chr20-58840179-G-A

Position:

• chr20-58840179-G-A

Variant summary

Our verdict is Uncertain significance. Variant got 4 ACMG points: 4P and 0B. PM2 PP3_Moderate

The NM_016592.5(GNAS):​c.73G>A​(p.Gly25Ser) variant causes a missense change. The variant allele was found at a frequency of 0.00000137 in 1,459,218 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 (no stars).

• Frequency:
  • Genomes: not found (cov: 32)
  • Exomes 𝑓: 0.0000014 (0 hom.)
• Consequence: GNAS NM_016592.5 missense
• Clinical Significance: Uncertain significance no assertion criteria provided U:1
• Conservation: PhyloP100: 4.10

Genes affected

GNAS (HGNC:4392): (GNAS complex locus) This locus has a highly complex imprinted expression pattern. It gives rise to maternally, paternally, and biallelically expressed transcripts that are derived from four alternative promoters and 5' exons. Some transcripts contain a differentially methylated region (DMR) at their 5' exons, and this DMR is commonly found in imprinted genes and correlates with transcript expression. An antisense transcript is produced from an overlapping locus on the opposite strand. One of the transcripts produced from this locus, and the antisense transcript, are paternally expressed noncoding RNAs, and may regulate imprinting in this region. In addition, one of the transcripts contains a second overlapping ORF, which encodes a structurally unrelated protein - Alex. Alternative splicing of downstream exons is also observed, which results in different forms of the stimulatory G-protein alpha subunit, a key element of the classical signal transduction pathway linking receptor-ligand interactions with the activation of adenylyl cyclase and a variety of cellular reponses. Multiple transcript variants encoding different isoforms have been found for this gene. Mutations in this gene result in pseudohypoparathyroidism type 1a, pseudohypoparathyroidism type 1b, Albright hereditary osteodystrophy, pseudopseudohypoparathyroidism, McCune-Albright syndrome, progressive osseus heteroplasia, polyostotic fibrous dysplasia of bone, and some pituitary tumors. [provided by RefSeq, Aug 2012]

GNAS-AS1 (HGNC:24872): (GNAS antisense RNA 1) This gene produces a paternally-imprinted antisense RNA transcript that helps regulate the GNAS complex locus, which encodes the alpha subunit of the stimulatory G protein. Defects in this gene are a cause of pseudohypoparathyroidism type Ib.[provided by RefSeq, Jun 2010]

ACMG classification

Verdict is Uncertain_significance. Variant got 4 ACMG points.

• PM2: Very rare variant in population databases, with high coverage
• PP3: MetaRNN computational evidence supports a deleterious effect, 0.878

Transcripts

RefSeq

Gene	Transcript	HGVSc	HGVSp	Effect	#exon/exons	MANE	Protein	UniProt
GNAS	NM_016592.5	c.73G>A	p.Gly25Ser	missense_variant	1/13	ENST00000371075.7	NP_057676.1
GNAS-AS1	NR_002785.2	n.819+1758C>T		intron_variant, non_coding_transcript_variant

Ensembl

Gene	Transcript	HGVSc	HGVSp	Effect	#exon/exons	TSL	MANE	Protein	Appris	UniProt
GNAS	ENST00000371075.7	c.73G>A	p.Gly25Ser	missense_variant	1/13	1	NM_016592.5	ENSP00000360115
GNAS-AS1	ENST00000424094.6	n.819+1758C>T		intron_variant, non_coding_transcript_variant		1

Frequencies

GnomAD3 genomes Cov.: 32

GnomAD3 exomes AF: 0.00000813 AC: 2 AN: 245866 Hom.: 0 AF XY: 0.00000745 AC XY: 1 AN XY: 134296

Gnomad AFR exome AF: 0.00

Gnomad AMR exome AF: 0.0000580

Gnomad ASJ exome AF: 0.00

Gnomad EAS exome AF: 0.00

Gnomad SAS exome AF: 0.00

Gnomad FIN exome AF: 0.00

Gnomad NFE exome AF: 0.00

Gnomad OTH exome AF: 0.00

GnomAD4 exome AF: 0.00000137 AC: 2 AN: 1459218 Hom.: 0 Cov.: 36 AF XY: 0.00000138 AC XY: 1 AN XY: 726082

Gnomad4 AFR exome AF: 0.00

Gnomad4 AMR exome AF: 0.0000447

Gnomad4 ASJ exome AF: 0.00

Gnomad4 EAS exome AF: 0.00

Gnomad4 SAS exome AF: 0.00

Gnomad4 FIN exome AF: 0.00

Gnomad4 NFE exome AF: 0.00

Gnomad4 OTH exome AF: 0.00

GnomAD4 genome Cov.: 32

Bravo AF: 0.00000378

ClinVar

Significance: Uncertain significance

Submissions summary: Uncertain:1

Revision: no assertion criteria provided

Submissions by phenotype

GNAS-related disorder Uncertain:1

Uncertain significance, no assertion criteria provided

clinical testing

PreventionGenetics, part of Exact Sciences

Oct 23, 2023

The GNAS c.73G>A variant is predicted to result in the amino acid substitution p.Gly25Ser. Of note, this variant can also be referred to as c.-51548G>A (pre-coding) in the more commonly reported isoform NM_000516. To our knowledge, this variant has not been reported in the literature. This variant is reported in 0.0058% of alleles in individuals of Latino descent in gnomAD (http://gnomad.broadinstitute.org/variant/20-57415234-G-A). At this time, the clinical significance of this variant is uncertain due to the absence of conclusive functional and genetic evidence. -

Computational scores

Source: dbNSFP v4.3

Name	Calibrated prediction	Score	Prediction
BayesDel_addAF	Uncertain	0.058	T
BayesDel_noAF	Uncertain	0.020
CADD	Uncertain	25
DANN	Uncertain	0.99
DEOGEN2	Uncertain	0.58	D;D;D
Eigen	Uncertain	0.37
Eigen_PC	Uncertain	0.34
FATHMM_MKL	Benign	0.68	D
LIST_S2	Benign	0.72	.;.;T
M_CAP	Benign	0.0054	T
MetaRNN	Pathogenic	0.88	D;D;D
MetaSVM	Benign	-0.73	T
MutationAssessor	Benign	1.1	L;L;L
MutationTaster	Benign	1.0	N;N;N
PrimateAI	Pathogenic	0.81	D
PROVEAN	Benign	-2.2	N;N;N
REVEL	Uncertain	0.37
Sift	Pathogenic	0.0	D;D;D
Sift4G	Benign	0.34	T;T;T
Polyphen		1.0	D;D;D
Vest4		0.74
MutPred		0.78		Gain of glycosylation at G25 (P = 0.0141);Gain of glycosylation at G25 (P = 0.0141);Gain of glycosylation at G25 (P = 0.0141);
MVP		0.73
ClinPred		0.71	D
GERP RS		3.6
RBP_binding_hub_radar		0.0
RBP_regulation_power_radar		1.8

Splicing

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

Publications

LitVar

Other links and lift over

dbSNP: rs1230896240; hg19: chr20-57415234;