CELL BIOLOGY OF THE NEURON Polarity ... - Tavernarakis Lab

Cell Biology of the Neuron: Polarity, Plasticity and Regeneration, Crete 2011
RNA-Binding Protein Hermes Regulates Axon
Guidance and Branching in the Developing Visual
System
Hanna Hornberg, Daniel Maurus, Francis Wollerton-van Horck, Maarten Zwart,
William Harris, Christine Holt
Department of Physiology, Development and Neuroscience, University of
Cambridge, Downing St, CB2 3DY, Cambridge, UK
In the developing visual system, retinal ganglion cells (RGCs) project
topographically along the anterior-posterior (A-P) and dorsal-ventral (D-V) axes
to their target area in the optic tectum, where they arborize and form synaptic
connections. The formation of this circuit is tightly regulated both by extracellular
guidance cues in the environment, and by intracellular processes in the RGC
axons such as RNA localization and translation. Here, we reveal the functional
role of the RNA-binding protein Hermes (also known as RBPMS) in retinal axon
navigation in vivo. Hermes is expressed exclusively in RGCs in the CNS and is
present in their growing axons and growth cones where it localises in granules.
Antisense morpholino knockdown of Hermes in embryonic zebrafish caused
axons along the D-V axis to make positional errors in the optic tract, and to enter
the tectum through an indirect route . Axons also failed to map correctly along the
A-P axis. Furthermore, Hermes knockdown in both zebrafish and Xenopus
significantly impaired retinal axon branching in the tectum. Overexpression of a
dominant negative Hermes protein defective in a domain required for granular
localisation in Xenopus also impaired branching, suggesting that proper
localization of Hermes is critical to its function. These results show that Hermes
contributes to both mapping and arborisation and suggests an important role in
several aspects of circuit formation.
Presented by: Hornberg, Hanna
Poster No 050
Green Session
132