Non-Canonical Responses to DNA damage in Drosophila Polyploid Cells

 描述(申请人提供)：多倍体细胞含有两组以上的同源染色体。多倍体细胞既有自然产生的，也有病理产生的。包括心脏、肝脏和胎盘在内的几个重要器官含有多倍体细胞。此外，许多癌症以多倍体或接近多倍体的状态存在。尽管多倍体很普遍，但其生物学意义仍不清楚。一种模型是，多倍体细胞中额外的染色体组缓冲了基因组损伤剂的影响，从而使多倍体细胞对DNA损伤更耐受。当受到DNA损伤时，二倍体细胞会激活一种规范反应，以防止DNA损伤的细胞进入细胞周期。在缺乏这种反应的情况下，DNA受损的细胞进入有丝分裂，并经常通过一种被称为有丝分裂灾难(MC)的糟糕的细胞死亡过程而死亡。与二倍体细胞相比，人们对多倍体细胞如何应对DNA损伤知之甚少。我的目标是研究多倍体细胞对DNA损伤的反应。此前，我们的实验室发现，果蝇直肠乳头(以下简称乳头细胞)细胞与许多多倍体细胞不同，它经历了有丝分裂的增殖。因此，果蝇乳头细胞使我能够研究DNA损伤对自然发生的有丝分裂多倍体细胞的影响。与二倍体细胞相比，我们的实验室发现乳头细胞显示出更高的染色体不稳定性，这表明它们缺乏规范的DNA损伤反应。我发现，不同类型的DNA损伤会在乳头细胞中引发不同的、非规范的反应。具体地说，乳头细胞对X射线照射引起的DNA损伤高度耐受，但会死亡 在DNA复制异常后，通过非规范的(caspase非依赖性)MC。因此，我的中心假设是多倍体有丝分裂细胞在DNA损伤后使用非规范机制。在目标1中，我将确定多倍体乳头细胞在辐射诱导的DNA损伤中存活的非规范机制。我希望揭开细胞从规范的DNA损伤反应中剥离出来的基本机制，从而在高水平的辐射诱导的DNA损伤中存活下来。在目标2中，我将确定多倍体乳头细胞在再次复制诱导的DNA损伤时经历细胞死亡的非规范机制。这项研究应该有助于揭示人们对MC知之甚少的机制，这是一种在缺乏典型DNA损伤反应的细胞中至关重要的细胞死亡机制。综上所述，我提议的研究将确定多倍体乳头细胞对DNA损伤做出反应的具体机制。多倍体的生物学意义在很大程度上仍未得到研究。我发现多倍体细胞和二倍体细胞的一个主要区别是它们对DNA损伤的反应。由于缺乏规范的DNA损伤反应和多倍体都是许多癌症的复发特征，了解多倍体细胞对DNA损伤的不同反应方式在多倍体癌症的治疗中至关重要。

 DESCRIPTION (provided by applicant): Polyploid cells contain more than two complete sets of homologous chromosomes. Polyploid cells occur both naturally and pathologically. Several vital organs, including the heart, liver and placenta contain polyploid cells. Further, many cancers exist in a polyploid or near polyploid state. Despite the prevalence of polyploidy, its biological implications remain unclear. One model is that extra sets of chromosomes in polyploid cells buffer the effects of genome damaging agents, thus making polyploid cells more tolerant of DNA damage. When subjected to DNA damage, diploid cells activate a canonical response to prevent cells with DNA damage from entering the cell cycle. In the absence of this response, cells enter mitosis with damaged DNA and frequently die via a poorly characterized cell death process known as mitotic catastrophe (MC). In contrast to diploid cells, little is known about how a polyploid cell responds to DNA damage. My objective is to examine how polyploid cells respond to DNA damage. Previously, our lab found that unlike many polyploid cells, Drosophila rectal papillar (hereafter: papillar cells) cells undergo mitotic proliferation. Thus, Drosophila papillar cells allow me to investigate the effects of DNA damage on naturally occurring mitotic polyploid cells. Compared to diploid cells, our lab has found that papillar cells show elevated rates of chromosomal instability, suggesting that they lack a canonical DNA damage response. I have found that distinct types of DNA damage elicit distinct, non-canonical responses in papillar cells. Specifically, papillar cells are highly tolerant of X-irradiation induced DNA damage but die via non-canonical (caspase-independent) MC following aberrant DNA replication. Therefore, my central hypothesis is that polyploid mitotic cells employ non-canonical mechanisms following DNA damage. In Aim 1 I will determine the non-canonical mechanism by which polyploid papillar cells survive irradiation induced DNA damage. I expect to uncover the basic mechanism by which cells stripped of canonical DNA damage responses can survive high levels of irradiation induced DNA damage. In Aim 2 I will determine the non-canonical mechanism by which polyploid papillar cells undergo cell death in response to re-replication induced DNA damage. This research should shed light on the poorly understood mechanisms of MC, a cell death mechanism that is crucial in cells lacking canonical DNA damage responses. Taken together, my proposed research will identify specific mechanisms by which polyploid papillar cells respond to DNA damage. The biological implications of polyploidy remain largely unstudied. I have found that one main difference between polyploid cells and diploid cells is their response to DNA damage. Since both lack of canonical DNA damage responses and polyploidy are recurring features in numerous cancers, understanding distinct ways by which polyploid cells respond to DNA damage is crucial in treatment of polyploid cancers.