Development Genes and Evolution

, Volume 211, Issue 11, pp 533–544 | Cite as

Structure and expression of an Otx5-related gene in the dogfish Scyliorhinus canicula: evidence for a conserved role of Otx5 and Crx genes in the specification of photoreceptors

  •  T. Sauka-Spengler
  •  B. Baratte
  •  D. Shi
  •  S. Mazan
Original Article

Abstract.

We report the full-length coding sequence and the expression pattern during neurulation and early organogenesis of ScOtx5, a novel member of the Otx gene family in the dogfish Scyliorhinus canicula. Phylogenetic analyses confirm that ScOtx5 is closely related to the XenopusXlOtx5/5b genes, and also to the Crx genes characterized in mammals and zebrafish. This supports the hypothesis that these genes define a third gnathostome Otx orthology class. During neurulation, ScOtx5 transcripts are detected in the foregut diverticulum and the anterior neuroectoderm. At the onset of organogenesis, ScOtx5 is transcribed over a broad domain spanning the whole prosencephalon and mesencephalon, albeit with a much lower signal intensity than its paralogues Otx1 and Otx2. At later stages, four major expression sites are observed: the developing eye and epiphysis, the olfactory placodes and a broad epidermal domain in the dorsal part of the head. In the embryonic eye, the signal is first detected in the presumptive pigmented retina and slightly later in the adjacent outer layer of the neural retina, fated to photoreceptors. The comparison of this expression pattern with those of osteichthyan Otx genes suggests that a role in the specification of photoreceptors may correspond to a functional specialization of Otx5 and Crx genes, fixed early in the gnathostome lineage, prior to the splitting of chondrichthyans and osteichthyans. In contrast, the roles played by ScOtx5 in the retinal pigmented epithelium or in the olfactory placodes may be fulfilled by different combinations of paralogous genes in other gnathostome taxa.

Otx5 Crx Dogfish Photoreceptor specification Multigene family 

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Copyright information

© Springer-Verlag 2001

Authors and Affiliations

  •  T. Sauka-Spengler
    • 1
  •  B. Baratte
    • 2
  •  D. Shi
    • 3
  •  S. Mazan
    • 1
  1. 1.Equipe Développement et Evolution des Vertébrés, UPRES-A 8080, Université Paris-Sud, 91405 Orsay, France
  2. 2.Station Biologique de Roscoff, Place George Teissier, BP 74, 29682 Roscoff, France
  3. 3.Groupe de Biologie Expérimentale, Laboratoire de Biologie Moléculaire et Cellulaire du Développement, CNRS UMR 7622, Université Pierre et Marie Curie, 75005 Paris, France

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