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 is not well understood. The protracted maturation of these cells during postnatal development has made their derivation from human pluripotent stem cells (hPSCs) extremely difficult, precluding hPSC-based disease modeling of their role in neuropsychiatric diseases. Here we present a cortical assembloid system that supports the development of PVALB+ cortical interneurons which match the molecular profiles of primary PVALB+ interneurons and display their distinctive electrophysiological features. Further, we characterized cortical interneuron development in a series of CRISPR-generated isogenic structural variants associated with schizophrenia and identified variant-specific phenotypes in cortical interneuron migration and the molecular profile of PVALB+ cortical interneurons. These findings reveal plausible mechanisms on how disruption of cortical interneuron development may impact schizophrenia risk and provide an exciting human experimental platform to facilitate the study of PVALB+ cortical interneurons.