Vertebrate craniofacial development: novel approaches and new dilemmas

Unexpected patterns of neuroblast, angioblast and myoblast movement and tissue organization have been defined using lineage tracing and transplantation methods. The most novel and enigmatic new data derive from analyses of genes in the Hox - and Pax -gene families. In addition to the characterization of expression patterns, the effects of Hox -gene knock-out and retinoic acid treatment have been assessed. These basic studies are complemented by the identification of correlations between inherited craniofacial anomalies, for example Waardenburg's syndrome, and the function of specific genes.