Frizzled 8a function is required for oligodendrocyte development in the zebrafish spinal cord

Oligodendrocytes are the myelinating cells in the central nervous system. The development of oligodendrocytes is mediated by complex signaling networks, including Wnt signaling. Although Wnt signaling has been studied in various aspects of neurogenesis, the distinct roles of various Frizzled receptors that mediate the Wnt signaling in the CNS remain virtually unknown. In order to understand the specific function of Wnt signaling in oligodendrocyte development, we focused on the Frizzled 8a (Fz8a) receptor. Here we show that Fz8a plays a critical role in the specification and maturation of oligodendrocyte progenitor cells (OPCs) in the ventral spinal cord. Loss of Fz8a function perturbed the proliferation and organization of radial glial cells that give rise to OPCs in the ventral precursor region of spinal cord. In addition, we demonstrate that Wnt signaling activation after the specification of OPCs blocks the formation of mature oligodendrocytes and results in the elimination of OPCs.