Retinal axon pathfinding: cellular events controlled by subcellular compartment-restricted second messengers

The precise connectivity of the visual system is crucial for the sound processing of visual information by the brain. Reconstructing a precise network between the retina and the brain is thus a requirement for regenerative strategies aiming at restoring vision in pathologies caused by the loss of retinal ganglion cells, including glaucoma. Understanding the mechanisms underlying retinal axon connectivity in the normal developing brain might serve as a starting point for such therapeutic strategies.
While they are extending towards their targets in the brain, developing retinal axons integrate attractive and repulsive cues via signals of cellular second messenger including Ca2+, cAMP and cGMP. However, these signaling molecules are also involved in a myriad of other cellular processes. We have recently shown that subcellular compartmentation of second messengers is crucial for the regulation of axonal behavior by guidance molecules (Averaimo et al, 2016). The compartments involved differ according to the guidance cue and include lipid rafts, the non-raft plasma membrane and cell adhesion-related subcellular domains. Each compartment control a specific axonal behaviors. The proposed project aims at identifying the downstream cellular events controlled by each local second messenger code with a focus on membrane trafficking.

The trainee will use a set of genetically-encoded tools recently developed by our team (Ros et al 2019; Ros et al 2020) and enabling subcellular manipulation of second messenger signals in living axons. Advanced imaging technologies will be used for this project, including live imaging of vesicle trafficking and second messenger concentration changes in developing axons (TIRF, FLIM/FRET microscopy) as well as optogenetics to control the concentration of signaling molecules with subcellular resolution.
These approaches will be complemented by the use of retinal organoids to evaluate whether the mechanisms identified in the mouse visual system are transferable to human retinal ganglion cells. These latter investigations will be conducted in Arthur Bergen’s lab (Amsterdam UMC).

What can you expect?
The successful candidate will be gain expertise in developmental neuroscience, and in cell biology of the neuron. She/He will be trained for live imaging, cutting-edge microscopy, optogenetics, cell culture and retinal organoids. In addition, she/he will benefit from the training activities scheduled by the EGRET-AAA program (workshops, meetings, …).

This project is a joint-doctorate between the Vision Institute (Sorbonne University, Paris;; and the Amsterdam UMC. The trainee will be hosted by the Vision Institute where she/he will join the Nicol lab, under supervision of prof. Xavier Nicol. Here, the trainee will have access to cutting-edge microscopy setups to perform functional imaging with subcellular resolution and optogenetic stimulation. Furthermore, she/he will conduct a secondment project in the Bergen lab (Amsterdam UMC), under supervision of prof. Arthur Bergen, where the equipment and expertise in generating retinal organoids are available.

Who are we looking for?
We are seeking a talented and energetic student with strong interpersonal and communication skills. The successful candidate must hold a Neuroscience or Cell Biology Master (other Master programs will be considered as well) by the end of the 2022-2023 academic year. Fluency in English is mandatory but ability to speak French is not required.


  • A plasma membrane microdomain compartmentalizes ephrin-generated cAMP signals to prune developing retinal axon arbors. Averaimo S et al. Nat Commun. 2016.
  • SponGee: A Genetic Tool for Subcellular and Cell-Specific cGMP Manipulation. Ros O et al. Cell Rep. 2019
  • SpiCee: A Genetic Tool for Subcellular and Cell-Specific Calcium Manipulation. Ros O et al. Cell Rep. 2020.
  • An alternative approach to produce versatile retinal organoids with accelerated ganglion cell development. Wagstaff PE et al. Sci Rep. 2021.