rs866260675

Positions:

• chr5-80778719-G-A
• chr5-80778719-G-C

Variant summary

Our verdict is Pathogenic. Variant got 10 ACMG points: 10P and 0B. PVS1_Moderate PP5_Very_Strong

The NM_002439.5(MSH3):​c.2319-1G>A variant causes a splice acceptor change involving the alteration of a conserved nucleotide. The variant allele was found at a frequency of 0.00000705 in 1,418,538 control chromosomes in the GnomAD database, with no homozygous occurrence. In-silico tool predicts a pathogenic outcome for this variant. 3/3 splice prediction tools predicting alterations to normal splicing. Variant has been reported in ClinVar as Likely pathogenic (★★).

• Frequency:
  • Genomes: not found (cov: 32)
  • Exomes 𝑓: 0.0000070 (0 hom.)
• Consequence: MSH3 NM_002439.5 splice_acceptor
• Scores: Splicing: ADA: 1.000
• Clinical Significance: Pathogenic/Likely pathogenic criteria provided, multiple submitters, no conflicts P:7
• Conservation: PhyloP100: 7.21

Genes affected

MSH3 (HGNC:7326): (mutS homolog 3) The protein encoded by this gene forms a heterodimer with MSH2 to form MutS beta, part of the post-replicative DNA mismatch repair system. MutS beta initiates mismatch repair by binding to a mismatch and then forming a complex with MutL alpha heterodimer. This gene contains a polymorphic 9 bp tandem repeat sequence in the first exon. The repeat is present 6 times in the reference genome sequence and 3-7 repeats have been reported. Defects in this gene are a cause of susceptibility to endometrial cancer. [provided by RefSeq, Mar 2011]

ACMG classification

Verdict is Pathogenic. Variant got 10 ACMG points.

• PVS1: Splicing +-2 bp (donor or acceptor) variant, product NOT destroyed by NMD, known LOF gene, truncates exone, which is 0.03397774 fraction of the gene. Cryptic splice site detected, with MaxEntScore 9, offset of 41, new splice context is: tcactctccttttattgtAGaaa. Cryptic site results in frameshift change. If cryptic site found is not functional and variant results in exon loss, it results in inframe change.
• PP5: Variant 5-80778719-G-A is Pathogenic according to our data. Variant chr5-80778719-G-A is described in ClinVar as [Likely_pathogenic]. Clinvar id is 253325.Status of the report is criteria_provided_multiple_submitters_no_conflicts, 2 stars. Variant chr5-80778719-G-A is described in Lovd as [Pathogenic]. Variant chr5-80778719-G-A is described in Lovd as [Likely_pathogenic].

Transcripts

RefSeq

Gene	Transcript	HGVSc	HGVSp	Effect	#exon/exons	MANE	Protein	UniProt
MSH3	NM_002439.5	c.2319-1G>A		splice_acceptor_variant		ENST00000265081.7	NP_002430.3

Ensembl

Gene	Transcript	HGVSc	HGVSp	Effect	#exon/exons	TSL	MANE	Protein	Appris	UniProt
MSH3	ENST00000265081.7	c.2319-1G>A		splice_acceptor_variant		1	NM_002439.5	ENSP00000265081	P2
MSH3	ENST00000658259.1	c.2151-1G>A		splice_acceptor_variant				ENSP00000499617	A2
MSH3	ENST00000667069.1	c.2124-1G>A		splice_acceptor_variant				ENSP00000499502
MSH3	ENST00000670357.1	c.2319-1G>A		splice_acceptor_variant, NMD_transcript_variant				ENSP00000499791

Frequencies

GnomAD3 genomes Cov.: 32

GnomAD4 exome AF: 0.00000705 AC: 10 AN: 1418538 Hom.: 0 Cov.: 27 AF XY: 0.00000988 AC XY: 7 AN XY: 708470

