Cardio-Specific Gene Expression and Genetic Analysis of Myocardial Disorders

(A)心脏功能重要基因的心脏特异性调控机制：对于心脏肥厚的机制，我们使用体外培养心肌细胞拉伸模型表明，涉及MAP激酶的细胞内信号级联反应至少部分是由心肌血管紧张素II介导的，心肌肾素-血管紧张素系统导致心肌细胞肥厚和间质纤维化。我们还阐明了心肌基因如细胞因子（IL-6）、激素（ANP、BNP、肾素、血管紧张素）、钾通道和钙泵在缺血、机械负荷、钙和甲状腺激素下的表达和转录调控机制。此外，我们以小鼠Csx （cardio-specific homeobox）基因为探针，分离出人类Csx基因，发现人和小鼠Csx基因的氨基酸序列非常相似，表明Csx基因在物种中具有高度保守性。(B)心肌疾病相关基因分析在日本肥厚性心肌病（HCM）患者中检测到心脏β -肌球蛋白重链基因的14个错义突变，其中13个突变与高加索患者不同。在47个受影响的日本家庭中，有11个家庭与心脏β -肌球蛋白重链基因没有关联，表明日本HCM患者的遗传异质性。我们还在心肌肥大的线粒体心肌病患者中发现了tRNA-Leu基因的点突变和线粒体DNA的缺失。此外，我们发现日本扩张型心肌病与HLA-DR位点相关，日本长QT综合征（Romano-Ward综合征）与HRAS和11p15.5染色体上的D11S922位点相关。

(A) Mechanisms of Cardio-Specific Regulation of the Genes Important to cardiac FunctionsAs for the mechanisms of cardiac hypertrophy, we showed using an in vitro stretch-model of cultured cardiac myocytes that the intracellular signaling cascades involving MAP kinase is, at least in part, mediated by myocardial angiotensin II and that myocardial renin-angiotensin system causes hypertrophy of cardiac myocytes and interstitial fibrosis. We also clarified the mechanisms regulating the expression and transcription of cardiac genes such as cytokine (IL-6), hormones (ANP,BNP,renin, angiotensin), potassium channel, and calcium pump in response to ischemia, mechanical load, calcium, and thyroid hormone. Furthermore, we isolated the human Csx gene using the murine Csx (cardio-specific homeobox) gene as a probe and found that the amino acid sequences of human and murine Csx genes are very similar, indicating that Csx gene is highly conserved among the species.(B) Analysis of the Genes Responsible for Myocardial DisordersFourteen missense mutations of the cardiac beta-myosin heavy chain gene were detected in Japanese patients with hypertrophic cardiomyopathy (HCM), and 13 out of these 14 mutations were different from those found in Caucasian patients. In 11 out of 47 affected Japanese families, there was no linkage to cardiac beta-myosin heavy chain gene, indicating the genetic heterogeneity of Japanese patients with HCM.We also identified a point mutation in tRNA-Leu gene and deletions of mitochondrial DNA in patients with mitochondrial cardiomyopathy who had cardic hypertrophy. Furthermore, we found linkage of Japanese dilated cardiomyopathy to HLA-DR locus, and Japanese long QT syndrome (Romano-Ward syndrome) to HRAS and D11S922 loci on chromosome 11p15.5.