rs63750642

Positions:

• chr3-37014532-C-G
• chr3-37014532-C-T

Variant summary

Our verdict is Likely pathogenic. Variant got 7 ACMG points: 7P and 0B. PM1 PM2 PM5 PP3

The NM_000249.4(MLH1):​c.778C>G​(p.Leu260Val) variant causes a missense change involving the alteration of a conserved nucleotide. The variant allele was found at a frequency of 0.0000014 in 1,426,314 control chromosomes in the GnomAD database, with no homozygous occurrence. In-silico tool predicts a pathogenic 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. L260R) has been classified as Pathogenic.

• Frequency:
  • Genomes: not found (cov: 33)
  • Exomes 𝑓: 0.0000014 (0 hom.)
• Consequence: MLH1 NM_000249.4 missense
• Clinical Significance: Uncertain significance criteria provided, single submitter U:1
• Conservation: PhyloP100: 7.57

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 7 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
• PM5: Other missense variant is known to change same aminoacid residue: Variant chr3-37014533-T-G is described in ClinVar as [Pathogenic]. Clinvar id is 90350.Status of the report is reviewed_by_expert_panel, 3 stars.
• PP3: MetaRNN computational evidence supports a deleterious effect, 0.777

Transcripts

RefSeq

Gene	Transcript	HGVSc	HGVSp	Effect	#exon/exons	MANE	UniProt
MLH1	NM_000249.4	c.778C>G	p.Leu260Val	missense_variant	9/19	ENST00000231790.8

Ensembl

Gene	Transcript	HGVSc	HGVSp	Effect	#exon/exons	TSL	MANE	Appris	UniProt
MLH1	ENST00000231790.8	c.778C>G	p.Leu260Val	missense_variant	9/19	1	NM_000249.4	P1

Frequencies

GnomAD3 genomes Cov.: 33

GnomAD4 exome AF: 0.00000140 AC: 2 AN: 1426314 Hom.: 0 Cov.: 26 AF XY: 0.00000281 AC XY: 2 AN XY: 711674

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: 0.00000185

Gnomad4 OTH exome AF: 0.00

GnomAD4 genome Cov.: 33

ClinVar

Significance: Uncertain significance

Submissions summary: Uncertain:1

Revision: criteria provided, single submitter

Submissions by phenotype

Hereditary cancer-predisposing syndrome Uncertain:1

Uncertain significance, criteria provided, single submitter

clinical testing

Ambry Genetics

May 19, 2015

The p.L260V variant (also known as c.778C>G), located in coding exon 9 of the MLH1 gene, results from a C to G substitution at nucleotide position 778. The leucine at codon 260 is replaced by valine, an amino acid with highly similar properties. This variant was not reported in population based cohorts in the following databases: Database of Single Nucleotide Polymorphisms (dbSNP), NHLBI Exome Sequencing Project (ESP), and 1000 Genomes Project. In the ESP, this variant was not observed in 6503 samples (13006 alleles) with coverage at this position. To date, this alteration has been detected with an allele frequency of approximately 0.002% (greater than 65000 alleles tested) in our clinical cohort. Based on protein sequence alignment, 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 borderline deleterious by MAPP-MMR in silico analyses (Chao E et al. Hum Mutat. 2008 Jun;29(6):852-60). Since supporting evidence is limited at this time, the clinical significance of p.L260V remains unclear. -

Computational scores

Source: dbNSFP v4.3

Name	Calibrated prediction	Score	Prediction
AlphaMissense	Benign	0.20
BayesDel_addAF	Pathogenic	0.41	D
BayesDel_noAF	Pathogenic	0.35
CADD	Pathogenic	26
DANN	Uncertain	1.0
DEOGEN2	Uncertain	0.74	D;.;.;.;.;.;.
Eigen	Uncertain	0.53
Eigen_PC	Uncertain	0.59
FATHMM_MKL	Pathogenic	0.99	D
LIST_S2	Pathogenic	0.98	D;D;.;.;.;D;D
M_CAP	Uncertain	0.13	D
MetaRNN	Pathogenic	0.78	D;D;D;D;D;D;D
MetaSVM	Benign	-0.30	T
MutationAssessor	Pathogenic	3.0	M;.;.;.;.;.;.
MutationTaster	Benign	1.0	D;D;D;D;D;D
PrimateAI	Uncertain	0.65	T
PROVEAN	Uncertain	-2.8	D;N;D;D;D;D;D
REVEL	Pathogenic	0.83
Sift	Uncertain	0.0040	D;D;D;D;D;D;D
Sift4G	Uncertain	0.041	D;D;D;D;D;T;D
Polyphen		0.97	D;.;.;.;.;.;.
Vest4		0.67
MutPred		0.65		Loss of sheet (P = 0.1501);.;.;.;.;.;.;
MVP		0.96
MPC		0.36
ClinPred		0.97	D
GERP RS		5.4
Varity_R		0.84
gMVP		0.62

Splicing

Name	Calibrated prediction	Score	Prediction
SpliceAI score (max)		0.060		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: rs63750642; hg19: chr3-37056023;