Identification des neurones situés en aval de l'horloge cérébrale chez D. melanogaster

par Rossana Serpe

Projet de thèse en Aspects moléculaires et cellulaires de la biologie

Sous la direction de François Rouyer.

Thèses en préparation à Paris Saclay en cotutelle avec l'University of Leicester , dans le cadre de École doctorale Signalisations et réseaux intégratifs en biologie (Kremlin-Bicêtre, Val-de-Marne) , en partenariat avec Neuro-PSI - Institut des Neurosciences Paris Saclay (laboratoire) et de Université Paris-Sud (établissement de préparation de la thèse) depuis le 15-11-2013 .


  • Résumé

    Sleep is a highly conserved mechanism in the animal kingdom, whose role remains poorly understood. In the last years, Drosophila melanogaster has been used as a model to decipher the molecular mechanisms of sleep. Indeed, rest in fruit fly features the common characteristics of mammalian sleep and it is known to be regulated by both circadian and homeostatic systems. This project is aiming to characterize the neuronal targets and the exact role of D. melanogaster circadian clock in sleep behavior. We first focus our attention on the Mushroom bodies (MBs), a prominent structure in arthropod brain which is reported to be involved in the control of sleep homeostasis, in addition to their function in memory and learning processes. Preliminary results in our laboratory indicate that exciting the clock neurons results in a strong Ca2+ rise in the MBs, which is compatible with a functional connection between the two systems. Coherently, we observed anatomical proximity between the clock neurons and the calyx of MBs, via GRASP (GFP Reconstitution Across Synaptic Partners) assay. Therefore, in order to assess their contribution to sleep behavior, we manipulated neuronal activity in circadian clock neurons and the MBs by using the UAS-GAL4 system. Interestingly, hyper-excitation of all brain clock neurons (about 150 cells in fly brain) severely affects sleep by making flies hyper-somnolent. Both day- and night-time sleep amount increase significantly, compared to controls. This suggests the existence of a sleep-promoting circuit within the clock neuron network. Thus, we attempted to understand which subset(s) of clock neurons is responsible for this behavior. Among clock cells, our results particularly revealed a strong and opposite phenotype when manipulations occur in a particular cluster of dorsal clock neurons (DN1p). Hyper-excitation of those neurons results in hypo-somnolent flies across 24 hours, compared to control. Conversely, silencing those cells leads to hyper-sleepy flies. The capability of DNs to influence sleep behavior appears to be light- independent, since the same results were observed in constant darkness conditions. At the moment, the characteristics of the sleep-relevant circuit involving DN1s neurons is being assessed.

  • Titre traduit

    Identification of the neurons downstream the Circadian Clock in D. melanogaster


  • Résumé

    Sleep is a highly conserved mechanism in the animal kingdom, whose role remains poorly understood. In the last years, Drosophila melanogaster has been used as a model to decipher the molecular mechanisms of sleep. Indeed, rest in fruit fly features the common characteristics of mammalian sleep and it is known to be regulated by both circadian and homeostatic systems. This project is aiming to characterize the neuronal targets and the exact role of D. melanogaster circadian clock in sleep behavior. We first focus our attention on the Mushroom bodies (MBs), a prominent structure in arthropod brain which is reported to be involved in the control of sleep homeostasis, in addition to their function in memory and learning processes. Preliminary results in our laboratory indicate that exciting the clock neurons results in a strong Ca2+ rise in the MBs, which is compatible with a functional connection between the two systems. Coherently, we observed anatomical proximity between the clock neurons and the calyx of MBs, via GRASP (GFP Reconstitution Across Synaptic Partners) assay. Therefore, in order to assess their contribution to sleep behavior, we manipulated neuronal activity in circadian clock neurons and the MBs by using the UAS-GAL4 system. Interestingly, hyper-excitation of all brain clock neurons (about 150 cells in fly brain) severely affects sleep by making flies hyper-somnolent. Both day- and night-time sleep amount increase significantly, compared to controls. This suggests the existence of a sleep-promoting circuit within the clock neuron network. Thus, we attempted to understand which subset(s) of clock neurons is responsible for this behavior. Among clock cells, our results particularly revealed a strong and opposite phenotype when manipulations occur in a particular cluster of dorsal clock neurons (DN1p). Hyper-excitation of those neurons results in hypo-somnolent flies across 24 hours, compared to control. Conversely, silencing those cells leads to hyper-sleepy flies. The capability of DNs to influence sleep behavior appears to be light- independent, since the same results were observed in constant darkness conditions. At the moment, the characteristics of the sleep-relevant circuit involving DN1s neurons is being assessed.