Molecular mechanisms and epigenetic signatures that specify thymus fate

描述（由申请方提供）：尽管胸腺在T细胞发育中起关键作用，但在胎儿发育期间指定初始胸腺命运所需的机制尚不清楚。了解这些机制将有助于发展战略，以产生功能性胸腺器官的文化，并恢复老年人，退化的胸腺。在小鼠胚胎发育期间，在E9.5和E11之间，在腹侧第三咽囊（pp）内胚层中指定了甲状腺;该囊的背侧区域产生甲状旁腺。由于第三个pp必须被模式化为两个不同的细胞命运，因此必须建立机制以确保两个器官都被正确指定。我们实验室和其他人以前的工作表明，BMP 2/4和FGF 8/10信号参与了胸腺命运的建立，而SHH信号是甲状旁腺命运所必需的。这两个信号通路似乎是相反的;然而，它们相互作用并调节器官特异性转录网络的机制仍有待建立。Richie和Manley实验室最近的合作实验表明，转录因子TBX 1是决定胸腺和甲状旁腺细胞命运的关键调节因子。我们已经表明，TBX 1在第三pp内胚层的甲状旁腺域中表达，但不在腹侧胸腺命运域中表达，并且异位TBX 1足以抑制Foxn 1表达。基于我们的初步数据，我们产生了一个可测试的模型，胸腺命运规范，其中表明，FGF 8和BMP 4是积极的调节剂，而SHH和Tbx 1拮抗胸腺发育。该项目使用一种新的方法来破译指定胸腺命运的内胚层祖细胞的分子网络，结合胚胎学，遗传学，分子生物学，生物信息学和表观遗传学。这些结果将为编程早期祖细胞产生支持胸腺生成的功能性胸腺上皮细胞网络提供合理的基础。我们将在以下特定目标中测试我们的模型。目标1.检验以下假设：多种机制抑制第3 pp内胚层腹侧结构域中的Tbx 1表达，并且这种抑制是建立胸腺命运所必需的。目标二。测试TBX 1抑制胸腺分化的能力是否受到时间限制，并确定异位TBX 1和/或SHH信号传导阻断胸腺命运的机制。目标3。检验器官特异性表观遗传标记的逐步建立决定胸腺命运，并依赖于BMP和FGF信号通路之间的合作的假设

DESCRIPTION (provided by applicant): Despite the critical role of the thymus in T cell development, the mechanisms required to specify initial thymus fate during fetal development are not known. Understanding these mechanisms will facilitate the development of strategies to generate functional thymus organs in culture, and to rejuvenate the aged, involuted thymus. Thymus fate is specified in the ventral 3rd pharyngeal pouch (pp) endoderm between E9.5 and E11 during mouse fetal development; the dorsal domain of this pouch gives rise to the parathyroid glands. As the 3rd pp must be patterned into two distinct cell fates, mechanisms must be in place to ensure that both organs are properly specified. Previous work from our labs and others have implicated BMP2/4 and FGF8/10 signals in establishing thymus fate, while SHH signaling is required for parathyroid fate. These two signaling pathways appear to act in opposition; however, the mechanisms by which they interact with each other and regulate organ-specific transcriptional networks remain to be established. Recent collaborative experiments from the Richie and Manley labs suggest that the transcription factor TBX1 is a key regulator of the decision between thymus and parathyroid cell fate. We have shown that Tbx1 is expressed in the parathyroid domain of the 3rd pp endoderm, but not in the ventral thymus fated domain, and that ectopic TBX1 is sufficient to suppress Foxn1 expression. Based on our preliminary data we generated a testable model of thymus fate specification in which suggest that FGF8 and BMP4 are positive regulators, whereas SHH and Tbx1 antagonize thymus development. This project uses a novel approach to decipher the molecular network that specifies endodermal progenitors to a thymus fate, combining embryology, genetics, molecular biology, bioinformatics, and epigenetics. The results will provide a rational basis for programming early progenitors to generate a functional thymic epithelial cell network that supports thymopoiesis. We will test our model in the following Specific Aims. Aim 1. Test the hypothesis that multiple mechanisms suppress Tbx1 expression in the ventral domain of 3rd pp endoderm, and that this suppression is required to establish thymus fate. Aim 2. Test whether the ability of TBX1 to inhibit thymus differentiation is temporally restricted, and identify the mechanism by which ectopic TBX1 and/or SHH signaling blocks thymus fate. Aim 3. Test the hypothesis that progressive establishment of organ-specific epigenetic signatures determines thymus fate, and depends on cooperation between the BMP and FGF signaling pathways