Study of the regulation of synapses in human organotypic cultures on electrophysiological and ultrastructural levels

01.03.2020 bis 28.02.2022

Techniques such as human organotypic cortical slice cultures have been recently developed as an ex vivo system to overcome the lack of transferability of data obtained in animal brains. Organotypic cultures enable the investigation of dynamic properties of human brain cells over a time period of weeks since they provide access to human neuronal networks that developed physiologically.
In the cerebral cortex most synapses are established in the neuropil, composed of dendrites, axons and glial processes. Here, most cortical synapses are excitatory (90%), while inhibitory ones are less numerous (10%). Recently, new electron microscopy techniques specialized on the 3D reconstruction of synapses have been developed, allowing the measurement of the density, spatial distribution, size and shape of synapses, as well as the reconstruction of other organelles.
Epilepsy has been shown to have an altered balance between excitation and inhibition, together with alterations of the synaptic machinery. In this disease, homeostatic plasticity (the ability of neurons to up- or downregulate their receptors in response to their firing rate) may participate in the slow onset of seizures and may also be involved in the loss of efficiency of some anti-epileptic drugs. Other factors contributing to the development of epilepsy include mutations in proteins of the synaptic machinery such as Stx1b, playing an important role in synaptic vesicle release. In this proposal we intend to investigate whether the mechanisms of homeostatic plasticity in rodents are also present in adult human neurons. Furthermore, we plan to characterize the effects of mutations in Stx1b. We propose to measure the density, spatial distribution, size and shape of synapses in organotypic cortical slice cultures under physiological conditions, after stimulus deprivation and after alteration of Stx1b function, and correlate these data with the electrical properties of neurons. Thus, this study will provide a deeper understanding of the pathophysiological mechanisms underlying epilepsy.