16-56276078-C-T

Position:

• chr16-56276078-C-T

Variant summary

Our verdict is Likely benign. Variant got -2 ACMG points: 2P and 4B. PM2 BP4_Strong

The NM_020988.3(GNAO1):​c.303+6C>T variant causes a splice donor region, intron 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 Uncertain significance (★).

• Frequency: Genomes: not found (cov: 33)
• Consequence: GNAO1 NM_020988.3 splice_donor_region, intron
• Scores: Splicing: ADA: 0.00005683
• Clinical Significance: Uncertain significance criteria provided, single submitter U:1
• Conservation: PhyloP100: 0.459

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]

ACMG classification

Verdict is Likely_benign. Variant got -2 ACMG points.

• PM2: Very rare variant in population databases, with high coverage
• BP4: Computational evidence support a benign effect (BayesDel_noAF=-0.67).

Transcripts

RefSeq

Gene	Transcript	HGVSc	HGVSp	Effect	#exon/exons	MANE	UniProt
GNAO1	NM_020988.3	c.303+6C>T		splice_donor_region_variant, intron_variant		ENST00000262493.12
GNAO1	NM_138736.3	c.303+6C>T		splice_donor_region_variant, intron_variant
GNAO1	XM_011523003.4	c.177+6C>T		splice_donor_region_variant, intron_variant
GNAO1	XR_007064866.1	n.1050+6C>T		splice_donor_region_variant, intron_variant, non_coding_transcript_variant

Ensembl

Gene	Transcript	HGVSc	HGVSp	Effect	#exon/exons	TSL	MANE	Appris	UniProt
GNAO1	ENST00000262493.12	c.303+6C>T		splice_donor_region_variant, intron_variant		1	NM_020988.3	P1

Frequencies

GnomAD3 genomes Cov.: 33

GnomAD4 exome Cov.: 30

GnomAD4 genome Cov.: 33

ClinVar

Significance: Uncertain significance

Submissions summary: Uncertain:1

Revision: criteria provided, single submitter

Submissions by phenotype

Early infantile epileptic encephalopathy with suppression bursts Uncertain:1

Uncertain significance, criteria provided, single submitter

clinical testing

Invitae

Jul 30, 2023

This sequence change falls in intron 3 of the GNAO1 gene. It does not directly change the encoded amino acid sequence of the GNAO1 protein. It affects a nucleotide within the consensus splice site. This variant is not present in population databases (gnomAD no frequency). This variant has not been reported in the literature in individuals affected with GNAO1-related conditions. ClinVar contains an entry for this variant (Variation ID: 461354). Variants that disrupt the consensus splice site are a relatively common cause of aberrant splicing (PMID: 17576681, 9536098). Algorithms developed to predict the effect of sequence changes on RNA splicing suggest that this variant is not likely to affect RNA splicing. 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. -

Computational scores

Source: dbNSFP v4.3

Name	Calibrated prediction	Score	Prediction
BayesDel_noAF	Benign	-0.67
CADD	Benign	17
DANN	Benign	0.65

Splicing

Name	Calibrated prediction	Score	Prediction
dbscSNV1_ADA	Benign	0.000057
dbscSNV1_RF	Benign	0.040
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

Publications

LitVar

Other links and lift over

dbSNP: rs1555504237; hg19: chr16-56309990;