Understanding how the master transcriptional regulator HOXA5 defines cell fate in the developing embryo

了解主转录调节因子 HOXA5 如何定义发育中胚胎的细胞命运

• 批准号: RGPIN-2020-06365
• 负责人: Jeannotte, Lucie
• 金额: $ 2.62万
• 依托单位: Université Laval
• 依托单位国家: 加拿大
• 项目类别: Discovery Grants Program - Individual
• 财政年份: 2022
• 资助国家: 加拿大
• 起止时间: 2022-01-01 至 2023-12-31
• 项目状态: 已结题
• 来源: https://www.nserc-crsng.gc.ca/ase-oro/Details-Detailles_eng.asp?id=745057
• 关键词: Understanding; how; master; transcriptional; regulator

Proper control of cell-type specific transcriptional programs is critical for normal development. Mutation of a single transcriptional regulator often produces pleiotropic phenotypes with organ-specific consequences. Therefore, it is fundamental to understand how a single transcription factor confers to cells and tissues their identity by controlling specific transcriptional programs. HOX proteins are evolutionary conserved transcription factors that play critical roles in embryogenesis, organogenesis and tissue homeostasis during postnatal life. Their mutations lead to multiple and various developmental defects and diseases. Despite their broad expression in numerous cell types, HOX proteins perform their regulatory functions in a context-dependent fashion. They bind to similar TNAT motif-rich DNA-binding sites, but confer different regulatory actions in vivo, raising the fundamental question of how specificity of HOX transcriptional outputs is attained. While the developmental role of Hox genes is established, understanding how they act still awaits the identification of target genes. Thus, HOX proteins represent ideal candidates to determine how individual transcription factors govern cell fate. Our long-term objective is to define how HOX transcription factors regulate target gene expression in a highly context-dependent manner during mammalian development. We use HOXA5 as a model, because the loss of Hoxa5 gene function in mice results in a plethora of well-characterized phenotypes and, most importantly, in death at birth due to the combination of respiratory system malformations. These defects include trachea occlusion resulting from cartilage anomalies, lung dysmorphogenesis due to reduced branching, hypoplasia and abnormal cell differentiation, and altered diaphragm innervation and musculature. These phenotypes evoke severe human diseases such as tracheal stenosis, lung hypoplasia and diaphragm eventration. No other single Hox mutants present such an overt respiratory system phenotype revealing the functional predominance of Hoxa5 in this developmental process. Hoxa5 pleiotropic action in the respiratory system suggests cell-specific mechanisms, and makes Hoxa5 an ideal model for studying how individual HOX proteins achieve cell-specificity to orchestrate organ system development. We hypothesize that HOXA5 transcription factor exerts part of its functions through activation of common transcriptional programs but also via the regulation of distinct, context-specific effectors. Our objectives are to define the molecular mechanisms involved in HOXA5 action during the formation of the respiratory system in order to elucidate how HOXA5 attains functional cell-specificity. Our aims are to: 1.Identify and compare the gene networks controlled by the HOXA5 master regulator in the developing trachea, lung and diaphragm 2.Determine the genetic and cellular mechanisms of HOXA5 function in the specific context of trachea formation

适当控制细胞类型的特定转录程序对正常发育至关重要。单一转录调控因子的突变通常会产生具有器官特异性后果的多效性表型。因此，了解单个转录因子如何通过控制特定的转录程序来赋予细胞和组织其身份是至关重要的。HOX蛋白是进化保守的转录因子，在胚胎发育、器官发育和出生后生命中的组织动态平衡中发挥重要作用。它们的突变会导致多种发育缺陷和疾病。尽管HOX蛋白在多种细胞类型中广泛表达，但它们以一种上下文相关的方式执行其调节功能。它们与类似的tnat基序丰富的DNA结合位点结合，但在体内具有不同的调节作用，提出了如何获得Hox转录输出的特异性的根本问题。虽然HOX基因的发育作用已经确立，但对它们如何作用的了解仍有待于目标基因的鉴定。因此，HOX蛋白是决定单个转录因子如何控制细胞命运的理想候选者。我们的长期目标是确定HOX转录因子在哺乳动物发育过程中如何以高度依赖于上下文的方式调节靶基因的表达。我们使用HOXA5作为一个模型，因为在小鼠中Hoxa5基因功能的丧失导致了过多的具有良好特征的表型，最重要的是，由于呼吸系统畸形的组合而导致出生时死亡。这些缺陷包括软骨异常引起的气管闭塞，因分支减少、发育不良和细胞分化异常而导致的肺形态异常，以及隔膜神经和肌肉结构的改变。这些表型会引起严重的人类疾病，如气管狭窄、肺发育不良和横隔膜膨出。没有其他单一的HOX突变体呈现如此明显的呼吸系统表型，揭示了Hoxa5在这一发育过程中的功能优势。Hoxa5在呼吸系统中的多效性表明了细胞特有的机制，并使Hoxa5成为研究单个HOX蛋白如何实现细胞特异性以协调器官系统发育的理想模型。我们假设HOXA5转录因子通过激活共同的转录程序发挥部分功能，但也通过调节不同的上下文特定的效应器。我们的目标是确定HOXA5在呼吸系统形成过程中作用的分子机制，以阐明HOXA5如何获得功能细胞特异性。我们的目标是：1.鉴定和比较HOXA5主调控子在发育中的气管、肺和横隔膜中控制的基因网络2.确定HOXA5在特定的气管形成背景下发挥作用的遗传和细胞机制