Shox2 and temporomandibular joint formation

摘要颞下颌关节强直在临床上被定义为受限的口。 由骨性或纤维性结合引起的，由骨性结合引起的 关节窝。尽管大多数TMJ强直事件发生在创伤或 感染，先天病例已有报道。目前，人们对TMJ知之甚少 形态发生及其潜在的遗传、细胞和分子机制。 特别是，对导致先天性TMJ的基因改变一无所知。 关节强直。同源异型盒基因Shox2在间充质细胞中特异表达 在上颌骨-下颌骨交界处，后来在未成熟的软骨细胞中 TMJ的髁突。脑神经脊区Shox2的条件性失活 细胞导致TMJ异型增生和强直。因此，Shox2突变小鼠作为一种 哺乳动物TMJ发育及其发育研究的独特模型系统 潜在的机制。我们推测Shox2在TMJ中起着至关重要的作用 通过直接调控Runx2的表达而发生发育。我们还假设相扑 Shox2a的修饰对于TMJ的形成是必不可少的。四个具体目标是 提出对这些假说进行检验。在目标1中，我们将确定Runx2是否是直接 Shox2下游靶基因的报告基因检测、EMSA检测和芯片检测。我们还将 确定磷酸化是否通过产生突变来削弱Shox2a的反式激活能力 Shox2a的构造性磷酸化状态或构造性模拟形式 去磷酸化状态。在目标2中，我们将定义Shox2a的相扑修改及其 对Shox2a转录能力的调节的影响。为了实现这一目标，我们 将进一步定义Shox2a和组蛋白3.3之间的相互作用，这可能会增强 Shox2a的转录能力。人类SHOXa将被并行包括在 建议进行的研究。在目标3中，我们将确定相扑修饰的作用 Shox2a通过表达突变形式的Shox2a参与TMJ的发育 不能在内源成分中模仿或构成求和状态 Shox2表达结构域。在最后一个目标中，我们将测试人类Shox和SHOX2是否 靶向插入基因在胚胎发育中的功能冗余 人Shox基因导入小鼠Shox2等位基因。

The temporomandibular joint (TMJ) ankylosis is clinically defined as limited mouth opening due to either a fibrous or bony union between the head of the condyle and the glenoid fossa. Although most incidents of TMJ ankylosis occur after trauma or an infection, congenital cases have been reported. Currently little is known about the TMJ morphogenesis and the underlying genetic, cellular and molecular mechanisms. Particularly, nothing is known about genetic alteractions that cause congenital TMJ ankylosis. The homeobox gene Shox2 is expressed specifically in the mesenchymal cells of the maxilla-mandibular junction and later in the immatured chondrocytes of the condyle of the TMJ. A conditional inactivation of Shox2 in cranial neural crest derived cells leads to dysplasia and ankylosis of the TMJ. Thus, Shox2 mutant mice serve as a unique model system for the studies of the mammalian TMJ development and its underlying mechanisms. We hypothesize that Shox2 plays a crucial role in TMJ development by regulating Runx2 expression directly. We also hypothesize that SUMO modification of Shox2a is essential for the TMJ formation. Four specific aims are proposed to test these hypotheses. In Aim 1, we will determine if Runx2 is a direct downstream target of Shox2 by reporter assay, EMSA and ChIP assay. We will also determine if phosphorylation impairs Shox2a's transactivating potency by creating mutant forms of Shox2a mimicking constitutively phosphorylation state or constitutively dephosphorylation state. In Aim 2, we will define SUMO modification of Shox2a and its consequences on the modulation of the Shox2a's transcriptional capacity. In this aim, we will further define the interaction between Shox2a and Histone 3.3, which may enhance the transcription capacity of Shox2a. The human SHOXa will be included in parallel in the proposed studies. In Aim 3, we will determine the role of SUMO modifcation of Shox2a in the TMJ development by expressing the mutated forms of Shox2a that either can not be sumoylated or mimic constitutively sumoylated status in the endogenous Shox2-expressing domains. In the last aim, we will test if human SHOX and SHOX2 are functionally redundant in embryonic development through targeted insertion of the human SHOX gene into the mouse Shox2 allele.