PROJECT SUMMARY The overall goal of this Application is to improve our understanding of the genetic and molecular control of adrenal gland homeostasis by studying how osteocalcin originating from maternal skeleton, affects adrenal growth and steroidogenesis of the offspring during development and after birth. Specifically we intend to 1] Establish that maternal Ocn is necessary for proper adrenal gland development and function. We will also 2] Establish genetically and in vivo that osteocalcin favors adrenal gland growth and steroidogenesis by signalling directly in the adrenal cortices through its receptor Gpr158. A third purpose of this application is to determine with precision the temporal course of osteocalcin’s effect on the adrenal gland development/function and investigate how maternal osteocalcin affects this process in the offspring. We will use mouse genetic, molecular and biochemical assays to investigate the molecular bases of the cross-talk between bone and the adrenal gland through osteocalcin in the regulation of adrenal steroid production. Together, this application will significantly advance our understanding of adrenal development and physiology in bony vertebrates by describing a novel regulation of adrenal gland development and steroidogenesis, which originates from the mother and is biologically relevant since its absence can be lethal.