Epilepsy, Behavioral Abnormalities, and Physiological Comorbidities in Syntaxin-Binding Protein 1 (STXBP1) Mutant Zebrafish.

Brian P Grone,Federico Sicca,Kyla R Hamling,Scott C Baraban,Maneesh G Kumar,Maria Marchese,Manisha Patel,Filippo M Santorelli,Christopher S Krasniak,Harold A Burgess

doi:10.1371/journal.pone.0151148

Abstract

Mutations in the synaptic machinery gene syntaxin-binding protein 1, STXBP1 (also known as MUNC18-1), are linked to childhood epilepsies and other neurodevelopmental disorders. Zebrafish STXBP1 homologs (stxbp1a and stxbp1b) have highly conserved sequence and are prominently expressed in the larval zebrafish brain. To understand the functions of stxbp1a and stxbp1b, we generated loss-of-function mutations using CRISPR/Cas9 gene editing and studied brain electrical activity, behavior, development, heart physiology, metabolism, and survival in larval zebrafish. Homozygous stxbp1a mutants exhibited a profound lack of movement, low electrical brain activity, low heart rate, decreased glucose and mitochondrial metabolism, and early fatality compared to controls. On the other hand, homozygous stxbp1b mutants had spontaneous electrographic seizures, and reduced locomotor activity response to a movement-inducing “dark-flash” visual stimulus, despite showing normal metabolism, heart rate, survival, and baseline locomotor activity. Our findings in these newly generated mutant lines of zebrafish suggest that zebrafish recapitulate clinical phenotypes associated with human syntaxin-binding protein 1 mutations.

Highlights

Mutations in the human syntaxin-binding protein 1 (STXBP1) gene are associated with a range of clinical outcomes
We investigated the spatial expression of stxbp1a and stxbp1b in developing zebrafish using whole-mount colorimetric in situ hybridization (ISH)
We report the generation of stxbp1a and stxbp1b mutant zebrafish to explore the effects of STXBP1 mutations in neurodevelopmental disorders including early infantile epileptic encephalopathy with burst suppression (EIEE)

Summary

Introduction

Mutations in the human syntaxin-binding protein 1 (STXBP1) gene are associated with a range of clinical outcomes. STXBP1 mutations were first identified in children with early infantile epileptic encephalopathy with burst suppression (EIEE; known as Ohtahara Syndrome) [1, 2] and subsequently found in patients diagnosed with other forms of epileptic encephalopathy including infantile spasms [3, 4], Lennox-Gastaut Syndrome [4], and Dravet Syndrome [5]. These epilepsies are primarily pediatric, catastrophic, pharmacoresistant, and associated with intellectual disability. STXBP1 mutations are sometimes associated with non-syndromic intellectual disability without epilepsy [6], or with ataxia or dyskinesia [7] that can PLOS ONE | DOI:10.1371/journal.pone.0151148 March 10, 2016

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