To determine the impact of PAR2 on the number of OPCs and mature oligodendroglia over the course of spinal cord myelin development, we enumerated Olig2 (Ab9610, Millipore) or CC-1/APC 1 (Ab16794, Abcam) immunopositive cells in 5 μm paraffin sections through the dorsal columns and in in the lateral white matter columns at P0, 7, 21, or 45. Olig2 is a basic helix-loop-helix transcription factor expressed by OPCs and oligodendroglia at the early stages of differentiation, whereas CC-1 is associated only with the mature phenotype (Ligon et al., 2006 (link); Kuhlmann et al., 2008 (link); Funfschilling et al., 2012 (link)). Immunoperoxidase stained sections were cover slipped with DPX Mountant (Sigma-Aldrich, St. Louis, MO), nuclei counterstained with 0.5% methyl green (Sigma-Aldrich), and all cells with a visible nucleus were counted from digital images. Counts of either Olig2 or CC-1+ cells with a methyl green stained nucleus were made within the entire dorsal column, or within the lateral column white matter, of at least 3 mice at each time point without knowledge of genotype.