20-10275495-G-A

Position:

• chr20-10275495-G-A

Variant summary

Our verdict is Uncertain significance. Variant got 3 ACMG points: 3P and 0B. PM2 PP2

The NM_130811.4(SNAP25):​c.4G>A​(p.Ala2Thr) variant causes a missense change involving the alteration of a conserved nucleotide. The variant allele was found at a frequency of 0.00000138 in 1,451,272 control chromosomes in the GnomAD database, with no homozygous occurrence. Variant has been reported in ClinVar as Uncertain significance (★★).

• Frequency:
  • Genomes: not found (cov: 33)
  • Exomes 𝑓: 0.0000014 (0 hom.)
• Consequence: SNAP25 NM_130811.4 missense
• Clinical Significance: Uncertain significance criteria provided, multiple submitters, no conflicts U:2
• Conservation: PhyloP100: 9.20

Genes affected

SNAP25 (HGNC:11132): (synaptosome associated protein 25) Synaptic vesicle membrane docking and fusion is mediated by SNAREs (soluble N-ethylmaleimide-sensitive factor attachment protein receptors) located on the vesicle membrane (v-SNAREs) and the target membrane (t-SNAREs). The assembled v-SNARE/t-SNARE complex consists of a bundle of four helices, one of which is supplied by v-SNARE and the other three by t-SNARE. For t-SNAREs on the plasma membrane, the protein syntaxin supplies one helix and the protein encoded by this gene contributes the other two. Therefore, this gene product is a presynaptic plasma membrane protein involved in the regulation of neurotransmitter release. Two alternative transcript variants encoding different protein isoforms have been described for this gene. [provided by RefSeq, Jul 2008]

SNAP25 (HGNC:):

ACMG classification

Verdict is Uncertain_significance. Variant got 3 ACMG points.

• PM2: Very rare variant in population databases, with high coverage
• PP2: Missense variant in gene, where missense usually causes diseases (based on misZ statistic), SNAP25. . Gene score misZ 2.9553 (greater than the threshold 3.09). Trascript score misZ 3.1929 (greater than threshold 3.09). GenCC has associacion of gene with presynaptic congenital myasthenic syndrome, congenital myasthenic syndrome 18, developmental and epileptic encephalopathy.

Transcripts

RefSeq

Gene	Transcript	HGVSc	HGVSp	Effect	#exon/exons	MANE	Protein	UniProt
SNAP25	NM_130811.4	c.4G>A	p.Ala2Thr	missense_variant	2/8	ENST00000254976.7	NP_570824.1

Ensembl

Gene	Transcript	HGVSc	HGVSp	Effect	#exon/exons	TSL	MANE	Protein	Appris	UniProt
SNAP25	ENST00000254976.7	c.4G>A	p.Ala2Thr	missense_variant	2/8	1	NM_130811.4	ENSP00000254976.3

Frequencies

GnomAD3 genomes Cov.: 33

GnomAD4 exome AF: 0.00000138 AC: 2 AN: 1451272 Hom.: 0 Cov.: 30 AF XY: 0.00000139 AC XY: 1 AN XY: 720920

Gnomad4 AFR exome AF: 0.00

Gnomad4 AMR exome AF: 0.00

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: 0.00000181

Gnomad4 OTH exome AF: 0.00

GnomAD4 genome Cov.: 33

Alfa AF: 0.0000282 Hom.: 0

Bravo AF: 0.0000151

ClinVar

Significance: Uncertain significance

Submissions summary: Uncertain:2

Revision: criteria provided, multiple submitters, no conflicts

Submissions by phenotype

Inborn genetic diseases Uncertain:1

Uncertain significance, criteria provided, single submitter

clinical testing

Ambry Genetics

Oct 03, 2017

The p.A2T variant (also known as c.4G>A), located in coding exon 1 of the SNAP25 gene, results from a G to A substitution at nucleotide position 4. The alanine at codon 2 is replaced by threonine, an amino acid with similar properties. This amino acid position is highly conserved in available vertebrate species. In addition, the in silico prediction for this alteration is inconclusive. Since supporting evidence is limited at this time, the clinical significance of this alteration remains unclear. -

Congenital myasthenic syndrome 18 Uncertain:1

Uncertain significance, criteria provided, single submitter

clinical testing

Labcorp Genetics (formerly Invitae), Labcorp

Jun 27, 2022

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. 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: "Tolerated"; PolyPhen-2: "Possibly Damaging"; Align-GVGD: "Class C0"). ClinVar contains an entry for this variant (Variation ID: 954664). This variant has not been reported in the literature in individuals affected with SNAP25-related conditions. This variant is not present in population databases (gnomAD no frequency). This sequence change replaces alanine, which is neutral and non-polar, with threonine, which is neutral and polar, at codon 2 of the SNAP25 protein (p.Ala2Thr). -

Computational scores

Source: dbNSFP v4.3

Name	Calibrated prediction	Score	Prediction
AlphaMissense	Benign	0.21
BayesDel_addAF	Uncertain	0.073	D
BayesDel_noAF	Benign	-0.13
CADD	Pathogenic	26
DANN	Pathogenic	1.0
DEOGEN2	Uncertain	0.45	T;.;.
Eigen	Pathogenic	0.80
Eigen_PC	Pathogenic	0.84
FATHMM_MKL	Pathogenic	1.0	D
LIST_S2	Uncertain	0.93	D;D;D
M_CAP	Benign	0.0057	T
MetaRNN	Uncertain	0.61	D;D;D
MetaSVM	Benign	-0.54	T
MutationAssessor	Benign	1.8	L;L;.
PrimateAI	Pathogenic	0.88	D
PROVEAN	Benign	-0.89	N;N;N
REVEL	Benign	0.27
Sift	Benign	0.16	T;T;T
Sift4G	Benign	0.17	T;T;T
Polyphen		1.0	D;D;.
Vest4		0.70
MutPred		0.13		Gain of phosphorylation at A2 (P = 0.0054);Gain of phosphorylation at A2 (P = 0.0054);Gain of phosphorylation at A2 (P = 0.0054);
MVP		0.34
MPC		0.44
ClinPred		0.96	D
GERP RS		6.1
Varity_R		0.27
gMVP		0.66

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

Publications

LitVar

Other links and lift over

dbSNP: rs769950821; hg19: chr20-10256143;