Centromere Function and Dicentric Chromosome Stability

染色体遗传确保了遗传和基因组信息的传递。异常染色体 数量(非整倍体)和染色体结构改变会导致出生缺陷、生殖异常和 癌症。着丝粒是染色体分离和基因组稳定所必需的基因。正常 染色体通常只有一个着丝粒，但基因组重排与出生缺陷和 癌症产生的染色体中有两个着丝粒在物理上相连。这些双着丝粒通常不是 在大多数模式生物中都是耐受的，正如近80年前芭芭拉·麦克林托克最初在玉米中所展示的那样。 矛盾的是，双着丝粒染色体经常出现在普通人群中，并且极其 在细胞分裂过程中保持稳定。研究人类双着丝粒染色体形成和命运的主要障碍 一直没有实验系统。为了绕过这个长期存在的问题，我们开发了化验方法 在实验中创造双着丝粒人类染色体，分子上反映那些自然发生的染色体和 在生物医学上是相关的。我们发现，在一些新生的双着丝粒中，着丝粒失活发生了。 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(DicXs)，保留两个活性着丝粒，非常稳定。这一发现似乎与此相矛盾 麦克林托克的双着丝粒命运模型。在这项建议中，我们将建立在我们之前对双着丝粒人类的研究基础上 利用可诱导的DICX分析系统探索控制稳定性的分子机制 保持两个活性着丝粒的DicX。我们将重点调查三个主要领域：1)确定 双着丝粒结构(即着丝粒间距)与着丝粒组成和着丝粒组成的分子联系 动粒结构；2)检测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)研究着丝粒蛋白遗传导致着丝粒变化的机制 DICX上的配置。我们的工作将把特定的基因组和表观遗传学事件放在双着丝粒的时间线上 利用一种强大的染色体工程系统形成和稳定 精确模拟人类频繁出现的染色体的双着丝粒染色体。这些研究也将是 对理解双着丝粒的形成和结构、完善长期建立的双着丝粒模型至关重要 稳定性，并为人类着丝粒功能的遗传提供了新的分子见解。

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.