Generation of sarcolipin heart-specific transgenic mice and molecular mechanism of atrial chamber-specific expression

体内超声心动图和血流动力学研究表明，与年龄匹配的对照组相比，肌磷脂(SLN)心脏特异转基因小鼠的心脏功能，尤其是舒张期功能受损。尽管SIN心脏特异转基因小鼠没有表现出心肌肥大或扩张，但心脏肥厚的分子标志物ANF和BNP表达上调，提示SLN心脏特异转基因MINE的心脏重构被掩盖。这些数据表明SLN通过调节SERCA2a活性而在心房功能中发挥重要作用。II.小鼠肌磷脂启动子及其转录调控的分析我们克隆了一个包含小鼠SLN基因5‘侧翼区的2.3kb的DNA片段，并检测了维甲酸对其启动子活性的影响。用F1-荧光素酶(-2237~+62个核苷酸)瞬时转染H9C2后，启动子活性增加40倍。瞬时转染一系列5‘→3’缺失的F1-荧光素酶构建体，发现SLN启动子活性的最小激活区域位于-32 6个核苷酸之间，RA的负调控元件位于-2 2 37~-32 6个核苷酸之间。这些结果表明，SLN基因的表达可能受维甲酸的调控，至少部分是在转录水平上。此外，我们还发现压力超负荷、维甲酸和甲状腺激素下调了SLN mRNAs的表达。

I. Cardiac dysfunction sarcolipin heart-specific transgenic miceIn vivo echocardiography and hemodynamic study demonstrated that cardiac function, especially diastolic function was impaired in sarcolipin (SLN) heart-specific transgenic mice when compared with those in age-matched control mice. Although SIN heart-specific transgenic mice did not exhibited either cardiac hypertrophy or dilation, molecular markers of cardiac hypertrophy such as ANF and BNP were up regulated, suggesting masked cardiac remodeling in SLN heart-specific transgenic mine. These data indicate that SLN play an important role in atrial function via regulation of SERCA2a activity.II. Anaiysisi of mouse sarcolipin promoter and its transcriptional regulationWe cloned a 2.3-kilobase pair DNA fragment encompassing the 5'-flanking region of the mouse SLN gene and examined the effect of retinoic acid on its promoter activity. Transient transfection of H9C2 with F1-luciferase (-2237 to +62 nucleotides) yielded a 40-fold increase in promoter activity. Transient transfection of a series of 5'→3' deletion constructs of F1-luciferase suggested that the minimal region for full activation of the SLN promoter activity is located up to -326 nucleotides and that negative regulatory elements of RA were located between -2237 and -326 nucleotides. The present data indicate that the expression of SLN mRNA is likely regulated by retinoic acid, at least in part, at transcriptional level. In addition, we found that pressure overload, retinoic acid and thyroid hormono down-regulated the expression of SLN mRNAs.