Modular control of jaw tendon specification by the Nr5a2 orphan nuclear receptor

项目摘要 为了使颌骨正常运作，颌骨骨骼必须通过以下方式与下面的肌肉结合 肌腱。肌腱损伤的发生率很高，在某些情况下可能导致颞下颌关节损伤。 关节紊乱，但肌腱的发育和修复在很大程度上还没有得到充分的研究。这具骨架和 与骨骼和肌腱不同的是，颌部的肌腱来自于脑神经脊细胞(CNCC)。 指源自中胚层的鳍/肢和脊椎。来自不同血统的肌腱依赖于 在相似或不同的上行信号上指定？这项提议考验了一个创新的想法，即 肌腱规范是模块化的，头部和躯干特定的转录因子启动肌腱 通过针对头部和躯干的关键腱细胞因子的增强剂发育，如硬化症。通过 在发育中的斑马鱼面部进行CNCC衍生物的单细胞RNA表达谱，我们有 发现nr5a2孤儿核受体的表达标志着细胞沿着发育轨迹 走向下颌肌腱的命运。利用突变和转基因斑马鱼模型，我们发现Nr5a2是必要的和 足以规范颌骨肌腱，但以软骨命运为代价。此外，通过检测开放 染色质指示CNCC以及头部和躯干腱细胞中的活性增强剂，我们发现了一个数字 可能的头部和躯干特异性硬化轴-a增强剂。在这项提议中，我们使用转基因和切割- 先进的基因组学技术，以测试Nr5a2直接结合并激活颌骨特定的硬化轴-a增强剂。 我们还在小鼠身上使用条件遗传学来测试Nr5a2在指定颌骨和 哺乳动物的中耳肌腱起源于下颌弓。完成这些目标将揭示 肌腱在身体不同部位被指定的调节逻辑，以及对 Nr5a2孤儿核受体在促进颌腱形成中的作用

Project Summary In order for the jaw to properly function, the jaw skeleton must be integrated to the underlying muscles through tendons. The prevalence of tendon injuries is high and in some cases can contribute to temporomandibular joint disorders, yet both the development and repair of tendons are largely understudied. The skeleton and tendons of the jaw are derived from cranial neural crest cells (CNCCs), in contrast to the skeleton and tendons of the fins/limbs and spine that are derived from mesoderm. Do tendons derived from different lineages depend on similar or distinct upstream signals for their specification? This proposal tests the innovative idea that tendon specification is modular, with head- and trunk-specific transcription factors initiating tendon development through head- and trunk-specific enhancers of critical tenocyte factors such as Scleraxis. By conducting single-cell RNA expression profiling of CNCC derivatives in the developing zebrafish face, we have found that expression of the nr5a2 orphan nuclear receptor marks cells along a developmental trajectory toward jaw tendon fate. Utilizing mutant and transgenic zebrafish models, we find that Nr5a2 is necessary and sufficient for specification of jaw tendon at the expense of cartilage fates. In addition, by assaying open chromatin indicative of active enhancers in CNCCs, as well as head versus trunk tenocytes, we find a number of putative head- and trunk-specific enhancers of scleraxis-a. In this proposal, we use transgenic and cutting- edge genomics techniques to test that Nr5a2 directly binds and activates jaw-specific scleraxis-a enhancers. We also use conditional genetics in mouse to test that Nr5a2 has a conserved role in specifying jaw and middle ear tendons derived from the mandibular arch in mammals. Completion of these aims will reveal the regulatory logic by which tendons are specified in different parts of the body, as well as a highly specific role for the Nr5a2 orphan nuclear receptor in promoting jaw tendon formation.