STUDYING SYNAPTIC SCAFFOLDING PROTEINS IN MATURE HUMAN IPSC DERIVED NEURONS

The study of synapse development and maturation has largely been undertaken in rodent cultures. In recent years neurons developed from human induced pluripotent stem cells hiPSCs have increasingly gained popularity. However synaptic maturation in stable system is difficult to achieve. A stable culture requires a mix of inhibitory neurons of different types and excitatory neurons. We devolved a culturing system including with a high degree of synaptic maturation and a mix of inhibitory and excitatory neurons. These neurons showed a high density of synapses and we were able to demonstrate synaptic scaling, a post-synaptic homeostatic plasticity mechanism.
We began to employ this system to study a synaptic scaffolding protein, we previously studied in rodent culture, called S-SCAM/MAGI-2. This postsynaptic scaffolding protein is crucial involved in maintaining synaptic organisation and stability of synapses. SCAM/MAGI-2 mutations are associated with increased risk for Alzheimer’s disease, epilepsy and most significantly schizophrenia. Besides its role in synapse stabilisation and function, S-SCAM/MAGI-2 interacts with signalling proteins facilitating synapse to nucleus signalling and influences the expression levels of multiple important synaptic proteins. Here, we show that S-SCAM/MAGI-2 is critical for synaptogenesis and synaptic maintenance in both, human and rodent neurons and can be partially substituted by MAGI-1. In human neurons we found evidence that S-SCAM/MAGI-2 influences gene expression via CREB signaling.