D;D;D
MetaSVM	Pathogenic	0.85	D
MutationAssessor	Uncertain	2.8	M;.;.;.;.;.
MutationTaster	Benign	1.0	D;D;D;D;D;D
PrimateAI	Uncertain	0.66	T
PROVEAN	Benign	-2.2	N;N;N;N;N;N
REVEL	Uncertain	0.60
Sift	Uncertain	0.0070	D;D;D;D;D;T
Sift4G	Uncertain	0.010	D;D;D;D;D;D
Polyphen		0.97	D;.;.;.;.;.
Vest4		0.66
MutPred		0.43		Loss of disorder (P = 0.0992);.;.;.;.;.;
MVP		0.90
MPC		0.074
ClinPred		0.94	D
GERP RS		5.9
Varity_R		0.94
gMVP		0.82

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: rs587778970; hg19: chr3-37090435;