Defining clock neuronal circuits that control seasonal behavior
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abstract
Each fall, coincident with decreasing day length, monarchs experience a switch in physiology and behavior by entering into reproductive diapause and migrating south, as opposed to their reproductive, non-migratory parents. To maintain a constant flight bearing to the south, migratory monarchs use circadian clocks located in the antennae to time-compensate the changes of the sun’s position in the sky over the course of the day suggesting the existence of a neural circuit between the antennae and the sun compass structure located in the brain, the central complex. Because rhythms of core circadian clock genes are also found in the antennae of non-migratory monarchs, antennal clock projections likely undergo seasonal rewiring to the central complex. To understand how plasticity in clock neuronal network underlies these seasonal adaptations, it is imperative to physically and functionally map the clock neuronal circuitry in monarch brain and antennae. To achieve this goal, we propose to leverage our expertise in the application of CRISPR/Cas9 in the monarch to develop strategies to efficiently knock-in reporter tags at clock gene loci both in vitro and in vivo, map the clock circuitry relevant to seasonal behavior by identifying brain clock and antennal clock projections, and use these reporters to determine how the clock circuits are rewired seasonally, i.e. as a function of the photoperiod. We will first develop a proof-of-concept knock-in approach in vitro in a monarch specific cell line that contains a light driven clock, and tag clock neurons with membrane tagged fluorescent reporters in vivo.
