The expression of a caudal homologue in a mollusc, Patella vulgata

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Abstract

We cloned and analyzed the expression of a caudal homologue (PvuCdx) during the early development of the marine gastropod, Patella vulgata. PvuCdx is expressed at the onset of gastrulation in the ectodermal cells that constitute the posterior edge of the blastopore, as well as in the paired mesentoblasts, the stem cells that generate the posterior mesoderm of the trochophore larva. During larval stages, PvuCdx is expressed in the posterior neurectoderm of the larva, as well as in part of the mesoderm. This is the first report of the expression of a caudal gene in a lophotrochozoan species. The striking similarities with the expression of caudal in other organisms, such as chordates, suggest that a posterior expression of caudal is ancestral to Bilateria.

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Results and discussion

The caudal/Cdx genes encode Hox-related homeodomain proteins that are involved in the patterning along the antero-posterior (AP) axis. In Drosophila, caudal is expressed in the most posterior part of the body and is required for the specification of the most posterior segment, the analia, as well as for the formation of the hindgut (Wu and Lengyel, 1998, Moreno and Morata, 1999, Schulz and Tautz, 1995). Three caudal genes are known in vertebrates and are expressed, during gastrulation and

Materials and methods

Using degenerate primers, we amplified and cloned, from a staged cDNA library (16 h.p.f.c.), a fragment of a putative Patella caudal gene, we named PvuCdx. Vector anchored RACE PCR allowed the isolation, of a full-length cDNA of 1680 bp. The sequence has been submitted to the EMBL nucleotide databasis, the accession number is AJ518062. Embryo rearing and whole mount in situ hybdrization were performed as described elsewhere (Lespinet et al., 2002).

Acknowledgements

We thank André van Loon for making available the Patella vulgata cDNA library. This work has been supported by the CNRS, the Université Paris-Sud and the Ministère de la Recherche. We want to dedicate this article to the memory of André Adoutte who died during the course of this work.

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