Schartl Manfred
University of Würzburg, Physiologische Chemie I, Theodor-Boveri Institut für Biowissenschaften der Universität Würzburg Am Hubland, 97074 Würzburg.
Bioessays. 2008 Sep;30(9):822-32. doi: 10.1002/bies.20807.
Genes that exert their function when they are introduced into a foreign genetic background pose many questions to our current understanding of the forces and mechanisms that promote either the maintenance or divergence of gene functions over evolutionary time. The melanoma inducing Xmrk oncogene of the Southern platyfish (Xiphophorus maculatus) is a stable constituent of the genome of this species. It displays its tumorigenic function, however, almost exclusively only after inter-populational or, even more severely, interspecific hybridization events. The Xiphophorus hybrid melanoma system has gained attention in biomedical research as a genetic model for studying tumor formation. From an evolutionary perspective, a prominent question is: how could this gene persist over millions of years? An attractive hypothesis is that Xmrk, acting as a detrimental gene in a hybrid genome, could be a speciation gene that shields the gene pool of its species from mixing with other closely related sympatric species. In this article, I briefly review our current knowledge of the molecular genetics and biochemical functions of the Xmrk gene and discuss aspects of its evolutionary history and presence with respect to this idea. While Xmrk as a potentially injurious oncogene has clearly survived for millions of years, its role as a speciation gene has to be questioned.
当基因被导入到外来遗传背景中发挥其功能时，这对我们目前对在进化过程中促进基因功能维持或分化的力量和机制的理解提出了许多问题。剑尾鱼（Xiphophorus maculatus）的黑色素瘤诱导Xmrk癌基因是该物种基因组的稳定组成部分。然而，它几乎只在种群间杂交或更严重的种间杂交事件后才表现出其致瘤功能。剑尾鱼杂交黑色素瘤系统作为研究肿瘤形成的遗传模型，在生物医学研究中受到了关注。从进化的角度来看，一个突出的问题是：这个基因是如何在数百万年中持续存在的？一个有吸引力的假说是，Xmrk在杂交基因组中作为一个有害基因，可能是一个物种形成基因，它保护其物种的基因库不与其他密切相关的同域物种混合。在本文中，我简要回顾了我们目前对Xmrk基因的分子遗传学和生化功能的了解，并讨论了其进化历史以及与这一观点相关的存在情况。虽然Xmrk作为一个潜在有害的癌基因显然已经存活了数百万年，但其作为物种形成基因的作用仍值得质疑。
