The Role of Cyclin A in Cardiac Development

描述(由申请人提供)：这是为即将成为临床助理教授的Hina W.Chaudhry医学博士申请导师医师科学家发展奖 自2000年7月1日起生效。她将在遗传学与发育教授黛布拉·沃尔吉穆斯博士的指导下，将80%的时间用于科学培训项目。本次培训将由一个主题为研究细胞周期蛋白A在心肌细胞发育、增殖和终末分化中的作用的项目推动。 第一个具体目标是基于心脏中结构性细胞周期蛋白A表达的转基因小鼠模型。这是基于观察到，在小鼠、大鼠和人类中，心脏中的细胞周期蛋白A水平在出生后不久急剧下降，与心脏的终末分化一致。小鼠模型的产生是基于这样的假设，即结构性表达将在发育的后期、新生期和成年期保持增殖。这些小鼠的表型特征是心脏大小、心肌细胞增生/肥大、心功能改变、核增多 倍性和DNA合成，其他细胞周期蛋白表达的改变，细胞凋亡，以及对损伤的反应改变。 第二个特定的目的是描述发生在细胞周期蛋白A与其激酶配对cdk2和cdc2结合的下游的分子事件。这是基于这样一种假设，即心肌细胞周期退出是通过一系列抑制来协调的，通过向下调节细胞周期蛋白A导致Rb或Rb-HKE蛋白的低磷酸化，并且构成 心脏中细胞周期蛋白A的表达可能导致这种蛋白的磷酸化状态的维持，从而导致负责DNA复制和细胞分裂的基因的持续转录。 第三个具体目的是试图了解心脏中细胞周期蛋白A下调的机制。启动子序列的甲基化是一种公认的表观遗传修饰，可导致基因沉默。被认为对基因转录至关重要的Cyclin A启动子序列将通过甲基化检测，并与 本课程将探讨细胞周期退出问题。 对这些具体目标的追求将提供关键的重点，在此期间，PI将在赞助商的直接监督下获得密集的培训经验，学习新的技术和科学研究方法，赞助商是国际公认的细胞周期和发育生物学领域的专家。除了与赞助商和直属实验室的成员进行日常互动外，该协会还将参加遗传与发育学院的一系列讲座，并通过医学系参加研讨会。此外，赞助商还举办了一系列正在进行的工作研讨会，实验室成员在研讨会上展示中间数据，并听取其他实验室成员和特邀教师的重要建议。这些智力资源，加上支持该项目的财政资源，将由医学主席提供，将使PI在培训期结束时发展成为一名独立的调查员。

DESCRIPTION (provided by applicant): This is an application for a Mentored Physician Scientist Development Award for Hina W. Chaudhry, M.D. who will be an assistant professor of clinical medicine as of July 1, 2000. She will spend 80 percent of her time in a program of scientific training under the guidance of Dr. Debra Wolgemuth, Professor of Genetics and Development. This training will be driven by a project whose theme is to investigate the role of cyclin A in cardiomyocyte development proliferation, and terminal differentiation. The first specific aim is based on a transgenic mouse model of constitutive cyclin A expression in the heart. This is based on the observation that cyclin A levels in the heart drop precipitously shortly after birth in mice, rats, and humans, coincident with terminal differentiation of the heart. The mouse model has been generated based on the hypothesis that constitutive expression will maintain proliferation through the later phases of development, the neonatal period, and adulthood. The phenotype of these mice will be characterized with respect to heart size, cardiomyocyte hyperplasia/hypertrophy, altered cardiac function, an increase in nuclear ploidy and DNA synthesis, alteration of expression of other cell cycle proteins, apoptosis, and an altered response to injury. The second specific aim seeks to characterize molecular events that occur downstream of cyclin A binding to its kinase partners, cdk2 and cdc2. This is based on the hypothesis that cardiomyocyte cell cycle exit is coordinated by a cascade of inhibition whereby down regulation of cyclin A results in hypophosphorylation of RB or an RB-hke protein, and that constitutive expression of cyclin A in the heart may result in the maintenance of a phosphorylated state of such a protein, thereby resulting in persistent transcription of genes responsible for DNA replication and cell division. The third specific aim seeks to understand the mechanism underlying the down regulation of cyclin A in the heart. Methylation of promoter sequences is a well-established epigenetic modification that can result in gene silencing. Sequences of the cyclin A promoter thought to be crucial for gene transcription will by assayed for methylation and a potential correlation with cell cycle exit will be explored. The pursuit of these specific aims will provide the critical focus during which time the PI will gain an intensive training experience, learning new techniques as well as the methods of scientific inquiry under the immediate supervision of the Sponsor, an internationally recognized expert in the field of cell cycle and developmental biology. In addition to daily interactions with the Sponsor and members of the immediate laboratory, the PI will participate in a series of lectures given by the faculty of Genetics and Development, and participate in seminars through the Department of Medicine. Additionally, the Sponsor holds a series of Work-in-Progress seminars, in which members of the laboratory present intermediate data and receive critical suggestions from other laboratory members and invited faculty. These intellectual resources, combined with the fiscal resources to support theproject which will be provided by the Chairman of Medicine, will enable the PI to develop into an independent investigator by the conclusion of the training period.