6-33438071-CAG-C

Position:

• chr6-33438071-CAG-C

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.1167_1168del​(p.Gly391GlnfsTer27) variant causes a frameshift change involving the alteration of a non-conserved nucleotide. The variant was absent in control chromosomes in GnomAD project. Variant has been reported in ClinVar as Pathogenic (★★). Variant results in nonsense mediated mRNA decay.

• Frequency: Genomes: not found (cov: 30)
• Consequence: SYNGAP1 NM_006772.3 frameshift
• Clinical Significance: Pathogenic criteria provided, multiple submitters, no conflicts P:8
• Conservation: PhyloP100: 2.50

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-AS1 (HGNC:53831): (SYNGAP1 antisense RNA 1)

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 6-33438071-CAG-C is Pathogenic according to our data. Variant chr6-33438071-CAG-C is described in ClinVar as [Pathogenic]. Clinvar id is 411566.Status of the report is criteria_provided_multiple_submitters_no_conflicts, 2 stars.

Transcripts

RefSeq

Gene	Transcript	HGVSc	HGVSp	Effect	#exon/exons	MANE	Protein	UniProt
SYNGAP1	NM_006772.3	c.1167_1168del	p.Gly391GlnfsTer27	frameshift_variant	8/19	ENST00000646630.1	NP_006763.2
SYNGAP1-AS1	NR_174954.1	n.330-592_330-591del		intron_variant, non_coding_transcript_variant

Ensembl

Gene	Transcript	HGVSc	HGVSp	Effect	#exon/exons	TSL	MANE	Protein	Appris	UniProt
SYNGAP1	ENST00000646630.1	c.1167_1168del	p.Gly391GlnfsTer27	frameshift_variant	8/19		NM_006772.3	ENSP00000496007	P1
SYNGAP1-AS1	ENST00000630418.1	n.378-592_378-591del		intron_variant, non_coding_transcript_variant		5

Frequencies

GnomAD3 genomes Cov.: 30

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

GnomAD4 genome Cov.: 30

ClinVar

Significance: Pathogenic

Submissions summary: Pathogenic:8

Revision: criteria provided, multiple submitters, no conflicts

Submissions by phenotype

Intellectual disability, autosomal dominant 5 Pathogenic:5

Pathogenic, criteria provided, single submitter	clinical testing	Revvity Omics, Revvity	Oct 10, 2023	- -
Pathogenic, criteria provided, single submitter	clinical testing	Labcorp Genetics (formerly Invitae), Labcorp	Oct 13, 2023	This sequence change creates a premature translational stop signal (p.Gly391Glnfs*27) 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: 30455457, 30541864, 31395010, 33639450). In at least one individual the variant was observed to be de novo. ClinVar contains an entry for this variant (Variation ID: 411566). For these reasons, this variant has been classified as Pathogenic. -
Pathogenic, criteria provided, single submitter	clinical testing	Victorian Clinical Genetics Services, Murdoch Childrens Research Institute	Dec 21, 2023	Based on the classification scheme VCGS_Germline_v1.3.4, this variant is classified as Pathogenic. Following criteria are met: 0102 - Loss of function is a known mechanism of disease in this gene and is associated with intellectual developmental disorder 5 (MIM#612621). (I) 0107 - This gene is associated with autosomal dominant disease. (I) 0201 - Variant is predicted to cause nonsense-mediated decay (NMD) and loss of protein (premature termination codon is located at least 54 nucleotides upstream of the final exon-exon junction). (SP) 0251 - This variant is heterozygous. (I) 0301 - Variant is absent from gnomAD (both v2 and v3). (SP) 0701 - Other NMD predicted variants comparable to the one identified in this case have very strong previous evidence for pathogenicity (DECIPHER). (SP) 0801 - This variant has strong previous evidence of pathogenicity in unrelated individuals. This variant has been reported many times as pathogenic and once as likely pathogenic (ClinVar). (SP) 1208 - Inheritance information for this variant is not currently available in this individual. (I) Legend: (SP) - Supporting pathogenic, (I) - Information, (SB) - Supporting benign -
Pathogenic, no assertion criteria provided	clinical testing	Pediatric Genetics Clinic, Sheba Medical Center	May 13, 2021	- -
Pathogenic, criteria provided, single submitter	clinical testing	Baylor Genetics	Sep 01, 2017	This frameshift variant is categorized as deleterious according to ACMG guidelines (PMID:18414213) and was found once in our laboratory de novo in a 10-year-old female with global delays, cerebellar ataxia, autsim, ptosis. -

not provided Pathogenic:2

Likely pathogenic, no assertion criteria provided	clinical testing	Molecular Genetics laboratory, Necker Hospital	Jul 16, 2018	- -
Pathogenic, criteria provided, single submitter	clinical testing	GeneDx	Jun 08, 2024	Frameshift 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; Not observed at significant frequency in large population cohorts (gnomAD); This variant is associated with the following publications: (PMID: 32593896, 30455457, 31395010, 33639450, 34580403, 31440721, 34924933, 38505260, 33057194, 35982159, 38045990, 30541864, 25326635) -

Inborn genetic diseases Pathogenic:1

Pathogenic, criteria provided, single submitter

clinical testing

Ambry Genetics

Nov 27, 2023

The c.1167_1168delAG (p.G391Qfs*27) alteration, located in coding exon 8 of the SYNGAP1 gene, consists of a deletion of 2 nucleotides from position 1167 to 1168, causing a translational frameshift with a predicted alternate stop codon after 27 amino acids. This alteration is expected to result in loss of function by premature protein truncation or nonsense-mediated mRNA decay. This variant was not reported in population-based cohorts in the Genome Aggregation Database (gnomAD). This variant has been reported in multiple children with seizures and cognitive impairment (Jimenez-Gomez, 2019; Pode-Shakked, 2021). Based on the available evidence, this alteration is classified as pathogenic. -

Computational scores

Source: dbNSFP v4.3

Splicing

Name	Calibrated prediction	Score	Prediction
SpliceAI score (max)		0.010		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: rs1060503378; hg19: chr6-33405848;