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Circadian remodeling of neuronal circuits involved in rhythmic behavior.

Fernández MP, Berni J, Ceriani MF - PLoS Biol. (2008)

Bottom Line: Indeed, such circadian changes in PDF intensity represent the only known mechanism through which the PDF circuit could communicate with its output.Here we describe a novel circadian phenomenon involving extensive remodeling in the axonal terminals of the PDF circuit, which display higher complexity during the day and significantly lower complexity at nighttime, both under daily cycles and constant conditions.In support to its circadian nature, cycling is lost in bona fide clockless mutants.

View Article: PubMed Central - PubMed

Affiliation: Laboratorio de Genética del Comportamiento, Instituto Leloir, Instituto de Investigaciones Bioquímicas-Buenos Aires-Consejo Nacional de Investigaciones Científicas y Técnicas (IIBBA-CONICET), Buenos Aires, Argentina.

ABSTRACT
Clock output pathways are central to convey timing information from the circadian clock to a diversity of physiological systems, ranging from cell-autonomous processes to behavior. While the molecular mechanisms that generate and sustain rhythmicity at the cellular level are well understood, it is unclear how this information is further structured to control specific behavioral outputs. Rhythmic release of pigment dispersing factor (PDF) has been proposed to propagate the time of day information from core pacemaker cells to downstream targets underlying rhythmic locomotor activity. Indeed, such circadian changes in PDF intensity represent the only known mechanism through which the PDF circuit could communicate with its output. Here we describe a novel circadian phenomenon involving extensive remodeling in the axonal terminals of the PDF circuit, which display higher complexity during the day and significantly lower complexity at nighttime, both under daily cycles and constant conditions. In support to its circadian nature, cycling is lost in bona fide clockless mutants. We propose this clock-controlled structural plasticity as a candidate mechanism contributing to the transmission of the information downstream of pacemaker cells.

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Related in: MedlinePlus

Changes in the Degree of Arborization of the PDF Circuit Are Preserved Under Constant Conditions(A–C) pdf >mCD8-GFP wild-type brains were dissected at CT2 and CT14 during the second day in constant darkness (DD2). CT refers to the time that has passed from the last lights OFF/ON transition. CT2 and CT14 indicate subjective day and night, respectively.(A) Confocal images representative of the subjective day (upper) and subjective night (bottom panels) stained with anti-PDF (red) and anti-GFP (green) antibodies.(B) The number of intersections is consistently lower during subjective night, although the PDF circuit is not particularly shortened.(C) Total axonal crosses are significantly different during subjective day and night, and the difference persists in older flies. Immunohistochemistry was performed at least three times for each group. Each timepoint represents a minimum of 60 brains; quantitation was performed blind. *** represents p < 0.0001 and ** represents p < 0.0005, non parametric Mann-Whitney test.
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pbio-0060069-g002: Changes in the Degree of Arborization of the PDF Circuit Are Preserved Under Constant Conditions(A–C) pdf >mCD8-GFP wild-type brains were dissected at CT2 and CT14 during the second day in constant darkness (DD2). CT refers to the time that has passed from the last lights OFF/ON transition. CT2 and CT14 indicate subjective day and night, respectively.(A) Confocal images representative of the subjective day (upper) and subjective night (bottom panels) stained with anti-PDF (red) and anti-GFP (green) antibodies.(B) The number of intersections is consistently lower during subjective night, although the PDF circuit is not particularly shortened.(C) Total axonal crosses are significantly different during subjective day and night, and the difference persists in older flies. Immunohistochemistry was performed at least three times for each group. Each timepoint represents a minimum of 60 brains; quantitation was performed blind. *** represents p < 0.0001 and ** represents p < 0.0005, non parametric Mann-Whitney test.

Mentions: Daily changes in axonal morphology could merely be the direct response to a changing environment, as opposed to be regulated by an endogenous mechanism. To determine whether this structural plasticity was under the control of the endogenous biological clock whole mount adult brains from flies kept under constant darkness (DD) were fixed and dissected at circadian time (CT) 2 and 14 (Figure 2A) during the second day after transfer to constant conditions (DD2). Under these conditions, a significant decrease in the total number of axonal crosses in brains examined during subjective night was found (Figure 2C), when compared to those fixed during subjective day, consistent with a role of the circadian clock controlling axonal plasticity under both 12 h light/dark (LD) and DD conditions.


Circadian remodeling of neuronal circuits involved in rhythmic behavior.

