Evolution of a Core Gene Network for Skeletogenesis in Chordates: ”
by Jochen Hecht, Sigmar Stricker, Ulrike Wiecha, Asita Stiege, Georgia Panopoulou, Lars Podsiadlowski, Albert J. Poustka, Christoph Dieterich, Siegfried Ehrich, Julia Suvorova, Stefan Mundlos, Volkhard Seitz
Author Summary
Important molecular mechanisms underlying mammalian skeletogenesis have been described but knowledge about the evolutionary origin of these gene networks is limited. The Runt gene family (Runx1–3) is of extraordinary importance for skeletogenesis. Runx2 deficient mice completely lack bone. Runx2 and Runx3 are essential for cartilage development and Runx2 regulates the key factor Indian hedgehog, which coordinates skeletogenesis. Here, we reconstructed Runt gene evolution in correlation to skeletal evolution. By analyzing lancelets, one of the closest living relatives of vertebrates, we revealed that the single Runt and Hedgehog family founder genes were co-expressed in primitive skeletal elements of the chordate stem species. Interestingly, at this stage the Runt and Hedgehog pathways were already directly linked to one another. Furthermore we isolated two Runt genes from a representative of jawless cartilaginous fish (hagfish) and three Runt genes from jawed cartilaginous fish (dogfish) which were all expressed in cartilage. The dogfish Runt genes were also found in teeth and placoid scales. This study suggests that Runt genes were involved in all ancient processes of chordate skeletogenesis. Furthermore the analysis supports the theory that most likely the gut was the tissue that originally secreted an acellular gill gut skeleton in the chordate ancestor.
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(Via PLoS Genetics: New Articles.)
