1. Department of Biology, University of Maryland, College Park, Maryland 20742, USA
2. Present address: Evolutionary Anatomy Unit, Department of Anatomy & Developmental Biology, University College London, Gower Street, London WC1E 6BT, UK

Correspondence to: William R. Jeffery¹ Email: jeffery@umd.edu
The EtZic DNA sequence has been deposited in GenBank under accession number AY176563.

Abstract

The neural crest, a source of many different cell types in vertebrate embryos, has not been identified in other chordates^{1, 2, 3}. Current opinion therefore holds that neural crest cells were a vertebrate innovation^{4, 5, 6, 7}. Here we describe a migratory cell population resembling neural crest cells in the ascidian urochordate Ecteinascidia turbinata. Labelling of embryos and larvae with the vital lipophilic dye DiI enabled us to detect cells that emerge from the neural tube, migrate into the body wall and siphon primordia, and subsequently differentiate as pigment cells. These cells express HNK-1 antigen and Zic gene markers of vertebrate neural crest cells. The results suggest that migratory cells with some of the features of neural crest cells are present in the urochordates. Thus, we propose a hypothesis for neural crest evolution beginning with the release of migratory cells from the CNS to produce body pigmentation in the common ancestor of the urochordates and vertebrates. These cells may have gained additional functions or were joined by other cell types to generate the variety of derivatives typical of the vertebrate neural crest.

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