Epigenetic control of preimplantation embryo development

描述（申请人提供）：组蛋白修饰的动态变化是配子染色质向胚胎染色质转变的基础。这些变化被认为是胚胎基因转录起始和多能性获得所必需的。这些转变的异常可能导致胚胎在早期植入前阶段的停滞。早期胚胎死亡是奶牛和人类不育的主要原因。在牛胚胎中，组蛋白H3赖氨酸27的甲基化是动态重塑的表观遗传标记之一。组蛋白H3赖氨酸27的三甲基化与转录沉默相关。我们推测，JMJD 3，一种组蛋白H3赖氨酸27去甲基化酶，是从H3 K27去除甲基化标记所必需的，这反过来又允许胚胎基因转录和正常胚胎发育的启动。为了验证这一假设，我们将通过siRNA注射诱导牛卵母细胞和植入前胚胎中JMJD 3的下调。具体目标1将确定是否母系遗传的JMJD 3是正常的牛胚胎发育所必需的。Specific Aim 2将利用染色质免疫沉淀来评估JMJD 3在胚胎基因组激活时对组蛋白甲基化重编程的作用。具体目标3旨在通过使用RNA-Seq分析早期胚胎的转录组来检查JMJD 3对基因组激活的作用。总之，这些实验将扩大我们对胚胎发育基本机制的理解。这些信息将有助于开发诊断工具和干预措施，以治疗动物和人类的不孕症。此外，揭示由卵母细胞引起的核重编程机制将有助于提高体细胞核移植的成功率，以产生用于农业和生物医学应用的克隆动物和用于再生医学应用的自体干细胞。

DESCRIPTION (provided by applicant): Dynamic changes in histone modification underlie the transition of gametic chromatin to embryonic chromatin. These changes are thought to be required for initiation of embryonic gene transcription and acquisition of pluripotency. Abnormalities in these transitions are likely to result in embryonic arrest at early preimplantation stages. Early embryonic mortality is a major cause of infertility in dairy cattle and humans. In bovine embryos, methylation of histone H3 lysine 27 is one of the epigenetic marks that are dynamically remodeled. Trimethylation of histone H3 lysine 27 is associated with silencing of transcription. We hypothesize that JMJD3, a histone H3 lysine 27 demethylases, is required for removal of methylation marks from H3K27, which in turn allows the initiation of embryonic gene transcription and normal embryo development. To test this hypothesis we will induce downregulation of JMJD3 in bovine oocytes and preimplantation embryos by siRNA injection. Specific Aim 1 will determine whether maternally inherited JMJD3 is required for normal bovine embryonic development. Specific Aim 2 will make use of chromatin immunoprecipitation to assess the role of JMJD3 on histone methylation reprogramming at the time of embryonic genome activation. Specific aim 3 is designed to examine the role of JMJD3 on genome activation by analyzing the transcriptome of early embryos using RNA-Seq. Together; these experiments will expand our understanding of the basic mechanisms underlying embryonic development. This information will aid in developing diagnostic tools and interventions to treat infertility disorders in animals and people. Also, uncovering the nuclear reprogramming mechanisms elicited by the oocyte will help improve the success of somatic cell nuclear transfer for the generation of cloned animals for agricultural and biomedical applications and autologous stem cells for regenerative medicine applications.