An interface of genetically engineered human forebrain assembloids and polymeric nanofiber scaffolds for multiscale profiling of interneuron migration disorders

Abstract Neuronal migration is a fundamental process during brain development in which different types of neurons migrate from their place of origin to the site where they reside and make networks crucial for the formation of proper brain architecture and its overall function. Interneuron migration anomalies due to genetic or environmental perturbations can lead to malfunctions in the neural circuitry and are observed in the case of multiple neuropsychiatric conditions. Variants in Erb-B2 Receptor Tyrosine Kinase 4 (ERBB4), a member of Tyr protein kinase family and the epidermal growth factor receptor subfamily that functions as a surface receptor in interneurons, have been associated with human neurodevelopment disorders such as schizophrenia, epilepsy, and intellectual disability. Animal studies elucidate the function of ERBB4 in neuronal migration, synaptogenesis, synaptic transmission, and plasticity. However, the exact mechanistic role of ERBB4 in the migration of GABAergic cortical interneurons in humans is unidentified. In this study, we employ CRISPR/Cas9 to knockout ERBB4 in human induced pluripotent stem cells and report its effect on the phenotype and global gene expression upon deriving dorsal and ventral human forebrain identity organoids. Additionally, fluorescent reporter knock-in using CRISPR/Cas9 at an interneuron-specific marker in the same hiPS cell line allowed distinct temporal fluorescence expression in the derived ventral forebrain organoids allowing the capture of tangential migration of labeled cortical interneurons in intact fused 3D assembloids, to pinpoint the role of ERBB4 in migration and function of these neurons. To capture the changes in migration dynamics of individual ERBB4−/− interneurons in high resolution, we recapitulated the migration behaviour. on nanofiber scaffolds that mimic the in vivo fibrous extracellular microenvironment. Our findings uncover the function of ERBB4 in the context of human interneuron migration.