Neuronal migration and differentiation in the development of the mouse dorsal cochlear nucleus

The dorsal cochlear nucleus (DCN) of mammals displays a cortical structure containing a number of cell types organized into distinct layers, In the pr esent study, the migratory mode of large multipolar cells and granule cells as well as the morphological differentiation of the projection neurons wer e investigated in the development of the mouse DCN, The classification of t he DCN neurons followed that of Ryugo and Willard, The mode of neuronal mig ration was examined by immunohistochemical bromodeoxyuridine labeling, Larg e multipolar neurons originated from the primary rhombic lip and small gran ule cells from the secondary rhombic lip, Large multipolar neurons migrated radially from the ventricular zone into the forming DCN, Granule cells wer e generated later than the large multipolar neurons and migrated via the su bependymal and subpial routes, Large multipolar neurons and small granule c ells were thus segregated early in the DCN development and intermixed later during perinatal maturation, Projection neurons retrogradely labeled by Di I application to the contralateral inferior colliculus showed neurite exten sion between the pial surface and the ventricular zone during migration in the DCN primordium. The retrogradely labeled projection neurons showed a we ll-differentiated morphology of the large multipolar neurons as early as th e late embryonic stage, The arrangement of the radial glial processes coinc ided with that of the migratory projection neurons, The migratory immature neurons showed close apposition with the radial glial processes, suggesting that glial scaffolds are involved in the migration and settlement of the l arge multipolar neurons, Thus, it is suggested that the mode of migration a nd settlement of large multipolar neurons and granule cells in the developi ng DCN is highly similar to that of Purkinje and granule cell migration in the cerebellar development, based on the findings of this study and the str uctural similarity between the cerebellum and DCN.