Commitment to the myocardial phenotype

对心肌表型的承诺

• 批准号: 6493625
• 负责人: PAUL ANTHONY KRIEG
• 金额: $ 28.8万
• 依托单位: UNIVERSITY OF ARIZONA
• 依托单位国家: 美国
• 财政年份: 2001
• 资助国家: 美国
• 起止时间: 2001-08-01 至 2002-07-31
• 项目状态: 已结题
• 来源: https://reporter.nih.gov/project-details/6493625
• 关键词: Xenopus; Xenopus oocyte; cell differentiation; cell population study; developmental genetics; gene expression; histogenesis; homeobox genes; myocardium; vertebrate embryology

In Drosophila, the homeobox gene tinman is absolutely required for development of the heart. In vertebrates, a small family of homeobox genes that are related to tinman have been identified, including tissues, their precise role in regulation of cardiac development remains unclear. This is illustrated by experiments investigators the role of the Nkx2-5 gene in cardiogenesis. Although, ablation of the Nkx2-5 gene in mouse results in embryonic death due to heart defects, the embryos contain a differentiated superficially normal , superficially normal heart and the major observable defect is a failure of looping morphogenesis. The role of Nk2-5 therefore, is not obviously similar to that of the tinman gene in the fly. The relatively minor consequences of Nkx-25 ablation, could be explained by the presence of additional tinman family genes with redundant activities, but at present the characterization of candidate rescuing genes is very preliminary. Therefore, the importance of the tinman gene family for vertebrate heart development is currently an unresolved question. In order to further explore the role of the tinman genes during heart development, we have carried out a series of experiments in the frog, Xenopus laevis. First, we have identified a novel member of the tinman family that is expressed early during heart development. Second we have carried out experiments in which expression of a dominant inhibitory mutant form of Nkx2-5 in the frog embryos results in total elimination of detectable myocardial differentiation. We proposed that this effect is achieved by inhibition of the function of multiple members of the tinman gene family. The long term objective of the proposed research is to understand the mechanism by which the vertebrate tinman-related genes regulate cardiac development. The specific experimental aims are as follows: -1) to further examine the mechanism leading to the elimination of myocardial gene expression. 2) to use a hormone-inducible expression systems to determine the time during development that Nkx2-5 plays its role in regulation of myocardial differentiation. 3). To determine whether Nkx2- 5, in combination with GATA-4 and SRF is sufficient to direct myocardial gene expression. 4) To identify the complete repertoire of tinman family members expressed during myocardial development of tinman family members expressed during myocardial development in Xenopus.

在果蝇中，同源盒基因tinman对于心脏的发育是绝对必要的。在脊椎动物中，已经确定了一个与tinman相关的小同源盒基因家族，包括组织，但它们在调节心脏发育中的确切作用仍不清楚。实验研究人员证实了Nkx2-5基因在心脏发生中的作用。虽然，在小鼠中，Nkx2-5基因的消融会导致由于心脏缺陷而导致的胚胎死亡，但胚胎含有分化的表面正常和表面正常心脏，主要可观察到的缺陷是环形态发生的失败。因此，Nk2-5在果蝇中的作用与tinman基因的作用并不明显相似。Nkx-25消融的相对较小的后果可以解释为存在额外的具有冗余活性的tinman家族基因，但目前候选拯救基因的表征是非常初步的。因此，tinman基因家族对脊椎动物心脏发育的重要性目前是一个未解决的问题。为了进一步探索tinman基因在心脏发育过程中的作用，我们在非洲爪蟾（Xenopus laevis）蛙身上进行了一系列实验。首先，我们已经确定了在心脏发育早期表达的tinman家族的新成员。其次，我们进行了实验，在青蛙胚胎中表达Nkx2-5的显性抑制突变形式导致完全消除可检测的心肌分化。我们提出这种效果是通过抑制tinman基因家族多个成员的功能来实现的。这项研究的长期目标是了解脊椎动物与铁蛋白相关的基因调控心脏发育的机制。具体实验目的如下：1)进一步探讨心肌基因表达消除的机制。2)利用激素诱导的表达系统确定Nkx2-5在发育过程中发挥心肌分化调节作用的时间。3)。确定Nkx2- 5联合GATA-4和SRF是否足以指导心肌基因表达。4)鉴定爪蟾心肌发育过程中表达的tinman家族成员的完整谱系。