chr6-33442989-CT-C

Position:

• chr6-33442989-CT-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.2438delT​(p.Leu813fs) 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: 31)
• Consequence: SYNGAP1 NM_006772.3 frameshift
• Clinical Significance: Pathogenic criteria provided, multiple submitters, no conflicts P:5
• Conservation: PhyloP100: 3.27

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 6-33442989-CT-C is Pathogenic according to our data. Variant chr6-33442989-CT-C is described in ClinVar as [Pathogenic]. Clinvar id is 6394.Status of the report is criteria_provided_multiple_submitters_no_conflicts, 2 stars. Variant chr6-33442989-CT-C is described in Lovd as [Pathogenic].

Transcripts

RefSeq

Gene	Transcript	HGVSc	HGVSp	Effect	#exon/exons	MANE	Protein	UniProt
SYNGAP1	NM_006772.3	c.2438delT	p.Leu813fs	frameshift_variant	15/19	ENST00000646630.1	NP_006763.2

Ensembl

Gene	Transcript	HGVSc	HGVSp	Effect	#exon/exons	TSL	MANE	Protein	Appris	UniProt
SYNGAP1	ENST00000646630.1	c.2438delT	p.Leu813fs	frameshift_variant	15/19		NM_006772.3	ENSP00000496007.1
SYNGAP1	ENST00000644458.1	c.2438delT	p.Leu813fs	frameshift_variant	15/19			ENSP00000495541.1
SYNGAP1	ENST00000449372.7	c.2396delT	p.Leu799fs	frameshift_variant	14/18	5		ENSP00000416519.4
SYNGAP1	ENST00000418600.7	c.2438delT	p.Leu813fs	frameshift_variant	15/19	5		ENSP00000403636.3
SYNGAP1	ENST00000645250.1	c.2261delT	p.Leu754fs	frameshift_variant	13/17			ENSP00000494861.1

Frequencies

GnomAD3 genomes Cov.: 31

GnomAD4 exome Cov.: 33

GnomAD4 genome Cov.: 31

ClinVar

Significance: Pathogenic

Submissions summary: Pathogenic:5

Revision: criteria provided, multiple submitters, no conflicts

Submissions by phenotype

Intellectual disability, autosomal dominant 5 Pathogenic:4

Pathogenic, criteria provided, single submitter	clinical testing	Baylor Genetics	Sep 01, 2017	This frameshift variant has been previously reported as disease-causing and was found once in our laboratory de novo in a 4-year-old female with global delays, autism, microcephaly, ataxic gait, hyperflexibility, nystagmus. -
Pathogenic, no assertion criteria provided	literature only	OMIM	Feb 05, 2009	- -
Pathogenic, criteria provided, single submitter	clinical testing	3billion	Feb 23, 2023	The variant is not observed in the gnomAD v2.1.1 dataset. This variant was predicted to result in a loss or disruption of normal protein function through nonsense-mediated decay (NMD) or protein truncation. Multiple pathogenic variants are reported downstream of the variant. The variant has been reported at least twice as pathogenic with clinical assertions and evidence for the classification (ClinVar ID: VCV000006394 / PMID: 19196676). Therefore, this variant is classified as Pathogenic according to the recommendation of ACMG/AMP guideline. -
Pathogenic, criteria provided, single submitter	clinical testing	Labcorp Genetics (formerly Invitae), Labcorp	Jan 19, 2024	This sequence change creates a premature translational stop signal (p.Leu813Argfs*23) 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: 19196676, 31395010). This variant is also known as L813RfsX22. ClinVar contains an entry for this variant (Variation ID: 6394). For these reasons, this variant has been classified as Pathogenic. -

not provided Pathogenic:1

Pathogenic, criteria provided, single submitter

clinical testing

GeneDx

Jun 06, 2022

Published functional studies demonstrate a damaging effect on the synaptic plasticity process (Araki et al., 2015); 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 in large population cohorts (gnomAD); This variant is associated with the following publications: (PMID: 23161826, 21237447, 21376300, 19196676, 25852444, 31395010, 25326635, 25569349) -

Computational scores

Source: dbNSFP v4.3

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: rs397515320; hg19: chr6-33410766;