MOLECULAR-BIOLOGY OF PITUITARY DEVELOPMENT AND DISEASE

The major endocrine cell types of the anterior and intermediate pituit ary arise in sequential order during development. Our laboratory seeks to understand the molecular basis for different lineages among these cell types. Previous data from our group and others have shown that th e POU-domain factor, Pit-1, and the orphan nuclear receptor, SF-1, are critical in the specification and maintenance of these cell types. Th e analysis of naturally occurring mutations revealed that Pit-1 is nee ded for development of three cell types, the thyrotropes (thyroid-stim ulating hormone), somatotropes (growth hormone), and lactotropes (prol actin). Recently, a genetically engineered mouse mutant demonstrated t hat SF-1 is required for the maintenance of the gonadotrope (luteinizi ng hormone/follicle-stimulating hormone) cellular phenotype. To date, a similar factor for the corticotrope and melanotrope lineages express ing propiomelanocortin (POMC) has not been identified. Surprisingly, t he serotonin (5-HT) neurotransmitter receptor 5-HT3 was found to be ex pressed in the anterior and intermediate lobes of the developing roden t pituitary. We are using this new marker to examine the molecular bas is of the POMC lineages.