CLONAL DISPERSION AND EVIDENCE FOR ASYMMETRIC CELL-DIVISION IN FERRETCORTEX

Cell lineage analysis with retroviral libraries suggests that clonal p rogeny disperse widely in rodent cortex. To determine whether widespre ad dispersion is a general mammalian plan and to investigate phylogene tic differences in cortical development, we analyzed cell lineage in t he ferret, a carnivore and near relative of the cat. The ferret posses ses a highly developed, folded cerebral cortex, characteristic of high er mammalian species. Progenitor cells of the ferret cerebral cortex w ere tagged with an amphotropic retroviral library encoding alkaline ph osphatase, and sibling relationships were determined using the polymer ase chain reaction. Neuronal clones were single neurons (52%) or large clones (48%; average, 7 neurons) containing neurons and glia in wides pread cortical locations. Neuronal clones in the ferret labeled at mid dle to late neurogenesis (embryonic day 33-35) contained large numbers of neurons and showed little tendency to cluster The large proportion of single neuron clones, contrasted with the large size of multicell clones, suggests that some progenitors divide asymmetrically, producin g a postmitotic neuron and regenerating a multipotential cell.