CNPase expression is characteristic of myelinating cells. (a) In the transgenic mouse where GFP is under the control of CNPase, GFP expression can be observed in cortical white matter (a) and sciatic nerve (b). The GFP is present in oligodendrocytes in white matter of the CNS and Schwann cells in the peripheral nerve. (c) Cross-section of the olfactory bulb from the CNPase mouse showing GFP expression in the olfactory nerve (arrow) and the outer nerve layer of the olfactory bulb (OB) where OECs are present as the only glia cell type. (f) Higher power image of the olfactory nerve from (c) showing GFP expression in the nuclei and cytoplasm of OECs in the outer nerve layer. (d) and (e) Immunohistochemistry for CNPase in a wild type mouse OB showing CNPase expression in deep white matter and outer margins of the bulb. Note that the round glomeruli are devoid of CNPase. Nuclei have been counterstained with DAPI (blue) in (c), (e), and (f). Scale bars: (a) = 8 μm, (b) = 12 μm, (c) = 500 μm, (d) = 150 μm and pertains to (d) and (e), (f) = 3 μm.