TBX5 and cardiac proliferation

描述（由申请人提供）：心脏细胞增殖早期步骤中涉及的分子途径的识别和表征对于了解先天性心脏病的病理学和治疗绝对至关重要。然而，迄今为止，控制胚胎心肌细胞周期进展的早期分子途径仍然很大程度上未知。为了解决这些问题，我们克隆并表征了非洲爪蟾 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，TBX5 在体内对于细胞周期的心脏 G1/S 转变既是必要的也是充分的。根据这些和其他研究，我们假设 TBX5 的功能是维持心脏祖细胞群的增殖。非洲爪蟾为解决这一假说提供了无与伦比的机会，因为可以获取无限的胚胎心脏组织、心脏外植体测定的发展、标记基因表达域和活体心脏组织中细胞周期特定阶段的EGFP转基因报告蛙的可用性，以及我们最近对标记发育中非洲爪蟾心脏中细胞周期成分的一组广泛抗体的描述。在这里，我们建议使用 TBX5 作为起点来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细胞周期蛋白 D1 和细胞周期蛋白 E2、表征心脏细胞周期调节中 SIN3B-TBX5 蛋白-蛋白相互作用的生物学意义以及通过鉴定通过 TBX5 发挥作用来调节心脏细胞周期的 G1 到 S 转变的内源性心脏有丝分裂原来实现。 公众健康相关性 分离和繁殖可在体内分化为心肌细胞的细胞群的能力为治疗多种心脏病提供了机会。该提案重点关注转录因子 TBX5（先天性心脏病 Holt Oram 综合征中突变的基因）的特征及其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，总体目标是使用 TBX5 作为起点，努力阐明控制心肌祖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.