PLP1 and major depressive disorder: However, no significant changes in the main constitutive proteins of myelin, including proteolipid protein 1 (PLP1), 2′,3′-cyclic nucleotide 3′ phosphodiesterase (CNP), myelin-associated glycoprotein (MAG), myelin oligodendrocyte glycoprotein (MOG), and myelin basic protein (MOBP), have been observed in suicidal patients with depression [59].