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Dev Biol May 1, 2014; 389 (1): 82-97.

The evolutionary history of vertebrate cranial placodes--I: cell type evolution.

Patthey C , Schlosser G , Shimeld SM .

Vertebrate cranial placodes are crucial contributors to the vertebrate cranial sensory apparatus. Their evolutionary origin has attracted much attention from evolutionary and developmental biologists, yielding speculation and hypotheses concerning their putative homologues in other lineages and the developmental and genetic innovations that might have underlain their origin and diversification. In this article we first briefly review our current understanding of placode development and the cell types and structures they form. We next summarise previous hypotheses of placode evolution, discussing their strengths and caveats, before considering the evolutionary history of the various cell types that develop from placodes. In an accompanying review, we also further consider the evolution of ectodermal patterning. Drawing on data from vertebrates, tunicates, amphioxus, other bilaterians and cnidarians, we build these strands into a scenario of placode evolutionary history and of the genes, cells and developmental processes that underlie placode evolution and development.

PubMed ID: 24495912
Article link: Dev Biol

Species referenced: Xenopus laevis
Genes referenced: avp drgx eya1 isl1 pax2 pax5 pax6 pax8 phox2a phox2b pitx1 six1 six3 six4 six6 tbx2 tlx1 tlx3

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