Jean-Maurice Dura Institut de Génétique Humaine jean-maurice.dura@igh.cnrs.fr M1 Neurosciences Neurobiologie du Développement HMBS116 année 2017/2018 Jeudi 27 Septembre 9h45 SC 25.05 Jeudi 18 Octobre 9h45 SC 20.02 Jeudi 25 Octobre 9h45 SC 20.02 Jeudi 8 Novembre 9h45 SC 25.01 Jeudi 15 Novembre 8h SC 25.01 Jeudi 22 Novembre 8h SC 16.01 Neuronal remodeling: Luo and Leary Annu Rev Neurosci 2005 Schuldiner and Yaron Cell Mol Life Sci 2015 Boulanger and Dura Biochim Biopys Acta 2015 Yaniv and Schuldiner WIREs Dev Biol 2016

Awasaki and Lee after Boulanger at al., Nature Neuroscience 2011

myoglanin (myo) encodes a Drosophila TGF-b ligand early L3 middle L3 wandering L3 cortex layer wand. L3 inner brain region Expression of myo transcripts in the larval brain Signals of myo transcripts (arrows) colocalized with the cell bodies of cortex glia and astrocyte-like glia Awasaki Nat Neur 2011

Effect of glial silencing of myo on MB remodeling Awasaki Nat Neur 2011

Expression of EcR-B1 in control and repo>myo-miRNA wandering L3 Awasaki Nat Neur 2011

Glial TGF-b governs neural remodeling Model of induction of EcR-B1 in the remodeling neurons by glial Myoglanin Awasaki Nat Neur 2011

A schematic representation of axon pruning in MB g neurons Yu and Schuldiner COiN 2014

APF Disappearance of clustered varicosities in the axon bundle of g neurons The surface of the lobe is smooth at L3 (A), but it appears eroded at 6 hr APF (B) cb: cell bodies; ca: calyx (dendrites); p: peduncle; m: medial lobe and axon branch; d: dorsal lobe and axon branch Awasaki and Ito Current Biology 2004

Single optical section are shown Disappearance of clustered varicosities in the axon bundle of g neurons Single optical section are shown Axon branches of g neurons are labeled uniformly at L3 (A), whereas holes of unlabeled regions appear at 6 hr APF (B) (arrowheads). Stars correspond to unlabeled axon bundle of a'b' neurons. Genotype: GAL4-201Y / UAS-cGFP Awasaki and Ito Current Biology 2004

Glia cells infiltrating into the mass of MB axons Awasaki and Ito Current Biology 2004

shibire gene is the Drosophila homolog of dynamin, which is involved in cellular membrane functions, including endocytosis, phagocytosis and membrane growth. Shits protein acts as a dominant-negative at a restrictive temperature. White Current Biology 2001

Effect of targeted disruption of glial function on glial infiltration and on axon pruning Morphology of glial cells labeled with GFP (green) was abnormal (arrows) and their processes infiltrate into the lobes neither at 6 (A) nor at 18 hr APF (B). Awasaki and Ito Current Biology 2004

Expression of Drpr (a glial cell corpse engulfment membrane receptor) in the glial processes infiltrating into the MB lobe Awasaki and Ito Current Biology 2004

Effect of targeted expression of EcR-DN in g neurons on glial infiltration Awasaki and Ito Current Biology 2004

Schematic model of the elimination of varicosities by infiltrated glia (A and B): diagram of the multiple axon branches of g neurons in L3 (A) and early pupa (B) at around 6h APF. (C-G): steps of infiltration and engulfing action of glial processes. Awasaki and Ito Current Biology 2004

Model for the role of glia in axon pruning Schematic model of the role of glia on developmentally programmed axon pruning Awasaki Neuron 2006

Model for the role of glia in axon pruning Boulanger BBA 2015

Hierarchy of the olfactory nervous system in insects and mammals Davis Neuron 2004

Is MB larval pruning is necessary for adult memory? Short Term Memory (STM): forms right after learning, based on transient events, lasting from a few minutes to a few hours. Long Term Memory (LTM): forms later with de novo protein synthesis, lasting from several hours to days.

Awasaki and Lee after Boulanger at al., Nature Neuroscience 2011

Ectopic expression of Hr39 into larval g blocks pruning GAL4-201Y,UAS-GFP/ + GAL4-201Y,UAS-GFP/ UAS-Hr39 larval g g adult g

Ectopic expression of Hr39 blocks  neuronal remodelling wt mutant a b a a’ a’ b b’ b’ g (adult) g (larval) Blocking  pruning effect on short term memory and long term memory?

Courtship behavior

Memory after courtship conditioning paradigm Short-term paradigm: 30’ with a mated female Retraining test (with a mated female) - last few hours (STM) Long-term paradigm: 5 hours with a mated female Retraining test (with a mated female) - last for days (LTM) CI - courtship index - % of time spent in courtship during a 300-s period. If CIexp = 0, then PI = 1 (complete memory) If CIexp = CIcont, then PI = 0 (no memory) CIcont - CIexp CIcont x 100% = ( 1 - CIexp ) PI - performance index x 100% PI = McBride et al., Neuron 1999; Kamyshev et al., Learn. Mem. 1999

Blocking neuronal remodeling of  neurons impairs STM but not LTM (ab) a’ b’ a b (larval) a’ a b b’ g a’ a b b’ g Blocking neuronal remodeling of  neurons impairs STM but not LTM Redt-Clouet et al., Eur J Neuroscience 2012

• MB larval pruning is necessary for adult STM not for LTM. Conclusions • MB larval pruning is necessary for adult STM not for LTM. • STM and LTM may be two parallel and independent memory systems. It is possible to get LTM without STM. sequential model : LRN ---------> STM ---------> LTM ---------> STM (g) ---------> LTM (ab) parallel model : LRN