Developmental expression of glial fibrillary acidic protein and glutamine synthetase mRNAs in normal and jimpy mice.

Astrogliosis is a prominent feature in the CNS of the dysmyelinating mutant, jimpy. In the following study the expression of the glial markers, glial fibrillary acidic protein (GFAP) and glutamine synthetase (GS) mRNAs were examined the cerebra of normal and jimpy mice. The relative abundance of GFAP and GS mRNAs increased rapidly in the CNS of normal mice during the first two postnatal weeks. During the third week the content of GFAP and GS mRNA remained constant. The pattern of developmental accumulation of these transcripts in jimpy animals was distinctly different. Levels of GFAP transcripts in 6- and 10-day-old jimpy animals were essentially the same as controls. In 14-day-old animals, however, the content of GFAP mRNA in jimpy had increased dramatically, and was 3-fold greater than that found in normal animals. The levels of GFAP message remained significantly elevated above control values for the life of the animals, approximately 22-24 days. In contrast, no significant difference in GS mRNA content was detected between control and jimpy brain tissue. The results of this study indicated that increased accumulation of GFAP mRNA was significant component of reactive gliosis and that the mechanisms responsible for the induction of GFAP were dissociated from those that regulate GS expression.