Developmental changes of synaptojanin expression in the human cerebrum andcerebellum

Synaptojanin is a highly abundant polyphosphoinositide phosphatase in nerve terminals, and has been thought to play roles in clathrin-mediated synapti c vesicle endocytosis and signaling. In order to determine the broader role of synaptojanin in the central nervous system, we examined synaptojanin ex pression in the cerebrum and cerebellum from the fetal to the adult period by means of immunohistochemical and Western blot analyses. Immunohistochemi stry consistently revealed the localization of synaptojanin in Cajal-Retziu s cells, cortical plate neurons, subplate neurons, intermediate neurons, ge rminal matrix cells and the ventricular neuroepithelium of the fetal cerebr um. In the fetal cerebellum, synaptojanin immunoreactivity was localized in the external granular cell layer, Purkinje cell layer neuropil, cytoplasm of Purkinje cells and internal granular cells. The immunoreactivity in thes e structures was decreased around birth. After birth, the synaptojanin immu noreactivity of cortical neurons in the cerebrum, Purkinje cell layer neuro pil, and internal granular cells and Purkinje cells in the cerebellum incre ased and reached a plateau after 11 years of age. These results were consis tent with the intensity observed on Western blot analysis. These developmen tal changes of synaptojanin suggest a broader role in not only synaptic ves icle recycling, but also the regulation of neuronal migration and synaptoge nesis in the fetal cerebrum and cerebellum. (C) 2001 Elsevier Science B.V. All rights reserved.