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Glia-related circadian plasticity in the visual system of Diptera.

Górska-Andrzejak J - Front Physiol (2013)

Bottom Line: It is observed in terminals of the compound eye photoreceptor cells, the peripheral oscillators expressing the clock genes.However, it has been found also in their postsynaptic partners, the L1 and L2 monopolar cells, in which the activity of the clock genes have not yet been detected.This paper summarizes the morphological and biochemical rhythms in glia of the optic lobe, shows how they contribute to circadian plasticity, and discusses how glial clocks may modulate circadian rhythms in the lamina.

View Article: PubMed Central - PubMed

Affiliation: Department of Cell Biology and Imaging, Institute of Zoology, Jagiellonian University Kraków, Poland.

ABSTRACT
The circadian changes in morphology of the first visual neuropil or lamina of Diptera represent an example of the neuronal plasticity controlled by the circadian clock (circadian plasticity). It is observed in terminals of the compound eye photoreceptor cells, the peripheral oscillators expressing the clock genes. However, it has been found also in their postsynaptic partners, the L1 and L2 monopolar cells, in which the activity of the clock genes have not yet been detected. The circadian input that the L1 and L2 receive seems to originate not only from the retina photoreceptors and from the circadian pacemaker neurons located in the brain, but also from the glial cells that express the clock genes and thus contain circadian oscillators. This paper summarizes the morphological and biochemical rhythms in glia of the optic lobe, shows how they contribute to circadian plasticity, and discusses how glial clocks may modulate circadian rhythms in the lamina.

No MeSH data available.


Anatomical relationships between glial cells (eg, epithelial glial cells of the lamina, dmng, distal medulla neuropil glia) and their putative targets, the L1 and L2 monopolar cells, as well as terminals of some clock neurons (LNs). (A) Diagram showing the relative locations of L1 and L2 in the lamina and distal medulla, the terminals of PDF immunoreactive lateral neurons (LNs), lamina neuropil epithelial glia (eg), and distal medulla neuropil glia (dmng). L, lamina; M, medulla. (B) Morphology of the L2 monopolar cell in the optic lobe of 21D-GAL4 × UAS-S65T-GFP transgenic flies. Cell bodies of L2 are distributed beneath the retina (R), in the region of the lamina cortex (Lc); the axons and dendrites of these cells are in the lamina neuropil (Ln), and their terminals in the medulla (M). Ch, external chiasm. Scale bar: 10 μm. (C,D) The region of the medulla seen as an insert in (B). (C) GFP labeled terminals of L2 and distal medulla neuropil glia (dmng) showing Ebony-like immunoreactivity. Scale bar: 10 μm. (D) The distal medulla neuropil glia (dmng) of Repo-Gal4 × UAS-S65T-GFP transgenic flies and terminals of PDH-immunoreactive LNs (PDF) labeled with anti-PDF antibody. The PDF-positive LNs send projections into the region where the terminals of L2 and Ebony-expressing dmng are located. Scale bar: 10 μm.
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Figure 3: Anatomical relationships between glial cells (eg, epithelial glial cells of the lamina, dmng, distal medulla neuropil glia) and their putative targets, the L1 and L2 monopolar cells, as well as terminals of some clock neurons (LNs). (A) Diagram showing the relative locations of L1 and L2 in the lamina and distal medulla, the terminals of PDF immunoreactive lateral neurons (LNs), lamina neuropil epithelial glia (eg), and distal medulla neuropil glia (dmng). L, lamina; M, medulla. (B) Morphology of the L2 monopolar cell in the optic lobe of 21D-GAL4 × UAS-S65T-GFP transgenic flies. Cell bodies of L2 are distributed beneath the retina (R), in the region of the lamina cortex (Lc); the axons and dendrites of these cells are in the lamina neuropil (Ln), and their terminals in the medulla (M). Ch, external chiasm. Scale bar: 10 μm. (C,D) The region of the medulla seen as an insert in (B). (C) GFP labeled terminals of L2 and distal medulla neuropil glia (dmng) showing Ebony-like immunoreactivity. Scale bar: 10 μm. (D) The distal medulla neuropil glia (dmng) of Repo-Gal4 × UAS-S65T-GFP transgenic flies and terminals of PDH-immunoreactive LNs (PDF) labeled with anti-PDF antibody. The PDF-positive LNs send projections into the region where the terminals of L2 and Ebony-expressing dmng are located. Scale bar: 10 μm.

Mentions: Studies on transgenic lines of Drosophila (21D-Gal4 × UAS-GFP), in which the morphology of L2 was labeled by cytoplasmic or membranous GFP reporter protein revealed, that in addition to the circadian changes in axon size and the number of feedback synapses, the entire structure of this cell (Figure 3) undergoes daily remodeling (Górska-Andrzejak et al., 2005; Weber et al., 2009). The size of cell nuclei and, more importantly, the size of a dendritic tree in the lamina also oscillate during the 24 h day, with the highest amplitude of changes at the beginning of the day (Górska-Andrzejak et al., 2005; Weber et al., 2009). Interestingly, L2 dendrites that are postsynaptic to photoreceptors are the longest at the beginning of the day (Weber et al., 2009), which coincides with the increase of the number of tetrad synapses in photoreceptor terminals (shown in Musca) and with the level of BRP in the lamina (shown in Drosophila) (Pyza and Meinertzhagen, 1993; Górska-Andrzejak et al., 2013). This coincidence strongly suggests the possibility of correlation, which however should be confirmed in a direct experiment. Presumably, there are also corresponding changes in L1, which partners L2 (Figures 2A, 3A), although analogous studies of L1 morphology have been so far hindered by the lack of a driver for L1.


Glia-related circadian plasticity in the visual system of Diptera.

