Creation of hyperactive transposons for mutagenesis in rodents

描述（由申请人提供）：大鼠是小鼠不适合的许多类型人类疾病的优选模型。与小鼠相反，大鼠和人类在细胞色素P450基因上也有更多的相似性，使大鼠成为毒理学和药理学研究的更有用的模型。大鼠也是糖尿病，关节炎，行为障碍（包括药物成瘾）和脑成像的首选模型。然而，直到最近，由于缺乏能够促进生殖系的大鼠干细胞系，以及缺乏有效的技术来修饰基因组序列，产生工程突变一直存在问题。转座生物制药公司已经率先使用移动的DNA元件（例如，转座子）以在大鼠生殖系中产生插入突变。到目前为止，我们已经制造了超过100个插入突变系（称为TKOTM敲除大鼠模型）。这种方法利用基因陷阱策略来选择随机整合的转座子，这使得能够快速识别序列标记的突变位点。在I期研究中，我们专注于合成来自三种不同转座子家族的超活性转座酶，即睡美人（SB）、piggyBac（PB）和TcBuster（TcB），以提高转座在生殖系中的效率。我们报告了PB家族中的一些高活性转座酶的成功产生。在II期研究中，我们将产生一个含有超过200，000个双报告基因陷阱插入突变的大鼠胚胎干（rES）细胞库; EGFP报告系统将用作polyA陷阱，以最大限度地提高在大约30，000个大鼠基因中产生插入突变的可能性，并使用无启动子的tdTomato报告基因筛选谱系特异性基因破坏。从长远来看，我们打算使用rES细胞库在每个位点产生大鼠敲除系。在II期研究中，我们将专注于开发神经，心脏和内皮细胞谱系中的转座子介导的敲除系，使用I期研究中创建的高活性PB转座酶，目的是产生一个敲除系库，这将对毒理学，行为和心血管研究等各种应用有价值。我们将开发高通量的体外分化方案，以筛选在96孔板中培养的rES细胞库。在谱系特异性分化方案后，将通过筛选含有tdTomato阳性细胞的威尔斯孔来鉴定神经、心脏和内皮细胞谱系中的潜在突变。将对阳性威尔斯孔中的rES细胞池进行亚克隆和再筛选，以鉴定携带潜在谱系特异性突变的单个克隆。将分离基因组DNA并用作splinkerette PCR的模板，splinkerette PCR常规用于扩增DNA插入侧翼的序列。我们将确定每个插入的基因组位点，并筛选每个基因的谱系特异性表达，以排除影响普遍表达位点的插入。我们将为学术和制药最终用户开发两种产品。首先，我们将通过将这些细胞注射到宿主囊胚中，从选定的rES细胞克隆中产生嵌合动物，并通过几轮回交分离出“不相关”突变，以产生用于人类疾病的额外TKOTM敲除大鼠模型。其次，我们将向学术和制药最终用户销售含有超出我们核心利益的基因突变的rES细胞克隆。突变动物、从突变雄性分离的精子和突变rES细胞将由国家大鼠资源和研究中心分发，并根据NIH共享生物医学研究模式生物的政策与学术界共享。 公共卫生相关性：在“创建用于啮齿动物突变的超活性转座酶”申请中，我们正在寻求II期资金，以使用我们创建的新型转座酶来产生人类疾病的新模型。我们已经证明了创建转座子介导的突变以模拟人类疾病用于基础和治疗研究应用的价值。我们以前所有的模型都是通过随机诱变获得的。在这个提案中，我们概述了一些研究，这些研究将使我们能够识别转座子介导的突变，这些突变可能会影响神经，心脏或血管功能。这种大鼠模型将提供新的和有价值的工具，以开发在人类中特别流行的疾病类别的新疗法。因此，如果成功的话，这个项目将有利于公共卫生的许多目标，使研究界能够容易地在模拟人类疾病的大鼠中产生突变。

DESCRIPTION (provided by applicant): The rat is a favored model for many types of human disease for which mice are not suitable. As opposed to the mouse, rats and humans also share more similarity in their cytochrome P450 genes, making the rat a more useful model for toxicology and pharmacology studies. The rat is also a favored model for diabetes, arthritis, behavioral disorders (including drug addiction), and brain imaging. However, until recently, generating engineered mutations has been problematic due to the lack of rat stem cell lines capable of contributing to the germ line, and the lack of efficient technologies to modify genomic sequences. Transposagen Biopharmaceuticals has pioneered the use of mobile DNA elements (e.g., transposons) to generate insertional mutations in the rat germ line. To date, we have over made over 100 insertional mutant lines (referred to as TKOTM Knockout Rat Models). This approach utilizes gene-trap strategies to select for randomly integrated transposons, which enable the rapid identification of sequence-tagged mutation sites. In Phase I studies, we focused on synthesizing hyperactive transposases, from three different families of transposons, Sleeping Beauty (SB), piggyBac (PB), and TcBuster (TcB), to increase the efficiency of transposition in the germ line. We report the successful generation of a number of hyperactive transposases in the PB family. In Phase II studies, we will generate a rat embryonic stem (rES) cell bank containing over 200,000 dual reporter gene-trap insertional mutations; a EGFP reporter system will be used as a polyA trap to maximize the probability of generating insertional mutations in each of the approximately 30,000 rat genes, and a promoterless tdTomato reporter to screen for lineage-specific gene disruptions. In the long term, we intend to use the rES cell bank to generate rat knockout lines in each locus. In Phase II studies, we will focus on developing transposon-mediated knockout lines in neural, cardiac, and endothelial cell lineages, using the hyperactive PB transposases created in Phase I studies, with the aim of generating a bank of knockout lines that that will be valuable for a wide variety of applications such as toxicology, behavioral, and cardiovascular research. We will develop high-throughput in vitro differentiation protocols to screen pools of rES cells cultured in 96-well formats. Potential mutations in neural, cardiac, and endothelial cell lineages will be identified by screening for wells that contain tdTomato positive cells after lineage-specific differentiation protocols. rES cell pools in positive wells will be subcloned and re-screened to identify the individual clone that carries the potential lineage specific mutation. Genomic DNA will be isolated and used as template for splinkerette PCR, which is used routinely to amplify sequences that flank DNA insertions. We will determine the genomic sites for each insertion and screen each gene for lineage-specific expression to rule out insertions that affect ubiquitously expressed loci. We will develop two products for academic and pharmaceutical end users. First, we will generate chimeric animals from selected rES cell clones by injecting these cells into host blastocysts, and segregate away the "irrelevant" mutations by several rounds of backcrosses to generate additional TKOTM Knockout Rat Models for human diseases. Second, we will market rES cell clones, containing mutations in genes that are beyond our core interests to academic and pharmaceutical end users. Mutant animals, sperm isolated from mutant males, and mutant rES cells will be distributed by the National Rat Resource and Research Center and shared with the academic community according to NIH policies for sharing model organisms for biomedical research. PUBLIC HEALTH RELEVANCE: In the application "Creation of hyperactive transposases for mutagenesis in rodents," we are seeking Phase II funding to use the novel transposases we created to generate new models of human disease. We have demonstrated the value of creating transposon-mediated mutations to model human diseases for basic and therapeutic research application. All of our previous models were obtained by random mutagenesis. In this proposal we outline studies that will enable us to identify transposon mediated mutations that will likely affect neural, heart, or blood vessel function. Such rat models will provide new and valuable tools to develop new therapies in classes of diseases that are particularly prevalent in humans. Thus, if successful, this project would benefit many goals of public health by making the production of mutations in the rat that model human diseases readily accessible to the research community.