Hardin, Paul individual record
Distinguished Professor

A diverse array of organisms including prokaryotic and eukaryotic microbes, plants, and animals display daily rhythms in physiology, metabolism and/or behavior. These rhythms are not passively driven by environmental cycles of light and temperature, but are actively controlled by endogenous circadian clocks that are set by environmental cycles, keep time in the absence of environmental cues, and activate overt physiological, metabolic and behavioral rhythms at the appropriate time of day. This remarkable conservation of circadian clock function through evolution suggests that maintaining synchrony with the environment is of fundamental importance. Our understanding of the circadian clock is particularly important for human health and well-being. The clearest examples of circadian clock dysfunction are those that result in abnormal sleep-wake cycles, but clock disturbances are also associated with other ailments including epilepsy, cerebrovascular disease, depression, and seasonal affective disorder. The realization that disorders of the sleep-wake cycle such as Familial Advanced Sleep Phase Syndrome can result from alterations in clock gene function underscores the clinical importance of understanding the molecular organization of the circadian system.

Work in my laboratory focuses on defining the molecular mechanisms that drive circadian clock function in the fruit fly, Drosophila melanogaster. We previously found that the core timekeeping mechanism is based on core and interlocked transcriptional feedback loops. Our studies currently focus on (1) defining post-translational regulatory mechanisms that operate in the core loop to set the 24 hour period, (2) determining whether interlocked loops are important for circadian timekeeping and/or output, (3) understanding how circadian oscillator cells are determined during development, and (4) defining mechanisms that control rhythms in olfactory and gustatory physiology and behavior.

selected publications
Academic Articles82
  • Zhang, Y., Iiams, S. E., Menet, J. S., Hardin, P. E., & Merlin, C (2022). TRITHORAX-dependent arginine methylation of HSP68 mediates circadian repression by PERIOD in the monarch butterfly. Proceedings of the National Academy of Sciences. 119(4), e2115711119.
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  • Rivas, G., Zhou, J., Merlin, C., & Hardin, P. E. (2021). CLOCKWORK ORANGE promotes CLOCK-CYCLE activation via the putative Drosophila ortholog of CLOCK INTERACTING PROTEIN CIRCADIAN. Current Biology. 31(19), 4207-4218.e4.
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  • Gunawardhana, K. L., Rivas, G., Caster, C., & Hardin, P. E. (2021). Crosstalk between vrille transcripts, proteins, and regulatory elements controlling circadian rhythms and development in Drosophila.. iScience. 24(1), 101893-101893.
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  • Mahesh, G., Rivas, G., Caster, C., Ost, E. B., Amunugama, R., Jones, R., Allen, D. L., & Hardin, P. E. (2020). Proteomic analysis of Drosophila CLOCK complexes identifies rhythmic interactions with SAGA and Tip60 complex component NIPPED-A.. Sci Rep. 10(1), 17951.
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  • Krishnan, P., Dryer, S. E., & Hardin, P. E. (2005). Measuring circadian rhythms in olfaction using electroantennograms. Young, M. W. (Eds.), Methods in Enzymology. 495-508.
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Conference Papers5
  • Yu, W., & Hardin, P. E. (2013). An RNAi screen of protein kinase genes identifies novel components of the circadian oscillator in Drosophila. JOURNAL OF PHYSIOLOGICAL SCIENCES. 63, S111-S111.
  • Benito, J., Zheng, H., Ng, F. S., Hardin, P. E., & Press, C. (2007). Transcriptional Feedback Loop Regulation, Function, and Ontogeny in Drosophila. CLOCKS AND RHYTHMS. 72, 437-444.
  • Benito, J., Zheng, H., Ng, F. S., & Hardin, P. E (2007). Transcriptional feedback loop regulation, function, and ontogeny in Drosophila.. Cold Spring Harb Symp Quant Biol. 72(1), 437-444.
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  • Zwiebel, L. J., Hardin, P. E., Hall, J. C., & Rosbash, M (1991). Circadian oscillations in protein and mRNA levels of the period gene of Drosophila melanogaster.. Biochem Soc Trans. 19(2), 533-537.
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  • Ng, F. S., Houl, J. H., Francis, C., Callaerts, P., & Hardin, P. E CLOCK expression and regulation during development in Drosophila. JOURNAL OF NEUROGENETICS. 20(3-4), 189-189.
in the news
chaired theses and dissertations
First Name
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mailing address
Texas A&M University; Biology; 3258 TAMU
College Station, TX 77843-3258