A minimally guided organoid model for cross-species comparisons of cerebellar development

The human cerebellum has undergone significant evolutionary expansion compared to other species, contributing to both motor and cognitive skills. However, the mechanisms underlying this process remain largely unknown as interrogating human cerebellar development alongside other species has to date been unfeasible. To address this, we developed a minimally guided cerebellar organoid protocol that combines unguided neural induction with precise temporal calibration of posteriorizing morphogens. This approach effectively overrides default telencephalic fate in cerebral organoids and induces stable cerebellar identities. Cerebellar organoids derived from both human and mouse ESCs exhibit species-specific size differences at comparable developmental stages and show robust induction of cerebellar master regulators and progenitor cell types. This model provides a powerful tool for investigating the mechanisms underlying cerebellar development in the context of both evolution and disease.