The aim of this project is to determine the differences in molecular organisation of synapses in healthy neurons and in neurons expressing GABAARs with mutations found in patients with genetic epilepsies.
The number of GABAARs present at synapses is one of the main determinants of inhibitory synaptic strength and it is altered in genetic epilepsies. Yet very little is known about the organisation of GABAARs and their interacting proteins in patients with epilepsy. We found that a lower expression level of mutant receptors often better correlates with severity of the disease than changes in GABAergic currents, as previously thought. Our preliminary results indicate that surface expression level and mobility of GABAARs at synapses may be key factors contributing to severity of epilepsy. This will be tested via the following aims:
1. To determine spatial distribution and mobility of mutant GABAARs and their inhibitory scaffold, Gephyrin.
2. To examine changes in molecular composition of excitatory synapses caused by defective GABAARs. This is important because the function of inhibitory and excitatory synapses is mutually regulated and can therefore point towards new treatment options.
3. To test plasticity of synapses that contain GABAARs implicated in epilepsy. Many people with epilepsy also have other neurological and neurodevelopmental deficits, indicating that mechanisms involved in synaptic plasticity may be obstructed.
Single molecule based super-resolution microscopy (STORM, PALM, single particle tracking and related techniques) will be used to visualize individual molecules and their interaction in neurons. We will generate simulated data to aid in the understanding of observed phenomena and computational methods based on machine learning will be implemented in data analysis routines.
This project will reveal differences in GABAAR organisation in mild and severe epilepsies. Studying GABAAR mobility and Gephyrin restructuring on timescales of seconds to minutes will shed light on changes in inhibitory synaptic plasticity, which is of central importance for patients with genetic epilepsies accompanied with neurodevelopmental disorders such as learning difficulties and intellectual disability. Together, these results will lead to more targeted diagnostic options and open alternative avenues for the treatment of epilepsy including personalised therapies, development of drugs that target GABAAR associated proteins and medications that promote GABAAR surface expression.
On a more general level, the single-molecule approach laid out here will contribute to our understanding long-term changes in the organization of neural circuits that support different stages of seizures in patients with genetic epilepsies.
A PhD student who would be working on this project would come out with a well-rounded knowledge of super-resolution microscopy and with a good understand of biology of inhibitory synapse.