Authors :
Presenting Author: Tao Yang, PhD – University of Michigan
Rajat Benerjee, PhD – University of Michigan
Yamei Deng, PhD – University of Michigan
Alexey Nesvizhskii, Ph.D. – University of Michigan, Bioinformatics and Molecular and Cellular Pathology
Michael Uhler, Ph.D. – University of Michigan
Jack Parent, MD – University of Michigan
Rationale:
De novo mutations in the Syntaxin-binding protein 1 (STXBP1), encoded by STXBP1, are among the most prevalent causes of variable neurodevelopmental disorders, including epileptic encephalopathy, developmental delay, and movement disorders. Although STXBP1 has been proposed as a critical presynaptic protein controlling synaptic vesicle exocytosis, clinical phenotypes also suggest that its biological function could be more diverse. Methods:
The expression pattern of STXBP1 was studied using immunostaining in vitro and in vivo. Synaptosome isolation was performed to investigate the synaptic and non-synaptic localization of STXBP1 in the brain. STXBP1 immunoprecipitation followed by mass spectrometry was conducted to identify protein complexes interacting with STXBP1. Cre-in utero electroporation (IUE) was done on Stxbp1F/F mice to generate an in vivo knockout (KO) cellular model for studying the in vivo function of Stxbp1.Results:
Our immunohistochemistry results demonstrated that Stxbp1 expression in the cerebral cortex was developmentally regulated in vivo and could be detected in neuronal soma and processes. STXBP1 was in both the synaptic and cytosolic fractions, interacting with neuronal cytoskeleton and membrane periodic structures. Interestingly, sparse Stxbp1 KO in mouse forebrain led to cell-autonomous cell death, which was rescued by either wild-type STXBP1 or pathogenic STXBP1 mutants. However, Stxbp1 KO neurons rescued by pathogenic mutants exhibited impaired growth of neuronal dendrites. Our results also showed that STXBP1 interacts with αII Spectrin and Arpc2 and is required for their localization on the neuronal membrane.Conclusions:
Our data suggest that STXBP1 has diverse functions in neurodevelopment and regulates the trafficking of membrane cytoskeleton proteins in the brain.Funding:
U54NS117170, Project 3 (Wang and Baraban): Cell Systems to Pre-Clinical Models.