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Aucun titre de diapositive

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Title: Aucun titre de diapositive


1
The mushroom bodies (MBs) in the adult Drosophila
brain
Rein et al., 2002 Current Biology
2
from Martin Heisenberg
3
modified from Armstong et al., Learning
Memory 1998
4
A wild-type ?? neuron
? lobe
? vertical branch
10mm
10mm
? lobe
? horizontal branch
midline
Srausfeld et al., MRT 2003
10mm
10mm
5
Developmental Geneticsof  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)

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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
8
Neuroblasts in the head and trunk
Noveen et al., Development 2000
9
Noveen et al., Development 2000
10
The MB primordia in the embryonic brain (frontal
view) KCs, Kenyon cells (MB cells)
Development of the MBs. (A) Embryonic MB
primordium (lateral view). (B) Larval MB. (C)
Late pupal and adult MBs.
11
The GAL4/UAS system
Brand Perrimon, Development 1993
12
G
a
l
4
mCD8-GFP
UAS
Visualise MBs
13
??? neurons (cell bodies dendrites axons) of
the MBs in one particular GAL4 line
14
???????????? axons (and neurons) of the MBs
some midline axons are also labeled in another
GAL4 line
15
MUSHROOM BODY SPECIFIC GAL4 LINES
GAL4-OK107
GAL4-201Y
GAL4-c739
?
  • AXONS
  • ??core AXONS

ALL AXONS
?? AXONS
?
?
a
acore
b
b
b
bcore
g
g
16
Marking mutant clones in a mosaic organism by the
MARCM technique
Mitotic recombination After DNA replication
Two distinct mosaic progeny
Parental cell
x
Repressor protein
Repressible marker
x
x
x
x
x
x
x
Mutant
FRT
x
Centro mere
Repressor
NB one can make clones in wild-type background
also! visualisation clones
17
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
18
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
19
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.
20
  • Summary of the structural organisation of the MB
  • 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

21
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).
N
N
G
FLP
Nb
A multi-cellular Nb clone
FLP
Two cell clones
22
In addition, mitotic recombination in a dividing
GMC can generate a single cell clone
FLP
Single-cell clone
23
A two cell clone

24
Three types of neurons ? , ???? and ??? The
question is how are they generated from a single
neuroblast?
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Lobe compositions of MB neuroblast clones
generated at different stages
27
Sequential generation of three distinct types of
MB neurons with characteristic axonal projections
28
Morphological characterization of the three types
of MB neurons
29
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)
30
Axon reorganization of ? neurons during
metamorphosis. Clones were generated in NHL and
examined 12, 18 and 24 hours APF
31
Summary of the mushroom body development
32
brain central brain optic lobes 200.000
neurons
central brain central complex MB
central complex 20.000 neurons
2 X MB 2 X 2.000 neurons 4000 neurons
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