NM_020988.3:c.770A>G

Variant names:

• chr16-56351430-A-G
• NM_020988.3:c.770A>G
• GNAO1 p.Asn257Ser

Variant summary

Our verdict is Uncertain significance. The variant received 5 ACMG points: 5P and 0B. PM1 PM2 PP3

The NM_020988.3(GNAO1):​c.770A>G​(p.Asn257Ser) variant causes a missense change involving the alteration of a conserved nucleotide. The variant allele was found at a frequency of 0.000000685 in 1,459,932 control chromosomes in the GnomAD database, with no homozygous occurrence. In-silico tool predicts a pathogenic outcome for this variant. No clinical diagnostic laboratories have submitted clinical-significance assessments for this variant to ClinVar.

• Frequency:
  • Genomes: not found (cov: 33)
  • Exomes 𝑓: 6.8e-7 (0 hom.)
• Consequence: GNAO1 NM_020988.3 missense
• Clinical Significance: Not reported in ClinVar
• Conservation: PhyloP100: 9.32
• Publications: 0 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), Ambry Genetics, G2P
• genetic developmental and epileptic encephalopathy

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

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

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

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 2 benign, 4 uncertain in NM_020988.3
• PM2: Very rare variant in population databases, with high coverage
• PP3: MetaRNN computational evidence supports a deleterious effect, 0.77

Variant Effect in Transcripts

ACMG analysis was done for transcript: NM_020988.3. You can select a different transcript below to see updated ACMG assignments.

RefSeq Transcripts

Sel.	Gene	Transcript	Tags	HGVSc	HGVSp	Effect	Exon Rank	Protein	UniProt
	GNAO1	NM_020988.3	MANE Select	c.770A>G	p.Asn257Ser	missense	Exon 7 of 9	NP_066268.1	P09471-1

Ensembl Transcripts

Sel.	Gene	Transcript	Tags	HGVSc	HGVSp	Effect	Exon Rank	Protein	UniProt
	GNAO1	ENST00000262493.12	TSL:1 MANE Select	c.770A>G	p.Asn257Ser	missense	Exon 7 of 9	ENSP00000262493.6	P09471-1
	GNAO1	ENST00000638705.1	TSL:1	c.770A>G	p.Asn257Ser	missense	Exon 7 of 8	ENSP00000491223.1	P09471-1
	GNAO1	ENST00000873096.1		c.794A>G	p.Asn265Ser	missense	Exon 7 of 9	ENSP00000543155.1

Frequencies

GnomAD3 genomes Cov.: 33

GnomAD4 exome AF: 6.85e-7 AC: 1 AN: 1459932 Hom.: 0 Cov.: 29 AF XY: 0.00000138 AC XY: 1 AN XY: 726432

African (AFR) AF: 0.00 AC: 0 AN: 33436

American (AMR) AF: 0.00 AC: 0 AN: 44718

Ashkenazi Jewish (ASJ) AF: 0.00 AC: 0 AN: 26132

East Asian (EAS) AF: 0.00 AC: 0 AN: 39690

South Asian (SAS) AF: 0.00 AC: 0 AN: 86218

European-Finnish (FIN) AF: 0.00 AC: 0 AN: 53392

Middle Eastern (MID) AF: 0.00 AC: 0 AN: 5768

European-Non Finnish (NFE) AF: 9.01e-7 AC: 1 AN: 1110254

Other (OTH) AF: 0.00 AC: 0 AN: 60324

GnomAD4 genome Cov.: 33

ClinVar

Not reported in ClinVar

Computational scores

Source: dbNSFP v4.9

Name	Calibrated prediction	Score	Prediction
AlphaMissense	Benign	0.23
BayesDel_addAF	Uncertain	0.025	T
BayesDel_noAF	Benign	-0.20
CADD	Uncertain	24
DANN	Uncertain	1.0
DEOGEN2	Uncertain	0.78	D
Eigen	Uncertain	0.60
Eigen_PC	Pathogenic	0.67
FATHMM_MKL	Pathogenic	0.99	D
LIST_S2	Uncertain	0.96	D
M_CAP	Benign	0.072	D
MetaRNN	Pathogenic	0.77	D
MetaSVM	Uncertain	0.28	D
MutationAssessor	Benign	1.3	L
PhyloP100		9.3
PROVEAN	Uncertain	-2.8	D
REVEL	Uncertain	0.56
Sift	Benign	0.17	T
Sift4G	Benign	0.88	T
Varity_R		0.70
Mutation Taster		=58/42	polymorphism

Splicing

Name	Calibrated prediction	Score	Prediction
SpliceAI score (max)		0.10		Details are displayed if max score is > 0.2

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

MaxEntScan Visualizer can be used to analyze the impact of this mutation on the neighboring sequence.

Other links and lift over

hg19: chr16-56385342;