Meeting Abstract
144.1 Monday, Jan. 7 Pattern and Polarity in the Development and Evolution of the Gnathostome Jaw: Both Conservation and Heterotopy in the Branchial Arches of the Shark, Scyliorhinus canicula DEPEW, M. J.*; COMPAGNUCCI, C.; FISH, J.; DEBIAIS, M.; COOLON, M.; BERTOCCHINI, F.; CASANE, D.; MAZAN, S.; UCSF; KCL; UCSF; CNRS; CNRS; Universidad de Cantabria; Universite ́ Paris Diderot; Station biologique de Roscoff michael.j.depew@gmail.com
The acquisition of jaws constitutes a landmark event in vertebrate evolution. Jaw development involves an intricate spatiotemporal series of reciprocal inductive and responsive interactions between the cephalic epithelia and mesenchyme. The coordinated regulation of these interactions is critical for both the ontogenetic registration of the jaws and the evolutionary elaboration of jaw morphology. A ‘Hinge and Caps’ model has been proposed that addresses the mechanisms of jaw development by placing the articulation, and subsequently the polarity, of the upper and lower jaws in the context of neural crest competence to respond to positionally located epithelial signals. This model has been built on evidence gathered mostly in amniotes and augmented by a much smaller data set on the zebrafish and Xenopus, as well as by work focused on the jawless lamprey. Chondrichthyans are the most basal extant gnathostomes, and comprise the crucial clade uniting aminiotes and aganthans; yet despite their critical phylogenetic position, evidence of the molecular and cellular underpinnings of jaw development in chondrichthyans is still lacking. Recent advances in genome and molecular developmental biology of the lesser spotted dogfish shark, Scyliorhinus canicula, make it ideal for the molecular study of chondrichthyan jaw development. Here, we have further examined the empirical foundation for the ‘Hinge and Caps’ model by investigating evidence of heterotopic (relative changes in position) and heterochronic (relative changes in timing) shifts in gene expression, relative to animotes such as mice, in the jaw primordia of S. canicula.
