NM_006772.3:c.484C>T

Variant names:

• chr6-33432781-C-T
• rs1554120589
• NM_006772.3:c.484C>T

Variant summary

Our verdict is Uncertain significance. The variant received 5 ACMG points: 6P and 1B. PM1 PM2 PP5_Moderate BP4

The NM_006772.3(SYNGAP1):​c.484C>T​(p.Arg162Cys) variant causes a missense change involving the alteration of a non-conserved nucleotide. The variant was absent in control chromosomes in GnomAD project. In-silico tool predicts a benign outcome for this variant. Variant has been reported in ClinVar as Pathogenic (★). Another variant affecting the same amino acid position, but resulting in a different missense (i.e. R162G) has been classified as Uncertain significance.

• Frequency: Genomes: not found (cov: 31)
• Consequence: SYNGAP1 NM_006772.3 missense
• Clinical Significance: Pathogenic criteria provided, single submitter P:2
• Conservation: PhyloP100: 0.669
• Publications: 0 publications found

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 Gene-Disease associations (from GenCC):

• complex neurodevelopmental disorder

  Inheritance: AD Classification: DEFINITIVE Submitted by: ClinGen
• intellectual disability, autosomal dominant 5

  Inheritance: AD Classification: DEFINITIVE, STRONG Submitted by: G2P, Labcorp Genetics (formerly Invitae)
• autosomal dominant non-syndromic intellectual disability

  Inheritance: AD Classification: SUPPORTIVE Submitted by: Orphanet
• SYNGAP1-related developmental and epileptic encephalopathy

  Inheritance: AD Classification: SUPPORTIVE Submitted by: Orphanet
• myoclonic-astatic epilepsy

  Inheritance: Unknown Classification: SUPPORTIVE Submitted by: Orphanet

ACMG classification

Our verdict: Uncertain_significance. The variant received 5 ACMG points.

• PM1: In a hotspot region, there are 2 aminoacids with missense pathogenic changes in the window of +-8 aminoacids around while only 1 benign, 5 uncertain in NM_006772.3
• PM2: Very rare variant in population databases, with high coverage
• PP5: Variant 6-33432781-C-T is Pathogenic according to our data. Variant chr6-33432781-C-T is described in ClinVar as Pathogenic. ClinVar VariationId is 438306.Status of the report is criteria_provided_single_submitter, 1 stars.
• BP4: Computational evidence support a benign effect (MetaRNN=0.24974942). . Strength limited to SUPPORTING due to the PP5.

Variant Effect in Transcripts

ACMG analysis was done for transcript: NM_006772.3. You can select a different transcript below to see updated ACMG assignments.

RefSeq Transcripts

Selected	Gene	Transcript	Tags	HGVSc	HGVSp	Effect	Exon Rank	Protein	UniProt
	SYNGAP1	NM_006772.3	MANE Select	c.484C>T	p.Arg162Cys	missense	Exon 5 of 19	NP_006763.2
	SYNGAP1	NM_001130066.2		c.484C>T	p.Arg162Cys	missense	Exon 5 of 18	NP_001123538.1

Ensembl Transcripts

Selected	Gene	Transcript	Tags	HGVSc	HGVSp	Effect	Exon Rank	Protein	UniProt
	SYNGAP1	ENST00000646630.1	MANE Select	c.484C>T	p.Arg162Cys	missense	Exon 5 of 19	ENSP00000496007.1
	SYNGAP1	ENST00000644458.1		c.484C>T	p.Arg162Cys	missense	Exon 5 of 19	ENSP00000495541.1
	SYNGAP1	ENST00000449372.7	TSL:5	c.484C>T	p.Arg162Cys	missense	Exon 5 of 18	ENSP00000416519.4

Frequencies

GnomAD3 genomes Cov.: 31

GnomAD4 exome Cov.: 37

GnomAD4 genome Cov.: 31

ClinVar

Significance: Pathogenic

Submissions summary: Pathogenic:2

Revision: criteria provided, single submitter

Submissions by phenotype

Intellectual disability, autosomal dominant 5 Pathogenic:1

Dec 09, 2016

Molecular Genetics Laboratory, BC Children's and BC Women's Hospitals

Significance: Likely pathogenic

Review Status: no assertion criteria provided

Collection Method: clinical testing

not provided Pathogenic:1

Feb 01, 2023

GeneDx

Significance: Pathogenic

Review Status: criteria provided, single submitter

Collection Method: clinical testing

Not observed at significant frequency in large population cohorts (gnomAD); In silico analysis supports that this missense variant does not alter protein structure/function; This variant is associated with the following publications: (PMID: 31395010, 35599849)

Computational scores

Source: dbNSFP v4.9

Name	Calibrated prediction	Score	Prediction
AlphaMissense	Pathogenic	0.79
BayesDel_addAF	Uncertain	0.014	T
BayesDel_noAF	Benign	-0.22
CADD	Pathogenic	28
DANN	Uncertain	1.0
DEOGEN2	Benign	0.18	T
Eigen	Benign	0.094
Eigen_PC	Benign	0.14
FATHMM_MKL	Benign	0.75	D
LIST_S2	Pathogenic	0.98	D
M_CAP	Benign	0.021	T
MetaRNN	Benign	0.25	T
MetaSVM	Benign	-1.1	T
MutationAssessor	Benign	0.69	N
PhyloP100		0.67
PrimateAI	Pathogenic	0.90	D
PROVEAN	Benign	-2.1	N
REVEL	Benign	0.15
Sift	Uncertain	0.025	D
Sift4G	Benign	0.070	T
Polyphen		0.99	D
Vest4		0.41
MutPred		0.34		Loss of MoRF binding (P = 0.0064)
MVP		0.66
MPC		2.4
ClinPred		0.76	D
GERP RS		3.5
RBP_binding_hub_radar		0.0
RBP_regulation_power_radar		1.7
Varity_R		0.13
gMVP		0.88
Mutation Taster		=4/96	disease causing (ClinVar)

Splicing

Name	Calibrated prediction	Score	Prediction
SpliceAI score (max)		0.020		Details are displayed if max score is > 0.2

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

Other links and lift over

dbSNP: rs1554120589; hg19: chr6-33400558;