In a talk given by Dr. Dan Cavanaugh, Cavanaugh explained the study conducted within the article, "The cell-intrinsic circadian clock is dispensable for lateral posterior clock neuron regulation of Drosophila rest-activity rhythms" (2025) by Guerrero, Cusick, Samaras, Shamon, and Cavanaugh. Within this study, Cavanaugh and colleagues aimed to assess the relationship between the lateral posterior group of clock neurons (LPNs) and rhythms of rest-activity in Drosophila melanogaster fruit flies.
Clock cells contain a negative loop of feedback between transcription and translation that allows for the tracking of the time of day. While fewer findings regarding LPNs are available, it has been proposed that these cells respond to light and temperature cues. Considering this, the researchers wanted to gain a further understanding of LPNs in comparison to other groups of clock cells, and cell-specific manipulations were done using the split-GAL4 system in order to accomplish this. It was observed that there was no alteration in locomotion or behavior of sleep in response to manipulation of LPN molecular clock function; though, LPNs were indicated to have an importance within the clock cell network in the means of communication with other cells.
In light of the potential to further understand LPNs, other groups of clock cells within the brain, and circadian rhythm, additional research has been done for this purpose. In particular, the article "Drosophila Temperature Preference Rhythms: An Innovative Model to Understand Body Temperature Rhythms" (2019) by Goda and Hamada describes a study conducted to explore mechanisms that contribute to alterations in body temperature from circadian regulation in Drosophila--congruent with the aforementioned association between clock cells and temperature.
Body temperature rhythm (BTR), as this article describes, is the fluctuation of body temperature throughout a 24 hour cycle that increases alongside wakefulness and declines when one sleeps. It corresponds with the body's circadian clock as well as other factors--such as metabolism. Despite this information, the mechanisms that give rise to alterations in BTR have been uncertain. Hence, Goda and colleagues attempted to determine them.
Of the researchers' findings, it was found that Drosophila fruit flies have a behavior of temperature preference, or Temperature Preference Rhythm (TPR). Notably, 25 degrees celsius is the preferred body temperature in the morning, and it rises throughout the day and decreases in the night. This observation not only paralleled the BTR of Drosophila, suggesting that TPR produces BTR, but this pattern resembled the BTR of humans. Moreover, this data that was collected proposes that TPR is controlled by an internal circadian clock.
In terms of the mechanisms that direct TPR, the researchers concluded that Diuretic Hormone 31 Receptor (DH31R) is a regulator of TPR during the daytime. DH31R is a G-protein coupled receptor activated by the DH31 ligand. In observation of the DH31R mutant flies within this study, daytime TPR was disrupted in dark-dark cycles. With this, the researchers were able to deduce that the activity of DH31R is linked to the function of BTR and the circadian clock. Moreover, findings indicated that the DH31 ligand may also regulate TPR at the onset of nighttime by acting on group two of dorsal neurons, DN2s. This was found by first identifying the neurons responsible for regulating TPR via DH31. The researchers expressed tethered-DH31 (t-DH31) in DN2s of DH31 mutant flies, and this dampened the decline in preferred temperature that was expected during nighttime. Hence, the researchers were able to further understand the significance of DH31 on TPR.
In short, Goda and Hamada explored body temperature patterns in relation to the endogenous circadian clock--likewise to how Cavanaugh had taken into account the effect of light and temperature on rest-activity rhythms. As there remains much to be discovered regarding the body's natural ability to track the time of day with clock cells, such as the function of LPNs or BTR in nocturnal species, these studies provided great insight into this process.
References
Goda, T., & Hamada, F. N. (2019). Drosophila Temperature Preference Rhythms: An Innovative Model to Understand Body Temperature Rhythms. International Journal of Molecular Sciences. 20(8). 1988.https://doi.org/10.3390/ijms20081988
Guerrero, C. Y. P., Cusick, M. R., Samaras, A. J., Shamon, N. S., Cavanaugh, D. J. (2025). The cell- intrinsic circadian clock is dispensable for lateral posterior clock neuron regulation of Drosophila rest-activity rhythms. Neurobiology of Sleep and Circadian Rhythms, 18, 100124. https://doi.ord/10.1016/j.nbscr.2025.100124.
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