16-56351473-G-C

Variant names:

• chr16-56351473-G-C
• rs758779535
• NM_020988.3:c.813G>C

Variant summary

Our verdict is Pathogenic. The variant received 14 ACMG points: 14P and 0B. PS1 PM1 PM2 PP3_Strong PP5_Moderate

The NM_020988.3(GNAO1):​c.813G>C​(p.Lys271Asn) variant causes a missense change involving the alteration of a conserved nucleotide. The variant was absent in control chromosomes in GnomAD project. In-silico tool predicts a pathogenic outcome for this variant. 12/20 in silico tools predict a damaging outcome for this variant. Variant has been reported in ClinVar as Likely pathogenic (★). Another nucleotide change resulting in the same amino acid substitution has been previously reported as Pathogenic in ClinVar. Another variant affecting the same amino acid position, but resulting in a different missense (i.e. K271E) has been classified as Uncertain significance.

• Frequency: Genomes: not found (cov: 33)
• Consequence: GNAO1 NM_020988.3 missense
• Clinical Significance: Likely pathogenic criteria provided, single submitter P:1
• Conservation: PhyloP100: 10.0
• 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 14 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 6 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, 0.98
• PP5: Variant 16-56351473-G-C is Pathogenic according to our data. Variant chr16-56351473-G-C is described in ClinVar as Likely_pathogenic. ClinVar VariationId is 530527.Status of the report is criteria_provided_single_submitter, 1 stars.

Transcripts

RefSeq

Gene	Transcript	HGVSc	HGVSp	Effect	Exon rank	MANE	Protein	UniProt
GNAO1	NM_020988.3	c.813G>C	p.Lys271Asn	missense_variant	Exon 7 of 9	ENST00000262493.12	NP_066268.1
GNAO1	XM_011523003.4	c.687G>C	p.Lys229Asn	missense_variant	Exon 7 of 9		XP_011521305.1

Ensembl

Gene	Transcript	HGVSc	HGVSp	Effect	Exon rank	TSL	MANE	Protein	Appris	UniProt
GNAO1	ENST00000262493.12	c.813G>C	p.Lys271Asn	missense_variant	Exon 7 of 9	1	NM_020988.3	ENSP00000262493.6

Frequencies

GnomAD3 genomes Cov.: 33

GnomAD4 exome Cov.: 29

GnomAD4 genome Cov.: 33

ClinVar

Significance: Likely pathogenic

Submissions summary: Pathogenic:1

Revision: criteria provided, single submitter

Submissions by phenotype

Developmental and epileptic encephalopathy Pathogenic:1

Apr 27, 2021

Labcorp Genetics (formerly Invitae), Labcorp

Significance: Likely pathogenic

Review Status: criteria provided, single submitter

Collection Method: clinical testing

This sequence change replaces lysine with asparagine at codon 271 of the GNAO1 protein (p.Lys271Asn). The lysine residue is highly conserved and there is a moderate physicochemical difference between lysine and asparagine. This variant is not present in population databases (ExAC no frequency). This variant has been observed in individual(s) with clinical features of developmental and epileptic encephalopathy (Invitae). In at least one individual the variant was observed to be de novo. ClinVar contains an entry for this variant (Variation ID: 530527). Algorithms developed to predict the effect of missense changes on protein structure and function are either unavailable or do not agree on the potential impact of this missense change (SIFT: "Deleterious"; PolyPhen-2: "Probably Damaging"; Align-GVGD: "Class C0"). In summary, the currently available evidence indicates that the variant is pathogenic, but additional data are needed to prove that conclusively. Therefore, this variant has been classified as Likely Pathogenic. -

Computational scores

Source: dbNSFP v4.3

Name	Calibrated prediction	Score	Prediction
AlphaMissense	Pathogenic	1.0
BayesDel_addAF	Pathogenic	0.41	D
BayesDel_noAF	Pathogenic	0.36
CADD	Pathogenic	31
DANN	Uncertain	1.0
DEOGEN2	Pathogenic	0.95	D;D;.;.;.
Eigen	Pathogenic	1.2
Eigen_PC	Pathogenic	1.1
FATHMM_MKL	Pathogenic	0.99	D
LIST_S2	Pathogenic	0.98	.;D;D;D;D
M_CAP	Pathogenic	0.51	D
MetaRNN	Pathogenic	0.98	D;D;D;D;D
MetaSVM	Pathogenic	1.1	D
MutationAssessor	Pathogenic	4.5	H;H;.;.;.
PhyloP100		10
PROVEAN	Pathogenic	-4.7	D;.;.;.;.
REVEL	Pathogenic	0.79
Sift	Pathogenic	0.0	D;.;.;.;.
Sift4G	Pathogenic	0.0	D;.;.;.;.
Polyphen		1.0	D;D;.;.;.
Vest4		0.92
MutPred		0.88		Loss of methylation at K271 (P = 0.0112);Loss of methylation at K271 (P = 0.0112);.;.;.;
MVP		0.95
ClinPred		1.0	D
GERP RS		5.9
Varity_R		0.96

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: rs758779535; hg19: chr16-56385385;