rs63749994

chr3-36993638-GC-TG

Variant summary

Our verdict is Uncertain significance. Variant got 4 ACMG points: 5P and 1B. PS1_Moderate PM1 PP3 BP6

The NM_000249.4(MLH1):c.91_92delinsTG(p.Ala31Cys) variant causes a missense change involving the alteration of a conserved nucleotide. Variant has been reported in ClinVar as Conflicting classifications of pathogenicity (no stars). Another nucleotide change resulting in same amino acid change has been previously reported as Likely pathogenicin UniProt. Another variant affecting the same amino acid position, but resulting in a different missense (i.e. A31S) has been classified as Uncertain significance.

• Frequency: Genomes: not found (cov: 33)
• Consequence: MLH1 NM_000249.4 missense
• Clinical Significance: Conflicting classifications of pathogenicity criteria provided, conflicting classifications U:7 B:6
• Conservation: PhyloP100: 9.49

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 4 ACMG points.

• PS1: Transcript NM_000249.4 (MLH1) is affected with MISSENSE_VARIANT having same AA change as one Pathogenic present in UniProt
• PM1: In a hotspot region, there are 11 aminoacids with missense pathogenic changes in the window of +-8 aminoacids around while only 2 benign, 16 uncertain in NM_000249.4
• PP3: No computational evidence supports a deleterious effect, but strongly conserved according to phyloP
• BP6: Variant 3-36993638-GC-TG is Benign according to our data. Variant chr3-36993638-GC-TG is described in ClinVar as [Conflicting_classifications_of_pathogenicity]. Clinvar id is 90442.We mark this variant Likely_benign, oryginal submissions are: {Likely_benign=5, Uncertain_significance=7, Benign=1}.

Transcripts

RefSeq

Gene	Transcript	HGVSc	HGVSp	Effect	#exon/exons	MANE	UniProt
MLH1	NM_000249.4	c.91_92delinsTG	p.Ala31Cys	missense_variant	1/19	ENST00000231790.8

Ensembl

Gene	Transcript	HGVSc	HGVSp	Effect	#exon/exons	TSL	MANE	Appris	UniProt
MLH1	ENST00000231790.8	c.91_92delinsTG	p.Ala31Cys	missense_variant	1/19	1	NM_000249.4	P1

Frequencies

GnomAD3 genomes Cov.: 33

We have no GnomAD4 exomes data on this position. Probably position not covered by the project.

GnomAD4 genome Cov.: 33

ClinVar

Significance: Conflicting classifications of pathogenicity

Submissions summary: Uncertain:7 Benign:6

Revision: criteria provided, conflicting classifications

Submissions by phenotype

Colorectal cancer, hereditary nonpolyposis, type 2 Uncertain:2 Benign:1

Likely benign, criteria provided, single submitter	clinical testing	Myriad Genetics, Inc.	Mar 14, 2023	This variant is considered likely benign. This variant is strongly associated with less severe personal and family histories of cancer, typical for individuals without pathogenic variants in this gene [PMID: 25085752]. -
Uncertain significance, criteria provided, single submitter	clinical testing	Center for Genomic Medicine, King Faisal Specialist Hospital and Research Center	Mar 29, 2024	- -
Uncertain significance, criteria provided, single submitter	clinical testing	Counsyl	Nov 26, 2015	- -

Hereditary cancer-predisposing syndrome Uncertain:2 Benign:1

Likely benign, criteria provided, single submitter	clinical testing	Ambry Genetics	Dec 28, 2018	This alteration is classified as likely benign based on a combination of the following: seen in unaffected individuals, population frequency, intact protein function, lack of segregation with disease, co-occurrence, RNA analysis, in silico models, amino acid conservation, lack of disease association in case-control studies, and/or the mechanism of disease or impacted region is inconsistent with a known cause of pathogenicity. -
Uncertain significance, criteria provided, single submitter	clinical testing	Color Diagnostics, LLC DBA Color Health	Apr 05, 2023	This missense variant replaces alanine with cysteine at codon 31 of the MLH1 protein. Computational prediction suggests that this variant may have deleterious impact on protein structure and function. A functional study reported the variant protein as partially to fully impaired compared to wild-type in an in vitro DNA mismatch repair assay (PMID: 20020535). This variant has been reported in individuals with personal and/or family history of Lynch Syndrome-associated cancers (PMID: 21404117, 27443514, 28874130) and an individual affected with breast or ovarian cancer (PMID: 28828701). This variant is present in gnomAD as combination of two constituent single nucleotide variants in 21 chromosomes, and in all individuals, they are predicted to be located on the same chromosome (in cis). The variant has been identified in 9/30614 chromosomes (0.029%) of South Asians. The available evidence is insufficient to determine the role of this variant in disease conclusively. Therefore, this variant is classified as a Variant of Uncertain Significance. -
Uncertain significance, criteria provided, single submitter	clinical testing	GeneKor MSA	Aug 01, 2018	- -

