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 effect of the mutation is an extreme reduction in central nervous system myelin in affected mice. However, both oligodendrocytes and astrocytes, the two types of central nervous system macroglia, have been shown to exhibit more subtle developmental and metabolic changes as a result of the mutation. These include early death and proliferation abnormalities in jimpy oligodendrocytes, and hypertrophy, increased pH and abnormal 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 mitoses, we find the total cell cycle to be lengthened in jimpy astrocytes by 5-6 h, with increases in several different phases. Since there is no evidence that astrocytes make myelin proteolipid protein, the results support previous studies which suggest that this gene may code for other proteins playing an important role in the development of many cell types.