PHENOTYPIC CHARACTERIZATION OF IPSC-DERIVED DOPAMINERGIC NEURONS FROM MAO-A/B DEFICIENT PATIENTS REVEALS INCREASED ELECTROPHYSIOLOGICAL ACTIVITY AND MORPHOLOGICAL COMPLEXITY

Monoamine oxidase A and B (MAO-A/B) metabolize neurotransmitters including serotonin and dopamine. Genetic deletions in MAO-A/B genes cause severe neurodevelopmental and behavioral disorders. Understanding cellular phenotypes associated with MAO deficiency is essential for developing targeted therapeutic interventions, including gene therapy.
This study characterizes functional and morphological phenotypes of iPSC-derived dopaminergic (DA) neurons from a MAO-A/B deficient patient compared to a healthy parental control, establishing baseline measurements for future gene therapy experiments.
DA neurons were generated from iPSCs of one MAO-A/B deficient patient and one healthy control. Microelectrode array recordings assessed functional network properties across developmental timepoints to day in vitro 35 in three independent experiments. Parameters included mean firing rate, burst frequency and duration, network burst dynamics, and synchronization patterns. Morphological characterization at DIV 30 used immunocytochemistry with MAP2 and tyrosine hydroxylase markers. Sholl analysis quantified dendritic length, branching nodes, covered surface area, and soma size.
MAO-A/B deficient neurons exhibited significantly elevated electrophysiological activity with consistently higher mean firing rates across developmental timepoints. Burst frequency increased while network burst duration shortened. Morphological analysis revealed striking structural differences: patient neurons displayed increased dendritic complexity with significantly longer total dendritic length, more dendritic nodes, and larger covered surface areas. Sholl analysis confirmed enhanced branching complexity at multiple distances from the soma.
iPSC-derived DA neurons from MAO-A/B deficient patients demonstrate hyperexcitability and enhanced dendritic arborization. These robust, reproducible phenotypes provide an ideal platform for evaluating AAV9-mediated MAO-A gene therapy and screening monoamine-modulating drugs, establishing critical baseline measurements for therapeutic rescue studies.