Integration of seasonal cues to modulate neuronal plasticity

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Project Summary Organisms adapt to seasonal changes in environmental conditions to survive. These adaptations rely predominantly on photoperiod (i.e., daylength), but are also influenced by temperature. Recent studies indicate that photoperiodic changes affect the neuronal composition of brain areas involved in circadian (i.e., daily) timekeeping and modulate the number of dopaminergic neurons, in a process known as neurotransmitter switching. Other studies show that the brain also undergoes profound structural changes across seasons. However, the relationship between these functional and structural changes in the brain and seasonal adaptations remains a major gap in knowledge. Moreover, whether other relevant seasonal cues, in particular temperature, contribute to these changes is not known. The overall goal of this project is to understand the nature and role of neuronal plasticity in the integration of seasonal cues to promote seasonal adaptations. My hypothesis is that seasonal adaptations are mediated by functional and structural plasticity in neurons from circadian and aminergic circuits in response to environmental cues. To test this, I propose 3 specific aims: investigate structural and functional plasticity of (1) the circadian clock neuronal network and of (2) aminergic circuits in response to seasonal cues and its impact on social and locomotor behavior, and (3) determine how the plastic changes in the circadian clock and aminergic circuits regulate brain connectivity and encode the behavioral output of these circuits. I will accomplish this project in the genetically tractable Drosophila model and will leverage a combination of versatile neurogenetics, high-resolution microscopy, and well-established behavioral analysis. Thus far in my postdoctoral career in the Chiu lab at UC Davis, I obtained training in molecular genetics and biochemistry, which I used to explore the role of circadian peptides in modulating seasonal adaptations in Drosophila. Moving forward, I will build on my current research to study the neuronal mechanisms of seasonal plasticity and behavior. During the K99 training period, I will use available tools in Drosophila to assess the functional and structural changes in the circadian clock neurons and aminergic circuits in response to seasonal cues. Moreover, I will test the functional consequences of these changes by using available genetically encoded sensors and by generating new, more sensitive, sensors to assess aminergic function in vivo under the guidance of Dr. Lin Tian. I will expand the use of these tools in the R00 stage to determine how the interaction between these two circuit systems modulate their functions and how they affect seasonal behavior concertedly. I believe that the mentorship of Drs. Chiu and Tian, together with the support provided by the K99/R00 award, will allow me to build a strong foundation that will enable my success as an independent investigator. The results of the proposed studies will elucidate the neuronal basis underlying sensory integrations in the context of seasonal adaptations, shedding light on the mechanisms behind seasonal modulation of health physiology and disorders.