NETWORK OF TANGENTIAL PATHWAYS FOR NEURONAL MIGRATION IN ADULT MAMMALIAN BRAIN

Cells in the brains of adult mammals continue to proliferate in the su bventricular zone (SVZ) throughout the lateral wall of the lateral ven tricle, Here we show, using whole mount dissections of this wall from adult mice, that the SVZ is organized as an extensive network of chain s of neuronal precursors, These chains are immunopositive to the polys ialylated form of NCAM, a molecule present at sites of plasticity, and TuJ1, an early neuronal marker. The majority of the chains are orient ed along the rostrocaudal axis and many join the rostral migratory str eam that terminates in the olfactory bulb. Using focal microinjections of DiI and transplantation of SVZ cells carrying a neuron-specific re porter gene, we demonstrate that cells originating at different rostro caudal levels of the SVZ migrate rostrally and reach the olfactory bul b where they differentiate into neurons, Our results reveal an extensi ve network of pathways for the tangential chain migration of neuronal precursors throughout the lateral wall of the lateral ventricle in the adult mammalian brain.