6-33443829-C-T

Position:

• chr6-33443829-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.3277C>T​(p.Gln1093Ter) 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 Pathogenic (★★). Variant results in nonsense mediated mRNA decay.

• Frequency:
  • Genomes: not found (cov: 32)
  • Exomes 𝑓: 0.0 (0 hom.)
  • Failed GnomAD Quality Control
• Consequence: SYNGAP1 NM_006772.3 stop_gained
• Clinical Significance: Pathogenic criteria provided, multiple submitters, no conflicts P:2
• Conservation: PhyloP100: 3.52

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 6-33443829-C-T is Pathogenic according to our data. Variant chr6-33443829-C-T is described in ClinVar as [Pathogenic]. Clinvar id is 488875.Status of the report is criteria_provided_multiple_submitters_no_conflicts, 2 stars. Variant chr6-33443829-C-T is described in Lovd as [Pathogenic].

Transcripts

RefSeq

Gene	Transcript	HGVSc	HGVSp	Effect	#exon/exons	MANE	UniProt
SYNGAP1	NM_006772.3	c.3277C>T	p.Gln1093Ter	stop_gained	15/19	ENST00000646630.1
SYNGAP1-AS1	NR_174954.1	n.329+2777G>A		intron_variant, non_coding_transcript_variant

Ensembl

Gene	Transcript	HGVSc	HGVSp	Effect	#exon/exons	TSL	MANE	Appris	UniProt
SYNGAP1	ENST00000646630.1	c.3277C>T	p.Gln1093Ter	stop_gained	15/19		NM_006772.3	P1
SYNGAP1-AS1	ENST00000630418.1	n.377+2777G>A		intron_variant, non_coding_transcript_variant		5

Frequencies

GnomAD3 genomes Cov.: 32

GnomAD4 exome Data not reliable, filtered out with message: AC0;AS_VQSR AF: 0.00 AC: 0 AN: 1410890 Hom.: 0 Cov.: 65 AF XY: 0.00 AC XY: 0 AN XY: 695378

Gnomad4 AFR exome AF: 0.00

Gnomad4 AMR exome AF: 0.00

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: 0.00

Gnomad4 OTH exome AF: 0.00

GnomAD4 genome Cov.: 32

ClinVar

Significance: Pathogenic

Submissions summary: Pathogenic:2

Revision: criteria provided, multiple submitters, no conflicts

Submissions by phenotype

Intellectual disability, autosomal dominant 5 Pathogenic:1

Pathogenic, criteria provided, single submitter

clinical testing

Baylor Genetics

Sep 01, 2017

This nonsense variant is categorized as deleterious according to ACMG guidelines (PMID:18414213) and was found once in our laboratory de novo in a 3-year-old male with global delays, autism, seizure disorder, global hypotonia. -

not provided Pathogenic:1

Pathogenic, criteria provided, single submitter

clinical testing

GeneDx

Jun 29, 2017

The Q1093X variant in the SYNGAP1 gene has been reported previously as a confirmed de novo variant in two unrelated patients with global developmental delay, speech delay, and ptosis. Additionally, one patient was also noted to have intellectual disability, autism spectrum disorder, and seizures (Parker et al., 2015; Fitzgerald et al., 2015). This variant is predicted to cause loss of normal protein function either through protein truncation or nonsense-mediated mRNA decay. The Q1093X variant is not observed in large population cohorts (Lek et al., 2016; 1000 Genomes Consortium et al., 2015; Exome Variant Server). -

Computational scores

Source: dbNSFP v4.3

Name	Calibrated prediction	Score	Prediction
BayesDel_addAF	Pathogenic	0.63	D
BayesDel_noAF	Pathogenic	0.60
CADD	Pathogenic	38
DANN	Uncertain	1.0
Eigen	Pathogenic	0.98
Eigen_PC	Pathogenic	0.80
FATHMM_MKL	Uncertain	0.89	D
MutationTaster	Benign	1.0	A;A;A;A
Vest4		0.85, 0.87, 0.85, 0.88
GERP RS		4.4
RBP_binding_hub_radar		0.0
RBP_regulation_power_radar		1.7

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: rs1554122363; hg19: chr6-33411606;