An intact Hox cluster. From ScienceDaily:
New research published in the journal genesis, by Kenneth Baughman, Dr. Eiichi Shoguchi, Professor Noriyuki Satoh of the Marine Genomics Unit at the Okinawa Institute of Science and Technology Graduate University, and collaborators from Australia, reports an intact Hox cluster in the Crown of Thorns starfish, Acanthaster planci. This surprising result contrasts with the relatively disorganized Hox cluster found in sea urchins, which are also echinoderms, classification of animals including starfish, sea lilies, and sea cucumbers. Stanford University Professor Christopher Lowe, who studies developmental biology in echinoderms, summarizes the paper: “The translocation of the Hox cluster in echinoderms has been a major red herring for understanding their evolution. It’s really good to have some hard data showing that some echinoderms exhibit some oddities that are not representative of all echinoderms.”
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Generally, the Hox cluster shows “colinearity,” in which gene order correlates with the location of expression, or the developmental stage of expression. “For example, anterior Hox genes are expressed in regions that are closer to the head of an embryo, and are expressed sooner during development, versus the posterior Hox genes,” explained Baughman. “Thus, we were surprised to see chordate-like Hox cluster organization in starfish, which have a radial body plan.” Echinoderms are classical model organisms for embryology, and more recently evo-devo. Baughman added, “Interacting with the speakers and students of theOIST Winter Course ‘Evolution of Complex Systems’ (OWECS) allowed me to appreciate the importance of finding an intact Hox cluster in starfish.”
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By the way, it is a pretty remarkable life form anyway.