Fernández MP, Berni J, Ceriani MF - PLoS Biol. (2008)

Changes in the Degree of Arborization of the PDF Circuit Are Preserved Under Constant Conditions(A–C) pdf >mCD8-GFP wild-type brains were dissected at CT2 and CT14 during the second day in constant darkness (DD2). CT refers to the time that has passed from the last lights OFF/ON transition. CT2 and CT14 indicate subjective day and night, respectively.(A) Confocal images representative of the subjective day (upper) and subjective night (bottom panels) stained with anti-PDF (red) and anti-GFP (green) antibodies.(B) The number of intersections is consistently lower during subjective night, although the PDF circuit is not particularly shortened.(C) Total axonal crosses are significantly different during subjective day and night, and the difference persists in older flies. Immunohistochemistry was performed at least three times for each group. Each timepoint represents a minimum of 60 brains; quantitation was performed blind. *** represents p < 0.0001 and ** represents p < 0.0005, non parametric Mann-Whitney test.
© Copyright Policy
Related In: Results  -  Collection

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getmorefigures.php?uid=PMC2270325&req=5

pbio-0060069-g002: Changes in the Degree of Arborization of the PDF Circuit Are Preserved Under Constant Conditions(A–C) pdf >mCD8-GFP wild-type brains were dissected at CT2 and CT14 during the second day in constant darkness (DD2). CT refers to the time that has passed from the last lights OFF/ON transition. CT2 and CT14 indicate subjective day and night, respectively.(A) Confocal images representative of the subjective day (upper) and subjective night (bottom panels) stained with anti-PDF (red) and anti-GFP (green) antibodies.(B) The number of intersections is consistently lower during subjective night, although the PDF circuit is not particularly shortened.(C) Total axonal crosses are significantly different during subjective day and night, and the difference persists in older flies. Immunohistochemistry was performed at least three times for each group. Each timepoint represents a minimum of 60 brains; quantitation was performed blind. *** represents p < 0.0001 and ** represents p < 0.0005, non parametric Mann-Whitney test.
Mentions: Daily changes in axonal morphology could merely be the direct response to a changing environment, as opposed to be regulated by an endogenous mechanism. To determine whether this structural plasticity was under the control of the endogenous biological clock whole mount adult brains from flies kept under constant darkness (DD) were fixed and dissected at circadian time (CT) 2 and 14 (Figure 2A) during the second day after transfer to constant conditions (DD2). Under these conditions, a significant decrease in the total number of axonal crosses in brains examined during subjective night was found (Figure 2C), when compared to those fixed during subjective day, consistent with a role of the circadian clock controlling axonal plasticity under both 12 h light/dark (LD) and DD conditions.

Bottom Line: Indeed, such circadian changes in PDF intensity represent the only known mechanism through which the PDF circuit could communicate with its output.Here we describe a novel circadian phenomenon involving extensive remodeling in the axonal terminals of the PDF circuit, which display higher complexity during the day and significantly lower complexity at nighttime, both under daily cycles and constant conditions.In support to its circadian nature, cycling is lost in bona fide clockless mutants.

View Article: PubMed Central - PubMed

Affiliation: Laboratorio de Genética del Comportamiento, Instituto Leloir, Instituto de Investigaciones Bioquímicas-Buenos Aires-Consejo Nacional de Investigaciones Científicas y Técnicas (IIBBA-CONICET), Buenos Aires, Argentina.

ABSTRACT
Clock output pathways are central to convey timing information from the circadian clock to a diversity of physiological systems, ranging from cell-autonomous processes to behavior. While the molecular mechanisms that generate and sustain rhythmicity at the cellular level are well understood, it is unclear how this information is further structured to control specific behavioral outputs. Rhythmic release of pigment dispersing factor (PDF) has been proposed to propagate the time of day information from core pacemaker cells to downstream targets underlying rhythmic locomotor activity. Indeed, such circadian changes in PDF intensity represent the only known mechanism through which the PDF circuit could communicate with its output. Here we describe a novel circadian phenomenon involving extensive remodeling in the axonal terminals of the PDF circuit, which display higher complexity during the day and significantly lower complexity at nighttime, both under daily cycles and constant conditions. In support to its circadian nature, cycling is lost in bona fide clockless mutants. We propose this clock-controlled structural plasticity as a candidate mechanism contributing to the transmission of the information downstream of pacemaker cells.

Show MeSH
Related in: MedlinePlus