Differential regulation of duplicated fatty acid-binding protein genes of zebrafish

人们认为，促使生物在生命进化中日益复杂的主要机制之一是基因和整个基因组的复制。我们正在研究斑马鱼细胞内脂结合蛋白(ILBP)编码的多基因家族中重复基因的调节和进化。这个家族包括斑马鱼的脂肪酸、视黄醇(一种维生素A衍生物)和视黄酸结合蛋白。ILBP参与了大量的细胞过程，从长链脂肪酸、胆盐和维甲酸的摄取和细胞内运输，到调节基因调控、神经发生和人类的疾病状态。我们选择斑马鱼作为我们研究的实验模式生物，因为它耐寒、抗病、容易饲养、成本低廉，在实验胚胎学和遗传分析中都有应用。此外，斑马鱼是一个研究脊椎动物发育的模式系统，在这个系统中，胚胎发育的各个阶段都得到了很好的描述。到目前为止，我们已经鉴定了斑马鱼iLBP多基因家族的22个成员。许多iLBP基因是复制的，这是由于大约2.3亿-4亿年前在鳍鱼谱系中发生的全基因组复制事件。我们已经证明了几个斑马鱼iLBP基因的转录是由饲料脂肪酸诱导的，我们建议测试这些iLBP基因的复制副本是否由于功能的进化而保留在斑马鱼基因组中(S)。本研究的目的是鉴定iLBP基因启动子中的顺式作用元件。此外，我们计划确定哪些核转录因子及其激活配体(例如，脂肪酸和氯贝特，一种已知能诱导某些哺乳动物脂代谢相关基因的药物)结合顺式元件来诱导特定的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相似或相同，我们以斑马鱼为模型系统的研究可能会为深入了解iLBP基因在人类发育和疾病(如糖尿病、动脉粥样硬化和肥胖)中的作用提供依据。

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 intracellular lipid-binding proteins (iLBP) of zebrafish. This family includes the fatty acid-, retinol- (a vitamin A derivative) and retinoic acid-binding proteins of zebrafish. iLBPs 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 regulation, neurogenesis, and disease states in humans. We chose zebrafish as the experimental model organism for our 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 22 members of the zebrafish iLBP multigene family. Many 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 iLBP genes is induced by dietary fatty acids and we propose to test whether duplicated copies of these iLBP genes have been retained in the zebrafish genome owing to evolution of function(s). The objectives of the proposed studies are to identity the cis-acting elements in the iLBP gene-promoters. Furthermore, we plan to determine which nuclear transcription factors and their activating ligands (e.g., fatty acids and clofibrate, a drug known to induce some mammalian genes involved in lipid metabolism) bind 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, our studies using zebrafish as a model system may provide insights into the roles of the iLBP genes implicated in human development and disease, such as diabetes, atherosclerosis and obesity.