PROJECT SUMMARY
Sleep disorders affect over 10% of the population, and adequate sleep is essential for human health and
cognitive function. Sleep is also apparently conserved across the animal kingdom. However, despite its
importance and ubiquity, surprisingly little is known about the genetic, molecular, and neuronal mechanisms that
govern sleep. Treatments for sleep disorders hinge on a better understanding of these mechanisms. Exogenous
melatonin has long been recognized as a sleep-promoting molecule in humans, but endogenous melatonin has
only recently been shown to be required for normal sleep levels. The latter studies were performed using
zebrafish, a diurnal vertebrate whose brain resembles that of mammals and whose sleep is regulated by the
same genes and neuronal populations that control sleep in mammals. Zebrafish larvae are highly amenable to
high-throughput behavioral analysis and to genetic and neuronal manipulations. I plan to further exploit the
tractability and convenience of zebrafish larvae to characterize the downstream signaling pathways and neuronal
populations through which melatonin exerts its sleep-promoting effects. First, I will test the hypothesis that one
or more melatonin receptor orthologs mediates the effects of melatonin on sleep by generating zebrafish
containing mutations in each gene and assaying these mutants for sleep defects. Second, I will identify the
neuronal populations that act downstream of melatonin by examining melatonin-induced changes in cfos
expression and in GCaMP6s fluorescence, both indicators of neuronal activity, in populations of cells across the
entire larval zebrafish brain. Third, I will test the hypothesis that melatonin promotes sleep by stimulating
adenosine signaling, a pathway known to promote sleep in both zebrafish and mammals. The results of these
experiments will help to confirm the role of endogenous melatonin as an important sleep regulator, and will
identify genetic and neuronal substrates of melatonin-induced sleep. Because melatonin and adenosine are
thought to mediate circadian and homeostatic sleep regulation, respectively, a possible interaction between
these two molecules will lead to exciting new hypotheses about how homeostatic and circadian control of sleep
are coordinated. The results of this study may eventually help guide the development and implementation of new
therapies, and the refinement of existing therapies, for sleep and sleep-related disorders.