chr20-10275516-A-C

Position:

• chr20-10275516-A-C

Variant summary

Our verdict is Uncertain significance. Variant got 5 ACMG points: 5P and 0B. PM1 PM2 PP2

The NM_130811.4(SNAP25):​c.25A>C​(p.Asn9His) variant causes a missense change involving the alteration of a conserved nucleotide. The variant was absent in control chromosomes in GnomAD project. Variant has been reported in ClinVar as Uncertain significance (★). Another variant affecting the same amino acid position, but resulting in a different missense (i.e. N9S) has been classified as Benign.

• Frequency: Genomes: not found (cov: 33)
• Consequence: SNAP25 NM_130811.4 missense
• Clinical Significance: Uncertain significance criteria provided, single submitter U:1
• Conservation: PhyloP100: 8.58

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

Verdict is Uncertain_significance. Variant got 5 ACMG points.

• PM1: In a helix (size 72) in uniprot entity SNP25_HUMAN there are 11 pathogenic changes around while only 3 benign (79%) in NM_130811.4
• 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	UniProt
SNAP25	NM_130811.4	c.25A>C	p.Asn9His	missense_variant	2/8	ENST00000254976.7

Ensembl

Gene	Transcript	HGVSc	HGVSp	Effect	#exon/exons	TSL	MANE	Appris	UniProt
SNAP25	ENST00000254976.7	c.25A>C	p.Asn9His	missense_variant	2/8	1	NM_130811.4	P5
SNAP25-AS1	ENST00000421143.6	n.6-78579T>G		intron_variant, non_coding_transcript_variant		5

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

Congenital myasthenic syndrome 18 Uncertain:1

Uncertain significance, criteria provided, single submitter

clinical testing

Labcorp Genetics (formerly Invitae), Labcorp

Jan 15, 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"). 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 asparagine, which is neutral and polar, with histidine, which is basic and polar, at codon 9 of the SNAP25 protein (p.Asn9His). -

Computational scores

Source: dbNSFP v4.3

Name	Calibrated prediction	Score	Prediction
AlphaMissense	Benign	0.16
BayesDel_addAF	Uncertain	0.025	T
BayesDel_noAF	Benign	-0.20
CADD	Uncertain	24
DANN	Uncertain	0.99
DEOGEN2	Uncertain	0.45	T;.;.
Eigen	Uncertain	0.60
Eigen_PC	Pathogenic	0.68
FATHMM_MKL	Pathogenic	0.99	D
LIST_S2	Pathogenic	0.97	D;D;D
M_CAP	Benign	0.0068	T
MetaRNN	Uncertain	0.43	T;T;T
MetaSVM	Benign	-0.67	T
MutationAssessor	Benign	1.7	L;L;.
MutationTaster	Benign	1.0	D;D
PrimateAI	Pathogenic	0.86	D
PROVEAN	Benign	-1.8	N;N;N
REVEL	Benign	0.29
Sift	Benign	0.039	D;D;T
Sift4G	Uncertain	0.054	T;T;T
Polyphen		0.95	P;D;.
Vest4		0.78
MutPred		0.19		Gain of catalytic residue at L11 (P = 0.112);Gain of catalytic residue at L11 (P = 0.112);Gain of catalytic residue at L11 (P = 0.112);
MVP		0.34
MPC		0.39
ClinPred		0.87	D
GERP RS		6.1
Varity_R		0.65
gMVP		0.80

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

No publications associated with this variant yet.

Other links and lift over

hg19: chr20-10256164;