Accumulation of GFA, the monomeric precursor of the gliofilaments, during development in normal mice and dysmyelinating mutants

Astrocytic reactivity during the myelination period in the mouse was studied with immunochemical method, ie, quantitative determination of the soluble pool of the GFA protein. There is normally a maximum content at the time of early myelinogenesis in any structure; then the GFA level decreases and finally keeps constant for a long period during the adult life. This evolutive pattern is also observed in the dysmyelinating mutant quaking, with a permanent shift toward higher values especially in areas of earlier maturation. In the jimpy mutant, practically devoid of myelin, the increase of GFA occurs but does not stop until death, at 25 days postnatal. This study points out 1) the capacity of astrocytes to synthesize surprisingly high amounts of soluble GFA at periods of intense metabolic activity, and 2) the reactivity of astrocytes in relation to the degree of deficiency of the myelinating oligodendrocytes.