CAN GONADAL-STEROIDS INFLUENCE CELL POSITION IN THE DEVELOPING BRAIN

The preoptic area/anterior hypothalamus (POA/AH) is a site where hormo nes dramatically influence development. The POA/AH is comprised of mul tiple subgroups, but little is known about the derivation of these sub groups during development. Results from several laboratories suggest t hat some cells in the POA/AH originate from progenitor cells in other regions of the developing nervous system. We are exploring pathways fo r migration in the developing POA/AH in two ways. First, we are examin ing the distribution of radial glial processes as potential migratory guides using immunocytochemistry. We have identified a transient patte rn of radial glial processes from the lateral ventricles to the pial s urface at the base of the POA/AH. Additionally, the expression of a mo lecule in radial glial processes originating in the third ventricle wa s decreased by prenatal treatment with testosterone. Second, we are ut ilizing time-lapse video microscopy in vitro to assess the extent and direction of movements of fluorescent dye-labeled cells at different a ges in brain slice preparations from the POA/AH of developing rats. Da ta from these studies indicate that cell migration in the POA/AH inclu des movements along dorsal-ventral routes and from lateral to medial p ositions, in addition to the predicted medial to lateral pathway away from the third ventricle. Several researchers have examined effects of gonadal steroids on neurite outgrowth, cell differentiation, cell dea th, and synaptogenesis. The determination of cell position, however, m ay be a key event influenced by gonadal steroids earlier in developmen t. The characterization of migratory pathways that contribute to perma nent changes in brain structure and ultimately function is essential f or unraveling the process of sexual differentiation. (C) 1994 Academic Press, Inc.