The search for non-chordate retinoic acid signaling: lessons from chordates

Authors

  • Marcos S. Simões-costa,

    1. Laboratório de Genética e Cardiologia Molecular InCor—HC.FMUSP São Paulo-SP 05403-000, Brazil
    2. Departamento de Biologia Celular e do Desenvolvimento, ICB-USP, São Paulo-SP 05508-900, Brazil
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  • Ana Paula Azambuja,

    1. Laboratório de Genética e Cardiologia Molecular InCor—HC.FMUSP São Paulo-SP 05403-000, Brazil
    2. Departamento de Biologia Celular, Universidade Federal do Paraná, Curitiba-PR 81531-990, Brazil
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  • José Xavier-Neto

    Corresponding author
    1. Laboratório de Genética e Cardiologia Molecular InCor—HC.FMUSP São Paulo-SP 05403-000, Brazil
    • Laboratório de Genética e Cardiologia Molecular, Instituto do Coração—HCFMUSP, Av. Dr. Eneas Carvalho Aguiar, 44, Bloco II—10 Andar, 05403-000 São Paulo/SP, Brazil
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Abstract

Signaling by retinoic acid (RA) is an important pathway in the development and homeostasis of vertebrate and invertebrate chordates, with a critical role in mesoderm patterning. Classical studies on the distribution of nuclear receptors of animals suggested that the family of RA receptors (RARs/NR1B) was restricted to chordates, while the family of RA X receptors (RXR/NR2B) was distributed from cnidarians to chordates. However, the accumulation of data from genome projects and studies in non-model species is questioning this traditional view. Here we discuss the evidence for non-chordate RA signaling systems in the light of recent advances in our understanding of carotene (pro-Vitamin A) metabolism and of the identification of potential RARs and members of the NR1 family in echinoderms and lophotrochozoan trematodes, respectively. We conclude, as have others before (Bertrand et al., 2004. Mol Biol Evol 21(10):1923–1937), that signaling by RA is more likely an ancestral feature of bilaterians than a chordate innovation. J. Exp. Zool. (Mol. Dev. Evol.) 310B:54–72, 2008. © 2006 Wiley-Liss, Inc.

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