Molecular patterning of the hard palate during palatogenesis

摘要/概要 哺乳动物的腭在解剖学上分为前部的骨性硬腭和后部的肌性硬腭 软腭然而，前硬腭是如何形成的，腭部的成骨是如何控制的， 仍然未知。最近的研究表明，在发育中的鳃弓中，TALE超类 同源结构域蛋白质，特别是Meis蛋白质，建立了所有弓共同的基态， 它们的衍生物，而Hox转录因子充当组织特异性辅因子来指定关键身份。 然而，这提出了一个基本问题，即哪些因素与TALE因素相互作用， 无霍克斯第一弓及其衍生物，包括腭。同源盒基因Shox 2是 在腭前间充质中特异性表达，与将来的硬腭骨重叠 域我们以前已经证明，Shox 2突变不仅导致罕见的前裂， 第二腭，但也显着减少骨形成的硬腭，其中，连同 -/- Shox 2肢体中茎突的实际损失表明Shox 2在器官模式中的重要作用， 骨骼生成我们的初步研究表明Shox 2突变导致早产/异位妊娠。 + Runx 2在表达Shox 2的腭细胞中的表达。来自E13腭架的Shox 2细胞上的RNA-Seq 和四肢表明在缺乏Shox 2的情况下成骨基因的全基因组表达升高， 与颅神经嵴谱系细胞中Shox 2过表达抑制的观察结果一致 成骨此外，Shox 2 ChIP-Seq在发育中的腭和肢体上揭示了全基因组的 Shox 2优先占据Hox结合的基因的响应性顺式调节元件， TALE蛋白，这表明在无Hox的发育中的腭中，Shox 2与TALE一起起作用。 影响硬腭形成和调节骨生成的因素。根据上述观察，我们 假设在无Hox的腭架中，Shox 2与TALE因子相互作用以建立硬腭 通过拮抗Meis转录输出来防止过早成骨。在本申请中， 提出了三个具体目标来严格检验这一新的假设：1）检验Shox 2 表达阻止发育中的腭中的过早成骨; 2）测试Shox 2 拮抗Meis的转录输出并建立Shox 2的功能机制; 3） 确定组织特异性染色质景观并鉴定腭下的特异性增强子元件 阵这些结果将为腭发育的研究提供新的知识， 为今后组织工程化腭骨的临床应用提供了坚实的基础 治疗/修复腭裂缺陷。

Abstract/Summary The mammalian palate is anatomically divided into the anterior bony hard palate and the posterior muscular soft palate. However, how the anterior hard palate is patterned and how the palatal osteogenesis is controlled remain unknown. It was recently demonstrated that in the developing branchial arches, the TALE superclass homeodomain proteins particularly Meis proteins set up a ground state that is common to all the arches and their derivatives whereas Hox transcription factors act as tissue-specific cofactor to specify the arch identity. However, this raises a fundamental question as what factors interact with TALE factors to specify and pattern the Hox-free first arch and its derivatives including the palate. The homeobox gene Shox2 is expressed specifically in the anterior palatal mesenchyme, overlapping with the future bony hard palate domain. We have shown previously that Shox2 mutation leads to not only a rare type anterior clefting of the secondary palate, but also the significantly reduced bone formation in the hard palate, which, together with -/- the virtual loss of the stylopod in Shox2 limb, indicates an essential role for Shox2 in organ patterning and skeletogenesis. Our preliminary studies present evidence that Shox2 mutation leads to premature/ectopic + expression of Runx2 in Shox2-expressing palatal cells. RNA-Seq on Shox2 cells from E13 palatal shelves and limbs demonstrates a genome-wide elevated expression of osteogenic genes in the absence of Shox2, consistent with the observation that Shox2 overexpression in cranial neural crest lineage cells inhibits osteogenesis. Moreover, Shox2 ChIP-Seq on the developing palate and limb reveals genome-wide preferential occupation of Shox2 on the responsive cis-regulatory elements of genes bound by Hox and TALE proteins, suggesting that in the Hox-free developing palate, Shox2 functions together with TALE factors to pattern the hard palate and regulates osteogenesis. Based on the abovementioned observations, we hypothesize that in the Hox-free palatal shelf, Shox2 interacts with TALE factors to establish the hard palate identity by antagonizing Meis transcriptional output to prevent premature osteogenesis. In this application, three specific aims are proposed to test this novel hypothesis rigorously: 1) to test the hypothesis that Shox2 expression prevents premature osteogenesis in the developing palate; 2) to test the hypothesis that Shox2 antagonizes the transcription output of Meis and to establish the functional mechanisms for Shox2; 3) to determine the tissue specific chromatin landscape and identify specific enhancer elements underlying palate formation. The results obtained will provide novel knowledge for understanding of palate development and cleft palate formation, and provide solid foundation for future tissue engineering of palatal bone for clinical treatment/repair of cleft palate defects.