Baptiste Marthy Will défend his Ph.D. Thesis entitled “Axonal trafficking quantified by high-resolution wavefront microscopy” on Monday 23rd of November at 02:15 p.m. at institut Fresnel, in the Pierre Cotton room.
The talk will be in French, but the slides will be in English. For those who can not attend in person, a Zoom link will be available a few days before the defense.
Composition of Jury:
– Christophe LETERRIER , Jury President
– Pierre MARQUET, Reviewer
– François TREUSSART, Reviewer
– Lydia DANGLOT, Examiner
– Pierre BON, Examiner
– Guillaume BAFFOU, Thesis Supervisor
– Maxime CAZORLA, Thesis Co-Supervisor
Abstract: Neurons rely on specialized vesicles to carry material from their cell body to the tip of their axon. These vesicles are small (between 50 and 1000 nanometer diameter) and move fast (up to a few micrometers per second). A multitude of vesicle populations exists, each associated with a given function. A population is usually imaged by fluorescence microscopy, which reports the presence of a molecule specific to that population, called a marker. This contrast reveals only the chosen population and remains blind to all the others. This thesis explores the use of a quantitative phase microscope to analyze axonal transport. The contrast is the wavefront distortion induced by a sample, which is proportional to the local concentration of molecules, namely the dry mass density. Measuring the dry mass of a vesicle gives access to how much material it carries, a readout hardly accessible to fluorescence microscopy. Rat cortical neurons are cultured in microfluidic chips, where axons grow in long, straight microchannels, isolated from cell bodies and dendrites. The axonal traffic is analyzed by a bimodal microscope, where fluorescent markers give the identity of vesicles, and wavefront imaging measures their dry mass. The wavefront signal generated by vesicles remains weakly contrasted, so a dedicated image analysis pipeline has been developed to extract the mass of moving vesicles in axons. Coupled with fluorescence imaging, the technique reports the mass distribution within an identified population. Used alone, it quantifies axonal transport label-free and at large scale. This thesis establishes mass as a novel readout of interest for the axonal trafficking community.
