MOTILITY AND CYTOSKELETAL ORGANIZATION OF MIGRATING CEREBELLAR GRANULE NEURONS

To characterize CNS neuronal precursor migration along astroglial fibe rs, we examined the motility of the migratory leading process and cyto skeletal-based mechanisms of locomotion of early postnatal mouse cereb ellar granule neurons in vitro. To visualize the surface motility of t he leading process, granule neurons were labeled with the fluorescent lipophilic dye, PKH-26, and imaged by time lapse fluorescence microsco py. The motile behavior and cytoskeletal organization of the migrating neuron had several distinctive features. As the migrating neuron move d along the glial fiber, the leading process rapidly extended, project ing up to 40 mu m, and retracted, withdrawing towards the cell soma. B road lamellipodia were common along the entire length of the leading p rocess, giving it a ruffled appearance. Within the cell soma, a cage-l ike distribution of microtubules encircled the nucleus and actin filam ents formed a subcortical rim underneath the plasma membrane. Disrupti on of actin filaments with cytochalasin B inhibited migration, suggest ing involvement of actin subunit assembly in neuronal migration. Both microtubules and actin filaments were heavily concentrated in the lead ing process; the leading process did not show the development of a dis tinct actin-rich domain at its tip.