Effects of vitamin A and other retinoids on the differentiation and morphogenesis of the integument and limbs of vertebrates

Abstract

Exogenous vitamin A is a well-known teratogen and modifies the course of cell differentiation, embryonic development, and morphogenesis. Recent evidence has shown that vitamin A and related compounds (the "retinoids") are likely natural morphogens, carrying out important roles in such processes as limb development and epithelial differentiation. Retinoids can modify the differentiation of individual cells and can induce specific modifications of morphogenesis in such structures as epithelial appendages, developing limbs, and regenerating limbs. Evidence is accumulating that there may be a common mechanism of action underlying these diverse phenomena. Retinoids may enter cells and induce changes in gene transcription in a manner similar to that reported for steroid and thyroid hormones and their receptors. Retinoids are particularly useful probes in the study of cell differentiation and morphogenesis because an understanding of their action can provide clues to the mechanisms involved in the complex processes of normal differentiation, morphogenesis, and pattern regulation.