title: Differential distribution of retinoic acid synthesis in the chicken embryo as determined by immunolocalization of the retinoic acid synthetic enzyme, RALDH-2.
abstract: Retinaldehyde dehydrogenase type 2 (RALDH-2) is a major retinoic acid generating enzyme in the early embryo. Here we report the immunolocalization of this enzyme (RALDH-2-IR) in stage 6-29 chicken embryos; we also show that tissues that exhibit strong RALDH-2-IR in the embryo contain RALDH-2 and synthesize retinoic acid. RALDH-2-IR indicates dynamic and discrete patterns of retinoic acid synthesis in the embryo, particularly within the somitic mesoderm, lateral mesoderm, kidney, heart, and spinal motor neurons. Prior to somitogenesis, RALDH-2-IR is present in the paraxial mesoderm with a rostral boundary at the level of the presumptive first somite; as the somites form, they exhibit strong RALDH-2-IR. Cervical presomitic mesoderm exhibits RALDH-2-IR but thoracic presomitic mesoderm does not. Neural crest cells do not express detectable levels of RALDH-2, but migrating crest cells are associated with RALDH-2 expressing mesoderm. The developing limb mesoderm expresses little RALDH-2-IR; however, RALDH-2-IR is strongly expressed in tissues adjacent to the limb. The most lateral, earliest-projecting motor neurons at all levels of the spinal cord exhibit RALDH-2-IR. Subsequently, many additional motor neurons in the brachial and lumbar cord regions express RALDH-2-IR. Motor neuronal expression of RALDH-2-IR is present in the growing axons as they extend to the periphery, indicating a potential role of retinoic acid in nerve influences on peripheral differentiation. With the exception of a transient expression in the facial/vestibulocochlear nucleus, cranial motor neurons do not express detectable levels of RALDH-2-IR.
authors.affiliation: Department of Anatomy and Neurobiology, University of Vermont, Burlington, Vermont, 05405, USA.
authors.forename: K
authors.initials: K
authors.lastname: Berggren
authors.forename: P
authors.initials: P
authors.lastname: McCaffery
authors.forename: U
authors.initials: U
authors.lastname: Dräger
authors.forename: C J
authors.initials: CJ
authors.lastname: Forehand
mesh_terms: D000445:Aldehyde Oxidoreductases / Q000032:analysis / Q000235:genetics / Q000378:metabolism*; D000818:Animals; D001369:Axons / Q000201:enzymology; D019521:Body Patterning; D002642:Chick Embryo / Q000166:cytology / Q000201:enzymology / Q000502:physiology*; D003391:Cranial Nerves / Q000196:embryology / Q000201:enzymology; D005121:Extremities; D018507:Gene Expression Regulation, Developmental; D006321:Heart / Q000196:embryology; D007668:Kidney / Q000196:embryology / Q000201:enzymology; D008648:Mesoderm / Q000201:enzymology / Q000502:physiology; D051379:Mice; D009046:Motor Neurons / Q000201:enzymology; D009206:Myocardium / Q000201:enzymology; D009928:Organ Specificity; D050697:Retinal Dehydrogenase; D013116:Spinal Cord / Q000196:embryology / Q000201:enzymology; D014212:Tretinoin / Q000378:metabolism*
chemical_list: D014212:Tretinoin; D000445:Aldehyde Oxidoreductases; D050697:Retinal Dehydrogenase