Forebrain assembloids support the development of fast-spiking human PVALB+ cortical interneurons and uncover schizophrenia-associated defects.

Disruption of parvalbumin positive (PVALB+) cortical interneurons is implicated in the pathogenesis of schizophrenia. However, how these defects emerge during development remains poorly understood. The protracted, postnatal maturation of PVALB+ cortical interneurons has complicated human pluripotent stem cell (hPSC)-based models for studying their role in neuropsychiatric disease. Here, we present a forebrain assembloid system yielding PVALB+ cortical interneurons that match the molecular identity and distinctive electrophysiology of primary PVALB+ interneurons. We further established a series of isogenic hPSC lines carrying structural variants associated with schizophrenia and identified variant-specific phenotypes affecting cortical interneuron migration, the molecular profile of PVALB+ cortical interneurons, and their ability to regulate cortical network activity, including γ-band oscillations. These findings offer plausible mechanisms for how the disruption of cortical interneuron development may impact schizophrenia risk and provide a human experimental platform to study PVALB+ cortical interneurons in health and disease.