3-37017542-T-C

Variant names:

• chr3-37017542-T-C
• rs1253275403
• NM_000249.4:c.827T>C

Variant summary

Our verdict is Likely pathogenic. Variant got 8 ACMG points: 8P and 0B. PM2 PM5 PP3_Strong

The NM_000249.4(MLH1):​c.827T>C​(p.Ile276Thr) variant causes a missense change involving the alteration of a conserved nucleotide. The variant allele was found at a frequency of 0.00000205 in 1,461,880 control chromosomes in the GnomAD database, with no homozygous occurrence. 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. I276R) has been classified as Pathogenic.

• Frequency:
  • Genomes: not found (cov: 32)
  • Exomes 𝑓: 0.0000021 (0 hom.)
• Consequence: MLH1 NM_000249.4 missense
• Clinical Significance: Uncertain significance criteria provided, multiple submitters, no conflicts U:5
• Conservation: PhyloP100: 7.70

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 Likely_pathogenic. Variant got 8 ACMG points.

• PM2: Very rare variant in population databases, with high coverage
• PM5: Other missense variant is known to change same aminoacid residue: Variant chr3-37017542-T-G is described in Lovd as [Pathogenic].
• PP3: MetaRNN computational evidence supports a deleterious effect, 0.971

Transcripts

RefSeq

Gene	Transcript	HGVSc	HGVSp	Effect	Exon rank	MANE	Protein	UniProt
MLH1	NM_000249.4	c.827T>C	p.Ile276Thr	missense_variant	Exon 10 of 19	ENST00000231790.8	NP_000240.1

Ensembl

Gene	Transcript	HGVSc	HGVSp	Effect	Exon rank	TSL	MANE	Protein	Appris	UniProt
MLH1	ENST00000231790.8	c.827T>C	p.Ile276Thr	missense_variant	Exon 10 of 19	1	NM_000249.4	ENSP00000231790.3

Frequencies

GnomAD3 genomes Cov.: 32

GnomAD3 exomes AF: 0.00000398 AC: 1 AN: 251476 Hom.: 0 AF XY: 0.00000736 AC XY: 1 AN XY: 135912

Gnomad AFR exome AF: 0.00

Gnomad AMR exome AF: 0.00

Gnomad ASJ exome AF: 0.00

Gnomad EAS exome AF: 0.00

Gnomad SAS exome AF: 0.00

Gnomad FIN exome AF: 0.00

Gnomad NFE exome AF: 0.00000879

Gnomad OTH exome AF: 0.00

GnomAD4 exome AF: 0.00000205 AC: 3 AN: 1461880 Hom.: 0 Cov.: 31 AF XY: 0.00000275 AC XY: 2 AN XY: 727244

Gnomad4 AFR exome AF: 0.00

Gnomad4 AMR exome AF: 0.00

Gnomad4 ASJ exome AF: 0.00

Gnomad4 EAS exome AF: 0.00

Gnomad4 SAS exome AF: 0.00

Gnomad4 FIN exome AF: 0.00

Gnomad4 NFE exome AF: 0.00000180

Gnomad4 OTH exome AF: 0.0000166

GnomAD4 genome Cov.: 32

ClinVar

Significance: Uncertain significance

Submissions summary: Uncertain:5

Revision: criteria provided, multiple submitters, no conflicts

Submissions by phenotype

Hereditary cancer-predisposing syndrome Uncertain:2

Jun 18, 2024

Color Diagnostics, LLC DBA Color Health

Significance: Uncertain significance

Review Status: criteria provided, single submitter

Collection Method: clinical testing

This missense variant replaces isoleucine with threonine at codon 276 of the MLH1 protein. Computational prediction suggests that this variant may have deleterious impact on protein structure and function (internally defined REVEL score threshold >= 0.7, PMID: 27666373). To our knowledge, functional studies have not been reported for this variant. This variant has not been reported in individuals affected with MLH1-related disorders in the literature. This variant has been identified in 1/251476 chromosomes in the general population by the Genome Aggregation Database (gnomAD). A different missense variant at the same codon, c.827T>G (p.Ile276Arg), has been reported as disease-causing in ClinVar by InSiGHT (ClinVar variation ID: 520540). 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. -

