JAK/STAT PATHWAY CONTROL OF CELL COMPETITION DURING DEVELOPMENT.

描述(申请人提供)：控制细胞竞争的分子机制在治疗生长缺陷、癌症生物学和再生医学方面具有巨大的潜力。细胞竞争是一种质量控制机制，以确保只有“最适合”的细胞才能为成年机体做出贡献。它与早期的 癌症阶段，转化的细胞代谢率升高，占据了一片野生型细胞。细胞竞争是沿着相邻细胞群体的界面诱导的， 代谢率不同：生长速度较高的细胞(获胜者)以低生长率的细胞(失败者)为代价进行繁殖。在果蝇中的研究表明，dmyc的过度表达是人类癌基因c-myc在许多肿瘤中重排的唯一苍蝇同源物，它赋予细胞赢家地位，这与诱导从头开始的核糖体生物发生密切相关。这项建议中的工作表明，JAK/STAT信号通路的持续激活导致细胞成为赢家，以牺牲失败者邻居的利益为代价生长，而途径活性的降低则赋予“失败者”状态，导致消除。四个JAK或七个STATS的过度激活会导致几种人类癌症。在果蝇中只有一个JAK和一个STAT(称为Stat92E)，这种遗传冗余的缺乏使果蝇成为解决这一途径在细胞竞争中作用的理想系统。本申请中的初步数据显示，Stat92E不能通过dMyc发挥作用，反之亦然。此外，与dMyc不同的是，高活性的Stat92E不能诱导核糖体的生物发生。然而，表达高活性Stat92E或升高的dMyc的获胜者会导致几个细胞直径之外的失败者死亡。这些结果表明，激活的Stat92E是一个超级竞争者，并强烈表明Stat92E和dMyc独立运行，并聚集在共同的靶基因上，编码导致失败者死亡的可溶性蛋白。这项应用的广泛、长期目标是确定JAK/STAT途径活性增加的获胜者使用的竞争分子机制。全基因组表达谱将被用来识别与对照组(目标1)相比，患有高活性Stat92E的获胜者的目标基因表达发生了变化。在果蝇翼盘中的克隆生长试验将被用来产生表达高活性Stat92E但缺乏候选基因的获胜者，然后确定这些细胞是否仍然能够杀死位于几个细胞直径之外的失败者(目标2)。这项应用的目标与NICHD的使命非常相关，其中之一是“学习生长和发育”，因为这项提议中的实验可能会发现正常生长所需的基因，这些基因可能会被转化的细胞所选择。

DESCRIPTION (provided by applicant): The molecular mechanisms controlling cell competition hold great potential for advances in treating growth deficiencies, in cancer biology and in regenerative medicine. Cell competition is a quality-control mechanism to insure that the only the "fittest" cells contribute to the adult organism. It shares many properties with the early stages of cancer, in which transformed cells with elevated metabolic rates take over a field of wild-type cells. Cell competition is induced along the interface of adjacent cell populations that differ in metabolic rates: cells with the higher growth rate (winners) reproduce at the expense of those with the lower one (losers). Work in Drosophila has shown that over-expression of dmyc, the sole fly homolog of the human oncogene c-myc that is re-arranged in many tumors, confers winner status on cells, and this is strongly correlated with inducing de novo ribosome biogenesis. The work in this proposal shows that sustained activation of the JAK/STAT signaling pathway causes cells to become winners that grow at the expense of their loser neighbors, while reduction in pathway activity imparts "loser" status, resulting in elimination. Hyper-activation of the four JAKs or seven STATs causes several human cancers. There is a single JAK and a single STAT (called Stat92E) in Drosophila, and this lack of genetic redundancy makes Drosophila an ideal system in which to address the role of this pathway in cell competition. The preliminary data in this application show that Stat92E does not function through dMyc and vice versa. Furthermore, unlike dMyc, hyper-active Stat92E does not induce ribosome biogenesis. However, winners expressing hyper-active Stat92E or elevated dMyc cause the death of losers located several cell diameters away. These results demonstrate that activated Stat92E is a super-competitor and strongly suggest that Stat92E and dMyc operate independently and converge on common target genes encoding soluble proteins that cause death in losers. The broad, long-term objectives of this application are to determine the molecular mechanisms of competition used by winners with increased activity of the JAK/STAT pathway. Genome-wide expression profiling will be used to identify target genes that have altered expression in winners with hyper-active Stat92E as compared to controls (Aim 1). A clonal growth assay in the Drosophila wing disc will be used to generate winners that express hyper-active Stat92E but lack the candidate gene and then to determine if these cells can still kill losers located several cell diameters away (Aim 2). The goals of this application are extremely pertinent to the mission of the NICHD, one of which is "learning about growth and development," as the experiments in this proposal will likely uncover genes required for normal growth and that may be co-opt by transformed cells.