Human organoid screen links transient translational modulation to progenitor progression in corticogenesis

Human pluripotent stem cell-derived models are increasingly used to recapitulate aspects of human corticogenesis, including the emergence of diverse cortical cell types and their progression through developmental states. These systems offer an opportunity to dissect the molecular mechanisms regulating transitions between cell states, but methods for perturbing them systematically at scale remain limited. Here, we developed a semi-automated culture and high-throughput arrayed screening platform for human cortical organoids. Using a library of 1,280 small molecules designed to systematically target major signaling and regulatory pathways, we screened for modulators of EOMES, which encodes for the transcription factor TBR2, and identified Emetine, an inhibitor of translation elongation, as the top hit. The effect of Emetine on cortical cell-state progression was reproduced across human pluripotent stem cell lines, non-human primate cortical organoids, and primary human cortical tissue but not broadly across translation inhibitors. Moreover, transient exposure resulted in a shift from dividing radial glia towards cortical glutamatergic neurons. Mechanistically, nascent-proteome profiling revealed an early and coordinated remodeling of newly translated proteins that preceded detectable transcriptional changes, placing translational regulation upstream of the ensuing cell-state transition. Together, these findings highlight a role for specific translational inhibitors in promoting cortical cell-state progression and establish a scalable platform for systematic perturbation and discovery in human neural organoids.