Gnomad4 AFR exome AF: 0.00

Gnomad4 AMR exome AF: 0.0000224

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: 0.00000839

Gnomad4 OTH exome AF: 0.00

GnomAD4 genome Cov.: 32

Alfa AF: 0.0000423 Hom.: 0

ClinVar

Significance: Pathogenic/Likely pathogenic

Submissions summary: Pathogenic:7

Revision: criteria provided, multiple submitters, no conflicts

Submissions by phenotype

not provided Pathogenic:3

Pathogenic, criteria provided, single submitter	clinical testing	CeGaT Center for Human Genetics Tuebingen	Jul 01, 2024	MSH3: PVS1, PM2, PM3, PS4:Moderate, PS3:Supporting -
Pathogenic, criteria provided, single submitter	clinical testing	Labcorp Genetics (formerly Invitae), Labcorp	Jan 15, 2024	This sequence change affects an acceptor splice site in intron 16 of the MSH3 gene. RNA analysis indicates that disruption of this splice site induces altered splicing and likely results in a shortened protein product. This variant is not present in population databases (gnomAD no frequency). Disruption of this splice site has been observed in individuals with MSH3-associated polyposis (PMID: 27476653; Invitae). It has also been observed to segregate with disease in related individuals. ClinVar contains an entry for this variant (Variation ID: 253325). Studies have shown that disruption of this splice site results in skipping of exon 17, but is expected to preserve the integrity of the reading-frame (PMID: 27476653; Invitae). For these reasons, this variant has been classified as Pathogenic. -
Pathogenic, criteria provided, single submitter	clinical testing	GeneDx	Sep 27, 2023	Published functional studies demonstrate a damaging effect: in-frame loss of adjacent exon 17 (Adam et al., 2016); Canonical splice site variant predicted to result in an in-frame loss of the adjacent exon in a gene for which loss of function is a known mechanism of disease; Not observed at significant frequency in large population cohorts (gnomAD); This variant is associated with the following publications: (PMID: 31589614, 33193653, 34843512, 28875981, 34961301, 27476653) -

Familial adenomatous polyposis 4 Pathogenic:2

Likely pathogenic, criteria provided, single submitter	clinical testing	Myriad Genetics, Inc.	Aug 30, 2023	This variant is considered likely pathogenic. This variant occurs within a consensus splice junction and is predicted to result in abnormal mRNA splicing of either an out-of-frame exon or an in-frame exon necessary for protein stability and/or normal function. -
Pathogenic, no assertion criteria provided	literature only	OMIM	Aug 31, 2016	- -

Hereditary cancer-predisposing syndrome Pathogenic:1

Pathogenic, criteria provided, single submitter

clinical testing

Ambry Genetics

Jan 04, 2022

The c.2319-1G>A intronic variant results from a G to A substitution one nucleotide upstream from coding exon 17 of the MSH3 gene. Alterations that disrupt the canonical splice site are expected to result in aberrant splicing. In silico splice site analysis predicts that this alteration will weaken the native splice acceptor site. The resulting transcript is predicted to be in-frame and is not expected to trigger nonsense-mediated mRNA decay; however, direct evidence is unavailable. The exact functional effect of the altered amino acid sequence is unknown; however, the impacted region is critical for protein function (Ambry internal data). This variant has been reported in the heterozygous state in studies of individuals with gastrointestinal cancers (Djursby M et al. Front Genet, 2020 Sep;11:566266; Vogelaar IP et al. Eur J Hum Genet, 2017 11;25:1246-1252). In another study, this variant was identified in conjunction with a MSH3 frameshift mutation in two siblings with multiple colorectal adenomatous polyps (one sibling was also diagnosed with astrocytoma, duodenal adenomas, thyroid adenomas, and intraductal papillomas). This patient had constitutional MSH3 loss on immunohistochemical staining. The same study found that c.2319-1G>A caused abnormal splicing resulting in the loss of exon 17, which is expected to cause an in-frame deletion of 39 amino acids at the protein level (Adam R et al. Am. J. Hum. Genet., 2016 Aug;99:337-51). Based on internal structural analysis, loss of exon 17 impacts the lever domain and is predicted to impair DNA binding (Gupta S et al. Nat. Struct. Mol. Biol., 2011 Dec;19:72-8; Ambry internal data). RNA studies have demonstrated that this alteration results in abnormal splicing in the set of samples tested (Ambry internal data). This variant is considered to be rare based on population cohorts in the Genome Aggregation Database (gnomAD). This nucleotide position is highly conserved in available vertebrate species. Based on the supporting evidence, this alteration is interpreted as a disease-causing mutation. -

Endometrial carcinoma Pathogenic:1

Pathogenic, criteria provided, single submitter

clinical testing

Baylor Genetics

May 24, 2023

- -

Computational scores

Source: dbNSFP v4.3

Name	Calibrated prediction	Score	Prediction
BayesDel_addAF	Pathogenic	0.44	D
BayesDel_noAF	Pathogenic	0.39
CADD	Pathogenic	33
DANN	Uncertain	0.99
Eigen	Pathogenic	1.2
Eigen_PC	Pathogenic	1.1
FATHMM_MKL	Pathogenic	0.99	D
MutationTaster	Benign	1.0	D
GERP RS		5.7
RBP_binding_hub_radar		0.0
RBP_regulation_power_radar		1.7

Splicing

Name	Calibrated prediction	Score	Prediction
dbscSNV1_ADA	Pathogenic	1.0
dbscSNV1_RF	Pathogenic	0.94
SpliceAI score (max)		0.78		Details are displayed if max score is > 0.2
DS_AL_spliceai		0.78		Position offset: 1

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

Publications

LitVar

Other links and lift over

dbSNP: rs866260675; hg19: chr5-80074538;