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A peripheral pacemaker drives the circadian rhythm of synaptic boutons in Drosophila independently of synaptic activity
Stockholm University, Faculty of Science, Department of Zoology.
Stockholm University, Faculty of Science, Department of Zoology.
Responsible organisation
2008 (English)In: Cell and Tissue Research, ISSN 0302-766X, E-ISSN 1432-0878, Vol. 334, no 1, 103-109 p.Article in journal (Refereed) Published
Abstract [en]

Circadian rhythms in the morphology of neurons have been demonstrated in the fly Drosophila melanogaster. One such rhythm is characterized by changes in the size of synaptic boutons of an identified flight motor neuron, with larger boutons during the day compared with those at night. A more detailed temporal resolution of this rhythm shows here that boutons grow at a time of increased locomotor activity during the morning but become gradually smaller during the day and second period of increased locomotor activity in the evening. We have experimentally manipulated the synaptic activity of the fly during short periods of the day to investigate whether changes in bouton size might be a consequence of the different levels of synaptic activity associated with the locomotion rhythm of the fly. In the late night and early morning, when the flies normally have an intense period of locomotion, the boutons grow independently of whether the flies are active or completely paralyzed. Bouton size is not affected by sleep-deprivation during the early night. The cycle in bouton size persists for 2 days even in decapitated flies, which do not move, reinforcing the notion that it is largely independent of synaptic activity, and showing that a pacemaker other than the main biological clock can drive it.

Place, publisher, year, edition, pages
2008. Vol. 334, no 1, 103-109 p.
Keyword [en]
neuronal plasticity, circadian rhythms, synaptic activity, neuromuscular junction, Drosophila melanogaster (Insecta)
National Category
Cell Biology
URN: urn:nbn:se:su:diva-25554DOI: 10.1007/s00441-008-0670-0ISI: 000259141500011OAI: diva2:199964
Available from: 2008-10-24 Created: 2008-10-22 Last updated: 2012-08-17Bibliographically approved
In thesis
1. Circadian plasticity in the neuromuscular junction of Drosophila melanogaster
Open this publication in new window or tab >>Circadian plasticity in the neuromuscular junction of Drosophila melanogaster
2008 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

A biological clock exists in many organisms and controls rhythmic behaviors such as the activity pattern of locomotion. At the cellular level, it has been shown that circadian rhythms in the morphology of neurons exist in the fruit fly Drosophila melanogaster. The studies presented in this thesis contribute to an increased understanding of this novel aspect of neuronal plasticity and its regulation.

We demonstrated the existence of a circadian rhythm in the morphology of neuromuscular terminals that innervate two identified flight muscles. Synaptic boutons are larger during the day than during the night under light:dark conditions (LD) as well as in constant darkness (DD). However, this rhythm is abolished in normal flies older than 30 days and in arrhythmic ones with null mutations in the clock genes period (per) or timeless (tim). Furthermore, these clock mutants show a completely different branching pattern indicating that the proteins PER and TIM not only function in well-described mechanisms in the circadian clock but also on neuronal morphology.

We found that boutons grow during a period of six hours around light´s on and decrease again during six hours around light´s off. In order to test a possible relationship between synaptic activity and bouton rhythm, we manipulated synaptic activity of the fly during critical periods of morning and evening times when the flies show an increased activity pattern. We also decapitated the animals, which results in flies that do not move. Bouton size is largely independent of synaptic activity and seems to be driven by a peripheral pacemaker.

We found the expression of tim in glial cells and focused on their possible role as a peripheral pacemaker. Rescue and knock down experiments showed slight effects on the rhythm of bouton size indicating that the expression of tim in glial cells could be part of the mechanism governing the rhythmic change of motor terminals.

Furthermore, we investigated the question of whether bouton rhythm also involves changes in synapses. After paralyzing flies for a twelve-hour interval, we investigated the number of boutons and synapses as well as the distribution of synapses per bouton. Synapse numbers did not change but the other parameters were affected by paralysis, which might suggest that synaptic activity and/or endocytosis are involved in the formation of boutons and synapses. Furthermore, we noticed that the majority of boutons either contain none or only a small number of synapses.

Place, publisher, year, edition, pages
Stockholm: Zoologiska institutionen, 2008. 130 p.
National Category
Research subject
Functional Zoomorphology
urn:nbn:se:su:diva-8282 (URN)978-91-7155-765-0 (ISBN)
Public defence
2008-11-14, Nordenskiöldsalen, Geovetenskapens hus, Svante Arrhenius väg 8 C, Stockholm, 10:00
Available from: 2008-10-24 Created: 2008-10-22Bibliographically approved

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Cantera, Rafael
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