Venugopalan Shankar R, Amen Melanie A, Wang Jianbo, Wong Leeyean, Cavender Adriana C, D'Souza Rena N, Akerlund Mikael, Brody Steve L, Hjalt Tord A, Amendt Brad A
Texas A&M Health Science Center, Institute of Biosciences and Technology, Houston, TX 77030, USA.
Hum Mol Genet. 2008 Dec 1;17(23):3643-54. doi: 10.1093/hmg/ddn258. Epub 2008 Aug 22.
Axenfeld-Rieger syndrome (ARS) patients with PITX2 point mutations exhibit a wide range of clinical features including mild craniofacial dysmorphism and dental anomalies. Identifying new PITX2 targets and transcriptional mechanisms are important to understand the molecular basis of these anomalies. Chromatin immunoprecipitation assays demonstrate PITX2 binding to the FoxJ1 promoter and PITX2C transgenic mouse fibroblasts and PITX2-transfected cells have increased endogenous FoxJ1 expression. FoxJ1 is expressed at embryonic day 14.5 (E14.5) in early tooth germs, then down-regulated from E15.5-E17.5 and re-expressed in the inner enamel epithelium, oral epithelium, tongue epithelium, sub-mandibular salivary gland and hair follicles during E18.5 and neonate day 1. FoxJ1 and Pitx2 exhibit overlapping expression patterns in the dental and oral epithelium. PITX2 activates the FoxJ1 promoter and, Lef-1 and beta-catenin interact with PITX2 to synergistically regulate the FoxJ1 promoter. FoxJ1 physically interacts with the PITX2 homeodomain to synergistically regulate FoxJ1, providing a positive feedback mechanism for FoxJ1 expression. Furthermore, FoxJ1, PITX2, Lef-1 and beta-catenin act in concert to activate the FoxJ1 promoter. The PITX2 T68P ARS mutant protein physically interacts with FoxJ1; however, it cannot activate the FoxJ1 promoter. These data indicate a mechanism for the activity of the ARS mutant proteins in specific cell types and provides a basis for craniofacial/ tooth anomalies observed in these patients. These data reveal novel transcriptional mechanisms of FoxJ1 and demonstrate a new role of FoxJ1 in oro-facial morphogenesis.
携带PITX2点突变的Axenfeld-Rieger综合征（ARS）患者表现出广泛的临床特征，包括轻度颅面畸形和牙齿异常。确定新的PITX2靶点和转录机制对于理解这些异常的分子基础至关重要。染色质免疫沉淀分析表明PITX2与FoxJ1启动子结合，PITX2C转基因小鼠成纤维细胞和转染PITX2的细胞内源性FoxJ1表达增加。FoxJ1在胚胎第14.5天（E14.5）的早期牙胚中表达，然后在E15.5 - E17.5期间下调，并在E18.5和出生后第1天在成釉器内层上皮、口腔上皮、舌上皮、下颌下唾液腺和毛囊中重新表达。FoxJ1和Pitx2在牙齿和口腔上皮中表现出重叠的表达模式。PITX2激活FoxJ1启动子，Lef-1和β-连环蛋白与PITX2相互作用以协同调节FoxJ1启动子。FoxJ1与PITX2同源结构域发生物理相互作用以协同调节FoxJ1，为FoxJ1表达提供正反馈机制。此外，FoxJ1、PITX2、Lef-1和β-连环蛋白共同作用激活FoxJ1启动子。PITX2 T68P ARS突变蛋白与FoxJ1发生物理相互作用；然而，它不能激活FoxJ1启动子。这些数据表明了ARS突变蛋白在特定细胞类型中的作用机制，并为这些患者中观察到的颅面/牙齿异常提供了基础。这些数据揭示了FoxJ1新的转录机制，并证明了FoxJ1在口腔面部形态发生中的新作用。
