In vivo analysis of glial cell phenotypes during a viral demyelinating disease in mice

Recent studies on the O-2A lineage have also made use of the O4 antibody (Sommer and Schachner, 1981; Schachner et al., 1981; Keilhauer et al., 1985) which reacts with the O-2A progenitor at a later stage of its development before it expresses galactocerebroside, a differentiation marker for oligodendrocytes (Dubois-Dalcq, 1987) . When 04 positive cells are sorted from the murine neonatal brain and cerebellum, they can differentiate into type 2 astrocytes or oligodendrocytes (Trotter and Schachner, 1989) . In addition, differentiated oligodendrocytes and type 2 astrocytes isolated from the CNS of adult rats and mice express the 04 antigen (Wolswijk and Noble, 1989) . The 04 antibody reacts only weakly with neurons (Schachner et al., 1981) and appears to stain glial cells of different species in a consistent way (rat, mouse, chicken, human; Sommer and Schachner, 1981 ; our own unpublished observations). In contrast, A2B5 antibody does not consistently stain putative glial precursor cells in mouse (our own unpublished observations) and human (Kim et al., 1986) . For all these reasons, we have used the 04 antibody to study O-2A lineage cells in the normal mouse spinal cord and in mice affected with a demyelinating disease. The A59 strain of mouse hepatitis virus reliably caused demyelination in C57 black mice, with a predominance of lesions in the spinal cord. (Woyciechowska et al., 1984; Lavi et al., 1984a,b; Kristensson et al., 1986) . The virus replicates exclusively in glial cells of both white and grey matter of the spinal cord in the early phase of the disease (Godfraind, C., unpublished observations; Jordan et al., 1989b) . At two weeks post inoculation (WPI), the virus becomes restricted to the white matter where demyelination occurs and, at 4 WPI, virus is mostly cleared probably because the infected mice develop a vigorous immune response to the virus (Woyciechowska et al., 1984) . Clinical recovery and myelin repair proceed efficiently in the following weeks (Woyciechowska et al., 1984) . Thus cellular events related to demyelination and to successful remyelination can be followed closely in the spinal cord of these infected mice. We have previously used in situ hybridization to study myelin basic protein gene expression in this model (Kristensson et al., 1986) . At the start of remyelination, a subset of MBP transcripts which are highly expressed in developing animals during normal myelination are increased in abundance (Jordan et al., 1989a,c) .