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Towards the nonlinear optical read-out of cellular activity

Boek - Dissertatie

Understanding the pathophysiology of many complex neural disorders (like Alzheimer's, Parkinson's, depression, obsessive compulsive disorder, etc.) requires the ability to selectively interfere and record the neuralactivity underlying the brain processes. 'Optogenetics' describes a variety of techniques for specifically controlling the neural activity withlight (Fiala et al. 2010). Optical control has several advantages in comparison to classical electrical or pharmacological control. Bygenetic targeting, control can be achieved in a cell type-specific manner. In contrast, electrical stimulation and drug compounds can interferewith all cell types. In the case of electrical stimulation because of the unselective nature of electricity (e.g. it chooses the path of least resistance). Non-specific effects are a major concern of pharmaceuticals.Although the current state of the art is rich in in vivo demonstrations of neural activation, a lot still has to be learned on the activation processes at cellular and molecular scales. This would allow discriminating between direct cellular events (i.e. membrane depolarization and hyperpolarization, action potential generation) and 2nd order signaling and network effects. Such discrimination is not possible in in vivo preparations due to their complexity.This project will focus on molecular and in vitro cellular investigation of linear and nonlinear optical properties of opsins relevant for the cellular activation and also for their use as voltage sensitive probes. Two-photon optical property data is only available for the wild-type Channelrhodopsin 2 and a particular mutant C1V1, while the library of available opsins is increasing tremendously (Materials et al. 1998; Birge 1990). Also, very little is known about the spatial localization of opsins expressed in mammalian neurons. Although a lot has been achieved using genetic engineering of known opsins, mutagenesis has the disadvantage of unanticipated effects in different systems and mixed impacts in the opsin.The concrete goals of this project are (1) to quantify the molecular nonlinear optical parameters of several opsins (hyperpolarizability(β), two-photon absorption (TPA) cross section) and (2) to investigatethe membrane localization and activation of opsins expressed in cells under two-photon illumination. The data obtained would allow further deploying the potential of optogenetics by building efficient in vivo stimulation strategies (relevant for all neuromodulation applications) as well as in combining neuromodulation with optical readout (relevant for all basic research in neurophysiology).
Jaar van publicatie:2019