Role of calcium signals for metabolic syndromes in children.

钙网蛋白（CRT）是一种内质网钙结合蛋白，对心脏发育至关重要。α-肌球蛋白重链启动子介导的钙网蛋白心脏特异性过表达导致转基因小鼠完全性心脏传导阻滞和猝死为了进一步研究钙网蛋白在心脏发育中的作用机制及其功能，我们利用cre-loxP系统构建了钙网蛋白时空表达的转基因小鼠。将含有CAG启动子、loxP侧翼的氯霉素乙酰转移酶（chloramphenicolacetyltransferas，CAT）基因和CRT cDNA的转基因小鼠显微注射到C57 BL/6小鼠原核细胞中，获得loxP-CRT转基因小鼠。这些小鼠与Nkx2.5-Cre小鼠杂交，Nkx2.5-Cre小鼠在Nkx2.5启动子的控制下表达cre重组酶，Nkx2.5启动子是早期心脏发育所必需的转录因子。繁殖导致具有钙网蛋白心脏特异性过表达的转基因小鼠（Nkx2.5-CRT转基因小鼠）。与对照小鼠相比，Nkx2.5-CRT转基因小鼠的心脏钙网蛋白蛋白水平增加了44倍。钙网蛋白的过度表达与PR间期、QRS间期延长、心动过缓和6- 10周龄的猝死有关。此外，一些NKx2.5-CRT转基因小鼠在7周龄时显示出明显的水肿。RT-PCR分析显示，在Nkx2.5-CRT转基因小鼠心脏中，超极化激活的环核苷酸门控通道1（HCN 1）的表达下降，HCN 1是心脏起搏器活性的重要组成部分。这些表明carleticulin影响心律失常，破坏心脏信号传导，如HCN家族。总之，这些转基因小鼠是一种新的致命性心律失常模型，并为分析内质网蛋白，如钙网蛋白在心脏发生的有用模型。

Calreticulin (CRT) is a Ca^<2+>-binding protein of the endoplasmic reticulum and essential for cardiac development. Cardiac specific overexpression of calreticulin by α-myosin heavy chain promoter results in complete heart block and sudden death in transgenic mice. For further investigating mechanism of calreticulin in cardiac development and its function, we generate transgenic mice that cause temporal and spatial overexpression of calreticulin using cre-loxP system. By microinjection of the transgene which contains a CAG promotor, a loxP-flanked chloramphenicol acetyltransferas (CAT) gene, and CRT cDNA into pronuclear cells of C57BL/6 mice, we made loxP-CRT transgenic mice. The mice were cross-bred with Nkx2.5-Cre mice which express cre recombinase under control of Nkx2.5 promoter, a transcription factor essential for early cardiac development. The breeding were resulted in transgenic mice with cardiac specific overexpression of calreticulin (Nkx2.5-CRT transgenic mice). Cardiac calreticulin protein levels of Nkx2.5-CRT transgenic mice were increased by 44-fold compared with control mice. Overexpression of calreticulin was associated with PR interval, QRS interval prolongation, bradycardia, and sudden death observed from 6- to 10-week-old. Furthermore, some NKx2.5-CRT transgenic mice revealed marked edema in 7-week-old. RT-PCR analysis revealed that the expression of hyperpolerization-activated cyclic nucleotide-gated channel1 (HCN1), essential component for cardiac pace maker activity, was receded in the heart of Nkx2.5-CRT transgenic mice. These suggested that carleticulin affect cardiac arrhythmia with disruption of cardiac signaling, such as HCN families. In conclusion, these transgenic mice are a novel model of fatal arrhythmia, and are useful model for analysis of endoplasmic reticulum protein such as calreticulin in cardiogenesis.