Early striatal hyperexcitability in an in vitro human striatal microcircuit model carrying the Parkinson's GBA-N370S mutation

<strong>ABSTRACT</strong> Understanding medium spiny neuron (MSN) physiology is essential to understand motor impairments in Parkinson’s disease (PD) given the architecture of the basal ganglia. Here, we developed a custom three-chamber microfluidic platform and established a cortico-striato-nigral microcircuit recapitulating the striatal presynaptic triad <em>in vitro</em> using induced pluripotent stem cell (iPSC)-derived neurons. We found that, although cortical glutamatergic projections facilitated MSN synaptic activity, dopaminergic transmission was essential for excitability maturation of MSNs <em>in vitro</em>. Replacement of wild-type iPSC-dopamine neurons (iPSC-DaNs) in the striatal microcircuit with those carrying the PD-related <em>GBA-N370S</em> mutation induced early hyperexcitability in iPSC-MSNs through reduction of voltage-gated sodium and potassium intrinsic currents. Such deficits were resolved in aged cultures or with antagonism of protein kinase A activity in nigrostriatal iPSC-DaNs. Hence, our results highlight the unique utility of modelling striatal neurons in a modular and highly physiological circuit which is essential to reveal mechanistic insights of the loss of electrical functional integrity in the striata of <em>GBA1</em> PD patients. <strong>FILE DESCRIPTIONS</strong> Source Data.xlsx: Tabular datasets plotted on main figures 1, 3, 4, 5 and 6. Supplementary Data.xlsx: Tabular datasets plotted on supplementary figures 1, 2 and 3. Key Resources Table.xlsx: Table containing key resources (primary and secondary antibodies, cell lines and software) used in this study. List of Primers.xlsx: Primers used in RT-qPCR.