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The 150 pacemaker neurons in Drosophila are organized into two groups of cells called M (morning) and E (evening) oscillators in the small and large lateral neurons (LNvs).[1] These two groups of cells were first observed by Colin Pittendrigh in 1976. As indicated by their names, the two oscillators control circadian rhythm at different times of the day, yet the two must coordinate to synchronize circadian activity.
PDF synchronizes phase of M oscillators, while in E oscillators PDF decelerates their cycling and supports their amplitude.[2] Stoleru et al. used mosaic transgenic animals with different circadian periods to study the two oscillators. Their study showed that M-cells periodically send a "reset" signal which determines the oscillations of the E-cells. It is believed that the reset signal is PDF, because it is M-cell specific and plays a large role in maintaining normal rhythmicity.[3]
PDF from s-LNv is responsible for the maintenance of a free-running rhythm, while PDF from large lateral ventral neurons is not required for normal behavior.[4] Experiments at Brandeis University have shown that PDF neuropeptide is localized in small lateral ventral neurons (s-LNv) that specifically control morning anticipatory behavior.[1] However, it has been found that large LNv working with other circadian neurons is sufficient to rescue the morning anticipation behavior and startle response in s-LNv-ablated flies.[5] Thus, PDF's role in setting the free-running rhythm and the timing of light dark cycles comes from both types of lateral ventral neurons.
Further evidence of distinct E and M peaks in Drosophila was provided by Grima et al.[6] This work confirmed that the small lateral ventral neurons, which express PDF, are necessary for the morning peak in Drosophila circadian rhythms.[6] Flies lacking functional s-LNv did not possess a lights-on anticipatory activity for the morning peak.[6]
In addition to the LNv, another study has found that a subset of the posterior dorsal neurons 1 (DN1(p)s) modulate the startle response to the onset of light, as flies with mutated ion channels in these neurons show reduced anticipatory behavior and free-running rhythms.[7] The deficit can be rescued by synapsing PDF-expressing neurons onto mutated DN1(p)s, as PDF neurons is sufficient to induce high level of Timeless (gene) protein, an essential protein that regulates circadian rhythm. [8]
Other behavioral aspects of Drosophila such as eclosion activity have been monitored with ectopic expression of pdf, which in this case is concentrated in the dorsal central brain.[9] These alterations in expression caused severely altered rhythmic behavior in eclosion of larvae, further substantiating the evidence that PDF modulates the rhythmic control of Drosophila behavior.[9]
- ^ a b Im SH, Taghert PH (July 2009). Mignot, Emmanuel (ed.). "The neuropeptide PDF acts directly on E oscillator neurons to regulate multiple features of circadian behavior". PLoS Biol. 7 (7): e1000154. doi:10.1371/journal.pbio.1000154. PMC 2702683. PMID 19621061.
{{cite journal}}: CS1 maint: unflagged free DOI (link) - ^ Duvall, Laura B.; Taghert, Paul H.; Bellen, Hugo J. (5 June 2012). "The Circadian Neuropeptide PDF Signals Preferentially through a Specific Adenylate Cyclase Isoform AC3 in M Pacemakers of Drosophila". PLoS Biology. 10 (6): e1001337. doi:10.1371/journal.pbio.1001337. PMC 3367976. PMID 22679392.
{{cite journal}}: CS1 maint: unflagged free DOI (link) - ^ Stoleru D, Peng Y, Nawathean P, Rosbash M (November 2005). "A resetting signal between Drosophila pacemakers synchronizes morning and evening activity". Nature. 438 (7065): 238–242. doi:10.1038/nature04192. PMID 16281038.
{{cite journal}}: CS1 maint: multiple names: authors list (link) - ^ Shafer OT, Taghert PH (2009). Nitabach, Michael N. (ed.). "RNA-interference knockdown of Drosophila pigment dispersing factor in neuronal subsets: the anatomical basis of a neuropeptide's circadian functions". PLoS ONE. 4 (12): e8298. doi:10.1371/journal.pone.0008298. PMC 2788783. PMID 20011537.
{{cite journal}}: CS1 maint: unflagged free DOI (link) - ^ Sheeba V, Fogle KJ, Holmes TC (2010). Tell, Fabien (ed.). "Persistence of morning anticipation behavior and high amplitude morning startle response following functional loss of small ventral lateral neurons in Drosophila". PLoS ONE. 5 (7): e11628. doi:10.1371/journal.pone.0011628. PMC 2905440. PMID 20661292.
{{cite journal}}: CS1 maint: multiple names: authors list (link) CS1 maint: unflagged free DOI (link) - ^ a b c Grima, Brigitte; Chélot, Elisabeth; Xia, Ruohan; Rouyer, François (14 October 2004). "Morning and evening peaks of activity rely on different clock neurons of the Drosophila brain". Nature. 431 (7010): 869–873. doi:10.1038/nature02935.
- ^ Zhang L, Chung BY, Lear BC, Kilman VL, Liu Y, Mahesh G, Meissner RA, Hardin PE, Allada R (April 2010). "DN1(p) circadian neurons coordinate acute light and PDF inputs to produce robust daily behavior in Drosophila". Curr. Biol. 20 (7): 591–599. doi:10.1016/j.cub.2010.02.056. PMC 2864127. PMID 20362452.
{{cite journal}}: CS1 maint: multiple names: authors list (link) - ^ Seluzicki, Adam; Flourakis, Matthieu; Kula-Eversole, Elzbieta; Zhang, Luoying; Kilman, Valerie; Allada, Ravi; Blau, Justin (18 March 2014). "Dual PDF Signaling Pathways Reset Clocks Via TIMELESS and Acutely Excite Target Neurons to Control Circadian Behavior". PLoS Biology. 12 (3): e1001810. doi:10.1371/journal.pbio.1001810.
{{cite journal}}:|access-date=requires|url=(help)CS1 maint: unflagged free DOI (link) - ^ a b Cite error: The named reference
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