Meeting Abstract

S2-2.3  Thursday, Jan. 3  The formation of the pharyngeal arches GRAHAM, A.; King’s College London, UK anthony.graham@kcl.ac.uk

A conserved feature of all vertebrate embryos is the presence of a series of bulges on the lateral surface of the head, the pharyngeal arches. These structures constitute an iterated series, with each arch forming a similar set of derivatives. Importantly, the development of the pharyngeal arches is complex as it involves interactions between disparate embryonic cell types: ectoderm, endoderm, mesoderm and neural crest. In the past it was believed that the neural crest played a key role in organising the pharyngeal arches but it is becoming increasingly apparent that the development of the pharyngeal series revolves around the pharyngeal endoderm. The segmentation of this tissue to form the pharyngeal pouches is central to the generation of the arches. The pharyngeal endoderm also provides positional cues for the neural crest, and is involved in the induction of a number of components of the pharyngeal arches. The segmentation of the pharyngeal endoderm would have been key to the evolution of pharyngeal gill slits, and it is likely that endodermal segmentation is a deuterostome characteristic and that this basic pattern was sequentially modified and over time the more complex pharyngeal arches of vertebrates emerged.