6-33441318-C-T

Position:

• chr6-33441318-C-T

Variant summary

Our verdict is Pathogenic. Variant got 18 ACMG points: 18P and 0B. PVS1 PM2 PP5_Very_Strong

The NM_006772.3(SYNGAP1):​c.2059C>T​(p.Arg687*) variant causes a stop gained change involving the alteration of a non-conserved nucleotide. 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 Likely pathogenic (★★). Variant results in nonsense mediated mRNA decay.

• Frequency: Genomes: not found (cov: 31)
• Consequence: SYNGAP1 NM_006772.3 stop_gained
• Clinical Significance: Pathogenic/Likely pathogenic criteria provided, multiple submitters, no conflicts P:11
• Conservation: PhyloP100: 2.69

Genes affected

SYNGAP1 (HGNC:11497): (synaptic Ras GTPase activating protein 1) This gene encodes a Ras GTPase activating protein that is a member of the N-methyl-D-aspartate receptor complex. The N-terminal domain of the protein contains a Ras-GAP domain, a pleckstrin homology domain, and a C2 domain that may be involved in binding of calcium and phospholipids. The C-terminal domain consists of a ten histidine repeat region, serine and tyrosine phosphorylation sites, and a T/SXV motif required for postsynaptic scaffold protein interaction. The encoded protein negatively regulates Ras, Rap and alpha-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid receptor trafficking to the postsynaptic membrane to regulate synaptic plasticity and neuronal homeostasis. Allelic variants of this gene are associated with intellectual disability and autism spectrum disorder. Alternative splicing results in multiple transcript variants. [provided by RefSeq, Nov 2016]

SYNGAP1 (HGNC:):

ACMG classification

Verdict is Pathogenic. Variant got 18 ACMG points.

• PVS1: Loss of function variant, product undergoes nonsense mediated mRNA decay. LoF is a known mechanism of disease.
• PM2: Very rare variant in population databases, with high coverage
• PP5: Variant 6-33441318-C-T is Pathogenic according to our data. Variant chr6-33441318-C-T is described in ClinVar as [Likely_pathogenic]. Clinvar id is 411584.Status of the report is criteria_provided_multiple_submitters_no_conflicts, 2 stars. Variant chr6-33441318-C-T is described in Lovd as [Pathogenic].

Transcripts

RefSeq

Gene	Transcript	HGVSc	HGVSp	Effect	#exon/exons	MANE	Protein	UniProt
SYNGAP1	NM_006772.3	c.2059C>T	p.Arg687*	stop_gained	12/19	ENST00000646630.1	NP_006763.2

Ensembl

Gene	Transcript	HGVSc	HGVSp	Effect	#exon/exons	TSL	MANE	Protein	Appris	UniProt
SYNGAP1	ENST00000646630.1	c.2059C>T	p.Arg687*	stop_gained	12/19		NM_006772.3	ENSP00000496007.1
SYNGAP1	ENST00000644458.1	c.2059C>T	p.Arg687*	stop_gained	12/19			ENSP00000495541.1
SYNGAP1	ENST00000449372.7	c.2059C>T	p.Arg687*	stop_gained	12/18	5		ENSP00000416519.4
SYNGAP1	ENST00000418600.7	c.2059C>T	p.Arg687*	stop_gained	12/19	5		ENSP00000403636.3
SYNGAP1	ENST00000645250.1	c.1882C>T	p.Arg628*	stop_gained	10/17			ENSP00000494861.1

Frequencies

GnomAD3 genomes Cov.: 31

GnomAD4 exome Cov.: 33

GnomAD4 genome Cov.: 31

ClinVar

Significance: Pathogenic/Likely pathogenic

Submissions summary: Pathogenic:11

Revision: criteria provided, multiple submitters, no conflicts

Submissions by phenotype

Intellectual disability, autosomal dominant 5 Pathogenic:5

Pathogenic, criteria provided, single submitter	clinical testing	Institute of Human Genetics, University of Leipzig Medical Center	Nov 19, 2020	- -
Pathogenic, criteria provided, single submitter	clinical testing	Labcorp Genetics (formerly Invitae), Labcorp	Aug 16, 2023	This sequence change creates a premature translational stop signal (p.Arg687*) in the SYNGAP1 gene. It is expected to result in an absent or disrupted protein product. Loss-of-function variants in SYNGAP1 are known to be pathogenic (PMID: 23161826, 23708187, 26989088). This variant is not present in population databases (gnomAD no frequency). This premature translational stop signal has been observed in individual(s) with clinical features of SYNGAP1-related conditions (PMID: 30440138, 30541864). ClinVar contains an entry for this variant (Variation ID: 411584). For these reasons, this variant has been classified as Pathogenic. -
Pathogenic, criteria provided, single submitter	clinical testing	Molecular Genetics Lab, CHRU Brest	-	- -
Pathogenic, criteria provided, single submitter	clinical testing	Fulgent Genetics, Fulgent Genetics	Oct 31, 2018	- -
Likely pathogenic, criteria provided, single submitter	clinical testing	Center for Genomic Medicine, King Faisal Specialist Hospital and Research Center	Apr 04, 2024	- -

not provided Pathogenic:4

Pathogenic, criteria provided, single submitter	clinical testing	Clinical Genetics Laboratory, Skane University Hospital Lund	Aug 05, 2022	- -
Pathogenic, no assertion criteria provided	clinical testing	Genome Diagnostics Laboratory, Amsterdam University Medical Center	-	- -
Pathogenic, criteria provided, single submitter	clinical testing	GeneDx	Sep 11, 2024	Published functional studies demonstrate significantly decreased protein stability and altered subcellular localization (PMID: 33308442); Not observed in large population cohorts (gnomAD); Nonsense variant predicted to result in protein truncation or nonsense mediated decay in a gene for which loss of function is a known mechanism of disease; This variant is associated with the following publications: (PMID: 30541864, 30440138, 33308442, 32913957, 33639450, 31440721, 35390071, 34924933, 33057194, 36583017, 35982159) -
Pathogenic, no assertion criteria provided	clinical testing	Joint Genome Diagnostic Labs from Nijmegen and Maastricht, Radboudumc and MUMC+	-	- -

Aggressive behavior;C0004941:Atypical behavior;C0005745:Ptosis;C0239676:High forehead;C0423110:Downslanted palpebral fissures;C0454644:Delayed speech and language development;C1835884:Triangular face;C1844505:Pointed chin;C1849367:Wide nasal bridge;C1854301:Motor delay;C1860493:Abnormal sternum morphology;C1860834:Infantile muscular hypotonia;C4025747:Bulbous tips of toes Pathogenic:1

Likely pathogenic, criteria provided, single submitter

clinical testing

Centre for Mendelian Genomics, University Medical Centre Ljubljana

Jan 01, 2017

- -

See cases Pathogenic:1

Pathogenic, criteria provided, single submitter

clinical testing

Institute of Human Genetics, University Hospital Muenster

Oct 10, 2022

ACMG categories: PVS1,PM2,PP5 -

Computational scores

Source: dbNSFP v4.3

Name	Calibrated prediction	Score	Prediction
BayesDel_addAF	Pathogenic	0.63	D
BayesDel_noAF	Pathogenic	0.51
CADD	Pathogenic	39
DANN	Uncertain	1.0
Eigen	Pathogenic	0.80
Eigen_PC	Pathogenic	0.67
FATHMM_MKL	Uncertain	0.80	D
Vest4		0.97, 0.97, 0.95
GERP RS		4.9

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: rs1060503383; hg19: chr6-33409095;