Investigating the molecular mechanisms that underlie tiling in
Drosophila R7 photoreceptorsJennifer Salamé
George Fox University
Topographical maps: a major principle of organization in the nervous system
cell body
synapse
These synapses do not overlap (i.e. are "tiled").
Human retina is an example of a topographical map
Fly R7 photoreceptors: a great model to study tiling
Neuron circuit development occurs through two steps: axon pathfinding and synapse formation
Neuron circuit development occurs through two steps: axon pathfinding and synapse formation
Synapse Formation
1. filopodia search 2. cell adhesion stabilizes
3. pre-synaptic componentsaccumulate
4. post-synaptic assembly
R7 axons require an Activin signal to tile
Wild-type R7s imp3 mutant R7s
Test the hypothesis that excessive synapse formation causes the tiling defect
Test the hypothesis that excessive synapse formation causes the tiling defect
Excessive synapse formation
Axon pathfinding error
Necessary
Approach 1: test whether synapse formation is necessaryfor the tiling defect
Necessary
Not necessary
Approach 1: test whether synapse formation is necessaryfor the tiling defect
Create syd-1, imp3 R7s
Wild type
imp3 mutant:tiling defect
imp3, syd-1double mutant:?????
syd-1 mutant:cannot form synapses
imp3
syd-1
Test for non-complementation
Create a syd-1, imp3 double mutantchromosome
syd-1
Bal
xBal
imp3 Bal
Bal
x
imp3 syd-1
Bal
syd-1, imp3 has a tiling defect
Approach 2: test whether excessive synapse formation is sufficient to cause a tiling defect
Approach 2: test whether excessive synapse formation is sufficient to cause a tiling defect
yes sufficient
not sufficient
C. elegans rsy-1 mutant neurons form excessive synapses
Create drsy-1 mutant R7s in Drosophila
FRT82 drsy-1(Del)
Bal
x
xdrsy-1(Del)
FRT82 Bal
Bal
FRT82 drsy-1(Del)
Bal
Test with PCR and eye color
FRT82 Positive Control Candidates
Bal
drsy-1 mutants do not have a tiling defect
Effect on synapse formation of drsy-1 mutation is inconclusive
Conclusions• Synapse formation is not necessary for a tiling defect• Excessive synapse formation may not be sufficient to
cause a tiling defect• Disrupting Activin pathway seems to affect axon
pathfinding
Axon pathfinding error
Future Research Directions
• Quantify synapses in drsy-1 mutants• Quantify synapses in tiling defect mutants• Identify genes regulated by Activin pathway in
R7s
Acknowledgments
• UO Institute of Molecular Biology
• Dr. Tory Herman• Jennifer Jeffress• Erik Lyons• Jon Kniss• Scott Holbrook
•U
niversity of Oregon SPU
R Program
•D
r. Peter O’D
ay
•Chelsie Fish
•O
ther SPUR Interns!
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