chr9-127682510-G-T

Position:

• chr9-127682510-G-T

Variant summary

Our verdict is Pathogenic. Variant got 17 ACMG points: 17P and 0B. PM2 PM5 PP2 PP3_Strong PP5_Very_Strong

The NM_001032221.6(STXBP1):​c.1652G>T​(p.Arg551Leu) variant causes a missense change involving the alteration of a conserved nucleotide. The variant was absent in control chromosomes in GnomAD project. In-silico tool predicts a pathogenic outcome for this variant. Variant has been reported in ClinVar as Likely pathogenic (★★). Another variant affecting the same amino acid position, but resulting in a different missense (i.e. R551C) has been classified as Pathogenic.

• Frequency: Genomes: not found (cov: 33)
• Consequence: STXBP1 NM_001032221.6 missense
• Clinical Significance: Pathogenic/Likely pathogenic criteria provided, multiple submitters, no conflicts P:2
• Conservation: PhyloP100: 9.86

Genes affected

STXBP1 (HGNC:11444): (syntaxin binding protein 1) This gene encodes a syntaxin-binding protein. The encoded protein appears to play a role in release of neurotransmitters via regulation of syntaxin, a transmembrane attachment protein receptor. Mutations in this gene have been associated with infantile epileptic encephalopathy-4. Alternatively spliced transcript variants have been described. [provided by RefSeq, Feb 2010]

STXBP1 (HGNC:):

ACMG classification

Verdict is Pathogenic. Variant got 17 ACMG points.

• PM2: Very rare variant in population databases, with high coverage
• PM5: Other missense variant is known to change same aminoacid residue: Variant chr9-127682509-C-T is described in Lovd as [Pathogenic].
• PP2: Missense variant in gene, where missense usually causes diseases (based on misZ statistic), STXBP1. . Gene score misZ 4.263 (greater than the threshold 3.09). Trascript score misZ 5.8379 (greater than threshold 3.09). GenCC has associacion of gene with intellectual disability, autosomal dominant non-syndromic intellectual disability, Dravet syndrome, undetermined early-onset epileptic encephalopathy, autism spectrum disorder, developmental and epileptic encephalopathy, West syndrome, atypical Rett syndrome, developmental and epileptic encephalopathy, 4.
• PP3: MetaRNN computational evidence supports a deleterious effect, 0.965
• PP5: Variant 9-127682510-G-T is Pathogenic according to our data. Variant chr9-127682510-G-T is described in ClinVar as [Likely_pathogenic]. Clinvar id is 373210.Status of the report is criteria_provided_multiple_submitters_no_conflicts, 2 stars.

Transcripts

RefSeq

Gene	Transcript	HGVSc	HGVSp	Effect	#exon/exons	MANE	Protein	UniProt
STXBP1	NM_003165.6	c.1652G>T	p.Arg551Leu	missense_variant	18/20	ENST00000373302.8	NP_003156.1
STXBP1	NM_001032221.6	c.1652G>T	p.Arg551Leu	missense_variant	18/19	ENST00000373299.5	NP_001027392.1

Ensembl

Gene	Transcript	HGVSc	HGVSp	Effect	#exon/exons	TSL	MANE	Protein	Appris	UniProt
STXBP1	ENST00000373302.8	c.1652G>T	p.Arg551Leu	missense_variant	18/20	1	NM_003165.6	ENSP00000362399.3
STXBP1	ENST00000373299.5	c.1652G>T	p.Arg551Leu	missense_variant	18/19	1	NM_001032221.6	ENSP00000362396.2