not provided Uncertain:1 Benign:2

Likely benign, criteria provided, single submitter	clinical testing	GeneDx	Jul 20, 2020	In silico analysis, which includes protein predictors and evolutionary conservation, supports a deleterious effect; This variant is associated with the following publications: (PMID: 27150160, 20020535, 16395668, 21404117, 12624141, 28874130, 27443514, 31159747) -
Likely benign, criteria provided, single submitter	clinical testing	Quest Diagnostics Nichols Institute San Juan Capistrano	Jul 18, 2023	- -
Uncertain significance, criteria provided, single submitter	clinical testing	Revvity Omics, Revvity	Aug 20, 2021	- -

Breast and/or ovarian cancer Uncertain:1

Uncertain significance, criteria provided, single submitter

clinical testing

CHEO Genetics Diagnostic Laboratory, Children's Hospital of Eastern Ontario

Aug 11, 2021

- -

Muir-Torré syndrome;C1333991:Colorectal cancer, hereditary nonpolyposis, type 2;C5399763:Mismatch repair cancer syndrome 1 Uncertain:1

Uncertain significance, criteria provided, single submitter

clinical testing

Fulgent Genetics, Fulgent Genetics

Oct 31, 2018

- -

not specified Benign:1

Likely benign, criteria provided, single submitter

clinical testing

Women's Health and Genetics/Laboratory Corporation of America, LabCorp

May 23, 2022

Variant summary: MLH1 c.91_92delinsTG (p.Ala31Cys) results in a non-conservative amino acid change located in the DNA mismatch repair protein family, N-terminal and Histidine kinase/HSP90-like ATPase of the encoded protein sequence. Four of five in-silico tools predict a damaging effect of the variant on protein function. The variant allele was found at a frequency of 7.8e-05 in 282508 control chromosomes. This frequency is not significantly higher than expected for a pathogenic variant in MLH1 causing Hereditary Nonpolyposis Colorectal Cancer (7.8e-05 vs 0.00071), allowing no conclusion about variant significance. c.91_92delinsTG has been reported in the literature in settings of multigene panel testing among individuals affected with a variety of cancers such as (example, Auclair_2006, Hardt_2011, Parc_2003, Ring_2016, Rossi_2017, Zidan_2017). These report(s) do not provide unequivocal conclusions about association of the variant with Hereditary Nonpolyposis Colorectal Cancer/Lynch Syndrome. Multiple co-occurrences with other pathogenic variant(s) have been observed in the UMD database and at our laboratory (UMD-MSH2 c.1156C>T , p.Arg389X; MLH1 c.1852_1854del; , p.Lys618del ; Our laboratory-BRCA1 c.3700_3704delCTAAA; CHEK2 c.1169A>C, p.Y390S), providing supporting evidence for a benign role. Functional studies show the variant to not affect splicing and to have significantly higher repair activity compared to putatively pathogenic variants, performing slightly comparable to wild type function (Auclair_2006, Drost_2010). Eight clinical diagnostic laboratories have submitted clinical-significance assessments for this variant to ClinVar after 2014 without evidence for independent evaluation. Multiple laboratories reported the variant with conflicting assessments (VUS, n=5; Likely benign/Benign, n=3). Based on the evidence outlined above, the variant was classified as likely benign. -

Hereditary nonpolyposis colorectal neoplasms Benign:1

Benign, criteria provided, single submitter

clinical testing

Invitae

Jan 21, 2024

- -

Computational scores

Source: dbNSFP v4.3

Splicing

Find out detailed SpliceAI scores and Pangolin per-transcript scores at spliceailookup.broadinstitute.org

Publications

LitVar

Other links and lift over

dbSNP: rs63749994; hg19: chr3-37035129;