Identification of a Sulf2-dependant astrocyte subtype that stands out through the expression of Olig2 in the ventral spinal cord

During spinal cord development, both spatial and temporal mechanisms operate to generate glial cell diversity. Here, we addressed the role of the Heparan Sulfate-editing enzyme Sulf2 in the control of gliogenesis in the mouse developing spinal cord and found an unanticipated function for this enzyme. Sulf2 is expressed in ventral spinal progenitors at initiation of gliogenesis, including in Olig2-expressing cells of the pMN domain known to generate most spinal cord oligodendrocyte precursor cells (OPCs). We found that Sulf2 is dispensable for OPC development but required for proper generation of an as-yet-unidentified astrocyte precursor cell (AP) subtype. These cells, like OPCs, express Olig2 while populating the spinal parenchyma at embryonic stages but also retain Olig2 expression as they differentiate into mature astrocytes. We therefore identify a spinal Olig2-expressing AP subtype that segregates early under the influence of the extracellular enzyme Sulf2.