Control of nonapoptotic C. elegans cell death similar to neurodegeneration

我们的长期目标是了解一种新的形态学保守的非凋亡性细胞因子的分子基础。 我们发现了发育细胞死亡程序，并确定其在哺乳动物发育中的作用， 疾病程序性细胞死亡是一种主要的细胞命运。细胞凋亡是一种被广泛研究的细胞死亡过程， 需要半胱天冬酶蛋白酶，并伴有染色质致密化和细胞质收缩。 令人惊讶的是，缺乏凋亡效应子的小鼠可以存活到成年。这些观察表明，非 凋亡性细胞死亡可能在动物发育中起关键作用。虽然促进坏死细胞死亡的基因 已经描述了，这些不是发展所必需的。因此，替代性发育细胞 死亡途径存在，如果是这样的话，什么样的分子机制控制着它们的执行，是一个重大的悬而未决的问题。 问题我们对C. elegans连接细胞提供了直接证据， 凋亡细胞死亡途径在动物发育过程中起作用。连接细胞死亡发生在缺乏 C.线虫半胱天冬酶和其他凋亡基因也不是必需的，也不是自噬相关基因 或坏死。垂死的连接细胞的形态特征是缺乏染色质凝聚， 细胞核有锯齿状突起，细胞器肿胀。值得注意的是，具有相似特征的细胞死亡（连接子） 细胞型死亡，LCD）也发生在脊椎动物中，并且是神经元变性的特征。 多谷氨酰胺病我们最近描述了一个控制C的途径。elegans LCD。这是第一次这样的 非凋亡发育细胞死亡程序的框架。LCD由Wnt信号控制， 与发育时序和MAPKK途径平行发挥作用，以控制 HSF-1，一种保守的热休克转录因子。let-70/Ube 2D 2，编码保守的E2泛素- 结合酶是HSF-1的关键靶标。E3组件CUL-3/cullin、RBX-1和BTBD-2功能 LCD用LET-70/UBE 2D 2。LCD途径成分参与脊椎动物细胞变性 流程. pqn-41编码一种自聚集的富含谷氨酰胺的蛋白质， 导致神经退化的蛋白质tir-1/Sarm以及E3组分BTBD-2，促进远端轴突 在小鼠轴突切开后的变性，支持保守的细胞拆除作用。在这里，我们将建立在 这些研究旨在揭示LCD途径的靶点，并研究与哺乳动物发育的相关性。我们将：（1） 研究HSF-1在LCD中的功能与其热休克反应作用的不同。(2)确定BTBD-2目标 基因和评估在LCD控制中的作用。(3)利用我们对LCD机制的了解来研究其 在小鼠苗勒管变性和早期胚胎发育过程中的保护，其中细胞 死亡是非凋亡的，并且在形态学上类似于LCD。我们的研究结果可能有助于理解 在人类发育和疾病中的细胞死亡过程。

Our long-term goal is to understand the molecular basis of a novel morphologically-conserved non-apoptotic developmental cell-death program we uncovered, and to determine its roles in mammalian development and disease. Programmed cell death is a major cell fate. Apoptosis, an extensively studied cell death process, requires caspase proteases and is accompanied by chromatin compaction and cytoplasmic shrinkage. Surprisingly, mice lacking apoptotic effectors survive to adulthood. These observations suggest that non- apoptotic cell death may play key roles in animal development. Although genes promoting necrotic cell death have been described, these are not required for development. Thus, whether alternative developmental cell death pathways exist, and if so, what molecular mechanisms govern their execution, is a major outstanding question. Our studies of the C. elegans linker cell provide direct evidence that caspase-independent non- apoptotic cell death pathways operate during animal development. Linker cell death occurs in the absence of C. elegans caspases, and other apoptosis genes are also not required, nor are genes implicated in autophagy or necrosis. The morphology of a dying linker cell is characterized by lack of chromatin condensation, a crenellated nucleus, and swelling of cytoplasmic organelles. Remarkably, cell death with similar features (linker cell-type death, LCD) also occurs in vertebrates, and is characteristic of neuronal degeneration in polyglutamine diseases. We recently described a pathway governing C. elegans LCD. This is the first such framework for a non-apoptotic developmental cell-death program. LCD is controlled by Wnt signals that function in parallel with a developmental-timing and a MAPKK pathway to control non-canonical activity of HSF-1, a conserved heat-shock transcription factor. let-70/Ube2D2, encoding a conserved E2 ubiquitin- conjugating enzyme, is a key target of HSF-1. The E3 components CUL-3/cullin, RBX-1, and BTBD-2 function with LET-70/UBE2D2 for LCD. LCD pathway components are involved in vertebrate cell-degenerative processes. pqn-41, encoding a self-aggregating glutamine-rich protein, is reminiscent of polyglutamine repeat proteins causing neurodegeneration. tir-1/Sarm as well as the E3 component BTBD-2, promote distal axon degeneration following axotomy in mice, supporting conserved cell dismantling roles. Here we will build on these studies to uncover LCD pathway targets, and study relevance to mammalian development. We will: (1) Investigate how HSF-1 function in LCD differs from its heat-shock response roles. (2) Identify BTBD-2 target genes and assess roles in LCD control. (3) Use our knowledge of the LCD mechanism to investigate its conservation during Müllerian duct degeneration and early embryonic development in the mouse, where cell death is non-apoptotic and morphologically similar to LCD. Our results may contribute to an understanding of cell death processes in human development and disease.