Mar 29, 2023

Ambry Genetics

Significance: Uncertain significance

Review Status: criteria provided, single submitter

Collection Method: clinical testing

The p.I276T variant (also known as c.827T>C), located in coding exon 10 of the MLH1 gene, results from a T to C substitution at nucleotide position 827. The isoleucine at codon 276 is replaced by threonine, an amino acid with similar properties. This alteration was seen in 1/732 breast cancer patients, 0/189 colorectal cancer patients and 0/490 cancer-free elderly controls in a Turkish population (Akcay IM et al. Int J Cancer, 2021 Jan;148:285-295). This amino acid position is well conserved in available vertebrate species. In addition, this alteration is predicted to be deleterious by in silico analysis. Since supporting evidence is limited at this time, the clinical significance of this alteration remains unclear. -

Lynch syndrome Uncertain:1

May 31, 2023

All of Us Research Program, National Institutes of Health

Significance: Uncertain significance

Review Status: criteria provided, single submitter

Collection Method: clinical testing

This missense variant replaces isoleucine with threonine at codon 276 of the MLH1 protein. Computational prediction suggests that this variant may have deleterious impact on protein structure and function (internally defined REVEL score threshold >= 0.7, PMID: 27666373). To our knowledge, functional studies have not been reported for this variant. This variant has not been reported in individuals affected with hereditary cancer in the literature. A different missense variant, p.Ile276Arg, at this codon has been reported as disease-causing in ClinVar by InSiGHT (ClinVar variation ID: 520540). This variant has been identified in 1/251476 chromosomes 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. -

not provided Uncertain:1

Dec 16, 2024

GeneDx

Significance: Uncertain significance

Review Status: criteria provided, single submitter

Collection Method: clinical testing

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; This variant is associated with the following publications: (PMID: 32658311, 22753075, 38940262) -

Hereditary nonpolyposis colorectal neoplasms Uncertain:1

Oct 29, 2024

Labcorp Genetics (formerly Invitae), Labcorp

Significance: Uncertain significance

Review Status: criteria provided, single submitter

Collection Method: clinical testing

This sequence change replaces isoleucine, which is neutral and non-polar, with threonine, which is neutral and polar, at codon 276 of the MLH1 protein (p.Ile276Thr). This variant is present in population databases (no rsID available, gnomAD 0.0009%). 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: 449833). Invitae Evidence Modeling incorporating data from in vitro experimental studies (internal data) indicates that this missense variant is not expected to disrupt MLH1 function with a negative predictive value of 95%. RNA analysis performed to evaluate the impact of this missense change on mRNA splicing indicates it does not significantly alter splicing (internal data). 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	0.20
BayesDel_addAF	Pathogenic	0.38	D
BayesDel_noAF	Pathogenic	0.32
CADD	Pathogenic	27
DANN	Uncertain	1.0
DEOGEN2	Pathogenic	0.86	D;.;.;.;.;.;.
Eigen	Uncertain	0.66
Eigen_PC	Uncertain	0.64
FATHMM_MKL	Pathogenic	0.99	D
LIST_S2	Uncertain	0.95	D;D;.;.;.;D;D
M_CAP	Uncertain	0.19	D
MetaRNN	Pathogenic	0.97	D;D;D;D;D;D;D
MetaSVM	Uncertain	0.59	D
MutationAssessor	Pathogenic	3.8	H;.;.;.;.;.;.
PrimateAI	Uncertain	0.58	T
PROVEAN	Uncertain	-3.8	D;D;D;D;D;D;D
REVEL	Pathogenic	0.85
Sift	Uncertain	0.0020	D;D;D;D;D;D;D
Sift4G	Uncertain	0.0050	D;D;D;D;D;D;D
Polyphen		0.74	P;.;.;.;.;.;.
Vest4		0.93
MutPred		0.91		Gain of disorder (P = 0.0078);.;.;.;.;.;.;
MVP		0.92
MPC		0.31
ClinPred		0.99	D
GERP RS		5.3
Varity_R		0.80
gMVP		0.72

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: rs1253275403; hg19: chr3-37059033;