Molecular Basis of Robertsonian Translocation Formation

描述(申请人提供)：尽管染色体异常在人类中发生的频率很高，但其发生的分子机制尚不清楚。罗伯特曼易位(ROB)是人类最常见的染色体重排，指的是13、14、15、21和22号染色体顶端着丝粒之间的全臂交换。这些重排极大地导致了胎儿损耗、智力低下和出生缺陷。新罗布的形成速度非常快。我们假设ROB是通过两种不同的机制形成的；一个是导致公共ROB(13q14q)和ROB(14q21q)的定向过程，另一个是导致其余八个较罕见类别的更随机的过程。为了阐明相关机制，我们建议在两类最常见的罗伯逊易位中鉴定包含断裂点的区域，即ROB(13q14q)和ROB(14q21q)，并克隆参与易位形成的序列(S)。这将有助于通过以下特定目的来阐明罗伯逊易位、顶着丝粒染色体上这些区域的形成和进化的机制(S)： (1)绘制13、14和21号染色体近端短臂断裂区的物理图谱。 (2)确定ROB(13q14q)和ROB(14q21q)断裂点的序列，并将其牵涉到ROB地层中。 (3)通过确定卫星IFI DNA使端着丝粒短臂易于重排的机制，找出易于ROB形成的因素。 (4)观察卵母细胞顶体染色体之间的空间关系，比较卵母细胞内顶体短臂之间以及卵母细胞与精母细胞之间的减数分裂交换点的出现频率。 (5)确定灵长类中卫星III DNA亚家族的进化保守性。对这类常见的结构重排的研究对于理解基因组其他区域中结构性和获得性易位的形成具有更广泛的意义，有助于洞察高度重复DNA中性别之间的重组差异，并有助于我们理解顶着丝粒染色体的不分离。此外，顶端着丝粒短臂上序列的克隆和定位将有助于深入了解这些染色体之间这些序列的协同进化，并有助于全面了解哺乳动物，特别是灵长类动物的染色体进化。最后，这项研究正在探索我们基因组的一个区域，这个区域在很大程度上被人类基因组计划所忽视。这项研究中产生的试剂将有助于全面了解人类染色体的组织，并可能有助于了解卫星DNA在染色体结构、组织和功能中所起的作用。

DESCRIPTION (provided by applicant): Despite the high frequency at which chromosomal abnormalities occur in humans, the molecular mechanisms underlying their occurrence are poorly understood. Robertsoman translocations (ROB), whole arm exchanges between the acrocentric chromosomes 13, 14, 15, 21, and 22, are the most common chromosomal rearrangements in humans. These rearrangements contribute greatly to fetal wastage, mental retardation, and birth defects. The formation of de novo ROB occurs at an exceptionally high rate. We have postulated that ROB form through two distinct mechanisms; a directive process resulting in the common rob(13q14q) and rob(14q21q), and a more random process resulting in the remaining eight rarer classes. To elucidate the mechanisms involved, we propose to identify the region containing the breakpoints in the two most common classes of Robertsonian translocations, rob (13q14q) and rob(14q21q) and clone the sequence(s) involved in the translocation formation. This will allow for the elucidation of the mechanism(s) of Robertsonian translocation formation and evolution of these regions on the acrocentnc chromosomes through the following specific aims: (1) Develop physical maps of the breakpoint regions in the proximal short arms of chromosomes 13, 14, and 21. (2) Determine the sequences at the rob(13q14q) and rob(14q21q) breakpoints and implicate them in ROB formation. (3) Identify factors that predispose to ROB formation through determining the mechanism through which satellite ifi DNA makes the acrocentric short arms susceptible to rearrangement. (4) Examine the spatial relationship between the acrocenthc chromosomes in oocytes and compare the frequency of meiotic exchange foci between acrocentric short arms within oocytes and between oocytes and spermatocytes. (5) Determine the evolutionary conservation of subfamilies of satellite III DNA among primates. The study of this common class of structural rearrangements has broader implications to understanding constitutional and acquired translocation formation in other regions of the genome, providing insight into recombination differences between the sexes within highly repetitive DNA, and facilitating our understanding of nondisjunction of the acrocentric chromosomes. Additionally, the cloning and mapping of sequences on the acrocentric short arms will give insight into the concerted evolution of these sequences among these chromosomes and contribute to the general understanding of chromosome evolution in mammals, and specifically in primates. Finally, this research is exploring a region of our genome that has been largely ignored by the effort of the Human Genome Project. The reagents produced in this research will contribute to the overall understanding of the organization of the human chromosome and may lead to an understanding of the role satellite DNA plays in chromosome structure, organization and function.