Electrophysiological and Morphological Characterization of human-derived neurons carrying ACTG1 actin mutation

Human actinopathies are a group of rare autosomal dominant disorders caused by heterozygous missense mutations in genes encoding actin. In particular, mutations in the ACTG1 gene, encoding the γ-cytoskeletal actin, a major isoform in neuronal cells, lead to diseases known as Non-Muscular Actinopathies (NMAs), which may result in severe neurological symptoms. In developing neurons, the actin cytoskeleton has a crucial involvement in neurite formation, elongation, branching, signal transduction, formation of synaptic structures and in neuronal migration process. In mature neurons, actin is the predominant cytoskeletal component of synapses, both at the pre- and postsynaptic levels. Mutations in actin genes can alter the stability or polymerization of actin filaments, impairing the protein's functionality and causing significant morphological and functional changes in neuronal cells. As of now, isoform-specific functions of actin in neurons remain poorly understood and the molecular mechanisms driving these disorders remain largely unknown. In this study, patient-derived induced Pluripotent Stem Cells (iPSCs), wild-type or harboring mutations in the ACTG1 gene, were differentiated in neuronal cells. Electrophysiology and confocal microscopy were used to analyze the relationship between actin mutation and cellular functionality and morphology. Our results show significant differences between pathogenic and wild-type neurons in amplitude of voltage-dependent currents, as well as a significant increase in neuronal branching throughout the maturation period, highlighting a specific relationship between actin and neuronal features. Future work will involve a deeper understanding of the mechanisms underlying NMAs and the connection between actin mutations and neuronal abnormalities, ultimately aiding in the development of novel therapeutic approaches.