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Protein structure and phenotypic analysis of pathogenic and population missense variants in STXBP1

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dc.creator Suri, M
dc.creator Evers, JMG
dc.creator Laskowski, RA
dc.creator O'Brien, S
dc.creator Baker, Kate
dc.creator Clayton-Smith, J
dc.creator Dabir, T
dc.creator Josifova, D
dc.creator Joss, S
dc.creator Kerr, B
dc.creator Kraus, A
dc.creator McEntagart, M
dc.creator Morton, J
dc.creator Smith, A
dc.creator Splitt, M
dc.creator Thornton, JM
dc.creator Wright, CF
dc.date 2018-03-26T10:53:15Z
dc.date 2018-03-26T10:53:15Z
dc.date.accessioned 2019-03-20T08:23:10Z
dc.date.available 2019-03-20T08:23:10Z
dc.identifier https://www.repository.cam.ac.uk/handle/1810/274335
dc.identifier 10.17863/CAM.21457
dc.identifier.uri https://evidence.thinkportal.org/handle/123456789/32248
dc.description Background: Syntaxin-binding protein 1, encoded by STXBP1, is highly expressed in the brain and involved in fusing synaptic vesicles with the plasma membrane. Studies have shown that pathogenic loss-of-function variants in this gene result in various types of epilepsies, mostly beginning early in life. We were interested to model pathogenic missense variants on the protein structure to investigate the mechanism of pathogenicity and genotype–phenotype correlations. Methods: We report 11 patients with pathogenic de novo mutations in STXBP1 identified in the first 4293 trios of the Deciphering Developmental Disorder (DDD) study, including six missense variants. We analyzed the structural locations of the pathogenic missense variants from this study and the literature, as well as population missense variants extracted from Exome Aggregation Consortium (ExAC). Results: Pathogenic variants are significantly more likely to occur at highly conserved locations than population variants, and be buried inside the protein domain. Pathogenic mutations are also more likely to destabilize the domain structure compared with population variants, increasing the proportion of (partially) unfolded domains that are prone to aggregation or degradation. We were unable to detect any genotype–phenotype correlation, but unlike previously reported cases, most of the DDD patients with STXBP1 pathogenic variants did not present with very early-onset or severe epilepsy and encephalopathy, though all have developmental delay with intellectual disability and most display behavioral problems and suffered seizures in later childhood. Conclusion: Variants across STXBP1 that cause loss of function can result in severe intellectual disability with or without seizures, consistent with a haploinsufficiency mechanism. Pathogenic missense mutations act through destabilization of the protein domain, making it prone to aggregation or degradation. The presence or absence of early seizures may reflect ascertainment bias in the literature as well as the broad recruitment strategy of the DDD study.
dc.description The DDD study presents independent research commissioned by the Health Innovation Challenge Fund (grant number HICF-1009-003), a parallel funding partnership between the Wellcome Trust and the Department of Health, and the Wellcome Trust Sanger Institute (grant number WT098051).
dc.publisher Wiley
dc.publisher Molecular Genetics & Genomic Medicine
dc.rights Attribution 4.0 International
dc.rights http://creativecommons.org/licenses/by/4.0/
dc.subject epilepsy
dc.subject Exome Aggregation Consortium
dc.subject genomics
dc.subject Munc18
dc.subject protein structure
dc.subject syntaxin-binding protein 1
dc.title Protein structure and phenotypic analysis of pathogenic and population missense variants in STXBP1
dc.type Article


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