Frequencies

GnomAD3 genomes Cov.: 33

GnomAD4 exome Cov.: 31

GnomAD4 genome Cov.: 33

ClinVar

Significance: Pathogenic/Likely pathogenic

Submissions summary: Pathogenic:2

Revision: criteria provided, multiple submitters, no conflicts

Submissions by phenotype

Early infantile epileptic encephalopathy with suppression bursts Pathogenic:1

Likely pathogenic, criteria provided, single submitter

clinical testing

Labcorp Genetics (formerly Invitae), Labcorp

Jul 17, 2023

This sequence change replaces arginine, which is basic and polar, with leucine, which is neutral and non-polar, at codon 551 of the STXBP1 protein (p.Arg551Leu). This variant is not present in population databases (gnomAD no frequency). This variant has not been reported in the literature in individuals affected with STXBP1-related conditions. ClinVar contains an entry for this variant (Variation ID: 373210). Advanced modeling of protein sequence and biophysical properties (such as structural, functional, and spatial information, amino acid conservation, physicochemical variation, residue mobility, and thermodynamic stability) performed at Invitae indicates that this missense variant is expected to disrupt STXBP1 protein function. This variant disrupts the p.Arg551 amino acid residue in STXBP1. Other variant(s) that disrupt this residue have been determined to be pathogenic (PMID: 23409955, 26514728, 26865513, 27069701). This suggests that this residue is clinically significant, and that variants that disrupt this residue are likely to be disease-causing. In summary, the currently available evidence indicates that the variant is pathogenic, but additional data are needed to prove that conclusively. Therefore, this variant has been classified as Likely Pathogenic. -

not provided Pathogenic:1

Pathogenic, criteria provided, single submitter

clinical testing

GeneDx

Nov 30, 2016

The R551L variant in the STXBP1 gene has not been reported previously as a pathogenic variant nor as a benign variant, to our knowledge. The R551L variant was not observed in approximately 6500 individuals of European and African American ancestry in the NHLBI Exome Sequencing Project, indicating it is not a common benign variant in these populations. The R551L variant is a non-conservative amino acid substitution, which is likely to impact secondary protein structure as these residues differ in polarity, charge, size and/or other properties. In addition, this substitution occurs at a position that is conserved across species, and in silico analysis predicts this variant is probably damaging to the protein structure/function. Missense variants in the same residue (R551C and R551H) have been reported in the Human Gene Mutation Database in association with STXBP1-related disorders (Stenson et al., 2014), supporting the functional importance of this region of the protein. We therefore interpret R551L as a pathogenic variant. -

Computational scores

Source: dbNSFP v4.3

Name	Calibrated prediction	Score	Prediction
AlphaMissense	Pathogenic	0.99
BayesDel_addAF	Pathogenic	0.44	D
BayesDel_noAF	Pathogenic	0.39
CADD	Pathogenic	33
DANN	Uncertain	1.0
DEOGEN2	Benign	0.19	.;T;.;T;.;T;D;T
Eigen	Pathogenic	1.1
Eigen_PC	Pathogenic	1.0
FATHMM_MKL	Pathogenic	0.99	D
LIST_S2	Pathogenic	0.99	D;.;D;D;D;D;D;D
M_CAP	Pathogenic	0.80	D
MetaRNN	Pathogenic	0.96	D;D;D;D;D;D;D;D
MetaSVM	Pathogenic	0.83	D
MutationAssessor	Pathogenic	3.2	.;.;M;.;.;.;M;.
MutationTaster	Benign	1.0	D;D
PrimateAI	Uncertain	0.74	T
PROVEAN	Pathogenic	-6.8	.;.;D;.;.;.;D;.
REVEL	Pathogenic	0.94
Sift	Pathogenic	0.0	.;.;D;.;.;.;D;.
Sift4G	Pathogenic	0.0010	.;.;D;.;.;.;D;D
Polyphen		1.0	.;.;D;.;.;.;D;.
Vest4		0.96, 0.95
MutPred		0.81		.;.;Loss of catalytic residue at R551 (P = 0.0817);Loss of catalytic residue at R551 (P = 0.0817);Loss of catalytic residue at R551 (P = 0.0817);.;Loss of catalytic residue at R551 (P = 0.0817);.;
MVP		0.89
MPC		2.3
ClinPred		1.0	D
GERP RS		5.6
RBP_binding_hub_radar		0.0
RBP_regulation_power_radar		2.7
Varity_R		0.95
gMVP		0.99

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: rs796053374; hg19: chr9-130444789;