Disrupted Neuronal Microexons Drive Hyperarousal via cAMP Signaling, Zebrafish Study Reveals
核心洞察
An international study shows that altered neuronal microexons cause hyperarousal and insomnia in zebrafish through dysregulated cAMP signaling.
Researchers found that a chemical inhibitor targeting cAMP completely normalized hyperactivity and sleep disturbances in mutated fish.
The cAMP-PKA-CREB pathway acts as a "neuronal thermostat," with elevated cAMP driving permanent overexcitation in the forebrain.
The altered presence of tiny fragments of neuronal genes, called microexons, directly causes hyperarousal and insomnia in zebrafish, according to an international study led by the Pompeu Fabra University (搜索) (UPF) and the Centre for Genomic Regulation (搜索) (CRG). Published in Science Advances, the findings establish a mechanistic link between disrupted alternative splicing, elevated cAMP signaling, and persistent behavioral overexcitation — a pathway that may illuminate the neurobiological underpinnings of sleep disturbances in autism (搜索) and schizophrenia (搜索).
An abnormal pattern of neural microexon presence leads to a hyperarousal state characterized by heightened neural activity and insomnia, commonly associated with stress but also observed in neurodevelopmental disorders. Arousal regulation is highly conserved in evolution, making the zebrafish model a relevant system for understanding these mechanisms in humans.
Microexon Disruption Alters Sleep and Behavior
The study demonstrates that zebrafish larvae with altered neural microexon presence exhibit a profoundly disrupted sleep pattern. "They sleep less frequently, for shorter durations and take longer to fall asleep," explained Tahnee Mackensen, first author of the study. "It is fascinating to see how, by analysing the movement of this transparent larvae, you can recall fish internal states."
Beyond behavioral changes, the researchers identified a molecular cascade underlying the hyperarousal. Mis-splicing alters cAMP levels — a signal produced within cells that regulates neuronal activity — making neurons more or less excitable. "Abnormal fish are permanently overexcited," Mackensen clarified. The mutated fish display increased activity in the forebrain and elevated cAMP signaling, which drives daytime hyperactivity.
cAMP as a Neuronal Thermostat
The research team demonstrated that the hyperarousal phenotype is pharmacologically reversible. Reducing cAMP with a chemical inhibitor lowered the activity of mutated fish to normal levels. Conversely, maintaining elevated cAMP levels in normal fish — either by inducing its synthesis or reducing its degradation — imitated highly aroused behavior, confirming that cAMP is key to driving arousal behavior. As Mackensen described it, "in neurons, cAMP acts as a thermostat for its activity."
The study identifies the cAMP–PKA–CREB signaling axis as a central driver of mutant hyperarousal. Pharmacological inhibition of cAMP signaling rescues mutant hyperactivity and associated transcriptional changes, while wild-type cAMP activation phenocopies the mutant. Down-regulation of immediate early genes and reduced CREB phosphorylation further suggest adaptation to sustained neuronal activation.
Evolutionary Conservation and Human Relevance
The constellation of behavioral and neuronal shifts observed in abnormal zebrafish had also been reported in fruit flies in a previous study by the same group. "We do know that the alteration of these microexons causes sleep deprivation in fish and flies," explained Manuel Irimia, who led the research. "This mechanism is likely to be conserved in mammals, including humans, but maybe not in the exactly very same way."
In humans, sleep disturbances and sensory hypersensitivity are frequent in neurological disorders like autism (搜索) and schizophrenia (搜索) — two conditions reported to have altered microexon regulation. "Despite not being causative of the disease, we know that changes in protein production can contribute to symptoms of the disorder," Irimia noted. "In this sense, it is plausible to study whether the treatment to restore the arousal state in fish also corrects or alleviates the symptoms in other species."
The cAMP-regulated arousal pathway is also implicated in anxiety and depression. Mackensen emphasized the broader significance, stating that "this could be just the tip of the iceberg," underscoring the need for continued investigation into how microexon splicing and cAMP modulation may inform therapeutic strategies for neurodevelopmental and psychiatric conditions.