rs876660926

Positions:

• chr3-36996698-A-G
• chr3-36996698-A-T

Variant summary

Our verdict is Uncertain significance. Variant got 3 ACMG points: 3P and 0B. PM2 PP3

The NM_000249.4(MLH1):​c.196A>G​(p.Thr66Ala) variant causes a missense change. 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 Uncertain significance (★★). Synonymous variant affecting the same amino acid position (i.e. T66T) has been classified as Likely benign.

• Frequency: Genomes: not found (cov: 32)
• Consequence: MLH1 NM_000249.4 missense
• Clinical Significance: Uncertain significance criteria provided, multiple submitters, no conflicts U:5
• Conservation: PhyloP100: 6.76

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]

MLH1 (HGNC:):

ACMG classification

Verdict is Uncertain_significance. Variant got 3 ACMG points.

• PM2: Very rare variant in population databases, with high coverage
• PP3: MetaRNN computational evidence supports a deleterious effect, 0.781

Transcripts

RefSeq

Gene	Transcript	HGVSc	HGVSp	Effect	#exon/exons	MANE	Protein	UniProt
MLH1	NM_000249.4	c.196A>G	p.Thr66Ala	missense_variant	2/19	ENST00000231790.8	NP_000240.1

Ensembl

Gene	Transcript	HGVSc	HGVSp	Effect	#exon/exons	TSL	MANE	Protein	Appris	UniProt
MLH1	ENST00000231790.8	c.196A>G	p.Thr66Ala	missense_variant	2/19	1	NM_000249.4	ENSP00000231790.3

Frequencies

GnomAD3 genomes Cov.: 32

GnomAD4 exome Cov.: 30

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

Uncertain significance, criteria provided, single submitter	clinical testing	Color Diagnostics, LLC DBA Color Health	Oct 04, 2018	- -
Uncertain significance, criteria provided, single submitter	clinical testing	Ambry Genetics	Aug 30, 2024	The p.T66A variant (also known as c.196A>G), located in coding exon 2 of the MLH1 gene, results from an A to G substitution at nucleotide position 196. The threonine at codon 66 is replaced by alanine, an amino acid with similar properties. This amino acid position is well conserved in available vertebrate species. In addition, the in silico prediction for this alteration is inconclusive. Based on the available evidence, the clinical significance of this variant remains unclear. -

Lynch syndrome Uncertain:1

Uncertain significance, criteria provided, single submitter

clinical testing

All of Us Research Program, National Institutes of Health

Mar 04, 2023

- -

not provided Uncertain:1

Uncertain significance, criteria provided, single submitter

clinical testing

PreventionGenetics, part of Exact Sciences

Jan 10, 2018

- -

Hereditary nonpolyposis colorectal neoplasms Uncertain:1

Uncertain significance, criteria provided, single submitter

clinical testing

Labcorp Genetics (formerly Invitae), Labcorp

Jan 18, 2020

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 are either unavailable or do not agree on the potential impact of this missense change (SIFT: "Tolerated"; PolyPhen-2: "Possibly Damaging"; Align-GVGD: "Class C0"). This variant has not been reported in the literature in individuals with MLH1-related disease. ClinVar contains an entry for this variant (Variation ID: 234208). This variant is not present in population databases (ExAC no frequency). This sequence change replaces threonine with alanine at codon 66 of the MLH1 protein (p.Thr66Ala). The threonine residue is moderately conserved and there is a small physicochemical difference between threonine and alanine. -

Computational scores

Source: dbNSFP v4.3

Name	Calibrated prediction	Score	Prediction
AlphaMissense	Benign	0.081
BayesDel_addAF	Pathogenic	0.24	D
BayesDel_noAF	Uncertain	0.11
CADD	Uncertain	24
DANN	Uncertain	1.0
DEOGEN2	Uncertain	0.62	D
Eigen	Uncertain	0.36
Eigen_PC	Uncertain	0.47
FATHMM_MKL	Uncertain	0.95	D
LIST_S2	Uncertain	0.96	D
M_CAP	Benign	0.064	D
MetaRNN	Pathogenic	0.78	D
MetaSVM	Uncertain	0.11	D
MutationAssessor	Benign	0.84	L
PrimateAI	Uncertain	0.65	T
PROVEAN	Benign	-1.8	N
REVEL	Uncertain	0.56
Sift	Benign	0.034	D
Sift4G	Benign	0.20	T
Polyphen		0.42	B
Vest4		0.62
MutPred		0.41		Loss of ubiquitination at K70 (P = 0.1066);
MVP		0.97
MPC		0.20
ClinPred		0.85	D
GERP RS		5.8
RBP_binding_hub_radar		0.92
RBP_regulation_power_radar		2.6
Varity_R		0.35
gMVP		0.60

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: rs876660926; hg19: chr3-37038189;