3-37025875-A-C

Position:

• chr3-37025875-A-C

Variant summary

Our verdict is Uncertain significance. Variant got 2 ACMG points: 4P and 2B. PM1 PM2 BP4_Moderate

The NM_000249.4(MLH1):​c.1277A>C​(p.Gln426Pro) variant causes a missense change involving the alteration of a non-conserved nucleotide. The variant was absent in control chromosomes in GnomAD project. In-silico tool predicts a benign outcome for this variant. 14/21 in silico tools predict a benign 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. Q426L) has been classified as Uncertain significance.

• Frequency: Genomes: not found (cov: 31)
• Consequence: MLH1 NM_000249.4 missense
• Clinical Significance: Uncertain significance criteria provided, single submitter U:1
• Conservation: PhyloP100: -0.325

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 Uncertain_significance. Variant got 2 ACMG points.

• PM1: In a hotspot region, there are 2 aminoacids with missense pathogenic changes in the window of +-8 aminoacids around while only 2 benign, 17 uncertain in NM_000249.4
• PM2: Very rare variant in population databases, with high coverage
• BP4: Computational evidence support a benign effect (MetaRNN=0.21173015).

Transcripts

RefSeq

Gene	Transcript	HGVSc	HGVSp	Effect	#exon/exons	MANE	UniProt
MLH1	NM_000249.4	c.1277A>C	p.Gln426Pro	missense_variant	12/19	ENST00000231790.8

Ensembl

Gene	Transcript	HGVSc	HGVSp	Effect	#exon/exons	TSL	MANE	Appris	UniProt
MLH1	ENST00000231790.8	c.1277A>C	p.Gln426Pro	missense_variant	12/19	1	NM_000249.4	P1

Frequencies

GnomAD3 genomes Cov.: 31

GnomAD4 exome Cov.: 34

GnomAD4 genome Cov.: 31

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

Labcorp Genetics (formerly Invitae), Labcorp

Sep 07, 2020

Algorithms developed to predict the effect of missense changes on protein structure and function output the following: SIFT: "Tolerated"; PolyPhen-2: "Benign"; Align-GVGD: "Class C0". The proline amino acid residue is found in multiple mammalian species, suggesting that this missense change does not adversely affect protein function. These predictions have not been confirmed by published functional studies and their clinical significance is uncertain. 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. This variant has not been reported in the literature in individuals with MLH1-related conditions. This variant is not present in population databases (ExAC no frequency). This sequence change replaces glutamine with proline at codon 426 of the MLH1 protein (p.Gln426Pro). The glutamine residue is weakly conserved and there is a moderate physicochemical difference between glutamine and proline. -

Computational scores

Source: dbNSFP v4.3

Name	Calibrated prediction	Score	Prediction
AlphaMissense	Benign	0.061
BayesDel_addAF	Uncertain	0.045	T
BayesDel_noAF	Benign	-0.17
CADD	Benign	4.8
DANN	Benign	0.86
DEOGEN2	Benign	0.28	T;.;.;.;.;.
Eigen	Benign	-0.63
Eigen_PC	Benign	-0.67
FATHMM_MKL	Benign	0.14	N
LIST_S2	Benign	0.70	T;T;.;.;.;T
M_CAP	Benign	0.012	T
MetaRNN	Benign	0.21	T;T;T;T;T;T
MetaSVM	Benign	-1.0	T
MutationAssessor	Benign	1.1	L;.;.;.;.;.
MutationTaster	Benign	1.0	N;N;N;N;N;N
PrimateAI	Benign	0.29	T
PROVEAN	Benign	-0.20	N;N;N;N;N;N
REVEL	Uncertain	0.58
Sift	Benign	0.28	T;T;T;T;T;T
Sift4G	Benign	0.30	T;T;T;T;T;T
Polyphen		0.0	B;.;.;.;.;.
Vest4		0.44
MutPred		0.20		Gain of helix (P = 0.0425);.;.;.;.;.;
MVP		0.97
MPC		0.080
ClinPred		0.044	T
GERP RS		2.4
RBP_binding_hub_radar		0.0
RBP_regulation_power_radar		1.7
Varity_R		0.049
gMVP		0.19

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: rs876659252; hg19: chr3-37067366;