Selective mRNA translation in developmental disorders

摘要 大多数先天性疾病都是由Rasopathy引起的，每1000人中就有1人受到影响。特别是， Ras-MAPK途径基因突变导致不同的病理改变，包括颅面畸形， 精神障碍，肌肉骨骼缺陷，以及患癌症的倾向。尽管演示文稿可能有所不同 在不同的突变之间，几乎所有的Rasopathy都有共同的皮肤生长异常。在一个基因上 包括HRAS和KRAS在内的RAS途径成员的胚系突变已知会导致这些缺陷 Costello、Noonan和心面部皮肤综合征就是最好的例证。多年来， 对发育中的RAS的全面询问仅限于对DNA和 核糖核酸。虽然这些调查很重要，但基于翻译的机制基本上没有受到影响。这是 值得注意的是，有新的证据表明，发育障碍，如钻石-布莱克凡贫血 和Schwachman-Diamond和Treacher Collins综合征(Tahmasebi等人，2018年综述)是 与翻译设备中的损伤有因果关系。因此，我们目前对机械论的认识 Rasopathies的基础不完整，这是治疗创新的障碍。我们的长期目标是 揭示RAS介导的组织生长机制，这最终将产生创新的治疗方法 在发育过程中恢复正常的组织动态平衡，而不影响家务管理功能。vbl.使用 皮肤作为组织发育的明确模型，我们已经发现，过度活跃的HRA同时 通过重新连接翻译启动机制来推动专门的增殖和差异化计划 通过eIF2B5。利用我们实验室首创的最先进的活体基因筛查，我们拥有 确定了eIF2B5调控的影响自我更新和细胞命运选择的基因的调节。值得注意的是， 这些信使核糖核酸网络明显地被它们的功能所区分，泛素化成为一个关键的调节因子。 对细胞分化的影响。因此，我们假设RAS的激活促进了 在发育过程中支持非生理性组织生长的mRNA，其中增加了干细胞 通过分化成有丝分裂后的后代，通过丢失它们来平衡增殖。在本提案中，我们将 使用体内模型、活体显微镜和新开发的细胞和分子分析的融合 描述RAS和eIF2B5之间的相互作用如何影响组织动力学。我们将完成 目的如下：1)揭示eIF2B5依赖的泛素连接酶如何引导祖细胞更新和命运选择； 2)阐明激活的hRAs和eIF2B5如何引导mRNA特异性翻译来调节祖细胞 更新。总体而言，成功完成我们的目标将提供对细胞和 在发育过程中支持RAS驱动的非生理性生长的分子原理。最终，这些 新的见解将为新疗法的发展提供信息，这种疗法可以区别地抑制病理 影响RAS介导的组织失衡，同时维持对生命至关重要的动态平衡。

Abstract RASopathies cause the majority of congenital disorders affecting nearly 1 in 1000 individuals. In particular, mutations in RAS-MAPK pathway genes lead to distinct pathologies including craniofacial dysmorphology, mental impairment, musculoskeletal defects, and a predisposition to cancer. Although presentations may vary between different mutations, nearly all RASopathies share common skin growth abnormalities. At a genetic level, germline mutations to RAS pathway members including Hras and Kras are known to cause these defects which are best exemplified by Costello, Noonan, and Cardiofaciocutaneous syndromes. For years, comprehensive interrogation of RAS in development has been limited to genome-wide studies of DNA and RNA. While important, these investigations have left translation-based mechanisms largely untouched. This is remarkable in light of emerging evidence that developmental disorders, such as Diamond-Blackfan Anemia and Schwachman-Diamond and Treacher Collins syndromes (reviewed in Tahmasebi et al., 2018), are causally linked to impairments in the translation apparatus. Thus, our current knowledge of the mechanistic basis of RASopathies is incomplete, which is a barrier to therapeutic innovation. Our long-term goal is to uncover the mechanism of Ras-mediated tissue growth, which will ultimately yield innovative therapies to restore normal tissue homeostasis without compromising housekeeping functions during development. Using skin as a defined model of tissue development we have discovered that hyperactive Hras simultaneously drives specialized proliferation and differentiation programs by rewiring the translation initiation machinery through eIF2B5. Utilizing state-of-the-art in vivo genetic screens pioneered in our laboratory, we have determined the regulon of genes that eIF2B5 governs to impact self-renewal and cell fate choice. Remarkably, these mRNA networks are clearly demarcated by their function with ubiquitination emerging as a key regulator of cellular differentiation. As such, we hypothesize that activation of Ras promotes translation of a subset of mRNAs that support non-physiological tissue growth during development, where increased stem cell proliferation is balanced by their loss through differentiation into post-mitotic progeny. In this proposal we will use a confluence of in vivo models, intra-vital microscopy, and newly developed cellular and molecular assays to delineate how the interplay between RAS and eIF2B5 influences tissue dynamics. We will accomplish the following Aims: 1) Uncover how eIF2B5-dependent ubiquitin ligases directs progenitor renewal and fate choice; and 2) Elucidate how activated Hras and eIF2B5 direct mRNA specific translation to regulate progenitor renewal. Collectively, the successful completion of our Aims will provide a new understanding of cellular and molecular principles that support Ras-driven non-physiological growth during development. Ultimately, these new insights will inform the development of novel therapeutics, which can differentially inhibit the pathologic impact of Ras mediated tissue imbalance while maintain homeostasis which is essential for life.