chr3-37047664-T-C

Position:

• chr3-37047664-T-C

Variant summary

Our verdict is Likely pathogenic. Variant got 9 ACMG points: 9P and 0B. PM1 PM2 PP3_Strong PP5

The ENST00000231790.8(MLH1):​c.1877T>C​(p.Phe626Ser) 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). Another variant affecting the same amino acid position, but resulting in a different missense (i.e. F626L) has been classified as Uncertain significance.

• Frequency: Genomes: not found (cov: 31)
• Consequence: MLH1 ENST00000231790.8 missense
• Clinical Significance: Conflicting classifications of pathogenicity criteria provided, conflicting classifications P:1 U:2
• 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 Likely_pathogenic. Variant got 9 ACMG points.

• PM1: In a hotspot region, there are 5 aminoacids with missense pathogenic changes in the window of +-8 aminoacids around while only 2 benign, 17 uncertain in ENST00000231790.8
• PM2: Very rare variant in population databases, with high coverage
• PP3: MetaRNN computational evidence supports a deleterious effect, 0.941
• PP5: Variant 3-37047664-T-C is Pathogenic according to our data. Variant chr3-37047664-T-C is described in ClinVar as [Conflicting_classifications_of_pathogenicity]. Clinvar id is 89915.We mark this variant Likely_pathogenic, oryginal submissions are: {Likely_pathogenic=1, Uncertain_significance=2}.

Transcripts

RefSeq

Gene	Transcript	HGVSc	HGVSp	Effect	#exon/exons	MANE	Protein	UniProt
MLH1	NM_000249.4	c.1877T>C	p.Phe626Ser	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.1877T>C	p.Phe626Ser	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: Conflicting classifications of pathogenicity

Submissions summary: Pathogenic:1 Uncertain:2

Revision: criteria provided, conflicting classifications

Submissions by phenotype

Hereditary cancer-predisposing syndrome Pathogenic:1 Uncertain:1

Uncertain significance, criteria provided, single submitter	clinical testing	Color Diagnostics, LLC DBA Color Health	Dec 20, 2018	- -
Likely pathogenic, criteria provided, single submitter	clinical testing	Ambry Genetics	May 20, 2021	The p.F626S variant (also known as c.1877T>C), located in coding exon 16 of the MLH1 gene, results from a T to C substitution at nucleotide position 1877. The phenylalanine at codon 626 is replaced by serine, an amino acid with highly dissimilar properties. This alteration is detected in an individual whose colorectal tumor demonstrated loss of MLH1 and PMS2 expression on immunohistochemistry (IHC), and BRAF mutation analysis was negative (Ambry internal data). This alteration was also detected in conjunction with another MLH1 missense alteration (phase unknown) in 1 of 14 families, all of whom meet Amsterdam criteria; however, individual-level clinical data was not provided (Beck NE et al. Hum Genet, 1997 Feb;99:219-24). Based on internal structural analysis using published crystal structures, p.F626S is moderately destabilizing to the local structure (Ambry internal data). This variant is considered to be rare based on population cohorts in the Genome Aggregation Database (gnomAD). This amino acid position is highly 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. -

Hereditary nonpolyposis colorectal neoplasms Uncertain:1

Uncertain significance, criteria provided, single submitter

clinical testing

Labcorp Genetics (formerly Invitae), Labcorp

Dec 04, 2023

This sequence change replaces phenylalanine, which is neutral and non-polar, with serine, which is neutral and polar, at codon 626 of the MLH1 protein (p.Phe626Ser). This variant is not present in population databases (gnomAD no frequency). 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: 89915). 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 with a positive predictive value of 95%. 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	Pathogenic	0.94
BayesDel_addAF	Pathogenic	0.53	D
BayesDel_noAF	Pathogenic	0.52
CADD	Pathogenic	27
DANN	Uncertain	1.0
DEOGEN2	Pathogenic	0.95	D;.;.;.;.;.
Eigen	Uncertain	0.63
Eigen_PC	Uncertain	0.64
FATHMM_MKL	Pathogenic	0.97	D
LIST_S2	Uncertain	0.95	D;D;.;.;.;D
M_CAP	Pathogenic	0.53	D
MetaRNN	Pathogenic	0.94	D;D;D;D;D;D
MetaSVM	Uncertain	0.45	D
MutationAssessor	Pathogenic	3.7	H;.;.;.;.;.
MutationTaster	Benign	1.0	D;D;D;D;D;D
PrimateAI	Uncertain	0.79	T
PROVEAN	Pathogenic	-7.8	D;D;D;D;D;D
REVEL	Pathogenic	0.94
Sift	Pathogenic	0.0	D;D;D;D;D;D
Sift4G	Pathogenic	0.0010	D;D;D;D;D;D
Polyphen		1.0	D;.;.;.;.;.
Vest4		0.90
MutPred		0.80		Gain of disorder (P = 0.0024);.;.;.;.;.;
MVP		0.98
MPC		0.53
ClinPred		1.0	D
GERP RS		5.5
Varity_R		0.99
gMVP		0.96

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: rs587778952; hg19: chr3-37089155;