Gsx2 regulates oligodendrocyte precursor formation in the zebrafish spinal cord.

Nervous system development relies on sequential and coordinated formation of diverse neurons and glia from neural progenitor cells (NPCs). In the spinal cord, NPCs of the pMN domain produce neurons early in development followed by oligodendrocyte precursor cells (OPCs), which subsequently differentiate as oligodendrocytes (OLs), the myelinating glia of the central nervous system. The mechanisms that specify neural progenitor cells to the OL lineage are not yet well understood. Using zebrafish as an experimental model system, we generated single-cell RNA sequencing and single-nuclei ATAC sequencing data that identified a subpopulation of NPCs, called pre-OPCs, that appeared fated to produce OPCs. pre-OPCs uniquely express several genes that encode transcription factors specific to the OL lineage, including Gsx2, which regulates OPC formation in the mouse forebrain. To investigate Gsx2 function in zebrafish OPC specification, we used CRISPR/Cas9 genome editing to create gsx2 loss-of-function alleles. gsx2 homozygous mutant embryos initiated OPC formation prematurely and produced excess OPCs without altering OL differentiation. Using our single-nuclei multi-omics dataset, we predicted a gene regulatory network centered around gsx2 and identified genes that might be transcriptionally regulated by Gsx2. Taken together, our studies suggest that Gsx2 expression in pre-OPCs contributes to the timing of OPC specification.