Intracellular lipid-binding protein genes of zebrafish

在生命进化过程中，促进生物体复杂性增加的主要机制之一是基因和整个基因组的复制。我们正在研究属于斑马鱼细胞内脂结合蛋白（iLBP）多基因家族的重复基因的调控和进化。这个家族包括脂肪酸结合蛋白、视黄醇结合蛋白和视黄酸结合蛋白。从长链脂肪酸、胆盐和类维生素a的摄取和细胞内运输，到调节基因表达、神经发生和人类疾病，iLBP蛋白参与了无数的细胞过程。我们选择斑马鱼进行这些研究，因为它耐寒，抗病，容易和廉价的饲养，在实验胚胎学和遗传分析的应用中都很有用。此外，斑马鱼是研究脊椎动物发育的模型系统，其胚胎发生阶段具有很好的特征。迄今为止，我们已经鉴定了斑马鱼iLBP多基因家族的20个成员。许多斑马鱼的iLBP基因是由于2.3 -4亿年前鳐鱼谱系中发生的全基因组复制事件而复制的。我们已经证明，斑马鱼的几个重复iLBP基因的转录受到膳食脂肪酸的诱导是不同的，即只有一个重复基因被脂肪酸诱导，而不是姐妹重复，这表明这些基因的调控元件在进化上存在分歧。在本研究项目中，我们计划鉴定斑马鱼iLBP基因启动子中的顺式调控元件。此外，我们将确定哪些核转录因子及其激活配体（例如脂肪酸、类维生素a和clofibrate，一种已知能诱导许多哺乳动物参与脂质代谢的基因的药物）结合这些顺式元件来诱导特异性iLBP基因，以及这些顺式和反式作用因子是如何进化的。此外，由于控制斑马鱼正常胚胎发生、生长和繁殖的许多基因在哺乳动物中是相似或相同的，因此斑马鱼可以作为一个模型系统，以深入了解iLBP基因在人类发育和疾病（如糖尿病、动脉粥样硬化和肥胖）中的作用。

One of the major mechanisms thought to facilitate the increasing complexity of organisms in the evolution of life is duplication of genes and entire genomes. We are investigating the regulation and evolution of duplicated genes belonging to the multigene family coding for the intracellular lipid-binding proteins (iLBP) of zebrafish. This family includes the fatty acid-, retinol-, and retinoic acid-binding proteins. iLBP proteins have been implicated in a myriad of cellular processes from uptake and intracellular transport of long-chain fatty acids, bile salts and retinoids, to modulating gene expression, neurogenesis, and human disease. We chose zebrafish for these studies as it is hardy, disease resistant, easily and inexpensively reared, and useful in the application of both experimental embryology and genetic analysis. Moreover, zebrafish is a model system to study vertebrate development in which stages of embryogenesis are well characterized. To date, we have characterized 20 members of the zebrafish iLBP multigene family. Many zebrafish iLBP genes are duplicated owing to a whole genome duplication event that occurred in the ray-finned fish lineage ~230-400 million years ago. We have shown that transcription of several zebrafish duplicated iLBP genes is differentially induced by dietary fatty acids, i.e., only one duplicated gene is induced by fatty acids, and not the sister duplicate, suggesting evolutionary divergence of the regulatory elements in these genes. In this research progamme, we plan to identify the cis-acting regulatory elements in the zebrafish iLBP gene-promoters. Furthermore, we will determine which nuclear transcription factors and their activating ligands (e.g., fatty acids, retinoids, and clofibrate, a drug known to induce many mammalian genes involved in lipid metabolism) bind these cis-elements to induce specific iLBP genes, and how these cis- and trans-acting factors evolved. In addition, since many of the genes that control normal embryogenesis, growth and reproduction in zebrafish are similar, or the same, in mammals, zebrafish may serve as a model system to provide insights into the roles of the iLBP genes implicated in human development and diseases, such as diabetes, atherosclerosis and obesity.