Journal of Neuroscience, Vol 13, 1387-1402, Copyright © 1993 by Society for Neuroscience
Clonal patterns of cell proliferation, migration, and dispersal in the brainstem of the chicken embryo
SG Hemond and JC Glover
Department of Physiology, University of Oslo, Norway.
Retroviral-mediated gene transfer was used to study clonal patterns of
proliferation, migration, and dispersal in the brainstem of the chicken
embryo. Clones were generated at stages 13-17 (Hamburger and Hamilton,
1951), a period of neurogenesis in the brainstem neural tube subsequent to
the formation of rhombomeres. Clones were examined in separate experiments
at stages 24-27, when many neurons migrate and differentiate; at stages
28-29, when brainstem nuclei begin to form; and at stages 34-35, when
brainstem nuclei are fully formed. Stages 24- 29 are characterized by a
general variability in proliferative kinetics and migratory behavior. Clone
sizes range from 1 to 29 cells, and migration patterns range from strictly
radial (i.e., normal to the ventricular surface) to combined radial and
tangential (i.e., perpendicular to the radial component). There is,
however, an underlying systematic variation: (1) clones exhibiting
tangential migration contain on average more cells than clones exhibiting
only radial migration, and (2) the proportion of tangentially migrating
clones increases from medial to lateral. By stages 34-35 some individual
clones have apparently dispersed to disparate neuronal groups. The regional
diversity observed among clones suggests that position along the
mediolateral axis may determine the proliferative potential of progenitors
and the migratory behavior and subsequent dispersal of their descendants.