Da. Vouyiouklis et Pj. Brophy, MICROTUBULE-ASSOCIATED PROTEINS IN DEVELOPING OLIGODENDROCYTES - TRANSIENT EXPRESSION OF A MAP2C ISOFORM IN OLIGODENDROCYTE PRECURSORS, Journal of neuroscience research, 42(6), 1995, pp. 803-817
The morphological differentiation of oligodendrocytes is characterized
by the formation of multiple, microtubule-rich processes which endow
these cells with the ability to myelinate many axons simultaneously. S
ince microtubule-associated proteins (MAPs) strongly influence the str
ucture and function of microtubules, we have investigated their expres
sion in cultured differentiating oligodendrocytes in order to gain ins
ights into MAP function during process formation and stabilization. MA
P1B has been compared with two other structural MAPs: MAP4, which is a
n ubiquitously expressed protein, and MAP2, which hitherto was thought
to be confined to neurons and reactive astrocytes, Immunofluorescence
microscopy showed that the colocalization of MAP4 with microtubules i
n oligodendrocyte processes is not as extensive as found previously fo
r MAP1B (Vouyiouklis and Brophy: J Neurosci Res 35:257-267, 1993). Nev
ertheless, like MAP1B, the expression of MAP4 increases during oligode
ndrocyte differentiation. In contrast, the expression of MAP2 is trans
iently elevated in preoligodendrocytes but declines precipitously at t
he onset of terminal differentiation. Cells of the oligodendrocyte lin
eage exclusively express a novel isoform of MAP2c which is primarily l
ocalized in the cell bodies of preoligodendrocytes. This suggests that
MAP2c assists in the initiation of process extension rather than in t
he stabilization of microtubules in the cytoplasm-filled membranous ex
tensions of mature cells. MAP-tau was not expressed at any development
al stage by oligodendrocytes. The distinct subcellular localizations a
nd patterns of developmental expression of MAP1B, MAP4, and MAP2c sugg
est that these MAPs have different roles in the regulation of the micr
otubule network during the differentiation of myelin-forming oligodend
rocytes. (C) 1995 Wiley-Liss, Inc.