rs1555346244

Positions:

• chr14-75049259-A-C

Variant summary

Our verdict is Uncertain significance. Variant got 0 ACMG points: 2P and 2B. PM2 BP4_Moderate

The NM_001040108.2(MLH3):​c.397T>G​(p.Cys133Gly) variant causes a missense change involving the alteration of a non-conserved nucleotide. The variant allele was found at a frequency of 0.00000137 in 1,461,876 control chromosomes in the GnomAD database, with no homozygous occurrence. In-silico tool predicts a benign outcome for this variant. 15/21 in silico tools predict a benign outcome for this variant. Variant has been reported in ClinVar as Uncertain significance (★★).

• Frequency:
  • Genomes: not found (cov: 33)
  • Exomes 𝑓: 0.0000014 (0 hom.)
• Consequence: MLH3 NM_001040108.2 missense
• Clinical Significance: Uncertain significance criteria provided, multiple submitters, no conflicts U:2
• Conservation: PhyloP100: 2.20

Genes affected

MLH3 (HGNC:7128): (mutL homolog 3) This gene is a member of the MutL-homolog (MLH) family of DNA mismatch repair (MMR) genes. MLH genes are implicated in maintaining genomic integrity during DNA replication and after meiotic recombination. The protein encoded by this gene functions as a heterodimer with other family members. Somatic mutations in this gene frequently occur in tumors exhibiting microsatellite instability, and germline mutations have been linked to hereditary nonpolyposis colorectal cancer type 7 (HNPCC7). Several alternatively spliced transcript variants have been identified, but the full-length nature of only two transcript variants has been determined. [provided by RefSeq, Jul 2008]

ACMG classification

Verdict is Uncertain_significance. Variant got 0 ACMG points.

• PM2: Very rare variant in population databases, with high coverage
• BP4: Computational evidence support a benign effect (MetaRNN=0.2106798).

Transcripts

RefSeq

Gene	Transcript	HGVSc	HGVSp	Effect	#exon/exons	MANE	UniProt
MLH3	NM_001040108.2	c.397T>G	p.Cys133Gly	missense_variant	2/13	ENST00000355774.7

Ensembl

Gene	Transcript	HGVSc	HGVSp	Effect	#exon/exons	TSL	MANE	Appris	UniProt
MLH3	ENST00000355774.7	c.397T>G	p.Cys133Gly	missense_variant	2/13	5	NM_001040108.2	P1
MLH3	ENST00000380968.6	c.397T>G	p.Cys133Gly	missense_variant	2/12	1
MLH3	ENST00000556257.5	c.397T>G	p.Cys133Gly	missense_variant	2/7	5
MLH3	ENST00000553263.1	c.397T>G	p.Cys133Gly	missense_variant	2/2	2

Frequencies

GnomAD3 genomes Cov.: 33

GnomAD4 exome AF: 0.00000137 AC: 2 AN: 1461876 Hom.: 0 Cov.: 35 AF XY: 0.00 AC XY: 0 AN XY: 727236

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: 0.00

Gnomad4 FIN exome AF: 0.00

Gnomad4 NFE exome AF: 0.00000180

Gnomad4 OTH exome AF: 0.00

GnomAD4 genome Cov.: 33

ClinVar

Significance: Uncertain significance

Submissions summary: Uncertain:2

Revision: criteria provided, multiple submitters, no conflicts

Submissions by phenotype

not specified Uncertain:1

Uncertain significance, criteria provided, single submitter

clinical testing

Ambry Genetics

Sep 27, 2021

The p.C133G variant (also known as c.397T>G), located in coding exon 1 of the MLH3 gene, results from a T to G substitution at nucleotide position 397. The cysteine at codon 133 is replaced by glycine, an amino acid with highly dissimilar properties. This amino acid position is conserved. In addition, this alteration is predicted to be tolerated by in silico analysis. Since supporting evidence is limited at this time, the clinical significance of this alteration remains unclear. -

Colorectal cancer, hereditary nonpolyposis, type 7 Uncertain:1

Uncertain significance, criteria provided, single submitter

clinical testing

Labcorp Genetics (formerly Invitae), Labcorp

May 07, 2017

In summary, this variant is a novel missense change that is not predicted to affect protein function. There is no indication that it causes disease, but the available evidence is currently insufficient to prove that conclusively. 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 tolerated, but these predictions have not been confirmed by published functional studies. This variant is not present in population databases (ExAC no frequency) and has not been reported in the literature in individuals with an MLH3-related disease. This sequence change replaces cysteine with glycine at codon 133 of the MLH3 protein (p.Cys133Gly). The cysteine residue is weakly conserved and there is a large physicochemical difference between cysteine and glycine. -

Computational scores

Source: dbNSFP v4.3

Name	Calibrated prediction	Score	Prediction
AlphaMissense	Benign	0.11
BayesDel_addAF	Benign	-0.0092	T
BayesDel_noAF	Benign	-0.25
CADD	Benign	17
DANN	Benign	0.88
DEOGEN2	Benign	0.20	T;.;.;T;.
Eigen	Benign	-0.50
Eigen_PC	Benign	-0.46
FATHMM_MKL	Benign	0.46	N
LIST_S2	Benign	0.79	T;T;T;.;T
M_CAP	Benign	0.022	T
MetaRNN	Benign	0.21	T;T;T;T;T
MetaSVM	Benign	-0.65	T
MutationAssessor	Benign	-0.10	N;N;.;N;.
MutationTaster	Benign	1.0	N;N;N;N;N
PrimateAI	Benign	0.41	T
PROVEAN	Uncertain	-4.2	D;.;D;D;D
REVEL	Benign	0.27
Sift	Benign	0.33	T;.;T;T;T
Sift4G	Benign	0.30	T;T;T;T;.
Polyphen		0.75	P;P;.;P;.
Vest4		0.30
MutPred		0.53		Gain of catalytic residue at K131 (P = 0.0025);Gain of catalytic residue at K131 (P = 0.0025);Gain of catalytic residue at K131 (P = 0.0025);Gain of catalytic residue at K131 (P = 0.0025);Gain of catalytic residue at K131 (P = 0.0025);
MVP		0.73
MPC		0.13
ClinPred		0.36	T
GERP RS		1.9
Varity_R		0.19
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: rs1555346244; hg19: chr14-75515962;