Restoration dynamics of Xp chromosomes in cloned bovine embryos

描述（由申请人提供）：了解胚胎发生过程中的端粒动力学与人类疾病直接相关。最近在动物克隆方面的研究发现，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，如牛、猪和小鼠，这表明存在早期胚胎细胞检查和修复/恢复端粒缺陷的机制。因此，克隆胚胎为研究早期胚胎中调控端粒稳态的因素和途径提供了一个很好的模型系统。本R 03项目的目的是建立一个准确的端粒长度测定植入前阶段的胚胎，并确定克隆牛胚胎端粒恢复动力学。具体目标是：1）建立一种可靠的基于PCR的端粒长度测定方法--单端粒长度测定法（Single Telomere Length Assay，STELA）; 2）测定克隆牛胚胎中Xp染色体的端粒恢复动力学。我们要检验的中心假设是，端粒在克隆胚胎中以随机和染色体特异性的模式恢复。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，而且还将揭示胚胎发育中端粒长度如何调节的更基本问题。

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.