Górska-Andrzejak J - Front Physiol (2013)

Anatomical relationships between glial cells (eg, epithelial glial cells of the lamina, dmng, distal medulla neuropil glia) and their putative targets, the L1 and L2 monopolar cells, as well as terminals of some clock neurons (LNs). (A) Diagram showing the relative locations of L1 and L2 in the lamina and distal medulla, the terminals of PDF immunoreactive lateral neurons (LNs), lamina neuropil epithelial glia (eg), and distal medulla neuropil glia (dmng). L, lamina; M, medulla. (B) Morphology of the L2 monopolar cell in the optic lobe of 21D-GAL4 × UAS-S65T-GFP transgenic flies. Cell bodies of L2 are distributed beneath the retina (R), in the region of the lamina cortex (Lc); the axons and dendrites of these cells are in the lamina neuropil (Ln), and their terminals in the medulla (M). Ch, external chiasm. Scale bar: 10 μm. (C,D) The region of the medulla seen as an insert in (B). (C) GFP labeled terminals of L2 and distal medulla neuropil glia (dmng) showing Ebony-like immunoreactivity. Scale bar: 10 μm. (D) The distal medulla neuropil glia (dmng) of Repo-Gal4 × UAS-S65T-GFP transgenic flies and terminals of PDH-immunoreactive LNs (PDF) labeled with anti-PDF antibody. The PDF-positive LNs send projections into the region where the terminals of L2 and Ebony-expressing dmng are located. Scale bar: 10 μm.
© Copyright Policy - open-access
Related In: Results  -  Collection

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getmorefigures.php?uid=PMC3750947&req=5

Figure 3: Anatomical relationships between glial cells (eg, epithelial glial cells of the lamina, dmng, distal medulla neuropil glia) and their putative targets, the L1 and L2 monopolar cells, as well as terminals of some clock neurons (LNs). (A) Diagram showing the relative locations of L1 and L2 in the lamina and distal medulla, the terminals of PDF immunoreactive lateral neurons (LNs), lamina neuropil epithelial glia (eg), and distal medulla neuropil glia (dmng). L, lamina; M, medulla. (B) Morphology of the L2 monopolar cell in the optic lobe of 21D-GAL4 × UAS-S65T-GFP transgenic flies. Cell bodies of L2 are distributed beneath the retina (R), in the region of the lamina cortex (Lc); the axons and dendrites of these cells are in the lamina neuropil (Ln), and their terminals in the medulla (M). Ch, external chiasm. Scale bar: 10 μm. (C,D) The region of the medulla seen as an insert in (B). (C) GFP labeled terminals of L2 and distal medulla neuropil glia (dmng) showing Ebony-like immunoreactivity. Scale bar: 10 μm. (D) The distal medulla neuropil glia (dmng) of Repo-Gal4 × UAS-S65T-GFP transgenic flies and terminals of PDH-immunoreactive LNs (PDF) labeled with anti-PDF antibody. The PDF-positive LNs send projections into the region where the terminals of L2 and Ebony-expressing dmng are located. Scale bar: 10 μm.
Mentions: Studies on transgenic lines of Drosophila (21D-Gal4 × UAS-GFP), in which the morphology of L2 was labeled by cytoplasmic or membranous GFP reporter protein revealed, that in addition to the circadian changes in axon size and the number of feedback synapses, the entire structure of this cell (Figure 3) undergoes daily remodeling (Górska-Andrzejak et al., 2005; Weber et al., 2009). The size of cell nuclei and, more importantly, the size of a dendritic tree in the lamina also oscillate during the 24 h day, with the highest amplitude of changes at the beginning of the day (Górska-Andrzejak et al., 2005; Weber et al., 2009). Interestingly, L2 dendrites that are postsynaptic to photoreceptors are the longest at the beginning of the day (Weber et al., 2009), which coincides with the increase of the number of tetrad synapses in photoreceptor terminals (shown in Musca) and with the level of BRP in the lamina (shown in Drosophila) (Pyza and Meinertzhagen, 1993; Górska-Andrzejak et al., 2013). This coincidence strongly suggests the possibility of correlation, which however should be confirmed in a direct experiment. Presumably, there are also corresponding changes in L1, which partners L2 (Figures 2A, 3A), although analogous studies of L1 morphology have been so far hindered by the lack of a driver for L1.

Bottom Line: It is observed in terminals of the compound eye photoreceptor cells, the peripheral oscillators expressing the clock genes.However, it has been found also in their postsynaptic partners, the L1 and L2 monopolar cells, in which the activity of the clock genes have not yet been detected.This paper summarizes the morphological and biochemical rhythms in glia of the optic lobe, shows how they contribute to circadian plasticity, and discusses how glial clocks may modulate circadian rhythms in the lamina.

View Article: PubMed Central - PubMed

Affiliation: Department of Cell Biology and Imaging, Institute of Zoology, Jagiellonian University Kraków, Poland.

ABSTRACT
The circadian changes in morphology of the first visual neuropil or lamina of Diptera represent an example of the neuronal plasticity controlled by the circadian clock (circadian plasticity). It is observed in terminals of the compound eye photoreceptor cells, the peripheral oscillators expressing the clock genes. However, it has been found also in their postsynaptic partners, the L1 and L2 monopolar cells, in which the activity of the clock genes have not yet been detected. The circadian input that the L1 and L2 receive seems to originate not only from the retina photoreceptors and from the circadian pacemaker neurons located in the brain, but also from the glial cells that express the clock genes and thus contain circadian oscillators. This paper summarizes the morphological and biochemical rhythms in glia of the optic lobe, shows how they contribute to circadian plasticity, and discusses how glial clocks may modulate circadian rhythms in the lamina.

No MeSH data available.