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

Glycogen synthase kinase (GSK)-3 beta is a protein kinase in the wingless/wnt pathway and as such is involved in the regulation of growth and development of the neural tissue in Drosophila and in vertebrates. This enzyme is also abundantly expressed in the mammal adult brain, where it might play a role in the regulation of several substrates. The expression and the neuroanatomical 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 embryonic life up to 10 days of postnatal life. Its expression decreased thereafter and was lowest in the adult. GSK-3 beta was strongly expressed in developing neurons but only weakly expressed in layers containing neuroblasts. In the adult and during development, GSK-3 beta was detected in the pericarya and proximal part of dendrites. In the embryo, an intense GSK-3 beta immunoreactivity was also observed in axonal tracts. This axonal immunoreactivity had markedly decreased by 10 days of postnatal life and was absent at 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 most brain regions, although significant local variations of GSK3 beta expression were observed. The developmental evolution of GSK-3 beta compartmentalization in neurons parallels that of phosphorylated tau, a protein considered to be a physiological substrate for the kinase. (C) 1999 Elsevier Science B.V. All rights reserved.