Polyploidy after tissue injury: a Drosophila model

后生动物的组织在组织和功能上是多样的。这就需要各种机制， 在受伤时修复这些组织我们开创了果蝇后肠（大肠）的研究，以揭示新的 组织损伤调节使用这个模型，我们确定了一种损伤反应，通过这种反应，组织块被恢复， 增加DNA含量（倍性）和损伤后存活细胞的大小。这种倍性的增加涉及到 具有S期但没有细胞分裂的保守细胞周期，称为内周期。我们发现内旋回， 多倍体细胞在组织修复中的应用随后在多种损伤的哺乳动物组织中也有类似的发现， 包括肾脏膀胱和角膜此外，我们的工作揭示了特定的多倍体细胞调节， 后肠和邻近的中肠（小肠）之间的受损边界。在这个边界上，我们确定了 双后肠和中肠基因表达的“杂交”细胞。杂交细胞在损伤后变成多倍体， 与邻近中肠的干细胞进行广泛的相互作用。但是，如果混合区严重 损伤后，多倍体受到抑制，邻近的中肠干细胞形成增生性侵袭性肿瘤。类似 现在已经在哺乳动物器官边界，特别是在干细胞富集的， 易患癌症的胃/食管边界。 这项提议利用了我们的专业知识、新发现和遗传上适合的果蝇模型， 鉴定组织损伤后多倍体调节和功能。我们提出的工作的重要性是显而易见的 在保护损伤反应，保护损伤中的内循环，以及保护 我们研究的分子，包括JAK/STAT信号，Dichaete/SoxB 1和fizzy相关/cdh 1。我们的研究是 创新是因为它们表明组织可以通过精确控制多倍体基因组数量来再生， 激素信号和Sox转录协同控制损伤诱导的多倍体， 再生多倍体器官边界可抑制肿瘤发生。在目标1中，我们将揭示伤害的严重程度 决定了再生过程中多倍体的程度。为了回答这个问题，我们将确定定量 JAK/STAT信号传导参数在不同的损伤强度，并确定具体的途径步骤，协调 损伤程度与内循环数有关。aim 2将确定内循环发生的分子机制， 而不是有丝分裂。为了回答这个问题，我们将研究如何Dichaete，保守的成员， Sox转录因子家族，与激素信号传导合作，促进从损伤诱导的有丝分裂 循环到内循环。Aim 3将决定损伤后多倍体杂交细胞的起源和功能。到 为了回答这个问题，我们将区分干细胞依赖性和干细胞非依赖性模型。 器官边界再生此外，这一目标将揭示杂交区和多倍性在 抑制干细胞肿瘤的侵袭。这三个目标都利用了转录组数据和我们独特的精确度 损伤/遗传学系统来鉴定进化上保守的组织修复反应中的新分子参与者。

Metazoan tissues are diverse in organization and function. This necessitates diverse mechanisms to repair these tissues upon injury. We pioneered study of the Drosophila hindgut (large intestine) to reveal new tissue injury regulation. Using this model, we identified an injury response whereby tissue mass is restored by increasing the DNA content (ploidy) and size of cells that survive injury. This increase in ploidy involves a conserved cell cycle with S phases but no cell division, called the endocycle. Our discovery of endocycles and polyploid cells in tissue repair has been followed by similar discoveries in multiple injured mammalian tissues, including the kidney, bladder, and cornea. Additionally, our work revealed specialized polyploid cell regulation at the injured boundary between the hindgut and adjacent midgut (small intestine). At this boundary, we identified “hybrid” cells of dual hindgut and midgut gene expression. Hybrid cells become polyploid upon injury while engaging in extensive cross-talk with stem cells in the adjacent midgut. However, if the hybrid zone is severely injured, polyploidy is suppressed, and the adjacent midgut stem cells form hyperplastic invasive tumors. Similar hybrid zones have now been discovered at mammalian organ boundaries, notably at the stem cell-enriched, cancer-prone stomach/esophagus boundary. This proposal leverages our expertise, new findings, and the genetically amenable Drosophila model to identify regulation and function of polyploidy after tissue injury. The significance of our proposed work is evident in the conservation of the injury response, the conservation of endocycles in injury, and the conservation of the molecules we study, including JAK/STAT signaling, Dichaete/SoxB1, and fizzy-related/cdh1. Our studies are innovative because they show that tissues can regenerate by accurately controlling polyploid genome number, that hormonal signaling and Sox transcription cooperate to control injury-induced polyploidy, and that a regenerating polyploid organ boundary can suppress tumorigenesis. In Aim1, we will uncover how injury severity determines the extent of polyploidy during regeneration. To answer this question, we will identify quantitative parameters of JAK/STAT signaling at different injury strengths and identify specific pathway steps that coordinate injury level with endocycle number. Aim2 will identify the molecular mechanism by which endocycles occur after injury instead of mitosis. To answer this question, we will examine how Dichaete, a member of the conserved Sox transcription factor family, cooperates with hormone signaling to promote a switch from injury-induced mitotic cycles to endocycles. Aim3 will determine the origin and function of polyploid hybrid cells following injury. To answer this question, we will distinguish between stem cell-dependent and stem cell-independent models of organ boundary regeneration. Additionally, this aim will reveal the role of the hybrid zone and polyploidy in repressing stem cell tumor invasion. All three aims capitalize on transcriptomic data and our unique precision injury/genetics system to identify novel molecular players in an evolutionarily conserved tissue repair response.