Sequentially Acting SOX Proteins Orchestrate Astrocyte and Oligodendrocyte Specific Gene Expression

SOX transcription factors have important roles during astrocyte and oligodendrocyte development, but how glial genes are specified and activated in a sub-lineage specific fashion remains unknown. To address this question, we have defined glial specific gene expression in the developing spinal cord using single-cell RNA-sequencing. Moreover, conducting ChIP-seq analyses we show that these glial gene sets are extensively preselected already in multipotent neural precursor cells through the prebinding by SOX3. In the subsequent lineage-restricted glial precursor cells, astrocyte genes become additionally targeted by SOX9 at DNA-regions strongly enriched for Nfi binding-motifs, whereas oligodendrocyte genes become prebound by SOX9 only, at sites that during oligodendrocyte maturation are targeted by SOX10. Interestingly, reporter gene assays and functional studies in the spinal cord revealed that SOX3 binding represses the synergistic activation of astrocyte genes by SOX9 and NFIA, whereas oligodendrocyte genes are activated in a combinatorial manner by SOX9 and SOX10. These genome-wide studies demonstrate how sequentially expressed SOX proteins act on lineage-specific regulatory DNA-elements to coordinate glial gene expression both in a temporal and sub-lineage specific fashion. SOX3 ChIPseq (2 replicates), SOX9 ChIPseq (3 replicates), NFIA ChIPseq (2 replicates), Hsk27Ac ChIPseq (3 replicates), GPC RNAseq (4 replicates), Glial cells (3 replicates)