Craniofacial abnormalities involving the first branchial arch derivatives, including the jaw, palate and teeth, are a major class of birth defects in humans. Understanding the molecular genetic mechanisms behind craniofacial development is vital to devising innovative methods for the diagnosis, prevention and treatment of human defects. The long-term goal of my research is to characterize the transcriptional network that governs development of the first branchial arch, by identifying transcription factors and cis-regulatory elements important in this process, and determining their hierarchical relationship. Previous gene expression analysis suggested that the Lhx6 and Lhxd genes, which encode homeodomain transcription factors, may be major regulators of first branchial arch development, but the functional evidence to support this idea was scarce. My preliminary analysis of mouse mutants lacking both Lhxd and Lhx8 activity indicates that they are essential for the normal development of the palate and teeth. Therefore, my short-term goal is to further define the function and regulation of Lhx6 and LhxS in the first branchial arch using the mouse mutant model, as well as biochemical and molecular biology methods.
The specific aims of this proposal are 1) To characterize the phenotypes of Lhx6-/-8-/- mouse mutants at the anatomical, cellular and molecular level. Based on my preliminary data, I will focus on the secondary palate and tooth development. 2): To identify downstream targets of Lhxd and LhxS using genome-wide, unbiased approaches which combine transcriptional profiling and chromatin-immunoprecipitation. I will compare gene expression in the wild type and Lhx6-/-;8-/- first branchial arch using microarray analysis. In addition, I will perform chromatinimmunoprecipitation followed by DMA chip analysis (ChlP-chip) using an Lhx6 antibody to identify direct target genes of Lhx6 and the cis-regulatory elements that Lhx6 acts upon. 3) To identify enhancer elements that control Lhxd and Lhxd expression in the first branchial arch. I will identify candidate enhancers based on the evolutionary conservation of sequences. I will verify their activity in chick neural crest electroporation system and transgenic mice. I will then use bioinformatic tools to identify candidate regulatory proteins for these enhancers for further analysis. *. The results of my research will provide critical information on how disruption in Lhxd and LhxS gene function and expression can contribute to human craniofacial defects. In addition, the results will significantly enhance our overall knowledge on gene expression regulation during craniofacial and dental development, and thus facilitate identification and understanding of genetic defects behind human craniofacial birth defects.
| Jeong, Juhee; Cesario, Jeffry; Zhao, Yangu et al. (2012) Cleft palate defect of Dlx1/2-/- mutant mice is caused by lack of vertical outgrowth in the posterior palate. Dev Dyn 241:1757-69 |
| Flandin, Pierre; Zhao, Yangu; Vogt, Daniel et al. (2011) Lhx6 and Lhx8 coordinately induce neuronal expression of Shh that controls the generation of interneuron progenitors. Neuron 70:939-50 |
