NOVEL GENE DISCOVERED IN THE HEART

心脏的发育需要对基因表达进行精确的时空控制，以促进其增殖和分化。在胚胎和新生儿早期发育过程中，心脏通过细胞增殖生长。随后通过细胞增大或心肌肥大进一步生长。心肌细胞的增殖似乎是由一个单独的程序调节的，不同于控制心肌细胞分化的程序，不像大多数其他细胞类型。控制心肌细胞增殖的机制尚未确定。对这些机制的理解将为操纵细胞增殖以替换和/或修复心血管疾病造成的受损组织提供机会。我们已经鉴定、克隆并测序了心脏中一种与心肌细胞增殖相关的新基因（TAP）。western初步分析表明Tap蛋白仅在分裂的心肌细胞中表达，而在非分裂的心肌细胞中几乎不存在。我们的假设预测TAP是心肌细胞增殖所需的信号转导途径的必要组成部分。我们的长期目标是确定Tap在分裂的肌细胞中的功能。我们的具体目标是：(1)使用酵母双杂交筛选和共免疫沉淀鉴定心肌细胞中与Tap相关的细胞蛋白，以确定Tap在细胞中如何起作用。(2)通过在培养的成年、出生后21天和胚胎大鼠心室心肌细胞和HL-1心肌细胞系中过表达和阻断其表达，开始对Tap进行功能表征。由于该基因是全新的，这些研究将首次表明TAP在肌细胞中的功能作用，并为设计合理的、未来深入的研究提供基础。

Development of the heart requires the precise spatial and temporal control of gene expression for proliferation and differentiation. During embryonic and early neonatal development, the heart grows by cell proliferation. Further growth is later established through cell enlargement, or cardiac hypertrophy. Cardiac muscle cell proliferation appears to be regulated by a separate program, distinct from the program which controls differentiation of the myocyte, unlike most other cell types. The mechanisms governing the control of cardiomyocyte proliferation are yet to be established. An understanding of these mechanisms will provide an avenue of opportunity to manipulate cellular proliferation to replace and/or repair damaged tissue sustained from cardiovascular disease. We have identified, cloned and sequenced a novel gene (TAP) in the heart which is expressed in association with myocyte proliferation. Preliminary western analysis show that the Tap protein is expressed only in the dividing cardiomyocyte and is virtually absent from the non dividing myocyte. Our hypothesis predicts that TAP is a necessary component of a signal transduction pathway required for cardiomyocyte proliferation. Our long term goal is to determine the function of Tap in the dividing myocyte. Our specific aims are to: (1) Identify cellular proteins which associated with Tap in the cardiomyocyte using the yeast two-hybrid screen and co-immunoprecipitation in order to determine how Tap may function in the cell. (2) To begin to functionally characterize Tap by over expressing and blocking its expression in cultured adult, 21-day postnatal and embryonic rat ventricular cardiomyocytes and in the HL-1 cardiac muscle cell line. Since this gene is entirely novel these studies will provide the first indication of the functional role of TAP in the myocyte, and provide a foundation for the design of rational, future in depth studies.