MOBP levels are regulated by Fyn kinase and affect the morphological differentiation of oligodendrocytes

Oligodendrocytes are the myelinating glial cells of the central nervous system (CNS). Myelin is formed by extensive wrapping of oligodendroglial processes around axonal segments, which ultimately allows a rapid saltatory conduction of action potentials within the CNS and sustains neuronal health. The non-receptor tyrosine kinase Fyn is an important signaling molecule in oligodendrocytes. It controls the morphological differentiation of oligodendrocytes and is an integrator of axon-glial signaling cascades leading to localized synthesis of myelin basic protein (MBP), which is essential for myelin formation. The abundant myelin-associated oligodendrocytic basic protein (MOBP) resembles MBP in several aspects and has also been reported to be localized as mRNA and translated in the peripheral myelin compartment. The signals initiating local MOBP synthesis are so far unknown and the cellular function of MOBP remains elusive. Here, we show, by several approaches in cultured primary oligodendrocytes, that MOBP synthesis is stimulated by Fyn activity. Moreover, we reveal a new function for MOBP in oligodendroglial morphological differentiation.