J. Neurosci. 33, 6716–6725 (2013)

Circadian clocks are used by most animals to synchronize their behavior and physiology to the external environment. Circadian clock entrainment cues include daily light and temperature cycles. In Drosophila, temperature-induced synchronization of locomotive activity by central pacemaker neurons is regulated by input from peripheral tissues, but whether these pacemaker neurons can also receive direct inputs is not clear. Lee and Montell explored the possibility that the TRP family of cation channels, members of which are regulated by temperature, may act as a sensor in these neurons. They focused on Drosophila TrpA1 because it functions in a temperature range that matches the temperature synchronization of circadian rhythms. Whereas TrpA1-mutant flies responded to light cycles similarly to wild-type flies, the mutant flies had impaired temperature synchronization and were completely arrhythmic when a subset of pacemaker neurons were genetically ablated. The TrpA1 mutants also showed erratic variation in the expression of the clock protein Period, which undergoes a predictable oscillation in wild-type pacemaker neurons. This effect was accentuated when a subset of pacemaker neurons was absent. In transgenic rescue experiments, TrpA1 expression in pacemaker neurons contributed to the temperature synchronization of locomotive activity. These results suggest that synchronization of the circadian clock does not depend exclusively on inputs from peripheral neurons and that some pacemaker neurons expressing TrpA1 contribute to temperature-controlled activity patterns.