3-37048968-C-T

Position:

• chr3-37048968-C-T

Variant summary

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

The NM_000249.4(MLH1):​c.2054C>T​(p.Ser685Phe) 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).

• Frequency: Genomes: not found (cov: 32)
• Consequence: MLH1 NM_000249.4 missense
• Clinical Significance: Conflicting classifications of pathogenicity criteria provided, conflicting classifications P:3 U:1
• Conservation: PhyloP100: 7.34

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, 0.893

Transcripts

RefSeq

Gene	Transcript	HGVSc	HGVSp	Effect	#exon/exons	MANE	Protein	UniProt
MLH1	NM_000249.4	c.2054C>T	p.Ser685Phe	missense_variant	18/19	ENST00000231790.8	NP_000240.1

Ensembl

Gene	Transcript	HGVSc	HGVSp	Effect	#exon/exons	TSL	MANE	Protein	Appris	UniProt
MLH1	ENST00000231790.8	c.2054C>T	p.Ser685Phe	missense_variant	18/19	1	NM_000249.4	ENSP00000231790.3

Frequencies

GnomAD3 genomes Cov.: 32

GnomAD4 exome Cov.: 31

GnomAD4 genome Cov.: 32

ClinVar

Significance: Conflicting classifications of pathogenicity

Submissions summary: Pathogenic:3 Uncertain:1

Revision: criteria provided, conflicting classifications

Submissions by phenotype

Hereditary nonpolyposis colon cancer Pathogenic:1

Likely pathogenic, criteria provided, single submitter

clinical testing

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

Jun 20, 2023

Variant summary: MLH1 c.2054C>T (p.Ser685Phe) results in a non-conservative amino acid change located in the DNA mismatch repair protein Mlh1, C-terminal (IPR032189) 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 251222 control chromosomes. c.2054C>T has been reported in the literature in individuals with Lynch Syndrome (Zaib_2020) and observed to segregate with disease in related individuals. At least one publication reports experimental evidence evaluating an impact on protein function showing a decrease in expression of protein levels ((Zaib_2020). The following publication have been ascertained in the context of this evaluation (PMID: 32076465). Three submitters have cited clinical-significance assessments for this variant to ClinVar after 2014 and classified as VUS (n=1), likely pathogenic (n=1) and pathogenic (n=1). Based on the evidence outlined above, the variant was classified as likely pathogenic. -

Hereditary nonpolyposis colorectal neoplasms Pathogenic:1

Pathogenic, criteria provided, single submitter

clinical testing

Labcorp Genetics (formerly Invitae), Labcorp

Sep 19, 2022

Experimental studies have shown that this missense change affects MLH1 function (PMID: 32076465). For these reasons, this variant has been classified as Pathogenic. 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 expected to disrupt MLH1 protein function. ClinVar contains an entry for this variant (Variation ID: 422929). This missense change has been observed in individual(s) with Lynch syndrome (PMID: 32076465). It has also been observed to segregate with disease in related individuals. This variant is not present in population databases (gnomAD no frequency). This sequence change replaces serine, which is neutral and polar, with phenylalanine, which is neutral and non-polar, at codon 685 of the MLH1 protein (p.Ser685Phe). -

Hereditary cancer-predisposing syndrome Pathogenic:1

Likely pathogenic, criteria provided, single submitter

clinical testing

Ambry Genetics

Aug 04, 2023

The p.S685F variant (also known as c.2054C>T), located in coding exon 18 of the MLH1 gene, results from a C to T substitution at nucleotide position 2054. The serine at codon 685 is replaced by phenylalanine, an amino acid with highly dissimilar properties. This alteration was identified in the germline as well as somatic in unrelated individuals whose colorectal tumors displayed loss of both MLH1/PMS2 on immunohistochemistry (IHC) and somatic MLH1 copy-neutral loss of heterozygosity (CN-LOH) was identified, but MLH1 promoter hypermethylation was not detected (Ambry internal data). This alteration also segregated with early-onset colorectal cancer in 3 affected relatives of a family (Ambry internal data). Based on an internal structural assessment, this alteration destabilizes the C-terminal domain of the MLH1 protein (Berman HM et al. Nucleic Acids Res., 2000 Jan;28:235-42; www.rcsb.org; 10.2210/pdb3RBN/pdb). This variant was not reported in population-based cohorts in the Genome Aggregation Database (gnomAD) (Lek M et al. Nature, 2016 08;536:285-91). This amino acid position is well conserved in available vertebrate species. In addition, this alteration is predicted to be deleterious by in silico analysis. Based on the majority of available evidence to date, this variant is likely to be pathogenic. -

not provided Uncertain:1

Uncertain significance, criteria provided, single submitter

clinical testing

GeneDx

Nov 14, 2024

Not observed at significant frequency in large population cohorts (gnomAD); In silico analysis supports that this missense variant has a deleterious effect on protein structure/function; Has not been previously published as pathogenic or benign to our knowledge; This variant is associated with the following publications: (PMID: 12799449, 20533529, 22753075, 10592235, 32076465) -

Computational scores

Source: dbNSFP v4.3

Name	Calibrated prediction	Score	Prediction
AlphaMissense	Pathogenic	0.82
BayesDel_addAF	Pathogenic	0.50	D
BayesDel_noAF	Pathogenic	0.48
CADD	Pathogenic	27
DANN	Uncertain	1.0
DEOGEN2	Pathogenic	0.91	D;.;.;.;.;.
Eigen	Pathogenic	0.90
Eigen_PC	Pathogenic	0.88
FATHMM_MKL	Pathogenic	0.97	D
LIST_S2	Uncertain	0.96	D;D;.;.;.;D
M_CAP	Pathogenic	0.47	D
MetaRNN	Pathogenic	0.89	D;D;D;D;D;D
MetaSVM	Pathogenic	0.94	D
MutationAssessor	Uncertain	2.9	M;.;.;.;.;.
PrimateAI	Uncertain	0.56	T
PROVEAN	Uncertain	-3.4	D;D;D;D;D;D
REVEL	Pathogenic	0.83
Sift	Uncertain	0.0030	D;D;D;D;D;D
Sift4G	Uncertain	0.017	D;D;D;D;D;D
Polyphen		0.99	D;.;.;.;.;.
Vest4		0.87
MutPred		0.54		Loss of disorder (P = 0.0223);.;.;.;.;.;
MVP		0.97
MPC		0.38
ClinPred		0.99	D
GERP RS		5.9
RBP_binding_hub_radar		0.0
RBP_regulation_power_radar		1.1
Varity_R		0.94
gMVP		0.89

Splicing

Name	Calibrated prediction	Score	Prediction
SpliceAI score (max)		0.010		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: rs1064796101; hg19: chr3-37090459;