Mechanisms of asymmetric cell division during female meiosis

描述（由申请人提供）：我们的目标是了解定位雌性减数分裂纺锤体在卵皮质和介导极体形成的机制。从长远来看，我们希望阐明为什么不对称的减数分裂纺锤体定位是如此保守的动物门。本建议的具体目标是阐明介导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)驱动蛋白-1重链、驱动蛋白轻链和一种新的蛋白质KCA-1都是在中期-后期转换前将减数分裂纺锤体移动到卵皮质所必需的。与此相反，运动的减数分裂纺锤体卵皮质后，中期后期的过渡是驱动蛋白无关。我们将使用荧光显微镜和体外生物化学测试的假设，驱动蛋白/KCA-1复合物直接运输的纺锤体沿着细胞质微管和一个独特的机制是负责纺锤体易位在驱动蛋白和纺锤体旋转的情况下，在野生型减数分裂。2)微管切割蛋白Katanin的完全丧失导致减数分裂纺锤体组装失败，而Katanin功能的部分丧失导致异常长的减数分裂纺锤体和异常大的极体。我们将使用荧光显微镜和遗传学来测试的假设，微管切断活动限制减数分裂纺锤体的长度，从而极体的大小。3)SPE-11是在受精时引入卵子的精子蛋白，是极体形成所需的。我们将使用荧光显微镜和遗传学的组合来检验SPE-11通过与卵中保守的胞质分裂调节因子相互作用来介导极体形成的假设。减数分裂纺锤体与公共卫生有关有两个主要原因。首先，异常的纺锤体功能导致非整倍体，从而导致唐氏综合症和流产。第二，在动物克隆过程中，用患者匹配的干细胞治疗许多人类疾病的潜力目前受到异常减数分裂纺锤体组装的限制。因此，对减数分裂纺锤体功能的详细分子理解可能会导致预防出生缺陷的治疗，并允许人类疾病的干细胞治疗。

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.