NOVEL GENE DISCOVERED IN THE HEART

心脏的发育需要对增殖和分化的基因表达进行精确的时空控制。在胚胎和早期新生儿发育期间，心脏通过细胞增殖而生长。进一步的生长后来通过细胞扩大或心肌肥大来建立。与大多数其他类型的细胞不同，心肌细胞的增殖似乎由一个独立的程序来调节，与控制肌细胞分化的程序不同。控制心肌细胞增殖的机制尚未建立。对这些机制的了解将为控制细胞增殖以替换和/或修复因心血管疾病而受损的组织提供一条机会之路。我们已经鉴定、克隆和测序了心脏中一个与心肌细胞增殖相关的新基因(TAP)。初步的Western分析表明，Tap蛋白只在分裂的心肌细胞中表达，而在未分裂的心肌细胞中几乎不表达。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在分裂的心肌细胞中的功能。我们的具体目标是：(1)利用酵母双杂交筛选和免疫共沉淀法在心肌细胞中鉴定与Tap相关的细胞蛋白，以确定Tap在细胞中的功能。(2)通过在培养的成年、出生后21天和胚胎大鼠的心肌细胞和HL-1心肌细胞系中过表达和阻断Tap的表达，开始研究Tap的功能特性。由于该基因是全新的，这些研究将为TAP在心肌细胞中的功能作用提供第一个迹象，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.