Rj. Hardy et al., CYTOPLASMIC AND NUCLEAR-LOCALIZATION OF MYELIN BASIC-PROTEINS REVEALSHETEROGENEITY AMONG OLIGODENDROCYTES, Journal of neuroscience research, 46(2), 1996, pp. 246-257
Myelin basic proteins (MBPs) are major proteins of central nervous sys
tem (CNS) myelin, where they facilitate the apposition of cytoplasmic
faces of myelin lamellae. Myelin-bearing oligodendrocytes transport MB
P mRNA to myelin, where newly translated protein is directly inserted
into the myelin sheath, An apparent absence of MBPs in oligodendrocyte
perikarya has suggested that MBP localized to the soma is translation
ally inert, We now demonstrate by confocal immunofluorescence microsco
py that not only are MBPs present in the majority of oligodendrocyte p
erikarya but oligodendrocytes are heterogeneous with respect to their
localization of MBPs; MBPs are concentrated in some cells at the plasm
alemma and distributed in others throughout the cytoplasm and, surpris
ingly, the nucleus, MBPs are present in the nuclei of over half of oli
godendrocytes in the adult, but in almost all MBP+ oligodendrocytes du
ring myelinogenesis, Transport of MBPs into nuclei appears to be a reg
ulated process since some cells exhibit robust MBP accumulation in the
ir cytoplasm but exclude MBPs from their nuclei, We show that oligoden
drocyte nuclei contain all four major MBP isoforms, but that in transg
enic mice, the epitope-tagged 14 kD MBP isoform preferentially segrega
tes to the plasmalemma, Our data demonstrate that oligodendrocytes are
not required to exclude MBPs from their perikarya and suggest that MB
Ps have a specific function in the oligodendrocyte perikarya and nucle
us. (C) 1996 Wiley-Liss, Inc.