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Published on: January 12, 2020
Robo-3--mediated repulsive interactions guide R8 axons during Drosophila visual system development
Kartik S Pappu1, Marta Morey, Aljoscha Nern
1Department of Biological Chemistry, The Howard Hughes Medical Institute, The David Geffen School of Medicine, University of California, Los Angeles, CA 90095, USA.
Summary
Roundabout-3 (Robo3) guides developing R8 axons in the Drosophila visual system. Transient Robo3 expression ensures correct pathway selection, preventing aberrant connections and enabling proper neural circuit formation.
Area of Science:
- Neuroscience
- Developmental Biology
- Genetics
Background:
- Neuronal connections form through precise axon guidance.
- In Drosophila, photoreceptor (R) cells project axons to the brain, with R8 cells being the first to extend.
- The specific guidance mechanisms for posterior R8 axons remain unclear.
Purpose of the Study:
- To identify genes involved in R8 axon guidance.
- To elucidate the role of Roundabout-3 (Robo3) in R8 axon pathway selection.
- To understand how transient gene expression regulates neural circuit formation.
Main Methods:
- Microarray analysis to identify genes in R8 neurons.
- Analysis of robo3 mutants in Drosophila.
- Genetic rescue experiments using Robo1 and Robo2.
Main Results:
- Roundabout-3 (Robo3) is transiently and specifically expressed in R8 growth cones.
- robo3 mutant R8 axons misroute and fasciculate incorrectly.
- Robo1 or Robo2 can rescue the robo3 mutant phenotype.
- Persistent Robo3 expression disrupts layer-specific targeting.
Conclusions:
- Transient, cell-specific Robo3 expression is crucial for R8 axon pathway choice.
- Robo3 regulates the formation of neural circuits in the Drosophila visual system.
- The guidance function does not require Robo3-unique paralog activity.
