20-10277726-G-C

Variant names:

• chr20-10277726-G-C
• rs763997141
• NM_130811.4:c.114G>C

Variant summary

Our verdict is Likely pathogenic. The variant received 8 ACMG points: 8P and 0B. PM1 PM2 PP3_Strong

The NM_130811.4(SNAP25):​c.114G>C​(p.Glu38Asp) variant causes a missense, splice region change involving the alteration of a conserved nucleotide. The variant was absent in control chromosomes in GnomAD project. 2/3 splice prediction tools predicting alterations to normal splicing. Variant has been reported in ClinVar as Uncertain significance (★). Another nucleotide change resulting in the same amino acid substitution has been previously reported as Uncertain significance in ClinVar.

• Frequency: Genomes: not found (cov: 33)
• Consequence: SNAP25 NM_130811.4 missense, splice_region
• Scores: Splicing: ADA: 1.000
• Clinical Significance: Uncertain significance criteria provided, single submitter U:1
• Conservation: PhyloP100: 8.81
• Publications: 2 publications found

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-AS1 (HGNC:44312): (SNAP25 antisense RNA 1)

ACMG classification

Our verdict: Likely_pathogenic. The variant received 8 ACMG points.

• PM1: In a hotspot region, there are 2 aminoacids with missense pathogenic changes in the window of +-8 aminoacids around while only 1 benign, 5 uncertain in NM_130811.4
• PM2: Very rare variant in population databases, with high coverage
• PP3: Splicing predictors support a deleterious effect. Scorers claiming Pathogenic: dbscSNV1_ADA, dbscSNV1_RF. Scorers claiming Uncertain: max_spliceai. No scorers claiming Benign.

Transcripts

RefSeq

Gene	Transcript	HGVSc	HGVSp	Effect	Exon rank	MANE	Protein	UniProt
SNAP25	NM_130811.4	c.114G>C	p.Glu38Asp	missense_variant, splice_region_variant	Exon 3 of 8	ENST00000254976.7	NP_570824.1

Ensembl

Gene	Transcript	HGVSc	HGVSp	Effect	Exon rank	TSL	MANE	Protein	Appris	UniProt
SNAP25	ENST00000254976.7	c.114G>C	p.Glu38Asp	missense_variant, splice_region_variant	Exon 3 of 8	1	NM_130811.4	ENSP00000254976.3

Frequencies

GnomAD3 genomes Cov.: 33

GnomAD4 exome Cov.: 29

GnomAD4 genome Cov.: 33

ClinVar

Significance: Uncertain significance

Submissions summary: Uncertain:1

Revision: criteria provided, single submitter

Submissions by phenotype

Congenital myasthenic syndrome 18 Uncertain:1

Nov 27, 2023

Labcorp Genetics (formerly Invitae), Labcorp

Significance: Uncertain significance

Review Status: criteria provided, single submitter

Collection Method: clinical testing

This sequence change replaces glutamic acid, which is acidic and polar, with aspartic acid, which is acidic and polar, at codon 38 of the SNAP25 protein (p.Glu38Asp). This variant also falls at the last nucleotide of exon 3, which is part of the consensus splice site for this exon. This variant is not present in population databases (gnomAD no frequency). This variant has not been reported in the literature in individuals affected with SNAP25-related conditions. ClinVar contains an entry for this variant (Variation ID: 571417). An algorithm developed to predict the effect of missense changes on protein structure and function (PolyPhen-2) suggests that this variant is likely to be tolerated. 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 may disrupt the consensus splice site. 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
AlphaMissense	Uncertain	0.41
BayesDel_addAF	Uncertain	0.14	D
BayesDel_noAF	Uncertain	-0.040
CADD	Pathogenic	33
DANN	Uncertain	1.0
DEOGEN2	Uncertain	0.54	D;.;.
Eigen	Uncertain	0.51
Eigen_PC	Uncertain	0.59
FATHMM_MKL	Uncertain	0.97	D
LIST_S2	Uncertain	0.93	D;D;D
M_CAP	Benign	0.017	T
MetaRNN	Uncertain	0.50	D;D;D
MetaSVM	Benign	-0.38	T
MutationAssessor	Uncertain	2.3	M;M;.
PhyloP100		8.8
PrimateAI	Pathogenic	0.91	D
PROVEAN	Uncertain	-2.4	N;D;D
REVEL	Uncertain	0.45
Sift	Benign	0.11	T;T;T
Sift4G	Benign	0.092	T;T;T
Polyphen		0.52	P;B;.
Vest4		0.73
MutPred		0.32		Gain of MoRF binding (P = 0.1194);Gain of MoRF binding (P = 0.1194);Gain of MoRF binding (P = 0.1194);
MVP		0.45
MPC		2.3
ClinPred		0.80	D
GERP RS		5.6
Varity_R		0.64
gMVP		0.92
Mutation Taster		=22/78	disease causing

Splicing

Name	Calibrated prediction	Score	Prediction
dbscSNV1_ADA	Pathogenic	1.0
dbscSNV1_RF	Pathogenic	0.96
SpliceAI score (max)		0.45		Details are displayed if max score is > 0.2
DS_DL_spliceai		0.45		Position offset: 0

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

Other links and lift over

dbSNP: rs763997141; hg19: chr20-10258374;