Detection and Measurement of Retinoic Acid Production by Isolated Tissues Using Retinoic Acid-Sensitive Reporter Cell Lines

Retinoids are diffusible signaling molecules important for the normal development, growth, and physiology of vertebrate organisms A role for retinoids in early embryonic development has been suggested from studies in which exogenous retinoids were administered to developing vertebrate embryos _{in situ} . These treatments resulted in morphological alterations in a number of diverse tissues including craniofacial structures, limbs, the hindbrain of the central nervous system, and the vertebral column (1 –5 ). The nature and extent of these alterations were found to be influenced by the developmental stage at which retinoids were administered. Together, these observations led to the proposal that retinoids play a critical role in the patterning, organization, and growth of embryonic tissues Moreover, the ability of retinoids to carry out these functions appears to depend on their precise spatial and temporal distribution in embryos.