Sliced Human Cortical Organoids for Modeling Distinct Cortical Neuronal Layer Formation

Brain organoids provide unique platforms for modeling development and diseases by recapitulating the architecture of the embryonic brain. However, current organoid methods are limited by interior hypoxia and cell death due to insufficient surface diffusion, preventing generation of architecture representative of late developmental stages. Here, we establish the sliced neocortical organoid (SNO) system, which bypasses the diffusion limit to prevent cell death and sustains neurogenesis in organized neural progenitor zones throughout long-term cultures. This method leads to the formation of an expanded cortical plate that establishes distinct upper and deep cortical layers, resembling the third-trimester human neocortex. Using the SNO system, we further identify a critical role of WNT/β-Catenin signaling in regulating cortical neuron fate specification, which is disrupted by a psychiatric disorder-associated genetic mutation in patient iPSC-derived organoids. These results demonstrate the utility of SNOs as a model for investigating previously inaccessible human-specific late-stage cortical developmental and disease-relevant mechanisms