3-37004438-T-C

Variant summary

Our verdict is Likely pathogenic. Variant got 8 ACMG points: 8P and 0B. PM1 PM2 PM5 PP3_Moderate

The NM_000249.4(MLH1):c.344T>C(p.Ile115Thr) variant causes a missense change involving the alteration of a conserved nucleotide. The variant allele was found at a frequency of 0.00000205 in 1,461,838 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. I115N) has been classified as Likely pathogenic.

• Frequency:
  • Genomes: not found (cov: 33)
  • Exomes 𝑓: 0.0000021 (0 hom.)
• Consequence: MLH1 NM_000249.4 missense
• Clinical Significance: Uncertain significance criteria provided, single submitter U:1
• 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.

• PM1: In a hotspot region, there are 6 aminoacids with missense pathogenic changes in the window of +-8 aminoacids around while only 0 benign, 16 uncertain in NM_000249.4
• PM2: Very rare variant in population databases, with high coverage
• PM5: Other missense variant is known to change same aminoacid residue: Variant chr3-37004438-T-A is described in ClinVar as [Conflicting_classifications_of_pathogenicity]. Clinvar id is 525605.We mark this variant Likely_pathogenic, oryginal submissions are: {Likely_pathogenic=1, Uncertain_significance=2}.
• PP3: MetaRNN computational evidence supports a deleterious effect, 0.903

Transcripts

RefSeq

Gene	Transcript	HGVSc	HGVSp	Effect	#exon/exons	MANE	UniProt
MLH1	NM_000249.4	c.344T>C	p.Ile115Thr	missense_variant	4/19	ENST00000231790.8

Ensembl

Gene	Transcript	HGVSc	HGVSp	Effect	#exon/exons	TSL	MANE	Appris	UniProt
MLH1	ENST00000231790.8	c.344T>C	p.Ile115Thr	missense_variant	4/19	1	NM_000249.4	P1

Frequencies

GnomAD3 genomes Cov.: 33

GnomAD3 exomes AF: 0.00000796 AC: 2 AN: 251408 Hom.: 0 AF XY: 0.0000147 AC XY: 2 AN XY: 135870

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: 0.0000653

Gnomad FIN exome AF: 0.00

Gnomad NFE exome AF: 0.00

Gnomad OTH exome AF: 0.00

GnomAD4 exome AF: 0.00000205 AC: 3 AN: 1461838 Hom.: 0 Cov.: 30 AF XY: 0.00000413 AC XY: 3 AN XY: 727222

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: 0.0000348

Gnomad4 FIN exome AF: 0.00

Gnomad4 NFE exome AF: 0.00

Gnomad4 OTH exome AF: 0.00

GnomAD4 genome Cov.: 33

ExAC AF: 0.00000824 AC: 1

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

Mar 27, 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 (SIFT, PolyPhen-2, Align-GVGD) all suggest that this variant is likely to be disruptive, but these predictions have not been confirmed by published functional studies and their clinical significance is uncertain. This variant has not been reported in the literature in individuals with MLH1-related conditions. This variant is present in population databases (rs764120517, ExAC 0.006%). This sequence change replaces isoleucine with threonine at codon 115 of the MLH1 protein (p.Ile115Thr). The isoleucine residue is highly conserved and there is a moderate physicochemical difference between isoleucine and threonine. -

Computational scores

Source: dbNSFP v4.3

Name	Calibrated prediction	Score	Prediction
AlphaMissense	Pathogenic	0.95
BayesDel_addAF	Pathogenic	0.41	D
BayesDel_noAF	Pathogenic	0.54
Cadd	Pathogenic	27
Dann	Uncertain	1.0
DEOGEN2	Pathogenic	0.92	D;.;D
Eigen	Pathogenic	1.0
Eigen_PC	Pathogenic	0.93
FATHMM_MKL	Pathogenic	0.99	D
LIST_S2	Pathogenic	0.99	D;D;D
M_CAP	Pathogenic	0.39	D
MetaRNN	Pathogenic	0.90	D;D;D
MetaSVM	Pathogenic	1.1	D
MutationAssessor	Pathogenic	3.6	H;.;.
MutationTaster	Benign	1.0	D;D;D;D;D;D
PrimateAI	Uncertain	0.72	T
PROVEAN	Uncertain	-4.1	D;D;D
REVEL	Pathogenic	0.89
Sift	Uncertain	0.0010	D;D;D
Sift4G	Uncertain	0.0020	D;D;D
Polyphen		0.99	D;.;.
Vest4		0.82
MutPred		0.70		Gain of catalytic residue at I115 (P = 0.0077);.;.;
MVP		0.96
MPC		0.44
ClinPred		0.99	D
GERP RS		6.0
RBP_binding_hub_radar		0.0
RBP_regulation_power_radar		1.1
Varity_R		0.92
gMVP		0.92

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: rs764120517; hg19: chr3-37045929;