Identification of definitive and fetal zone markers in the human fetal adrenal gland reveals putative developmental genes.

Organogenesis is a coordinated process involving cell replication, differentiation, adhesion, and migration. We seek to understand the complex developmental signals involved in the ontogeny of the human fetal adrenal gland. The gland is comprised initially of two zones, the definitive and fetal zones. A third zone, the transitional zone, develops between them after midgestation. We have suggested that the definitive zone is comprised of a pool of progenitor cells that proliferate and differentiate into cells of the transitional and fetal zones. However, it has not been possible to demonstrate that definitive zone cells have this capacity because of the absence of protein markers unique to these cells; thus, they could not be purified or positively identified. We sought to identify definitive and fetal zone markers to facilitate cell sorting and identify molecules of biological interest in adrenal development. We performed subtractive hybridization, in situ hybridization, and immunofluorescence to identify unique markers of definitive zone cells. NovH and metallopanstimulin were identified by subtraction hybridization, primarily in the definitive zone. P-Glycoprotein, also principally on definitive zone cells, and the low density lipoprotein (LDL) receptor, predominantly on fetal zone cells, were identified by immunofluorescence. Identification of cellular markers unique to each zone of the fetal adrenal gland will enhance the ability to characterize the proliferative potential of definitive zone cells and assess their capacity to differentiate into cells of the transitional and fetal zones. Purified cells also will permit detailed molecular and mechanistic studies of regulation of human fetal adrenal development.