Context-dependent hyperactivity insyngap1aandsyngap1bzebrafish autism models

Abstract

AbstractBackground and AimsSYNGAP1 disorder is a prevalent genetic form of Autism Spectrum Disorder and Intellectual Disability (ASD/ID) and is caused byde novoor inherited mutations in one copy of theSYNGAP1gene. In addition to ASD/ID, SYNGAP1 disorder is associated with comorbid symptoms including treatment-resistant-epilepsy, sleep disturbances, and gastrointestinal distress. Mechanistic links between these diverse symptoms andSYNGAP1variants remain obscure, therefore, our goal was to generate a zebrafish model in which this range of symptoms can be studied.MethodsWe used CRISPR/Cas9 to introduce frameshift mutations in thesyngap1aandsyngap1bzebrafish duplicates (syngap1ab) and validated these stable models for Syngap1 loss-of-function. BecauseSYNGAP1is extensively spliced, we mapped splice variants to the two zebrafishsyngap1aandbgenes and identified mammalian-like isoforms. We then quantified locomotory behaviors in zebrafish syngap1ab larvae under three conditions that normally evoke different arousal states in wild type larvae: aversive, high-arousal acoustic, medium-arousal dark, and low-arousal light stimuli.ResultsWe show that CRISPR/Cas9 indels in zebrafishsyngap1aandsyngap1bproduced loss-of-function alleles at RNA and protein levels. Our analyses of zebrafish Syngap1 isoforms showed that, as in mammals, zebrafish Syngap1 N- and C-termini are extensively spliced. We identified a zebrafishsyngap1α1-like variant that maps exclusively to thesyngap1bgene. Quantifying locomotor behaviors showed thatsyngap1ablarvae are hyperactive compared to wild type but to differing degrees depending on the stimulus. Hyperactivity was most pronounced in low arousal settings, with overall movement increasing with the number of mutantsyngap1alleles.ConclusionsOur data support mutations in zebrafishsyngap1abas causal for hyperactivity associated with elevated arousal that is especially pronounced in low-arousal environments.