NM_020988.3:c.687C>A

Variant names:

• chr16-56336824-C-A
• rs546569747
• NM_020988.3:c.687C>A

Variant summary

Our verdict is Pathogenic. The variant received 12 ACMG points: 12P and 0B. PS1 PM1 PM2 PP3_Strong

The NM_020988.3(GNAO1):​c.687C>A​(p.Ser229Arg) 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 pathogenic outcome for this variant. Variant has been reported in ClinVar as Uncertain significance (★). Another nucleotide change resulting in the same amino acid substitution has been previously reported as Likely pathogenic in ClinVar. Synonymous variant affecting the same amino acid position (i.e. S229S) has been classified as Likely benign.

• Frequency: Genomes: not found (cov: 34)
• Consequence: GNAO1 NM_020988.3 missense
• Clinical Significance: Uncertain significance criteria provided, single submitter U:1
• Conservation: PhyloP100: 0.550
• Publications: 1 publications found

Genes affected

GNAO1 (HGNC:4389): (G protein subunit alpha o1) The protein encoded by this gene represents the alpha subunit of the Go heterotrimeric G-protein signal-transducing complex. Defects in this gene are a cause of early-onset epileptic encephalopathy. Two transcript variants encoding different isoforms have been found for this gene. [provided by RefSeq, Aug 2015]

GNAO1 Gene-Disease associations (from GenCC):

• developmental and epileptic encephalopathy, 17

  Inheritance: AD Classification: DEFINITIVE, STRONG Submitted by: Labcorp Genetics (formerly Invitae), G2P, Ambry Genetics
• genetic developmental and epileptic encephalopathy

  Inheritance: AD Classification: DEFINITIVE, SUPPORTIVE Submitted by: Orphanet, ClinGen
• movement disorder

  Inheritance: AD Classification: DEFINITIVE Submitted by: ClinGen, Illumina
• neurodevelopmental disorder with involuntary movements

  Inheritance: AD Classification: STRONG Submitted by: Labcorp Genetics (formerly Invitae)

ACMG classification

Our verdict: Pathogenic. The variant received 12 ACMG points.

• PS1: Transcript NM_020988.3 (GNAO1) is affected with MISSENSE_VARIANT having same AA change as one Pathogenic present in ClinVar.
• PM1: In a hotspot region, there are 5 aminoacids with missense pathogenic changes in the window of +-8 aminoacids around while only 0 benign, 5 uncertain in NM_020988.3
• PM2: Very rare variant in population databases, with high coverage
• PP3: MetaRNN computational evidence supports a deleterious effect, 0.971

Transcripts

RefSeq

Gene	Transcript	HGVSc	HGVSp	Effect	Exon rank	MANE	Protein	UniProt
GNAO1	NM_020988.3	c.687C>A	p.Ser229Arg	missense_variant	Exon 6 of 9	ENST00000262493.12	NP_066268.1
GNAO1	NM_138736.3	c.687C>A	p.Ser229Arg	missense_variant	Exon 6 of 8		NP_620073.2
GNAO1	XM_011523003.4	c.561C>A	p.Ser187Arg	missense_variant	Exon 6 of 9		XP_011521305.1
GNAO1	XR_007064866.1	n.1434C>A		non_coding_transcript_exon_variant	Exon 6 of 9

Ensembl

Gene	Transcript	HGVSc	HGVSp	Effect	Exon rank	TSL	MANE	Protein	Appris	UniProt
GNAO1	ENST00000262493.12	c.687C>A	p.Ser229Arg	missense_variant	Exon 6 of 9	1	NM_020988.3	ENSP00000262493.6

Frequencies

GnomAD3 genomes Cov.: 34

GnomAD4 exome Cov.: 31

GnomAD4 genome Cov.: 34

ClinVar

Significance: Uncertain significance

Submissions summary: Uncertain:1

Revision: criteria provided, single submitter

Submissions by phenotype

Developmental and epileptic encephalopathy Uncertain:1

Oct 25, 2020

Labcorp Genetics (formerly Invitae), Labcorp

Significance: Uncertain significance

Review Status: criteria provided, single submitter

Collection Method: clinical testing

This sequence change replaces serine with arginine at codon 229 of the GNAO1 protein (p.Ser229Arg). The serine residue is highly conserved and there is a moderate physicochemical difference between serine and arginine. This variant is not present in population databases (ExAC no frequency). In summary, the available evidence is currently insufficient to determine the role of this variant in disease. Therefore, it has been classified as a Variant of Uncertain Significance. Algorithms developed to predict the effect of sequence changes on RNA splicing suggest that this variant may create or strengthen a splice site, but this prediction has not been confirmed by published transcriptional studies. Advanced modeling of protein sequence and biophysical properties (such as structural, functional, and spatial information, amino acid conservation, physicochemical variation, residue mobility, and thermodynamic stability) performed at Invitae indicates that this missense variant is expected to disrupt GNAO1 protein function. This variant has not been reported in the literature in individuals with GNAO1-related conditions. -

Computational scores

Source: dbNSFP v4.3

Name	Calibrated prediction	Score	Prediction
AlphaMissense	Pathogenic	1.0
BayesDel_addAF	Pathogenic	0.46	D
BayesDel_noAF	Pathogenic	0.42
CADD	Pathogenic	28
DANN	Uncertain	1.0
DEOGEN2	Pathogenic	0.96	D;D;.;.;.
Eigen	Uncertain	0.50
Eigen_PC	Uncertain	0.34
FATHMM_MKL	Uncertain	0.78	D
LIST_S2	Pathogenic	0.98	.;D;D;D;D
M_CAP	Pathogenic	0.70	D
MetaRNN	Pathogenic	0.97	D;D;D;D;D
MetaSVM	Uncertain	0.78	D
MutationAssessor	Pathogenic	4.4	H;H;H;.;.
PhyloP100		0.55
PrimateAI	Pathogenic	0.89	D
PROVEAN	Pathogenic	-4.7	D;.;D;.;.
REVEL	Pathogenic	0.88
Sift	Pathogenic	0.0	D;.;D;.;.
Sift4G	Pathogenic	0.0	D;.;D;.;.
Polyphen		1.0	D;D;D;.;.
Vest4		0.97
MutPred		0.87		Loss of glycosylation at S229 (P = 0.08);Loss of glycosylation at S229 (P = 0.08);Loss of glycosylation at S229 (P = 0.08);.;.;
MVP		0.99
MPC		2.8
ClinPred		1.0	D
GERP RS		2.3
PromoterAI		-0.065	Neutral
Varity_R		0.98
gMVP		0.99

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

Other links and lift over

dbSNP: rs546569747; hg19: chr16-56370736;