Prenatal expression sf the GLUT4 glucose transporter in the mouse

The GLUT4 glucose transporter is primarily expressed in skeletal muscle, he art and adipose tissue, where its expression is postnatal, coincident with the acquisition of insulin-regulated glucose transport. In muscle, contract ion also regulates GLUT4 activity in the postnatal animal. Here we demonstr ate that GLUT4 is expressed in the developing mouse embryo with specific ti ssue and spatiotemporal patterns. From embryonic day 9 (E9; E1 = day of cop ulation plug) to postnatal day 70 (P70), mice were analyzed for GLUT4 mRNA and protein expression by in situ hybridization, immunohistochemistry and i mmunoblot. Specificity was confirmed with sense riboprobe hybridization and peptide competition, respectively. At E9, GLUT4 was detected in the crania l neural folds in the outer (mantle) layer of the neuroepithelium. At E10, expression was present throughout the developing heart and was prominent in the endocardial cushions through E12. At E10-12, GLUT4 was also prominent in craniofacial mesenchyme. GLUT4 expression in cartilage and bone was evid ent at E12 and was maintained throughout early postnatal life. GLUT4 was ap parent throughout embryonic development in the ventricular epithelium, chor oid plexus and in the developing cerebellum. At birth, cardiac expression w as reduced and GLUT4 was most evident in cartilage, bone and specific brain regions. In the latter, GLUT4 expression was most evident in the cerebellu m, specifically in the external granular layer through P7 and in the intern al granular layer thereafter. Maximal GLUT4 protein levels in the cerebellu m were measured between P14 and P21 and were reduced in the adult brain. Th ese findings suggest that GLUT4-mediated glucose transport may play importa nt roles during development of the brain and nonneuronal tissues in the mou se embryo. Copyright (C) 2000 S. Karger AG, Basel.