I am hiring a postdoc on an original interdisciplinary project: modeling the action potential of a “swimming neuron”, Paramecium (see this short description of the global project). Paramecium is a large unicellular eukaryote organism which swims in fresh water using its cilia. When it hits an obstacle, mechanosensitive channels open, depolarize the membrane and trigger a calcium-based action potential. In turn, the action potential triggers a reversal of the swimming direction, followed by a change of direction. This is called the “avoiding reaction”, and it is the basis of most Paramecium behavior (which can be surprisingly sophisticated). The goal of the global project is to develop an integrative model of Paramecium, that includes: sensory transduction, excitability and motility. In other words, a model of the behaving Paramecium in an environment.
The specific project for this postdoc is to develop a Hodgkin-Huxley type model of the action potential of Paramecium, together with a phenomenological model of electro-motor coupling, that is, the relation between action potential and cilia beating. In this way, we will obtain a physiological model of spontaneous behavior (adding sensory transduction, we will get a model of behavior in an environment).
There is a great deal of literature on Paramecium electrophysiology, mainly from the 1970s. Thus, we already know fairly well what type of ionic channels are present, their properties, and in some cases we also have blockers. We also have plenty of information on electromotor coupling (basically, calcium concentration modulates cilia beating direction and speed). But no (good) quantitative model has been developed. Thus, the project consists in making the appropriate electrophysiological measurements and then develop and fit models.
The funding is for 12 months. This may seem short but the project does not start from scratch. We have already done the following:
- Simple procedures for culture and cleaning (both elementary).
- A new technique to immobilize Paramecium and do electrophysiological recordings in a simple way (much simpler than in old studies). Thus, these recordings are not technically difficult any more. Note that this is not patch clamp but sharp electrode recordings, much simpler.
- Our own Python tools for recordings. These allow not only to do arbitrary protocols in a simple way, but also to test recording scripts on models.
- Tools for model fitting.
- Performed many electrophysiological recordings and identified conditions for good recordings.
- Preliminary video recordings of cilia beating using silica beads (which allow calculating direction and speed of movement using particle image velocimetry).
- Preliminary tests of fluorescent marker injection (which should allow calcium imaging).
- Tested a couple of channel blockers.
Thus, the project is already well advanced and we are looking for someone motivated to continue the experiments, and work on modeling with us. If you are mainly interested in the experimental side and not so much in the modeling side, this is fine too.
The project will take place in the Vision Institute in Paris, in collaboration with Alexis Prevost and Laetitia Pontani from Laboratoire Jean Perrin.
If you are interested, please contact me and send me a CV. Do not hesitate if you have any questions or want to discuss the project further, or practical aspects.