Nanoscale probing of single synapse function and BDNF Cell-to-Cell transfer

by Markus Andreas Stahlberg
Doctoral thesis
Date of Examination:2016-05-13
Date of issue:2016-12-22
Advisor:Dr. Camin Dean
Referee:Ph.D. Camin Dean
Referee:Prof. Dr. Stefan Hell
Referee:Prof. Dr. Dr. Detlev Schild
Persistent Address: http://dx.doi.org/10.53846/goediss-6056

 

 

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Abstract

English

Brain-derived neurotrophic factor (BDNF) is one of the key modulator/mediator molecules for synaptic plasticity in the adult nervous system and also coordinates neural development, survival, differentiation and axon growth during development in the central and the peripheral nervous system. The understanding of our brain critically depends on the detailed understanding of the regulatory mechanisms of molecules like BDNF. Recent research has implicated BDNF in synapse-specific strengthening of active synapses, but if BDNF is recruited specifically to active synapses to modulate their function is not known. Additionally, it is debated whether BDNF is released from post- or presynaptic sites and if BDNF affects exclusively neurons, or other cell types, like astrocytes, in addition. Here we propose and investigate a novel strategy to achieve focal stimulation of neurons using optogenetics, with the ultimate goal to study the influence of activity on the recruitment and release of the neurotrophic factor BDNF. We demonstrate the utility of current optogenetic tools to achieve highly focal depolarization and further examined a proof-of-principle of nanoscale optogenetic activation using an initial macroscale approach. Using dissociated and organotypic hippocampal cultures from the rat, in which we co-express BDNF-mRFP1 and a cytosolic fluorophore to identify the cell of origin, we tested the influence of focal optogenetic activation of specific sites on intracellular BDNF trafficking and further extended the study to investigate the intercellular transfer of BDNF to neighboring cells. We found that BDNF was preferentially taken up by astrocytes and provide evidence for BDNF-mediate physiological effects on the astrocytic population.
Keywords: Optogenetics; BDNF
 
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