Centromere Function and Dicentric Chromosome Stability

染色体遗传确保遗传和基因组信息的传递。异常染色体 染色体数目（非整倍体）和染色体结构改变导致出生缺陷，生殖异常， 癌着丝粒是染色体分离和基因组稳定所需的位点。正常 染色体通常只有一个着丝粒，但是，与出生缺陷相关的基因组重排， 癌症产生两个着丝粒物理连接的染色体。这些双着丝粒体通常 在大多数模式生物中耐受，正如近80年前Barbara McClintock最初在玉米中说明的那样。 巧合的是，双着丝粒染色体在一般人群中频繁出现，并且非常罕见。 在细胞分裂期间稳定。研究人类双着丝粒染色体形成和命运的主要障碍 是缺乏实验系统。为了解决这个长期存在的问题，我们开发了 实验性地创造出双着丝粒的人类染色体，这些染色体在分子上反映了自然发生的染色体， 与生物医学有关我们发现，在这些从头双着丝粒，着丝粒失活发生 通过部分着丝粒缺失。然而，我们的许多工程双着丝粒染色体，特别是双着丝粒染色体， X等染色体（dicX），保留两个活跃的着丝粒，非常稳定。这一发现似乎与 麦克林托克的双中心命运模型。在这个建议中，我们将建立在我们以前的研究双中心人类 利用诱导型dicX分析系统探索控制稳定性的分子机制， 有两个活跃的着丝粒。我们将集中在三个主要的调查领域：1）定义 双着丝粒结构（即着丝粒间距离）和着丝粒组成之间的分子联系， 动粒结构; 2）测试α卫星基因组结构和转录在双着丝粒中的作用 稳定性，以及3）研究导致不同着丝粒的着丝粒蛋白质遗传机制 配置在dicX上。我们的工作将把特定的基因组和表观遗传学事件的时间轴双中心 通过利用强大的染色体工程系统， 双着丝粒染色体，精确模拟那些经常出现在人类。这些研究也将 对于理解双中心的形成和结构、完善长期建立的双中心模型至关重要 稳定性，并提供了新的分子见解遗传的着丝粒功能在人类。

Chromosome inheritance ensures transmission of genetic and genomic information. Abnormal chromosome number (aneuploidy) and altered chromosome structure cause birth defects, reproductive abnormalities, and cancer. The centromere is the locus required for chromosome segregation and genome stability. Normal chromosomes typically have only one centromere, but, genome rearrangements associated with birth defects and cancer produce chromosomes in which two centromeres are physically linked. These dicentrics are not usually tolerated in most model organisms, as originally illustrated in maize by Barbara McClintock nearly 80 years ago. Paradoxically, dicentric chromosomes occur frequently in the general human population and are extremely stable during cell division. A major impediment in studying dicentric chromosome formation and fate in humans has been the absence of experimental systems. To circumvent this long-standing problem, we developed assays to experimentally create dicentric human chromosomes that molecularly mirror those that occur naturally and are biomedically relevant. We showed that in some of these de novo dicentrics, centromere inactivation occurred by partial centromere deletion. However, many of our engineered dicentric chromosomes, particularly dicentric X isochromosomes (dicXs), retain two active centromeres and are very stable. This finding appears to contradict McClintock's model of dicentric fate. In this proposal, we will build on our previous studies of dicentric human chromosomes by leveraging an inducible dicX assay system to explore molecular mechanisms governing stability of dicXs that maintain two active centromeres. We will focus on three major areas of investigation: 1) defining the molecular links between dicentric structure (i.e. inter-centromere distance) and centromere composition and kinetochore architecture; 2) testing the roles of alpha satellite genomic structure and transcription in dicentric stability, and 3) investigating mechanisms of centromere protein inheritance that result in varying centromere configurations on dicXs. Our work will place specific genomic and epigenetics events on the timeline of dicentric formation and stabilization by making use of a powerful chromosome engineering system that generates dicentric chromosomes that precisely model those that occur frequently in humans. These studies will also be critical for understanding dicentric formation and structure, refining long-established models of dicentric stability, and providing new molecular insights into inheritance of centromere function in humans.