TBX5 and cardiac proliferation

描述(由申请人提供)：鉴定和表征参与心脏细胞增殖早期步骤的分子通路对于了解先天性心脏病的病理和治疗是绝对关键的。然而，到目前为止，控制胚胎心脏细胞周期进展的早期分子通路在很大程度上仍不清楚。为了解决这些问题，我们克隆并鉴定了非洲爪哇T-box基因Tbx5，该基因在人类先天性心脏病Holt Oram综合征(HOS)中发生突变。我们已经证明，在体内，Tbx5对于心脏细胞周期的G1/S转换是必要和充分的。从这些和其他研究中，我们假设TBX5具有维持心脏祖细胞群体增殖的功能。非洲爪哇提供了一个无与伦比的机会来解决这一假设，因为无限的胚胎心脏组织的访问，心脏外植体分析的发展，绿色荧光蛋白转基因报告蛙的可用性，标记活的心脏组织中的基因表达区域和标记细胞周期的特定阶段，以及我们最近描述的一组广泛的抗体，标记发育中的非洲爪哇心脏细胞周期成分。在这里，我们建议以TBX5为起点，阐明控制心脏祖细胞增殖的分子网络。这将通过确定Tbx5是否直接调节胚胎心脏中的Cyclin D1和Cyclin E2，表征SIN3B-Tbx5蛋白-蛋白质相互作用在心脏细胞周期调控中的生物学意义，以及通过Tbx5鉴定内源性心脏有丝分裂原来调节心脏细胞周期从G1向S的转变来实现。 公共卫生相关性在体内分离和繁殖可分化为心肌细胞的细胞群的能力为治疗广泛的心脏疾病提供了机会。这项建议侧重于转录因子TBX5的特征，该基因在先天性心脏病Holt Oram综合征中突变，以及它在心脏增殖中的内源性作用。我们的近期目标是定义和表征TBX5发挥作用的分子途径，以此为出发点，开始阐明控制心肌细胞前体细胞存活和增殖的途径和分子网络。

DESCRIPTION (provided by applicant): The identification and characterization of the molecular pathways involved in the early steps of cardiac cell proliferation are absolutely critical to understanding the pathologies and treatment of congenital heart disease. However, to date the early molecular pathways that control the progression of the embryonic cardiac cell cycle remain largely unknown. To address these issues, we cloned and characterized the Xenopus T-box gene Tbx5, the gene mutated in the human congenital heart disease Holt Oram syndrome (HOS). We have shown that TBX5 is both necessary and sufficient in vivo for the cardiac G1/S-transition of the cell cycle. From these and other studies, we hypothesize that TBX5 functions to maintain proliferation of cardiac progenitor populations. Xenopus offers an unparalleled opportunity to address this hypothesis due to the access of unlimited embryonic cardiac tissue, the development of cardiac explant assays, the availability EGFP-transgene reporter frogs that mark gene expression domains and mark specific phases of the cell cycle in living cardiac tissues, and our recent description of an extensive panel of antibodies that mark cell cycle components in the developing Xenopus heart. Here we propose to use TBX5 as a starting point to elucidate the molecular networks which control the proliferation of cardiac progenitor cells. This will be accomplished by determining if TBX5 directly regulates cyclin D1 and cyclin E2 in the embryonic heart, characterizing the biological significance of the SIN3B-TBX5 protein-protein interaction in cardiac cell cycle regulation, and through the identification of the endogenous cardiac mitogens which function through TBX5 to regulate the G1 to S transition of the cardiac cell cycle. PUBLIC HEALTH RELEVANCE The ability to isolate and propagate cell populations that can differentiate into cardiomyocytes in vivo offers the opportunity to treat a wide range of cardiac diseases. This proposal focuses on the characterization of the transcription factor TBX5, the gene mutated in the congenital heart disease Holt Oram syndrome, and its endogenous role in cardiac proliferation. Our immediate goal is to define and characterize the molecular pathways by which TBX5 functions with the overall goal, to use TBX5 as a starting point in an effort to begin to elucidate the pathways and molecular networks which control the survival and proliferation of cardiomyocyte progenitor cells.