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ABSTRACT Drosophila’s innate response to gravity, geotaxis, has been used to assess the impact of aging and disease on motor performance. Despite its rich history, fly geotaxis continues to be largely measured manually and assessed through simplistic metrics, limiting analytic insights into the behavior. Here, we have constructed a fully programmable apparatus and developed a multi-object tracking software capable of following sub-second movements of individual flies, thus allowing quantitative analysis of geotaxis. The apparatus monitors 10 fly cohorts simultaneously, with each cohort consisting of up to 7 flies. The software tracks single flies during the entire run with ∼97% accuracy, yielding detailed climbing curve, speed and movement direction with 1/30 s resolution. Our tracking permits the construction of multi-variable metrics and the detection of transitory movement phenotypes, such as slips and falls. The platform is therefore poised to advance Drosophila geotaxis assay into a comprehensive assessment of locomotor behavior. 

Background and aimsSYNGAP1-related disorder (SYNGAP1-RD) 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 zebrafishsyngap1ablarvae 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 thatsyngap1abmutant larvae are hyperactive compared to wild-type but to differing degrees depending on the stimulus. Hyperactivity was most pronounced in low arousal settings, and hyperactivity was proportional to the number of mutantsyngap1alleles. LimitationsSyngap1loss-of-function mutations produce relatively subtle phenotypes in zebrafish compared to mammals. For example, while mouseSyngap1homozygotes die at birth, zebrafishsyngap1ab−/−survive to adulthood and are fertile, thus some aspects of symptoms in people withSYNGAP1-Related Disorder are not likely to be reflected in zebrafish. ConclusionOur data support mutations in zebrafishsyngap1abas causal for hyperactivity associated with elevated arousal that is especially pronounced in low-arousal environments. 

Sleep and circadian rhythm dysfunctions are common clinical features of Alzheimer’s disease (AD). Increasing evidence suggests that in addition to being a symptom, sleep disturbances can also drive the progression of neurodegeneration. Protein aggregation is a pathological hallmark of AD; however, the molecular pathways behind how sleep affects protein homeostasis remain elusive. Here we demonstrate that sleep modulation influences proteostasis and the progression of neurodegeneration inDrosophilamodels of tauopathy. We show that sleep deprivation enhanced Tau aggregational toxicity resulting in exacerbated synaptic degeneration. In contrast, sleep induction using gaboxadol led to reduced toxic Tau accumulation in neurons as a result of modulated autophagic flux and enhanced clearance of ubiquitinated Tau, suggesting altered protein processing and clearance that resulted in improved synaptic integrity and function. These findings highlight the complex relationship between sleep and regulation of protein homeostasis and the neuroprotective potential of sleep-enhancing therapeutics to slow the progression or delay the onset of neurodegeneration.