REAL chicken teeth

[Ken Kinman]

Dear All,
       Speaking of silenced genes, this week's publication on teeth in a chicken mutant is highly interesting.  These are real bird teeth, not laboratory-induced teeth from other vertebates (mice, etc.).  The developmental potential for teeth is still in the chicken genome itself.

       Minor mutations can occasionally cause major morphological change, sometimes even a cascade of related changes (although not always in the same part of the body).  While I appreciate John Grehan's efforts to warn us of the problems with reading too much into some gene sequences, one can also be led astray by attaching too much significance to certain morphological data sets as well.  I still believe his orang-human similarities are developmentally related, and claiming that they are independent does not make them so.  I've had similar conversations with theropod workers who claim their phylogenies have more synapomorphies than mine (as though quantity should trump quality).  It's not just a numbers game, and doubly so for dinosaurs because we don't have molecular data as an added test to detect homoplasy.  Clearly, we need to be more picky with BOTH our morphological data AND our molecular data!!!   One way to be able to do that more effectively in the future is to train a lot more developmental biologists.
   ----Ken Kinman
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Anyway, here's the citation to the chicken mutant paper.  Luckily, these mutants don't survive to adulthood (although that might be an interesting plot for a modern sequel to "The Birds").   ;-)

M.P. Harris, S.M. Hasso, M.W. J. Ferguson, and J.F. Fallon (February 2006).   The Development of Archosaurian First-Generation Teeth in a Chicken Mutant.  Current Biology, 16:371-377.

>From the summary:
 "The formation of teeth in the mutant is coupled with alterations in the specification of the oral/aboral boundary of the jaw.  We propose an epigenetic model of the developmental modification of dentition in avian evolution; in this model, changes in the relative position of a lateral signaling center over competent odontogenic mesenchyme led to loss of teeth in avians while maintaining tooth developmental potential."