肌钙蛋白（TnI）基因调控研究已成为心脏发育过程中蛋白表达调节研究的典范。目前已证实，哺乳动物胚胎型TnI（ssTnI）主要在心脏胚胎期表达，而成年型心脏TnI（cTnI）表达上调最终取代ssTnI，但胚胎型向成年型TnI表达转换及ssTnI表达失活的机制现尚不清楚。前期研究中发现cTnI不是导致ssTnI失活的因素,ssTnI基因表达调节区与核因子的相互作用决定了ssTnI表达水平。我们已成功克隆了ssTnI基因表达调节区，此区有潜在的启动活性。因此，我们将对该表达调节区域进行深入研究，通过降低增强因子表达或提高抑制子活性影响ssTnI表达，阐明该调节区中基因5'端非编码区的启动活性，观察各反式因子对顺式元件的识别与结合，深入探讨小鼠心脏发育过程中ssTnI基因失活的机制。研究TnI基因调节具有重要临床意义，重新开放失活的ssTnI基因将有助于弥补心脏TnI不足造成的心脏功能异常和疾病。

The proposal is a part of our studies on the regulation of myofibril protein expression in the heart. The troponin I (TnI) gene family is used as a model to study the regulation of myofibril gene expression during the maturation of cardiac muscle tissues. Fetal, or slow skeletal TnI (ssTnI) is expressed in the embryonic and fetal heart, and adult, or cardiac TnI (cTnI) expression is up-regulated after birth to replace ssTnI and predominates throughout adulthood in most mammals including humans. The mechanisms of the postnatal fetal-to-adult TnI isoform switch and ssTnI gene inactivation during heart development are still not clear. .In our previous studies, we have demonstrated that up-regulated cTnI itself is not a signal molecule that causes the down-regulation of ssTnI in the heart and ssTnI expression time-course in the heart can be partially influenced by thyroid hormone. We believe that the ssTnI gene regulatory region and the nuclear co-factors in cardiac myocytes should be critical for the regulation of ssTnI gene. We have successfully cloned mouse ssTnI gene regulatory region that includes the gene promoter and a 5' end intragenic region containing the first two non-coding exons, two introns and part of exon 3. To study mouse TnI gene has unique advantage since mouse is a more popular tool in biomedical research using transgenic models. Preliminary studies on this gene regulatory region have shown that it contains a potential promoter activity. In this proposal, we will characterize the cloned mouse ssTnI gene regulatory region to test the hypothesis that decreased enhancers and their binding activity or increased inhibitors in cardiac myocytes result in the repression of ssTnI gene expression during heart development. Three specific aims have been developed to address this hypothesis. Aim 1 will analyze the promoting activity of non-coding exons and introns on mouse ssTnI gene regulatory region. Aim 2 will determine the role of potential trans-factors (especially Yin Yang 1) on ssTnI expression in cardiac myocytes. Aim 3 will explore the mechanisms underlying the inactivation of fetal gene expression during heart development. .It is clinically important to elucidate the mechanisms underlying TnI gene regulation since TnI loss causes diastolic dysfunction and sudden cardiac death. The re-expression of fetal TnI, in case it is needed, may help the heart to maintain a normal function.