Mitochondrial accumulation and counting in oogenesis via the mitochondrial UPR

通过线粒体 UPR 进行卵子发生过程中的线粒体积累和计数

• 批准号: 9049825
• 负责人: Lilian Tawsein Lamech
• 金额: $ 5.43万
• 依托单位: SLOAN-KETTERING INST CAN RESEARCH
• 依托单位国家: 美国
• 财政年份: 2016
• 资助国家: 美国
• 起止时间: 2016-03-01 至 2019-02-28
• 项目状态: 已结题
• 来源: https://reporter.nih.gov/project-details/9049825
• 关键词: Aging; Animals; Automobile Driving; Binding; Binding Sites; Biogenesis; Caenorhabditis elegans; Cell Count; Cell Nucleus; Cell physiology; Cells; Cytosol; DNA biosynthesis; DNA copy number; DNA-Directed DNA Polymerase; Data; Defect; Embryonic Development; Ensure; Fertilization; Functional disorder; Genes; Genetic Transcription; Genome; Germ Cells; Goals; Homeostasis; Human Development; Infertility; Insulin Resistance; Malignant Neoplasms; Mitochondria; Mitochondrial DNA; Mitochondrial Proteins; Modeling; Molecular Chaperones; Monitor; Morphology; Muscle; Neurodegenerative Disorders; Neurons; Nuclear; Nuclear Localization Signal; Obesity; Oocytes; Oogenesis; Organelles; Oxidative Phosphorylation; Pathologic; Population; Process; Production; Protein Import; Proteins; Regulation; Research; Respiration; Role; Source; Stress; Testing; Variant; Work; cell type; genetic approach; human disease; insight; meetings; mitochondrial dysfunction; mitochondrial genome; neuronal cell body; progenitor; programs; public health relevance; response; trafficking; transcription factor

 DESCRIPTION (provided by applicant): Mitochondria are a major source of cellular energy. Their numbers vary significantly between cell types and correlate with cell functionality as high energy requiring cells such as muscle and neurons tend to have more mitochondria and mitochondrial DNA (mtDNA). Thus, mitochondrial biogenesis requires careful regulation, however, the mechanisms employed by differentiating cells to acquire the precise number remains poorly understood. Oogenesis is perhaps the most dramatic example of a rapid increase in mitochondria, which are replicated over a 100-fold from that found in the germ cell precursor, and is absolutely crucial for embryonic development. The initiation of this burst in mitochondrial biogenesis and how the oocyte determines when to turn it off remains elusive. Mitochondria in the mature oocyte are also kept transcriptionally silent until fertilization via an unknown mechanism. Preliminary data in our lab, which focuses on how cells monitor and respond to mitochondrial dysfunction, suggests a role for the mitochondrial unfolded protein response (UPRmt) in mitochondrial biogenesis in the C. elegans germline. During mitochondrial dysfunction, cells in essence count the number of functioning mitochondria by monitoring the import efficiency of the transcription factor, ATFS-1. ATFS-1 has a mitochondrial and a nuclear localization signal and is normally imported into mitochondria and degraded. During mitochondrial stress, import capacity is impaired causing ATFS-1 to accumulate in the cytosol, which then traffics to the nucleus to induce the UPRmt, which includes mitochondrial chaperones and the mtDNA polymerase. Interestingly, the soma of worms lacking ATFS-1 develop normally but germlines are defective suggesting a role in oocyte biogenesis. I aim to examine the role ATFS-1 in regulating mtDNA replication and suppression of mtDNA transcription during oogenesis. We propose a model where progenitor germ cells have a low number of mitochondria that is insufficient to import the constitutively expressed ATFS-1, resulting in ATFS-1 activation driving a mitochondrial biogenesis program. As the maturing oocyte produces more mitochondria and eventually reaches the optimal number for embryogenesis, import capacity increases to a point where ATFS-1 is imported and degraded. Using genetic approaches, I aim to test this model by altering ATFS-1 import efficiency in the germline by manipulating import capacity or the mitochondrial targeting sequence of ATFS-1 and determining mitochondrial number in the resultant oocytes. Subsequently, the effects of mitochondrial number on fertilization and subsequent embryogenesis will be examined. As we have previously shown that ATFS-1 can bind mtDNA and repress transcription, I will also examine the role of ATFS-1 in maintaining oocyte mitochondria in a "low activity" state until the initiation of embryogenesis. We anticipate these studies providing insight into pathologic conditions associated with mitochondrial dysfunction including infertility, cancers and neurodegenerative disease.

 描述（由申请人提供）：线粒体是细胞能量的主要来源。它们的数量在细胞类型之间变化很大，并且与细胞功能相关，因为需要高能量的细胞（如肌肉和神经元）往往具有更多的线粒体和线粒体DNA（mtDNA）。因此，线粒体生物合成需要仔细的调节，然而，分化细胞获得精确数量所采用的机制仍然知之甚少。卵子发生可能是线粒体快速增加的最引人注目的例子，线粒体的复制比生殖细胞前体中的线粒体复制了100倍以上，并且对胚胎发育绝对至关重要。线粒体生物发生中这种爆发的开始以及卵母细胞如何决定何时关闭它仍然是难以捉摸的。成熟卵母细胞中的线粒体也保持转录沉默，直到受精， 未知机制我们实验室的初步数据，重点是细胞如何监测和响应线粒体功能障碍，表明线粒体未折叠蛋白反应（UPRmt）在C.秀丽隐杆线虫生殖系在线粒体功能障碍期间，细胞本质上通过监测转录因子ATFS-1的输入效率来计数功能线粒体的数量。ATFS-1具有线粒体和核定位信号，并且通常被输入到线粒体中并降解。在线粒体应激期间，输入能力受损，导致ATFS-1在胞质溶胶中积累，然后运输到细胞核以诱导UPRmt，其包括线粒体伴侣蛋白和mtDNA聚合酶。有趣的是，缺乏ATFS-1的蠕虫的索马发育正常，但生殖系是有缺陷的，这表明在卵母细胞生物发生中的作用。本研究旨在探讨ATFS-1在卵子发生过程中调控mtDNA复制和抑制mtDNA转录的作用。我们提出了一个模型，其中祖生殖细胞具有少量的线粒体，不足以输入组成型表达的ATFS-1，导致ATFS-1激活驱动线粒体生物发生程序。随着成熟的卵母细胞产生更多的线粒体并最终达到胚胎发生的最佳数量，输入能力增加到ATFS-1被输入和降解的程度。使用遗传学方法，我的目标是通过操纵进口能力或线粒体靶向序列的ATFS-1，并确定在所得的卵母细胞中的线粒体数量来改变ATFS-1的进口效率，以测试这个模型。随后，将检查线粒体数量对受精和随后的胚胎发生的影响。正如我们以前已经表明，ATFS-1可以结合线粒体DNA和抑制转录，我也将检查的作用，ATFS-1在维持卵母细胞线粒体在一个“低活性”的状态，直到胚胎发生的开始。我们预计这些研究将提供与线粒体功能障碍相关的病理条件，包括不孕症，癌症和神经退行性疾病的见解。