Deciphering the Evolution of the Opioid/Orphanin Gene Family

有颌脊椎动物（颚口动物）大脑中化学通讯系统的一个显著特征是产生有用的神经肽化合物的基因的明显复制。 例如，在哺乳动物中，有四种神经肽前体（脑啡肽原、强啡肽原、阿黑皮素原和阿黑皮素原）产生阿片样肽（阿片样物质）或伤害感受样肽（阿片肽）。 这四个前体是一个基因家族的成员，阿片样物质/阿片样蛋白家族，这个家族中基因的明显冗余实际上反映了脊椎动物的进化历史。 在脊椎动物进化中的离散点的基因复制事件允许神经肽网络随时间分层，并导致这些肽产物的功能多样化，包括镇痛、伤害感受、运动控制和进食中的作用。 该项目结合了分子生物学程序与比较的方法来定义在nathostomes的nastrin/阿片样物质基因家族的进化辐射的趋势。 cDNA的克隆和测序，再加上通过实时PCR测量基因表达，将产生家族中每个基因的序列数据库，用于进行分支分析和鉴定新的阿片样物质序列。 通过检查选定的脊椎动物谱系，该基因家族的进化速度比哺乳动物或硬骨鱼慢，有可能对该基因家族的顺序进化的起源和过渡进行推断。 这些数据将测试'脑啡肽原假说'，即阿片类/阿片肽基因家族中的祖先基因是编码脑啡肽样产物的基因。 结果将提供一个新的水平的理解的进化机制的功能多样性，在这个重要的家庭的神经肽。 这个项目的影响将从神经内分泌学扩展到一般的分子神经生物学，以及促进物种多样性的进化生物学。 多学科本科生和研究生培养也是该项目的重要组成部分。

A striking feature of chemical communication systems in the brains of jawed vertebrates (gnathostomes) is the apparent duplication of genes that produce useful neuropeptide compounds. For example, in mammals there are four neuropeptide precursors (proenkephalin, prodynorphin, proopiomelanocortin, and proorphanin) that produce opiate-like peptides (opioids) or nociceptic-like peptides (orphanins). These four precursors are members of a gene family, the opioid/orphanin family, and the apparent redundancy of genes in this family in fact reflects the evolutionary history of the vertebrates. Gene duplication events at discrete points in vertebrate evolution have allowed for the layering of neuropeptide networks over time, and have led to a diversification in function of these peptide products, including roles in analgesia, nociception, motor control, and feeding. This project combines molecular biology procedures with a comparative approach to define trends in the evolutionary radiation of the orphanin/opioid gene family in gnathostomes. The cloning and sequencing of cDNAs, coupled with the measurement of gene expression by real-time PCR, will generate a database of sequences for each gene in the family that will be used to perform cladistic analyses and to identify novel opioid sequences. By examining selected vertebrate lineages where the evolution of this gene family has been slower than in mammals or teleost fish, it is possible to make inferences about the origin and transitions in the sequential evolution of this gene family. These data will test the 'proenkephalin hypothesis' that the ancestral gene in the opioid/orphanin gene family was a gene that coded for the enkephalin-like product. Results will provide a new level of understanding of the evolutionary mechanisms underlying the functional diversity in this important family of neuropeptides. The impact of this project will extend beyond neuroendocrinology to molecular neurobiology in general, and to evolutionary biology with respect to the trends that promote species diversity. Multi-disciplinary undergraduate and graduate training also is an important component of this project.