The dopamine-synthesizing cells in the swimming larva of the tunicate Ciona intestinalis are located only in the hypothalamus-related domain of the sensory vesicle

Authors

  • Frédéric Moret,

    1. ‘Development, Evolution, Plasticity of the Nervous System’, UPR 2197, Institut de Neurobiologie Alfred Fessard, C.N.R.S., 1, ave de la Terrasse, F-91198 Gif-sur-Yvette, France
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  • Lionel Christiaen,

    1. ‘Development, Evolution, Plasticity of the Nervous System’, UPR 2197, Institut de Neurobiologie Alfred Fessard, C.N.R.S., 1, ave de la Terrasse, F-91198 Gif-sur-Yvette, France
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  • Carole Deyts,

    1. ‘Development, Evolution, Plasticity of the Nervous System’, UPR 2197, Institut de Neurobiologie Alfred Fessard, C.N.R.S., 1, ave de la Terrasse, F-91198 Gif-sur-Yvette, France
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  • Maryline Blin,

    1. ‘Development, Evolution, Plasticity of the Nervous System’, UPR 2197, Institut de Neurobiologie Alfred Fessard, C.N.R.S., 1, ave de la Terrasse, F-91198 Gif-sur-Yvette, France
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  • Jean-Stéphane Joly,

    1. ‘Development, Evolution, Plasticity of the Nervous System’, UPR 2197, Institut de Neurobiologie Alfred Fessard, C.N.R.S., 1, ave de la Terrasse, F-91198 Gif-sur-Yvette, France
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  • Philippe Vernier

    1. ‘Development, Evolution, Plasticity of the Nervous System’, UPR 2197, Institut de Neurobiologie Alfred Fessard, C.N.R.S., 1, ave de la Terrasse, F-91198 Gif-sur-Yvette, France
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  • *

    Present address: CGMC UMR 5534, Bat Mendel, 43 Bd du 11 novembre 1918, F-69622 Villeurbanne, France.

Dr F. Moret, at *present address below, or Dr P. Vernier, as above.
E-mail: moret@cgmc.univ-lyon1.fr or vernier@iaf.cnrs-gif.fr

Abstract

Dopamine is a major neuromodulator synthesized by numerous cell populations in the vertebrate forebrain and midbrain. Owing to the simple organization of its larval nervous system, ascidian tunicates provide a useful model to investigate the anatomy, neurogenesis and differentiation of the dopaminergic neural network underlying the stereotypical swimming behaviour of its chordate-type larva. This study provides a high-resolution cellular analysis of tyrosine hydroxylase (TH)-positive and dopamine-positive cells in Ciona intestinalis embryos and larvae. Dopamine cells are present only in the sensory vesicle of the Ciona larval brain, which may be an ancestral chordate feature. The dopamine-positive cells of the ascidian sensory vesicle are located in the expression domain of homologues of vertebrate hypothalamic markers. We show here that the larval coronet cells also arise from this domain. As a similar association between coronet cells and the hypothalamus was reported in bony and cartilaginous fishes, we propose that part of the ascidian ventral sensory vesicle is the remnant of a proto-hypothalamus that may have been present in the chordate ancestor. As dopaminergic cells are specified in the hypothalamus in all vertebrates, we suggest that the mechanisms of dopamine cell specification are conserved in the hypothalamus of Ciona and vertebrates. To test this hypothesis, we have identified new candidate regulators of dopaminergic specification in Ciona based on their expression patterns, which can now be compared with those in vertebrates.

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