Rein et al., 2002 Current Biology The mushroom bodies (MBs) in the adult Drosophila brain

from Martin Heisenberg

modified from Armstong et al., Learning & Memory 1998

midline  horizontal branch Srausfeld et al., MRT  m A wild-type  neuron  vertical branch 10  m  lobe  lobe

Developmental Genetics of mushroom bodies (MB) MB are involved in olfactory learning. MB are relatively well described structure in the adult central brain. 4 neuroblasts in each hemisphere form one MB. Flies without MB are viable and fertile. Good markers of MB (Gal4 lines, antibodies) Clonal analysis (positive labelling : Gal 80)

Development of the Drosophila mushroom bodies: sequential generation of three distinct types of neurons from a neuroblast Lee et al., Development 1999 MARCM Mosaic analysis with a repressible cell marker for studies of gene function in neuronal morphogenesis Lee and Luo Neuron 1999

Noveen et al., Development 2000 Neuroblasts in the head and trunk

Noveen et al., Development 2000

Development of the MBs. (A) Embryonic MB primordium (lateral view). (B) Larval MB. (C) Late pupal and adult MBs. The MB primordia in the embryonic brain (frontal view) KCs, Kenyon cells (MB cells)

Brand & Perrimon, Development 1993 The GAL4/UAS system

Gal4 white + Visualise MBs UAS mCD8-GFP

 neurons (cell bodies + dendrites + axons) of the MBs in one particular GAL4 line

   ’  ’    axons (and neurons) of the MBs some midline axons are also labeled in another GAL4 line

 AXONS  AXONS  core AXONS ALL AXONS  '/  /'/'  MUSHROOM BODY SPECIFIC GAL4 LINES   ’’ ’’ GAL4-OK107 GAL4-201Y GAL4-c739  core  core    

Parental cell Mitotic recombination After DNA replication Two distinct mosaic progeny x x x FRT Mutant Centro mere Repressor x protein x Repressible marker x x x x x Marking mutant clones in a mosaic organism by the MARCM technique NB: one can make clones in wild-type background also!: visualisation clones

A single photoreceptor can be traced from cell body in eye disc (arrow in left panel) to the end of the extending axon in the optic lobe (arrow in right panel) e: eye disc b: brain

An adult MB neuroblast clone with five axonal bundles (3 medial and 2 dorsal). This clone was generated by inducing mitotic recombination in newly hatched larva

Three models of the projection of the MB neuroblast progeny (A) One neuroblast progeny project to a specific region, e.g. the  lobe( black cells) (B) A MB neuroblast clone contributes to the entire cellular repertoire of the MB (C) The progeny of the MB neuroblast are not confined to the MB. Some neurons project to other region of the brain.

Summary of the structural organisation of the MB (A)Each MB neuroblast generates a clonal unit that contains all the types of cells (B) The intact MB is a fourthfold structure of these clonal units

Nb G N N FLP A multi-cellular Nb clone Two cell clones FLP Two mutually exclusive types of marked clones. Either all postmitotic neurons generated subsequently in the same lineage will be labeled (upper), or only two neurons derived from the GMC will be labeled in the whole lineage (lower).

In addition, mitotic recombination in a dividing GMC can generate a single cell clone Single-cell clone FLP

A two cell clone

Three types of neurons: ,  ’  ’  and  The question is: how are they generated from a single neuroblast?

Lobe compositions of MB neuroblast clones generated at different stages

Sequential generation of three distinct types of MB neurons with characteristic axonal projections

Morphological characterization of the three types of MB neurons

Different behaviors of  and  ’  ’ neurons during metamorphosis Clones were generated at NHL for A and D, at early L3 for B and E, at late L3 for C and F. Morphologies were examined just before PF (A-C) or 18 h APF (D-F)

Axon reorganization of  neurons during metamorphosis. Clones were generated in NHL and examined 12, 18 and 24 hours APF

Summary of the mushroom body development

1 neuroblast 3 types of neurons -  -  ’  ’ -  2 x 4 neuroblats 2 x 2000 neurons2 x 1 MB brain = central brain + optic lobes = neurons central brain = central complex + MB central complex = neurons 2 X MB = 2 X neurons = 4000 neurons