rs121912957

Positions:

• chr3-36996633-C-G
• chr3-36996633-C-T
• chr3-36996633-C-A

Variant summary

Our verdict is Uncertain significance. Variant got 4 ACMG points: 4P and 0B. PM2 PP3_Moderate

The NM_001167617.3(MLH1):​c.-159C>G variant causes a 5 prime UTR premature start codon gain change. 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 (★★).

• Frequency: Genomes: not found (cov: 32)
• Consequence: MLH1 NM_001167617.3 5_prime_UTR_premature_start_codon_gain
• Clinical Significance: Uncertain significance criteria provided, multiple submitters, no conflicts U:2
• Conservation: PhyloP100: 4.74

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]

MLH1 (HGNC:):

ACMG classification

Verdict is Uncertain_significance. Variant got 4 ACMG points.

• PM2: Very rare variant in population databases, with high coverage
• PP3: MetaRNN computational evidence supports a deleterious effect, 0.855

Transcripts

RefSeq

Gene	Transcript	HGVSc	HGVSp	Effect	#exon/exons	MANE	Protein	UniProt
MLH1	NM_000249.4	c.131C>G	p.Ser44Cys	missense_variant	2/19	ENST00000231790.8	NP_000240.1

Ensembl

Gene	Transcript	HGVSc	HGVSp	Effect	#exon/exons	TSL	MANE	Protein	Appris	UniProt
MLH1	ENST00000231790.8	c.131C>G	p.Ser44Cys	missense_variant	2/19	1	NM_000249.4	ENSP00000231790.3

Frequencies

GnomAD3 genomes Cov.: 32

GnomAD4 exome Cov.: 30

GnomAD4 genome Cov.: 32

EpiCase AF: 0.0000545

EpiControl AF: 0.00

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

Labcorp Genetics (formerly Invitae), Labcorp

Nov 11, 2020

This sequence change replaces serine with cysteine at codon 44 of the MLH1 protein (p.Ser44Cys). The serine residue is moderately conserved and there is a moderate physicochemical difference between serine and cysteine. 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. This variant disrupts the p.Ser44 amino acid residue in MLH1. Other variant(s) that disrupt this residue have been determined to be pathogenic (PMID: 8145827, 9697702, 10037723, 12810663, 17510385, 22753075, 24362816). This suggests that this residue is clinically significant, and that variants that disrupt this residue are likely to be disease-causing. Experimental studies have shown that this variant affects MLH1 protein function (PMID: 15475387). This variant has not been reported in the literature in individuals with MLH1-related conditions. ClinVar contains an entry for this variant (Variation ID: 639639). This variant is not present in population databases (ExAC no frequency). -

Hereditary cancer-predisposing syndrome Uncertain:1

Uncertain significance, criteria provided, single submitter

clinical testing

Ambry Genetics

Nov 28, 2018

The p.S44C variant (also known as c.131C>G), located in coding exon 2 of the MLH1 gene, results from a C to G substitution at nucleotide position 131. The serine at codon 44 is replaced by cysteine, an amino acid with dissimilar properties. In a functional study using Saccharomyces cerevisiae yeast, this alteration was found to confer a pronounced loss of mismatch repair function (Ellison AR et al. Nucleic Acids Res., 2004 Oct;32:5321-38). This amino acid position is not well conserved in available vertebrate species. In addition, this alteration is predicted to be deleterious by in silico analysis. In addition, this alteration is predicted to be deleterious by MAPP-MMR in silico analyses (Chao EC et al. Hum. Mutat. 2008 Jun;29:852-60). Since supporting evidence is limited at this time, the clinical significance of this alteration remains unclear. -

Computational scores

Source: dbNSFP v4.3

Name	Calibrated prediction	Score	Prediction
AlphaMissense	Benign	0.22
BayesDel_addAF	Pathogenic	0.26	D
BayesDel_noAF	Pathogenic	0.14
CADD	Uncertain	24
DANN	Uncertain	0.98
DEOGEN2	Pathogenic	0.87	D
Eigen	Uncertain	0.32
Eigen_PC	Uncertain	0.39
FATHMM_MKL	Uncertain	0.96	D
LIST_S2	Uncertain	0.91	D
M_CAP	Uncertain	0.13	D
MetaRNN	Pathogenic	0.85	D
MetaSVM	Uncertain	0.60	D
MutationAssessor	Pathogenic	3.1	M
PrimateAI	Uncertain	0.60	T
PROVEAN	Uncertain	-3.5	D
REVEL	Pathogenic	0.72
Sift	Uncertain	0.0020	D
Sift4G	Uncertain	0.0030	D
Polyphen		0.24	B
Vest4		0.56
MutPred		0.88		Gain of methylation at K43 (P = 0.0203);
MVP		0.91
MPC		0.13
ClinPred		0.98	D
GERP RS		5.0
Varity_R		0.64
gMVP		0.85

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: rs63751109; hg19: chr3-37038124;