CNPase (2', 3��-cyclic nucleotide 3'-phosphodiesterase) catalyzes the in vitro hydrolysis of 2��, 3��-cyclic nucleotides to produce 2��-nucleotides. The in vivo molecular function and native substrate of this nucleotide phosphodiesterase remains under investigation (1). High CNPase expression is seen in oligodendrocytes and Schwann cells as CNPase accounts for roughly 4% of the total myelin protein in the central nervous system (2). CNPase binds to tubulin heterodimers and plays a role in tubulin polymerization, and oligodendrocyte process outgrowth (3). Typical myelination is seen in CNPase knock-out mice, but they suffer severe neurodegeneration from axonal loss and oligodendrocytes display abnormal paranodal loop structure prior to axonal degeneration. Paranodal loops typically contact the axolemma in axon-glial signaling; neurodegeneration in CNPase knock-out mice is a secondary consequence of impaired cell-cell communication (4).
