Construction of gene tagging system by means of the medaka fish transposable element Tol-2

在脊椎动物基因组中已经描述了几种末端反向重复序列的转座元件。其中一些被认为是活性的，因为在基因区域或插入元件的多态情况下存在。然而，没有成功地检测到从头切除或插入元件。我们在青冈鱼Oryzias layzias中发现了一种新的末端反向重复类转座元件。该元素被命名为TOL-2。通过对包含Tol-2拷贝的基因组区域的聚合酶链式反应分析，检测胚胎发育过程中Tol-2的切除。TOL-2全长4681bp。TOL-2包含4个ORF，它们与玉米的Ac、果蝇的HOBO和骁龙的Tam3具有氨基酸序列相似性，均为活性转座元件。因此，TOL-2是建立鱼类基因标签系统的独特材料。

Several transposable elements of the terminal-inverted-repeat class have been described in vertebrate genomes. Some of them are considered to be active because of the presence in genic regions or polymorphic situations of inserted elements. However, detection of de novo excision or insertion of the elements has not been successfully done. We have identified a novel terminal-inverted-repeat class transposable element in the medaka fish Oryzias latipes. The element was designated Tol-2. Excision of Tol-2 during embryogenesis was detected by a PCR analysis of a genomic region containing a Tol-2 copy. Tol-2 is 4681 bp in length. Tol-2 contains 4 ORFs which have amino acid sequence similarity with Ac of maize, hobo of Drosophila and Tam3 of snapdragon, which are all active transposable elements. Tol-2 is thus a unique material for establishing a gene tagging system in fish.