Developmental expression and localization of glycogen synthase kinase-3 beta in rat brain

Glycogen synthase kinase (GSK)-3 beta is a protein kinase in the wingless/w nt pathway and as such is involved in the regulation of growth and developm ent of the neural tissue in Drosophila and in vertebrates. This enzyme is a lso abundantly expressed in the mammal adult brain, where it might play a r ole in the regulation of several substrates. The expression and the neuroan atomical distribution of GSK-3 beta immunoreactivity in the rat brain from embryonic up to adult stages has been studied. GSK-3 beta was expressed in the developing brain with the highest expression observed from 18 days of e mbryonic life up to 10 days of postnatal life. Its expression decreased the reafter and was lowest in the adult. GSK-3 beta was strongly expressed in d eveloping neurons but only weakly expressed in layers containing neuroblast s. In the adult and during development, GSK-3 beta was detected in the peri carya and proximal part of dendrites. In the embryo, an intense GSK-3 beta immunoreactivity was also observed in axonal tracts. This axonal immunoreac tivity had markedly decreased by 10 days of postnatal life and was absent a t 20 days of postnatal life and in the adult. No GSK3 beta immunoreactivity was detected in astrocytes. The GSK-3 beta immunoreactivity was found in m ost brain regions, although significant local variations of GSK3 beta expre ssion were observed. The developmental evolution of GSK-3 beta compartmenta lization in neurons parallels that of phosphorylated tau, a protein conside red to be a physiological substrate for the kinase. (C) 1999 Elsevier Scien ce B.V. All rights reserved.