During early craniofacial development, cranial neural crest cells emigrate from seg-mentally distinct divisions of the hindbrain (rhombomeres) to populate the various branchial arches and subsequently differentiate into multiple neuronal and non-neu-ronal cell lineages of the head and neck region. Organ culture of the mandibular portion of the developing first branchial arch (1 ,2 ) facilitates investigations of molecular signaling events of crest cell differentiation during chondrogenesis, osteogenesis, odontogenesis, and myogenesis (3 -5 ). In addition, organs explanted in culture are assessable physically by microdissections, implantations, transplantations, and micro-injections, and can be readily manipulated by antisense oligonucleotides strategies, viral delivery, and immunoperturbation methodologies.
