Circadian Clock Dysfunction Exacerbate Autistic‐Like Behaviour and Wnt/β‐Catenin Signalling Dysregulation in ASD Mice and Treatment of Melatonin

Between 50% and 80% of children diagnosed with Autism Spectrum Disorder (ASD) are estimated to experience sleep disturbances, highlighting the importance of exploring the role of the circadian clock in ASD development. Previous studies have identified a potential link between Bmal1 deficiency and ASD in mouse models. In this study, we first characterise the expression patterns of circadian proteins. Subsequent behavioural tests and western blot analyses revealed that mice exposed to valproic acid (VPA) displayed autistic-like behaviours, along with altered circadian protein expression and disruption in Wnt signalling protein levels. Further studies showed that Bmal1 knockout exacerbates these behavioural changes and further impaired Wnt signalling and downstream protein expression in VPA-exposed mice. Notably, treatment with the circadian biomarker melatonin reversed Wnt downregulation and improved the behaviour deficit in VPA-exposed mice. The therapeutic effect of melatonin appears to be mediated by its regulation of the Wnt/β-catenin signalling pathway, which is linked to Bmal1-mediated circadian dysfunction. Together, our findings provide experimental evidence supporting the role of circadian dysregulation in ASD pathogenesis, highlight the therapeutic potential of melatonin in VPA-exposed mice, and suggest that Bmal1 may act as a co-activator in the Wnt-β-catenin signalling pathway.