Aberrant Neuronal Connectivity and Network Activity of Neurons Derived from Patients with Idiopathic Schizophrenia

Schizophrenia (SCZ) is a psychiatric disorder with a strong genetic determinant. A major hypothesis to explain disease aetiology comprises synaptic dysfunction associated with excitatory-inhibitory imbalance of synaptic transmission, ultimately contributing to impaired network oscillation and cognitive deficits associated with the disease. Here, we studied the morphological and functional properties of a highly defined co-culture of GABAergic and glutamatergic neurons derived from induced pluripotent stem cells (iPSC) from patients with idiopathic SCZ. Our results indicate upregulation of synaptic genes and increased excitatory synapse formation on GABAergic neurons in co-cultures. In parallel, we observed decreased lengths of axon initial segments, concordant with data from postmortem brains from patients with SCZ. Patch-clamp analyses revealed differential processing of excitatory input with markedly increased spontaneous excitatory postsynaptic currents (EPSC) recorded from GABAergic SCZ neurons and decreased spontaneous EPSC from glutamatergic SCZ neurons. Likewise, we observed decreased amplitudes of calcium signals selectively in GABAergic neurons while frequency was increased in both neuronal populations. Finally, MEA recordings from neuronal networks indicate increased synchronization of network activity. In conclusion, our results suggest selective deregulation of neuronal activity and synaptic transmission in SCZ samples, providing evidence for differential signal processing in GABAergic and glutamatergic neurons as a potential base for aberrant network synchronization.