Mechanisms of asymmetric cell division during female meiosis

描述（由申请人提供）：我们的目标是了解雌性减数分裂纺锤体在卵子皮层的定位和介导极体形成的机制。从长远来看，我们希望阐明不对称减数分裂纺锤体定位在动物门中如此保守的原因。本研究的具体目的是阐明秀丽隐杆线虫减数分裂纺锤体定位和极体形成的三种不同途径的详细机制。1)运动蛋白1重链、运动蛋白轻链和一种叫做KCA-1的新蛋白都需要在减数分裂中期到后期转变之前将纺锤体移动到卵皮层。相反，减数分裂纺锤体在中期和后期转变后向卵皮质的运动是不依赖于运动蛋白的。我们将使用荧光显微镜和体外生物化学来验证这样的假设，即驱动蛋白/KCA-1复合物沿着细胞质微管直接运输纺锤体，并且在野生型减数分裂期间，在没有驱动蛋白和纺锤体旋转的情况下，纺锤体易位是由一种独特的机制负责的。2)微管切断蛋白角朊蛋白的完全丧失导致减数分裂纺锤体组装失败，而角朊蛋白功能的部分丧失导致减数分裂纺锤体异常长和极体异常大。我们将使用荧光显微镜和遗传学来检验微管切断活性限制减数分裂纺锤体长度从而限制极体大小的假设。3) SPE-11是受精时引入卵子的一种精子蛋白，是极体形成所必需的。我们将结合荧光显微镜和遗传学来检验SPE-11通过与卵子中保守的细胞分裂调节因子相互作用介导极体形成的假设。减数分裂纺锤体与公共卫生有关主要有两个原因。首先，减数分裂纺锤体功能异常导致非整倍体，导致唐氏综合症和流产。其次，在动物克隆过程中，由于减数分裂纺锤体组装异常，用患者匹配的干细胞治疗许多人类疾病的潜力目前受到限制。因此，对减数分裂纺锤体功能的详细分子理解可能导致预防出生缺陷的治疗，并允许干细胞治疗人类疾病。

DESCRIPTION (provided by applicant): Our goal is to understand the mechanisms that position female meiotic spindles at the egg cortex and that mediate polar body formation. In the long term, we hope to elucidate the reasons why asymmetric meiotic spindle positioning is so conserved across animal phyla. The specific goals of this proposal are to elucidate the detailed mechanisms of three distinct pathways that mediate meiotic spindle positioning and polar body formation in Caenorhabitis elegans. 1) Kinesin-1 heavy chain, kinesin light chains and a novel protein called KCA-1 are each required to move the meiotic spindle to the egg cortex before the metaphase-anaphase transition. In contrast, movement of the meiotic spindle to the egg cortex after the metaphase-anaphase transition is kinesin-independent. We will use fluorescence microscopy and in vitro biochemistry to test the hypothesis that a kinesin/KCA-1 complex directly transports the spindle along cytoplasmic microtubules and that a distinct mechanism is responsible for both spindle translocation in the absence of kinesin and spindle rotation during wild-type meiosis. 2) Complete loss of the microtubule-severing protein, katanin, results in failure to assemble a meiotic spindle whereas partial loss of katanin function results in abnormally long meiotic spindles and abnormally large polar bodies. We will use fluorescence microscopy and genetics to test the hypothesis that microtubule-severing activity restricts meiotic spindle length and thereby polar body size. 3) SPE-11 is a sperm protein introduced into the egg at fertilization and which is required for polar body formation. We will use a combination of fluorescence microscopy and genetics to test the hypothesis that SPE-11 mediates polar body formation by interacting with conserved cytokinesis regulators in the egg. Meiotic spindles are relevant to public health for two major reasons. First, abnormal meiotic spindle function leads to aneuploidy that causes Down syndrome and miscarriage. Second, the potential for treating numerous human diseases with patient-matched stem cells is currently limited by abnormal meiotic spindle assembly during animal cloning. A detailed molecular understanding of meiotic spindle function could thus lead to treatments that prevent birth defects and that allow stem cell therapy of human diseases.