«Connectivity, Organization, and Network Coordination of the Drosophila Central Circadian Clock by Zepeng Yao A dissertation submitted in partial ...»
The various classes of clock neurons are described in the text and labeled in the schematic. The projections of each clock neuron class are depicted in the same color as their soma. The LPN projections have not been described. aMe, accessory medulla. See text for details. The figure is reprinted from Helfrich-Förster, C., Shafer, O.T., Wülbeck, C., Grieshaber, E., Rieger, D., and Taghert, P. (2007). Development and morphology of the clock-gene-expressing lateral neurons of Drosophila melanogaster. J. Comp. Neurol. 500, 47–70, with permission from John Wiley and Sons.
Neurochemistry of the Drosophila clock neuron network.
(a) A schematic of the expression patterns of Cryptochrome (CRY) and PDF receptor (PDFR) within the clock neuron network. Note that CRY and PDFR are co-expressed by many clock neurons. Re, retina; La, lamina; Me, medulla; aMe, accessory medulla. (b) A schematic of the expression of neuropeptides and neurotransmitters by the various clock neurons. PDF, pigmentdispersing factor; ITP, ion transport peptide; NPF, neuropeptide F; sNPF, short neuropeptide F;
IPNa, IPNamide. The expression of choline acetyltransferase (Cha) and vesicular glutamate transporter (GluT) indicates the presence of acetylcholine and glutamate, respectively. dpr, dorsal protocerebrum. This figure is reprinted from Curr. Opin. Insect Sci. 7. Hermann-Luibl, C., and Helfrich-Förster, C. Clock network in Drosophila. 65–70. Copyright (2015), with permission from Elsevier.
1.5 Models of the Drosophila clock neuron network function Studies employing cell ablation and mosaic genetic rescue approaches have suggested a dual-oscillator model of the Drosophila clock network function: The LNvs function collectively as a “morning oscillator” that promotes activity around dawn, whereas the LNds and the 5th sLNv function collectively as an “evening oscillator” that promotes activity around dusk (Grima et al., 2004; Stoleru et al., 2004). The LNvs are essential for robust circadian timekeeping in the absence of environmental cues (Renn et al., 1999), and are thought to be the dominant pacemaker of the clock network under short-day conditions and constant darkness (Stoleru et al., 2005, 2007). In contrast, it is thought that light activates output from the LNds/5th s-LNv, and these neurons become the dominant pacemaker under long-day conditions and constant light (Picot et al., 2007; Stoleru et al., 2007). This dual-oscillator model provides a powerful and elegant model for the functional division of the clock neuron network and the adaptation of the clock neuron network to day-length changes, but it does not account for many experimental observations (discussed by Yoshii et al., 2012).
In addition to the lateral clock neurons, recent work has highlighted the importance of another group of clock neurons, the DN1ps. DN1ps are capable of driving activity rhythms in the presence of light (Murad et al., 2007), and can promote activity both around dawn and dusk depending on the specific light and temperature conditions (Fujii and Amrein, 2010; Zhang et al., 2010a, 2010b). Furthermore, the DN1ps have been implicated as key output neurons of the clock network in the control of activity and sleep rhythms (Cavanaugh et al., 2014; Kunst et al., 2014).
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CHAPTER 2. Analysis of functional neuronal connectivity in the Drosophila brain 1