Cerebral Cortex Advance Access originally published online on December 15, 2005
Cerebral Cortex 2006 16(11):1571-1583; doi:10.1093/cercor/bhj094
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In vivo Evidence for Radial Migration of Neurons by Long-Distance Somal Translocation in the Developing Ferret Visual Cortex
1 Systems Neurobiology Laboratory, The Salk Institute for Biological Studies, 10010 N. Torrey Pines Road, La Jolla, CA 92037, USA, 2 Laboratory of Genetics, The Salk Institute for Biological Studies, 10010 N. Torrey Pines Road, La Jolla, CA 92037, USA, 3 Current address: Instituto de Neurociencias de Alicante, Consejo Superior de Investigaciones Científicas, Universidad Miguel Hernández, Sant Joan d'Alacant, Spain
Address correspondence to Víctor Borrell, Instituto de Neurociencias de Alicante, Consejo Superior de Investigaciones Científicas, Universidad Miguel Hernández, 03550 Sant Joan d'Alacant, Spain. Email: vborrell{at}umh.es.
During the development of the cerebral cortex, neurons generated in the cortical ventricular zone migrate radially toward the marginal zone. Radially migrating neurons are thought to display 1 of 2 morphologies: cells with a long, pia-contacting, apical process utilized for somal translocation early in development, when the cortex is still relatively thin; or cells with a short leading process, abundant at late stages of corticogenesis when neurons need to travel for longer distances. In large convoluted brains, like those of many primates and carnivores, radially migrating neurons must travel distances up to several millimeters before reaching their final destination, often following curvilinear trajectories. Here we analyze modes and morphologies of radially migrating neurons in convoluted brains by studying the visual cortex of developing ferrets. We provide in vivo and in vitro evidence for the existence of late-born cortical neurons that migrate radially by long-distance somal translocation within a long apical process extended to the cortical plate, in contrast to the early somal translocation observed in rodents. Long-distance translocating neurons in the ferret show a discontinuous rhythm of migration, alternating periods of advance with periods of stall. Furthermore, by combining different labeling methods we find the simultaneous presence in the developing ferret cortex of long-distance translocating neurons and neurons migrating within a short leading process.
Key Words: adenovirus • cerebral cortex • DiI • electroporation • gyrus • neurogenesis • neuron tracing • radial glia • time lapse