title: Retinoic acid signalling centres in the avian embryo identified by sites of expression of synthesising and catabolising enzymes.
abstract: Retinoic acid is an important signalling molecule in the developing embryo, but its precise distribution throughout development is very difficult to determine by available techniques. Examining the distribution of the enzymes by which it is synthesised by using in situ hybridisation is an alternative strategy. Here, we describe the distribution of three retinoic acid synthesising enzymes and one retinoic acid catabolic enzyme during the early stages of chick embryogenesis with the intention of identifying localized retinoic acid signalling regions. The enzymes involved are Raldh1, Raldh2, Raldh3, and Cyp26A1. Although some of these distributions have been described before, here we assemble them all in one species and several novel sites of enzyme expression are identified, including Hensen's node, the cardiac endoderm, the presumptive pancreatic endoderm, and the dorsal lens. This study emphasizes the dynamic pattern of expression of the enzymes that control the availability of retinoic acid as well as the role that retinoic acid plays in the development of many regions of the embryo throughout embryogenesis. This strategy provides a basis for understanding the phenotypes of retinoic acid teratology and retinoic acid-deficiency syndromes.
authors.affiliation: MRC Centre for Developmental Neurobiology, King's College London, Guy's Campus, London Bridge, London, United Kingdom.
authors.forename: Aida
authors.initials: A
authors.lastname: Blentic
authors.forename: Emily
authors.initials: E
authors.lastname: Gale
authors.forename: Malcolm
authors.initials: M
authors.lastname: Maden
mesh_terms: D000445:Aldehyde Oxidoreductases / Q000235:genetics / Q000378:metabolism*; D000818:Animals; D002642:Chick Embryo / Q000033:anatomy & histology / Q000502:physiology*; D003577:Cytochrome P-450 Enzyme System / Q000235:genetics / Q000378:metabolism*; D004628:Embryonic Structures / Q000033:anatomy & histology / Q000502:physiology; D018507:Gene Expression Regulation, Developmental; D017403:In Situ Hybridization; D051379:Mice; D009024:Morphogenesis / Q000502:physiology; D050697:Retinal Dehydrogenase; D000072516:Retinoic Acid 4-Hydroxylase; D015398:Signal Transduction / Q000502:physiology*; D014212:Tretinoin / Q000378:metabolism*
chemical_list: D014212:Tretinoin; D003577:Cytochrome P-450 Enzyme System; C000607080:Cyp26a1 protein, mouse; D000072516:Retinoic Acid 4-Hydroxylase; D000445:Aldehyde Oxidoreductases; D050697:Retinal Dehydrogenase