COBOURNE, MT; Department of Craniofacial DevelopmentDevelopmental regulation of branchial arch patterning in the mouse: Developmental regulation of branchial arch patterning in the mouse

Mammalian jaws form a highly specialised apparatus ultimately derived from derivatives of the first branchial arch. In addition to the skeletal components of the mandible and maxilla, these structures also contain teeth of the mature dentition. In recent years, the use of mouse genetics has resulted in considerable progress in understanding molecular mechanisms responsible for generating these regionally diverse structures. Integral to development of the jaw skeleton are signalling interactions between first arch-derived ectoderm and the underlying neural crest-derived ectomesenchymal cells that migrate into these regions. Recent evidence has suggested that in the early mouse embryo, regionally restricted expression of homeobox-containing genes, are responsible for generating early polarity of the branchial arches and establishing the molecular foundations for patterning of the diverse skeletal elements generated by these regions. Teeth also develop on the first branchial arch and are derived from the ectoderm and underlying ectomesenchyme. Reciprocal signalling interactions between these cell populations also control the odontogenic developmental programme, from early patterning of the future dental axis to the initiation of tooth development at specific sites within the ectoderm. In particular, members of the Fgf, Bmp, Hedgehog and Wnt families of signalling molecules induce regionally restricted expression of downstream target genes. Finally, the processes of morphogenesis and cellular differentiation ultimately generate a tooth of specific class with a species-specific shape.