ISOLATION AND CHARACTERIZATION OF DEFECTIVE JIMPY OLIGODENDROCYTES INCULTURE

This study characterizes jimpy oligodendrocyte-enriched secondary cult ures isolated from 10-12 days in vitro primary glial cell cultures der ived from 1-2-day-old jimpy mouse brains. Proliferation of defective o ligodendrocytes was carefully investigated with regard to the expressi on of myelin basic protein and proteolipid protein and their respectiv e mRNAs. Less than 5% of contaminating astrocytes (GFAP(+) cells) were usually present. The identity of jimpy oligodendrocytes was confirmed using an antibody directed against a peptide from the wild type prote olipid protein C-terminal sequence for immunocytochemistry and an olig onucleotide complementary to mRNA derived from exon 5 of the proteolip id protein gene for in situ hybridization. Both the antibody and the p robe recognize only normal oligondendrocytes while jimpy oligodendrocy tes always remain unstained. Proteolipid protein in normal and jimpy o ligodendrocytes was detected with antibody recognizing normal and muta ted forms. Between 80 and 95% of the cells in normal and jimpy culture s at 2 and 4 days in vitro in secondary cultures express myelin basic protein and proteolipid protein and their respective mRNAs. The percen tage of oligodendrocytes (PLP(+) or MBP(+)) in S phase of the cell cyc le was 7-10% for both normal and jimpy oligodendrocytes. This contrast s with the in vivo situation where the proliferation rate of oligodend rocytes in jimpy brains is higher than in normal brains. In addition, jimpy oligodendrocytes remain unresponsive to basic fibroblast growth factor treatment while a similar treatment stimulates the proliferatio n of normal oligodendrocytes.