Dynamics of chondroitin sulfotransferase expression for cranial motor neuron migration in rat hindbrain development

Abstract

The proper positioning of neurons for the establishment of functional connectivity of defined neural circuits relies on neuronal migration. We and others reported the restrictive role of chondroitin sulphate (CS) moieties of proteoglycans in axonal fasciculation. CS moieties are therefore hypothesized to regulate the timely orchestration of cranial motor neuron migration during hindbrain development by the differential sulfation patterns of the chondroitins between the migrating and ready-to-migrate neurons. Hindbrain explants of E11.5 Sprague Dawley rats were maintained in culture for time lapse video recording of individual neuronal somal movements. In control cultures, we observed the advancement of neuronal cell bodies in the direction of the leading process away from the explant core. In test cultures treated with chondroitinase ABC, the neuronal somata lost the direction movement but retained the motility. Immunocytochemistry confirmed the presence of CS56 epitopes among Tuj-1-positive neurons not only in the explant core and those advancing beyond the core, but also in the environments surrounding the migrating neuronal somata. Chondroitin-4-sulfotransferases 2 (C4ST2) showed relatively abundant mRNA expression among cells heading away from the core whereas chondroitin-4-sulfotransferase 1 (C4ST1) mRNA was found essentially in the centre of the explant by in situ hybridization. Thus far, the results suggest varying sulfation of chondroitins on proteoglycans expressed by neurons in determining the migratory phenotype.