Congenital anomalies of the craniofacial skeleton represent a major public health problem throughout the world. It is estimated that one in every 10,000 live births is afflicted by a craniofacial defect at great cost to the public as a result of the necessary repair and rehabilitation, as well as long term disability. Despite the obvious medical importance of craniofacial disease, the molecular genetic mechanisms underlying development of the craniofacial skeleton are poorly understood. This paucity of knowledge of the genetic basis of normal and pathologic craniofacial development severely impairs any hopes for successful therapeutic intervention. The applicant's laboratory is dedicated to elucidating the genetic mechanisms regulating the transition from an undifferentiated brachial arch mesenchyme to the intricately patterned cranial skeleton. the experimental approaches are heavily weighed towards utilizing transgenic and gene-targeted mice as a model system. In the first specific aim , the developmental progression of genetically manipulated embryonic stem cells will be studied in the context of wild type cells in genetically mosaic mouse embryos. The second specific aim will use a combination of tissue recombination and organ culture studies to understand the cellular basis of abnormal craniofacial skeletal organogenesis in a gene targeted mouse model. Finally, the last specific aim proposes to study the transcriptional regulation of a transgene which is expressed in a region specific fashion within the first branchial arch mesenchyme of transgenic mouse embryos. The knowledge obtained from this research program will include information about the fundamental cellular processes regulated by a pair-related homeobox gene which the applicant has previously demonstrated to be required for normal craniofacial development an a gene targeted mouse model. The proposed experiments will probe whether this homeobox gene impacts upon such cellular events as programmed cell death and region specific proliferation within the craniofacial mesenchyme. Other questions addressed include the role of this homeobox gene in regulating the expression of growth factors in the craniofacial primordia. The last aim focuses upon genetic mechanisms of region specific gene expression within the first branchial arch mesenchyme. In summary, this research proposal is relevant to human disease because it will provide information about the basic development events which control craniofacial formation in higher vertebrates. In addition, this research proposal will also provide insight into the molecular mechanisms underlying congenital anomalies which is a necessary prerequisite for therapy.
