Abstract
Oligodendrocytes, myelin-forming glia in the central nervous system (CNS), are the last major type of neural cells formed during the CNS development. Although the process of oligodendrogenesis has been relatively well delineated in the rodent brain at embryonic and early postnatal stages, it remains largely unknown whether analogous developmental processes are manifested in the human brain. Here, we report oligodendrogliogenesis in brain region-specific forebrain organoids, generated by using OLIG2-GFP knockin human pluripotent stem cell (hPSC) reporter lines. We found that OLIG2/GFP exhibited distinct temporal expression patterns in ventral forebrain organoids (VFOs) vs. dorsal forebrain organoids (DFOs). Two-photon calcium imaging demonstrated functional neurons and astrocytes in the DFOs. A small subset of cells in early stage DFOs expressed OLIG2 and subsequently gave rise to glutamatergic neurons. Interestingly, oligodendrogenesis could be induced in both VFOs and DFOs after neuronal maturation promoted by the newly-designed BrainPhys medium. More importantly, rebuilding neural network by fusing VFOs with DFOs to generate fused forebrain organoids (FFOs) could promote the maturation of the oligodendroglial cells. Furthermore, dorsally-derived oligodendroglial cells were able to outcompete ventrally-derived oligodendroglia and constituted the majority of the mature oligodendrocytes in FFOs after long-term culture. Thus, our organoid models that recapitulate the oligodendrogenesis with ventral and dorsal origins will serve to study the phenotypic and functional differences between human ventrally- and dorsally-derived oligodendroglia and to reveal disease mechanisms of neurodevelopmental disorders associated with cortical myelin defects.
