Restoration dynamics of Xp chromosomes in cloned bovine embryos

描述(由申请人提供)：了解胚胎发育过程中的端粒动力学与人类疾病有直接关系。最近的动物克隆研究发现，在牛、猪和小鼠身上，重建的胚胎能够将供体细胞中缩短的端粒恢复到该物种特有的正常范围，这表明早期胚胎细胞存在检查和修复/恢复端粒缺失的机制。因此，克隆胚胎为研究调节早期胚胎端粒稳态的因素和途径提供了良好的模型系统。本R03项目的目的是建立一种准确的植入前胚胎端粒长度测定方法，并测定克隆牛胚胎的端粒修复动力学。本研究的具体目的是：1)建立可靠的基于端粒长度分析的牛早期胚胎端粒长度分析方法(STELA)；2)研究克隆牛胚胎XP染色体的端粒修复动态。我们想要检验的中心假设是，克隆胚胎中的端粒是以随机的和染色体特有的模式恢复的。从这个系统中获得的知识不仅将回答克隆胚胎中端粒何时以及如何恢复的有趣问题，而且还将揭示更根本的问题，即端粒长度在胚胎发育中是如何调节的。

DESCRIPTION (provided by applicant): Understanding telomere dynamics during embryogenesis has direct relevance to human disease. Recent studies in animal cloning found that the reconstructed embryos were able to restore the shortened telomeres in the donor cells to the normal range specific of that species, in cattle, pigs and mice, indicating that mechanisms exist for early embryonic cells to check and repair/restore telomere deficiency. The cloned embryos, therefore, provide a good model system to study the factors and pathways that regulate telomere homeostasis in early stage embryos. The objective of this R03 project is to establish an accurate telomere length assay for preimplantation stage embryos and to determine the telomere restoration dynamics in cloned bovine embryos. The specific aims are: 1) to establish a reliable PCR based telomere length assay Single Telomere Length Assay (STELA) for preimplantation stage embryos; and 2) to determine the telomere restoration dynamics of Xp chromosomes in cloned bovine embryos. The central hypothesis we want to test is that the telomeres are restored in cloned embryos in a stochastic and chromosome specific pattern. Knowledge obtained from this system will not only answer the intriguing question of when and how the telomeres are restored in cloned embryos, but also shed light on the more fundamental question of how telomere lengths are regulated in embryo development.