On Variations in the Level of PER in Glial Clocks of Drosophila Optic Lobe and Its Negative Regulation by PDF Signaling

• Published in: Frontiers in physiology Vol. 9; p. 230
• Main Authors: Górska-Andrzejak, Jolanta, Chwastek, Elżbieta M, Walkowicz, Lucyna, Witek, Kacper
• Format: Journal Article
• Language: English
• Published: Switzerland Frontiers Media S.A 19.03.2018
• Subjects: circadian clocks; drosophila glia; glial oscillators; neuronal pacemakers; PDF; PER; Physiology; drosophila glia; PDF; Drosophila; glial oscillators; PER; circadian clocks; neuronal pacemakers
• ISSN: 1664-042X; 1664-042X
• DOI: 10.3389/fphys.2018.00230

We show that the level of the core protein of the circadian clock Period (PER) expressed by glial peripheral oscillators depends on their location in the optic lobe. It appears to be controlled by the ventral lateral neurons (LNvs) that release the circadian neurotransmitter Pigment Dispersing Factor (PDF). We demonstrate that glial cells of the distal medulla neuropil (dMnGl) that lie in the vicinity of the PDF-releasing terminals of the LNvs possess receptors for PDF (PDFRs) and express PER at significantly higher level than other types of glia. Surprisingly, the amplitude of PER molecular oscillations in dMnGl is increased twofold in PDF-free environment, that is in mutants. The mutants also reveal an increased level of glia-specific protein REPO in dMnGl. The photoreceptors of the compound eye (R-cells) of the PDF-null flies, on the other hand, exhibit de-synchrony of PER molecular oscillations, which manifests itself as increased variability of PER-specific immunofluorescence among the R-cells. Moreover, the daily pattern of expression of the presynaptic protein Bruchpilot (BRP) in the lamina terminals of the R-cells is changed in mutant. Considering that PDFRs are also expressed by the marginal glia of the lamina that surround the R-cell terminals, the LNv pacemakers appear to be the likely modulators of molecular cycling in the peripheral clocks of both the glial cells and the photoreceptors of the compound eye. Consequently, some form of PDF-based coupling of the glial clocks and the photoreceptors of the eye with the central LNv pacemakers must be operational.