AMPK signaling linked to the schizophrenia-associated 1q21.1 deletion is required for neuronal and sleep maintenance

Abstract

The human 1q21.1 deletion of ten genes is associated with increased risk schizophrenia. The deletion involves the {beta}-subunit of the AMP-activated protein kinase (AMPK) complex, a key energy sensor in the cell. Although neurons have a high demand for energy and low capacity to store nutrients, the role of AMPK in neuronal physiology is poorly defined. Here we show that AMPK is important in the nervous system for maintaining neuronal integrity and for stress survival and longevity in Drosophila. To understand its impact on behavior and potential contribution to the 1q21.1 deletion syndrome, we focused on sleep, as its main role is proposed to be to reestablish neuronal energy levels that are diminished during energy-demanding wakefulness. Sleep disturbances are one of the most common problems affecting individuals with psychiatric disorders. We show that AMPK is required to maintain proper sleep architecture and for sleep recovery following sleep deprivation. Neuronal AMPK{beta} loss specifically leads to sleep fragmentation and causes dysregulation of genes believed to play a role in sleep homeostasis. Our data also suggest that AMPK{beta} loss may contribute to the increased risk of developing mental disorders and sleep disturbances associated with the human 1q21.1 deletion. Sleep is regulated by circadian and homeostatic processes. While the circadian clock is well studied, the molecular mechanism underlying homeostasis remains largely unknown. Our data suggest that AMPK is required for sleep maintenance and may be involved in the homeostatic process of sleep regulation.\n\nAuthor SummaryThe human 1q21.1 chromosomal deletion is associated with increased risk of schizophrenia. Because this deletion affects only a small number of genes, it provides a unique opportunity to identify the specific disease-causing gene(s) using animal models. Here, we report the use of a Drosophila model to identify the potential contribution of one gene affected by the 1q21.1 deletion - PRKAB2 - to the pathology of the 1q21.1 deletion syndrome. PRKAB2 encodes a subunit of the AMP-activated protein kinase (AMPK) complex, the main cellular energy sensor. We show that AMPK deficiency reduces lifespan and causes structural abnormalities in neuronal dendritic structures, a phenotype which has been linked to schizophrenia. Furthermore, cognitive impairment and altered sleep patterning are some of the most common symptoms of schizophrenia. Therefore, to understand the potential contribution of PRKAB2 to the 1q21.1 syndrome, we tested whether AMPK alterations would cause defects in learning and sleep. Our study shows that lack of PRKAB2 and AMPK-complex activity, in the nervous system leads to reduced learning and to dramatic sleep disturbances. Thus, our data links a single 1q21.1-related gene with phenotypes that resemble common symptoms of schizophrenia, suggesting that this gene, PRKAB2, may contribute to the risk of developing schizophrenia.