3-37047652-T-C

Position:

• chr3-37047652-T-C

Variant summary

Our verdict is Pathogenic. Variant got 16 ACMG points: 16P and 0B. PM2 PM5 PP3_Strong PP5_Very_Strong

The NM_000249.4(MLH1):​c.1865T>C​(p.Leu622Pro) 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. 13/21 in silico tools predict a damaging outcome for this variant. Variant has been reported in ClinVar as Pathogenic (★★★). Another variant affecting the same amino acid position, but resulting in a different missense (i.e. L622H) has been classified as Pathogenic.

• Frequency: Genomes: not found (cov: 31)
• Consequence: MLH1 NM_000249.4 missense
• Clinical Significance: Pathogenic reviewed by expert panel P:3
• Conservation: PhyloP100: 7.81

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 Pathogenic. Variant got 16 ACMG points.

• PM2: Very rare variant in population databases, with high coverage
• PM5: Other missense variant is known to change same aminoacid residue: Variant chr3-37047652-T-A is described in Lovd as [Pathogenic].
• PP3: MetaRNN computational evidence supports a deleterious effect, 0.978
• PP5: Variant 3-37047652-T-C is Pathogenic according to our data. Variant chr3-37047652-T-C is described in ClinVar as [Pathogenic]. Clinvar id is 89911.Status of the report is reviewed_by_expert_panel, 3 stars. Variant chr3-37047652-T-C is described in Lovd as [Pathogenic].

Transcripts

RefSeq

Gene	Transcript	HGVSc	HGVSp	Effect	#exon/exons	MANE	Protein	UniProt
MLH1	NM_000249.4	c.1865T>C	p.Leu622Pro	missense_variant	16/19	ENST00000231790.8	NP_000240.1

Ensembl

Gene	Transcript	HGVSc	HGVSp	Effect	#exon/exons	TSL	MANE	Protein	Appris	UniProt
MLH1	ENST00000231790.8	c.1865T>C	p.Leu622Pro	missense_variant	16/19	1	NM_000249.4	ENSP00000231790	P1

Frequencies

GnomAD3 genomes Cov.: 31

GnomAD4 exome Cov.: 31

GnomAD4 genome Cov.: 31

ClinVar

Significance: Pathogenic

Submissions summary: Pathogenic:3

Revision: reviewed by expert panel

Submissions by phenotype

Lynch syndrome Pathogenic:1

Pathogenic, reviewed by expert panel

curation

International Society for Gastrointestinal Hereditary Tumours (InSiGHT)

Feb 21, 2019

Multifactorial likelihood analysis posterior probability >0.99 (1.000) -

Hereditary nonpolyposis colorectal neoplasms Pathogenic:1

Pathogenic, criteria provided, single submitter

clinical testing

Labcorp Genetics (formerly Invitae), Labcorp

Jun 03, 2022

This sequence change replaces leucine, which is neutral and non-polar, with proline, which is neutral and non-polar, at codon 622 of the MLH1 protein (p.Leu622Pro). This variant is not present in population databases (gnomAD no frequency). For these reasons, this variant has been classified as Pathogenic. This variant disrupts the p.Leu622 amino acid residue in MLH1. Other variant(s) that disrupt this residue have been determined to be pathogenic (PMID: 11748856, 17510385, 20858721, 23403630, 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 missense change affects MLH1 function (PMID: 30998989). 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: 89911). This missense change has been observed in individual(s) with clinical features of Lynch syndrome (PMID: 1749856, 21404117; Invitae). -

Hereditary cancer-predisposing syndrome Pathogenic:1

Likely pathogenic, criteria provided, single submitter

clinical testing

Ambry Genetics

Jan 21, 2019

The p.L622P variant (also known as c.1865T>C), located in coding exon 16 of the MLH1 gene, results from a T to C substitution at nucleotide position 1865. The leucine at codon 622 is replaced by proline, an amino acid with similar properties. This alteration has been reported in a patient with breast and colorectal cancer who met Bethesda criteria for Lynch syndrome and whose colorectal tumor showed loss of MLH1 and PMS2 proteins on immunohistochemical (IHC) analysis (Koehler U et al. Cancer Genet. Cytogenet., 2007 May;175:81-4). This alteration was also reported in an individual diagnosed with colon cancer at 43 who met Amsterdam II criteria for Lynch syndrome. This individual's colon tumor displayed high microsatellite instability (MSI-H) with loss of both MLH1/PMS2 on IHC analysis and co-occurrence with another MLH1 missense alteration was identified, p.A623S, but the phase (whether in cis or trans) was not reported (Hardt K et al. Fam. Cancer, 2011 Jun;10:273-84). This alteration was also identified as somatic in a MSI-H colon tumor that displayed loss of MLH1 and PMS2 on IHC analysis (Ambry internal data). Based on an internal structural assessment, this alteration leads to destabilization of the C-terminal domain. This amino acid position is highly 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) and pathogenic by the PON-MMR prediction tool (Ali H et al. Hum. Mutat., 2012 Apr;33:642-50). Based on the majority of available evidence to date, this variant is likely to be pathogenic. -

Computational scores

Source: dbNSFP v4.3

Name	Calibrated prediction	Score	Prediction
AlphaMissense	Pathogenic	0.99
BayesDel_addAF	Pathogenic	0.54	D
BayesDel_noAF	Pathogenic	0.53
CADD	Pathogenic	28
DANN	Pathogenic	1.0
DEOGEN2	Pathogenic	0.95	D;.;.;.;.;.
Eigen	Pathogenic	0.92
Eigen_PC	Pathogenic	0.85
FATHMM_MKL	Pathogenic	0.97	D
LIST_S2	Uncertain	0.95	D;D;.;.;.;D
M_CAP	Pathogenic	0.62	D
MetaRNN	Pathogenic	0.98	D;D;D;D;D;D
MetaSVM	Pathogenic	1.1	D
MutationAssessor	Pathogenic	3.6	H;.;.;.;.;.
MutationTaster	Benign	1.0	D;D;D;D;D;D
PrimateAI	Pathogenic	0.83	D
PROVEAN	Pathogenic	-6.4	D;D;D;D;D;D
REVEL	Pathogenic	0.97
Sift	Uncertain	0.0010	D;D;D;D;D;D
Sift4G	Pathogenic	0.0010	D;D;D;D;D;D
Polyphen		1.0	D;.;.;.;.;.
Vest4		0.96
MutPred		0.84		Loss of stability (P = 0.026);.;.;.;.;.;
MVP		0.98
MPC		0.51
ClinPred		0.99	D
GERP RS		5.5
RBP_binding_hub_radar		0.0
RBP_regulation_power_radar		1.1
Varity_R		0.99
gMVP		0.99

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: rs63750693; hg19: chr3-37089143;