CARDIAC DEVELOPMENT DURING SITUS INVERSUS EMBRYOGENESIS

作为胚胎心脏发育正常模式的一部分， 心脏通过心脏循环建立左右极性。 协调心脏循环并由此建立 哺乳动物的左侧心脏还有待鉴定。 一 获取这些因素信息的策略是生成 以及改变心脏疾病模式的突变的特征 发展 我们已经制定了一个有效的策略来筛选 转基因小鼠中的插入突变，最近 发现了一个有隐性突变的家庭， 反生的 在这个家族中，100%的纯合子转基因小鼠 有一个镜像反转的左右极性的 心脏以及其他主要内脏器官，包括肺， 肝、脾、胰和胃 新的突变并不是 与先前在小鼠中鉴定的IV突变等位。 以来 新突变是插入突变，转基因插入物 提供了一种分子探针，可用于分离基因组 失活基因所在的区域。 为了克隆新的反位基因并鉴定其功能， 它在调节心脏/胚胎发育中的作用， 这项建议的具体目标是：1）建立染色体 新的反转位突变的位置和物理图谱; 2） 确定该部位的结构和预测产物 inversus基因，并通过靶向验证该基因的功能 在ES细胞中的诱变; 3）定义突变的表达模式， 反位基因产物，特别是在建立 心脏的左-右极性，并表征内- 或编码的蛋白质的细胞外定位;和4） 嵌合体和双突变体心脏形态发生研究 胚胎 由于突变基因在 定义了正常心脏发育的极性， 编码蛋白的鉴定和 其在胚胎发生期间的表达模式将提供 有价值的分子信息 心脏形态发生

As part of the normal pattern of embryonic cardiac development, the heart establishes a left-right polarity through cardiac looping. The factor(s) that coordinate cardiac looping and thereby establish a left-sided heart in mammals have yet to be identified. One strategy to gain information about such factors is the generation and characterization of mutations that alter the patter of cardiac development. We have developed an efficient strategy to screen for insertional mutations in transgenic mice, and have recently identified a family with a recessive mutation that causes situs inversus. In this family, 100% of the homozygous transgenic mice have a mirror-image reversal of the left-right polarity of the heart as well as the other major internal organs, including lung, liver, spleen, pancreas and stomach. The new mutation is not allelic to the previously identified iv mutation in mice. Since the new mutation is an insertional mutation, the transgenic insert provides a molecular probe that can be used to isolate the genomic region where the inactivated gene is located. In order to clone the new situs inversus gene and the characterize its role in the regulation of cardiac/embryonic development, the specific aims of this proposal are to: 1) establish the chromosomal location and physical map of the new situs inversus mutation; 2) determine the structure and predicted product of this situs inversus gene and verify the function of the gene by targeted mutagenesis in ES cells; 3) define the pattern of expression of the situs inversus gene product, particularly during establishment of the left-right polarity of the heart, and characterize the intra- or extra-cellular localization of the encoded protein; and 4) investigate cardiac morphogenesis in chimeric and double mutant embryos. Since the mutated gene plays an essential role in defining the polarity of normal cardiac development, the identification of the encoded protein and the characterization of its pattern of expression during embryogenesis will provide valuable molecular information about a factor that coordinates cardiac morphogenesis.