JIMPY MUTATION AFFECTS ASTROCYTES - LENGTHENING OF THE CELL-CYCLE IN-VITRO

The jimpy mutation has been identified as a point mutation in the gene coding for the major myelin proteolipid protein. The most prominent e ffect of the mutation is an extreme reduction in central nervous syste m myelin in affected mice. However, both oligodendrocytes and astrocyt es, the two types of central nervous system macroglia, have been shown to exhibit more subtle developmental and metabolic changes as a resul t of the mutation. These include early death and proliferation abnorma lities in jimpy oligodendrocytes, and hypertrophy, increased pH and ab normal responses to high K+ in jimpy astrocytes. In the present study, we examine the effect of the mutation on the cell cycle of astrocytes . Using an immunocytochemical method to chart the percent of labeled m itoses, we find the total cell cycle to be lengthened in jimpy astrocy tes by 5-6 h, with increases in several different phases. Since there is no evidence that astrocytes make myelin proteolipid protein, the re sults support previous studies which suggest that this gene may code f or other proteins playing an important role in the development of many cell types.