MYELIN OLIGODENDROCYTE GLYCOPROTEIN (MOG) EXPRESSION IS ASSOCIATED WITH MYELIN DEPOSITION/

We investigated the onset of expression of the myelin/oligodendrocyte glycoprotein (MOG) mRNA and protein in the developing mouse central ne rvous system. In situ hybridization on brain sections at different sta ges of embryonic and postnatal development showed that MOG transcripts were first detected at birth in the medulla oblongata. During the fir st week after birth, cells expressing MOG mRNA were located in the ven tral longitudinal funiculus. During the second postnatal week, the pat tern of MOG mRNA expression extended rostrally to the mid-forebrain re gions and reached completion by the beginning of the third week. MOG t ranscription was delayed by several days with respect to myelin basic protein (MBP), and it appeared that while the MBP probe labeled both n on-myelinating and myelinating oligodendrocytes, only the latter were MOG-positive. In vitro, immunocytochemical analysis of MOG protein exp ression, performed on myelinating cultures derived from mouse brain em bryos at 15 days of gestation, confirmed the strict restriction of MOG expression to myelinating oligodendrocytes. In particular, oligodendr ocytes lining up their processes along axons, but not yet having start ed to deposit a myelin sheath, were still MOG negative. However, in th e same cultures, pseudo-myelinating oligodendrocytes (i.e., cells not associated with neurites, but forming whorls of myelin-like figures) w ere MOG positive. Similarly, rat CG4 cells, an oligodendrocyte-like ce ll line, expressed MOG only after they had extended sheet-like process es, which suggested that the activation of MOG transcription depends m ore on an intrinsic oligodendroglial maturation program of myelination than on a neuronal signal. (C) 1996 Wiley-Liss, Inc.