LOCALIZED DEPOSITION OF M-CADHERIN IN THE GLOMERULI OF THE GRANULAR LAYER DURING THE POSTNATAL-DEVELOPMENT OF MOUSE CEREBELLUM

M-cadherin is a Ca2+-dependent cell adhesion molecule of the cadherin family, initially localized at the areas of contact between myotubes d uring myogenesis, but also detected in the peripheral nerve and at the adult neuromuscular junction. In this study, searching for the expres sion of M-cadherin in the adult mouse brain, we observed a restricted expression of M-cadherin in one of the three layers of the cerebellar cortex: the granular layer. M-cadherin was accumulated in structures r ich in synapses and other intercellular junctions where messy fibers c onnect granule cell dendrites, the glomeruli. This molecule was not ex pressed in the cerebellum during the first steps of postnatal cerebell ar neurogenesis: granule cell proliferation and migration and Purkinje cell alignment. M-cadherin expression was first detected at postnatal day (P)11, after the establishment of the synaptic connections betwee n messy fibers and granule cell dendrites. It then accumulated in glom eruli during their phase of maturation which is characterized by the f ormation of puncta adherentia between granule cell dendrites. M-cadher in was undetectable in the cerebella of the weaver and staggerer mutan ts, lacking granule cells, and therefore mature glomeruli and puncta a dherentia. Furthermore, other components classically associated with i ntercellular junctions, i.e., alpha-caterin, beta-catenin and actin fi laments, closely paralleled M-cadherin appearance and colocalized with M-cadherin in the mature glomeruli. M-cadherin, which appears as a mo lecular marker of glomerulus maturation, might be implicated in the fo rmation, and be the ligand, of adherens junctions encountered in this structure. (C) 1997 Wiley-Liss, Inc.