The Role of Hox Transcription Factors in Cellular Plasticity

Hox 转录因子在细胞可塑性中的作用

• 批准号: 285766387
• 负责人: Professorin Dr. Ingrid Lohmann
• 金额: --
• 依托单位: Centre for Organismal Studies (COS)
• 依托单位国家: 德国
• 项目类别: Research Grants
• 财政年份: 2015
• 资助国家: 德国
• 起止时间: 2014-12-31 至 2023-12-31
• 项目状态: 已结题
• 来源: https://gepris.dfg.de/gepris/projekt/285766387?language=en
• 关键词: Role; Hox; Transcription; Factors; Cellular

Multicellular animals owe their complexity to their capacity to produce and maintain different lineages composed of multiple cell types that share virtually the same genomic DNA. Cell fates are controlled by networks of transcription factors (TFs) that act in the context of the genomic chromatin state to activate transcriptional programs realizing the distinct properties of cells of a given lineage. However, how TFs control different cell fates is still un unsolved question in biology. Hox TFs represent an excellent model to address this fundamental problem, since they are active in all lineages along the anterior-posterior (AP) axis of bilaterian animals. Our preliminary data using Ubx as a model show that Hox TFs, besides their well-described function in specifying regional identities along the AP axis, play a major role in the development and diversification of lineages, and that one of the mechanisms is the lineage-specific recruitment or stabilization of the Polycomb complex to Ubx chromatin sites for the repression of alternative fate and early lineage specification genes. Our results also imply that the Hox-encoded restriction of cellular and temporal plasticity is required for stably maintaining cell fates throughout the lifetime of a cell. One fundamental question arising from these findings is how an already committed lineage will develop in the absence of any functional Hox input and whether Hox-free cells are more plastic that Hox-expressing cells. We will tackle these questions by analyzing how a Hox-free cellular environment affects lineage development. To this end, we will eliminate the Hox code in the mesodermal lineage and will record the effects at the transcriptome level. In addition, we will characterize the identity and morphology of the lineage on the phenotypic level. To elucidate the mechanistic basis of the Hox-encoded suppression of multipotency, we will identify those genomic regions that are critical for lineage stabilization, as they are converted into an open and activatable status in the absence of Hox TFs. As a proof of concept, we will select candidate regions and test their function in lineage stabilization in vivo by lineage-specifically deleting these regions using CRISPR/Cas9 mediated genome engineering. And finally, we will compare the developmental potential of Hox-free and Hox-expressing cells to elucidate whether cells “stripped” of their Hox code are more plastic and can thus more easily change their identity when stimulated than cells expressing the inherent Hox code. To this end, we will mis-express a master-regulator of an alternative lineage in control and Hox-depleted mesodermal cells in vivo and will compare their phenotypic and molecular identities. In sum, we envision this study to be crucial in resolving the mechanistic basis of Hox-encoded lineage stabilization, which might prove to be highly relevant for reprogramming strategies.

多细胞动物之所以如此复杂，是因为它们有能力产生和维持由多种细胞类型组成的不同谱系，而这些细胞类型实际上共享相同的基因组DNA。细胞命运由转录因子（tf）网络控制，这些转录因子在基因组染色质状态下激活转录程序，实现特定谱系细胞的不同特性。然而，tf如何控制不同的细胞命运仍然是生物学中未解决的问题。Hox tf代表了解决这一基本问题的一个极好的模型，因为它们在沿两侧动物的前后（AP）轴的所有谱系中都是活跃的。我们使用Ubx作为模型的初步数据表明，Hox TFs除了在沿AP轴指定区域身份方面具有良好描述的功能外，还在谱系的发展和多样化中发挥重要作用，其中一种机制是谱系特异性招募或稳定Polycomb复合物到Ubx染色质位点，以抑制替代命运和早期谱系规范基因。我们的研究结果还表明，hox编码的细胞可塑性和时间可塑性的限制是在细胞的整个生命周期中稳定维持细胞命运所必需的。从这些发现中产生的一个基本问题是，在没有任何功能性Hox输入的情况下，已经确定的谱系将如何发展，以及无Hox细胞是否比表达Hox的细胞更具可塑性。我们将通过分析无hox细胞环境如何影响谱系发育来解决这些问题。为此，我们将消除中胚层谱系中的Hox编码，并记录转录组水平的影响。此外，我们将在表型水平上表征谱系的身份和形态。为了阐明Hox编码抑制多能性的机制基础，我们将确定那些对谱系稳定至关重要的基因组区域，因为它们在没有Hox tf的情况下转化为开放和可激活状态。作为概念验证，我们将选择候选区域，并通过使用CRISPR/Cas9介导的基因组工程特异性删除这些区域来测试它们在体内谱系稳定中的功能。最后，我们将比较无Hox和表达Hox的细胞的发育潜力，以阐明“剥离”Hox密码的细胞是否比表达固有Hox密码的细胞更具可塑性，因此在受到刺激时更容易改变其身份。为此，我们将在体内的对照和缺乏hox的中胚层细胞中错误表达另一种谱系的主调控因子，并比较它们的表型和分子特性。总之，我们设想这项研究对于解决hox编码谱系稳定的机制基础至关重要，这可能被证明与重编程策略高度相关。