NM_020988.3:c.662C>T

Variant names:

• chr16-56336799-C-T
• rs1555507479
• NM_020988.3:c.662C>T

Variant summary

Our verdict is Likely pathogenic. The variant received 8 ACMG points: 8P and 0B. PM1 PM2 PM5 PP3_Moderate

The NM_020988.3(GNAO1):​c.662C>T​(p.Ala221Val) variant causes a missense change. The variant allele was found at a frequency of 0.000000684 in 1,461,356 control chromosomes in the GnomAD database, with no homozygous occurrence. In-silico tool predicts a pathogenic outcome for this variant. Variant has been reported in ClinVar as Uncertain significance (★★). Another variant affecting the same amino acid position, but resulting in a different missense (i.e. A221D) has been classified as Likely pathogenic.

• Frequency:
  • Genomes: not found (cov: 34)
  • Exomes 𝑓: 6.8e-7 (0 hom.)
• Consequence: GNAO1 NM_020988.3 missense
• Clinical Significance: Uncertain significance criteria provided, multiple submitters, no conflicts U:2
• Conservation: PhyloP100: 6.16
• 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), 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: Likely_pathogenic. The variant received 8 ACMG points.

• PM1: In a hotspot region, there are 4 aminoacids with missense pathogenic changes in the window of +-8 aminoacids around while only 0 benign, 7 uncertain in NM_020988.3
• PM2: Very rare variant in population databases, with high coverage
• PM5: Other missense variant is known to change same aminoacid residue: Variant chr16-56336799-C-A is described in ClinVar as Likely_pathogenic. ClinVar VariationId is 522843.Status of the report is criteria_provided_multiple_submitters_no_conflicts, 2 stars.
• PP3: MetaRNN computational evidence supports a deleterious effect, 0.935

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.662C>T	p.Ala221Val	missense	Exon 6 of 9	NP_066268.1
	GNAO1	NM_138736.3		c.662C>T	p.Ala221Val	missense	Exon 6 of 8	NP_620073.2

Ensembl Transcripts

Sel.	Gene	Transcript	Tags	HGVSc	HGVSp	Effect	Exon Rank	Protein	UniProt
	GNAO1	ENST00000262493.12	TSL:1 MANE Select	c.662C>T	p.Ala221Val	missense	Exon 6 of 9	ENSP00000262493.6
	GNAO1	ENST00000262494.13	TSL:1	c.662C>T	p.Ala221Val	missense	Exon 6 of 8	ENSP00000262494.7
	GNAO1	ENST00000638705.1	TSL:1	c.662C>T	p.Ala221Val	missense	Exon 6 of 8	ENSP00000491223.1

Frequencies

GnomAD3 genomes Cov.: 34

GnomAD4 exome AF: 6.84e-7 AC: 1 AN: 1461356 Hom.: 0 Cov.: 31 AF XY: 0.00 AC XY: 0 AN XY: 727028

African (AFR) AF: 0.00 AC: 0 AN: 33478

American (AMR) AF: 0.00 AC: 0 AN: 44710

Ashkenazi Jewish (ASJ) AF: 0.00 AC: 0 AN: 26136

East Asian (EAS) AF: 0.00 AC: 0 AN: 39688

South Asian (SAS) AF: 0.00 AC: 0 AN: 86238

European-Finnish (FIN) AF: 0.00 AC: 0 AN: 53054

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

European-Non Finnish (NFE) AF: 8.99e-7 AC: 1 AN: 1111904

Other (OTH) AF: 0.00 AC: 0 AN: 60380

GnomAD4 genome Cov.: 34

ClinVar

ClinVar submissions as Germline

Significance: Uncertain significance

Revision: criteria provided, multiple submitters, no conflicts

Pathogenic	VUS	Benign	Condition
-	1	-	Developmental and epileptic encephalopathy (1)
-	1	-	not provided (1)

Computational scores

Source: dbNSFP v4.9

Name	Calibrated prediction	Score	Prediction
AlphaMissense	Pathogenic	0.96
BayesDel_addAF	Pathogenic	0.44	D
BayesDel_noAF	Pathogenic	0.39
CADD	Pathogenic	28
DANN	Pathogenic	1.0
DEOGEN2	Pathogenic	0.84	D
Eigen	Pathogenic	0.89
Eigen_PC	Pathogenic	0.84
FATHMM_MKL	Uncertain	0.94	D
LIST_S2	Uncertain	0.93	D
M_CAP	Uncertain	0.25	D
MetaRNN	Pathogenic	0.94	D
MetaSVM	Pathogenic	0.93	D
MutationAssessor	Uncertain	2.7	M
PhyloP100		6.2
PrimateAI	Pathogenic	0.90	D
PROVEAN	Uncertain	-3.5	D
REVEL	Pathogenic	0.92
Sift	Uncertain	0.0070	D
Sift4G	Uncertain	0.027	D
Polyphen		1.0	D
Vest4		0.77
MutPred		0.81		Gain of sheet (P = 0.1539)
MVP		0.94
MPC		2.6
ClinPred		0.98	D
GERP RS		5.3
PromoterAI		-0.13	Neutral
Varity_R		0.90
gMVP		0.97

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: rs1555507479; hg19: chr16-56370711;