Cleft lip (CL) or Cleft lip/palate (CL/P) occurs in about 1 in 700 live births, and while they are treatable, many individuals with these types of deformities will require lifelong care. Both of these conditions are the result of failures of the facial prominences to fuse during embryogenesis. CL and CL/P can occur as a single deformity or as part of a syndrome. Branchio-Occulo-Facial Syndrome (BOFS), for example, presents with facial clefting, ear and eye deformities and has been linked to mutations in the gene TFAP2A, encoding transcription factor AP-2?. One mouse model of this disease employs a null allele in combination with a hypomorphic or "weak" allele of AP-2?, creating a partial loss of AP-2? function. These mice develop a fully penetrant bilateral CL/P and our preliminary data suggest that it is small changes in growth and/or morphogenesis of the facial prominences that are responsible for failed fusion. Molecular analysis of this model shows increased expression of genes involved in Fgf signaling. Further, the loss of a single fgf8 allele in these mice is able to partially rescue the bilateral CL/P seen in the AP-2? hypomorphic mice to a unilateral CL/P. I, therefore hypothesize that AP-2? and FGF8 are elements of the same pathway during normal facial development and loss or mutation of AP-2? can affect the signaling interactions required for facial development. We will test this hypothesis by examining shape, gene expression and function in a mouse model that overexpresses FGF8 in the facial ectoderm and comparing this model to our AP-2 model. This proposal will generate shape data using 3D imaging and morphometrics. With this data we will be able to compare shape between the FGF8 overexpression model to the AP-2? hypomorphic mutation model and determine if these two genes are affecting development in the same manner during development. The gene expression data will allow us to 1) correlate shape change with gene expression, cell proliferation and death changes, allowing identification of pathways and mechanisms that may be causative of the growth changes. 2) The expression data will allow comparison of the two models on a molecular level to determine if they are affecting the same downstream targets, and thus, acting within the same pathway. Based on this data, we hope be able to build out how this pathway is interacting with other established facial development pathways to determine the overall facial gene regulatory network for facial development.
Cleft lip (CL) or Cleft lip/palate (CL/P) occurs in about 1 in 700 live births, and while they are treatable, many individuals with these types of deformities will require lifelong care. This proposal aims to increase our understanding of the underlying genetic and molecular causes of cleft lip and cleft palate and how different genes interact during the process of facial development. A more thorough understanding of the etiology of these disorders will help lead to better diagnostics and possibly treatments.
|Xu, Qiuping; Jamniczky, Heather; Hu, Diane et al. (2015) Correlations Between the Morphology of Sonic Hedgehog Expression Domains and Embryonic Craniofacial Shape. Evol Biol 42:379-386|
|Green, Rebecca M; Feng, Weiguo; Phang, Tzulip et al. (2015) Tfap2a-dependent changes in mouse facial morphology result in clefting that can be ameliorated by a reduction in Fgf8 gene dosage. Dis Model Mech 8:31-43|