ABNORMAL EXPRESSION OF THE PROLIFERATING CELL NUCLEAR ANTIGEN (PCNA) IN THE SPINAL-CORD OF THE HYPOMYELINATED JIMPY MUTANT MICE

In the present study, assessment of the expression of the proliferatin g cell nuclear antigen (PCNA), a nuclear acidic protein necessary for DNA replication that is expressed through the cell cycle, was used to investigate the proliferative capability of glial cells in the hypomye linated Jimpy mutant mice. Spinal cords from 10-12 and 20-22 day jimpy and normal animals were used for quantitative microscopic image analy sis. Simultaneous demonstration of cycling cells and oligodendroglia, astroglia or microglia was achieved through the sequential combination of PCNA immunostaining and selective markers for these glial cells. O ur results revealed that the density of PCNA-positive cells was higher in Jimpy than in normal spinal cords, this difference being more pron ounced at 20-22 days than at 10-12 days and more so in white than in g ray matter. In addition, Jimpy glial cells exhibited an abnormal PCNA expression, as demonstrated by quantification of the intensity of nucl ear immunostaining. In comparison to normal animals, the percentage of PCNA-positive cells showing intensely stained nuclei was higher in Ji mpy. About 50% of PCNA-positive cells in the Jimpy white matter were i dentified as cells from the oligodendrocyte line, 30% were microglial cells and 20% were astrocytes. The expression of PCNA in relation to t he proliferative capability and possible cell cycle abnormalities of t he different glial cell types in Jimpy is discussed.