lecture 9: appendage development
DESCRIPTION
LECTURE 9: Appendage development. Head. Tail. T1. A8. A7. T2. A6. T3. A5. A1. A2. A4. A3. Metamorphosis. Quiltwork Assembly of a Fly. L. 1. M. L. 2. L. 3. 3rd Larval Instar. L. 4. L. 5. Early Pupa. M. s. C. o. L. 1. L. 2. Mid-Pupa->Adult. L. 3. L. 6. L. - PowerPoint PPT PresentationTRANSCRIPT
Head Tail
T1 T2 T3 A1 A2 A4 A5 A6 A7A3
A8
Metamorphosis
Quiltwork Assembly of a Fly
Outline of Vein DevelopmentM L1
L2
L3
L4
L5
3rd Larval Instar
Early Pupa
ML1 L2
L3
L4
L5
L6
sCo
Mid-Pupa->Adult
L1
L2
L3
L4
L5
M
Fly Wing
The Players: A/P Axis
Engrailed (En) = Transcription factor expressed in posterior cells.
Hedgehog (Hh) = Signal whose expression is activated by En.
Dpp = Signal whose expression is activated by Hh signaling.
Sal = Transcription factor activated by Dpp signaling.
L2
L3
L4
L5
sal
Determining the Positions of Veins
hh
L2
dpp
dppAP En
En -> Hh -> Diffuses -> dpp in A/P Organizer
Dpp
Dpp -> Diffuses -> sal -> L2 vein
AP
L5
sal
sal
L3
L4
L3
L4
OrganizerA/P
dpp
L2
L3
L4
L5
hh- mutantL2
L3L4
L5
WTL2
L3
L4
L5
Hh Determines Positions of L3 and L4 Veins
hh dpp
dppAP En
L3
L4
En -> Hh -> Diffuses ->dpp in A/P Organizer
hh
dpp
Mutant with reduced hh function
AP En
L3L4
dpp
dpp- mutant
L2
L3
L4
L5
L2
DppAP
L5
salL3
L4sal
Mutant with reduced dpp function
WTL2
L3
L4
L5
L2
DppAP
L5
sal
sal
L3
L4
Dpp -> Diffuses -> sal -> L2 vein
Dpp Determines Positions of L2 and L5 veins
Veins Form At Boundaries Along the A/P Axis
L2L3 L4
salsal Dpp
A P
Dpp -> Diffuses -> sal -> L2 vein
L5
+
En
hh
dpp
+
dpp
A P
OrganizerA/P
En -> Hh -> Diffuses ->dpp in A/P Organizer
salsal Dpp
A P
Dpp defines anteriorborder of sal domain
+
En
hh
dpp
+
dpp
A P
En-5 defines position ofdpp stripe in wing disc
Hb
eve-3
Hb defines anteriorborder of eve-3 stripe
KniWingDisc
en-5
Eve-3 defines anteriorborder of en-5 stripe
Maternal Bicoid gradientdefines posterior limit of hb
Ant. Post.
Lowest level of Bcd needed to activate hb
Sal defines positionof L2 vein stripe
salDpp
++
Sal
L2
X
L2 A P
The Developmental Path From Bcd to the L2 Vein
The Players: D/V and P/D Axes
Apterous (Ap) = Transcription factor expressed in dorsal cells.
Notch (N) = Signaling system that induces margin at D/V border.
Distalless = Transcription factor activated at A/P & D/V intersection.
D ->V Signal
V -> D Signal
ap Expressing Cells
ap Non-expressing Cells
DV
Activation ofNotch AlongFuture Margin
Ap -> Notch -> Wing Margin = D/V Organizer
D/V Signaling Is Required for Wing Margin Formation and Wing Outgrowth
D/V Organizer -> Margin Formationand Wing Growth
ap- cells
Wing imaginal disc in larva Adult wing (viewed end on) Adult wing with ap- patch
Loss of ap in Dorsal Cells-> Margin Formation
Intersection of the D/V and A/P Organizers Induces Leg Outgrowth
D/V Organizer
A P
A/P Organizer
DistallessExpression
Distalless
Distal
Proximal
Normal Leg distallessMutant Leg
DV
Fig. 4.4
Hox2
ZPA Morphogen = Hh
FGF
Hox Gene B
ZPA induced byHox gene B + FGF
FGF and a second Hox gene activate Hh expression in ZPA
wing bud leg bud
FGF
Hox Gene A Hox Gene CHox Gene B
GastrulatingChicken Embryo
FGF
Hox genes activate autoregulatory FGF expression in limb buds
Initiation of Wing Development in Chickens
A PGrafted ZPA
[Hh]
distanceAnt. Post.
4
32 2
3
4
43
2
43
2
ZPA -> HhBMP-4
A P
[Hh]
distanceAnt. Post.
4
32 43
2Anterior
Posterior
43
22
A PFraction ofZPA Grafted
4
[Hh]
distanceAnt. Post.
32 2
Hh diffuses from ZPA and specifies digits 2-4 at different concentrations
Wing bud with second grafted ZPA -> complete mirror duplicated digits
Wing bud grafted with a fraction of ZPA -> partial mirror duplication
Hh is the ZPA Factor
Normal Wing
ZPA Transplant
ZPA Graft
0 mg/ml
4 mg/ml
8 mg/ml
16 mg/ml
Hh Soaked BeadsHh Expression
ZPA
A P/
Hh
Dpp
Hh Hh
BMP-4
A P
Fly wing disc
A/PAxis
Vertebrate Limb Bud
D/VAxis
P/DAxis
D
V
A P
NotchSignaling A P
DV
NotchSignaling
D
V
A P
Distalless
A P
DV
Distalless