Hikosaka Akira, Uno Yoshinobu, Matsuda Yoichi
Graduate School of Integrated Arts and Sciences, Hiroshima University, Higashi-Hiroshima, Japan.
Cytogenet Genome Res. 2015;145(3-4):230-42. doi: 10.1159/000430764. Epub 2015 Jun 3.
The T2 family of miniature inverted-repeat transposable elements (T2-MITE) is a prevalent MITE family found in both Xenopus(Silurana) tropicalis and X. laevis. Some subfamilies, particularly T2-A1 and T2-C, may have originated prior to the diversification of the 2 Xenopus lineages and currently include active members in X. tropicalis, whereas another subfamily, T2-E, may have lost its transposition activity even earlier. The distribution of each T2-MITE subfamily in X. tropicalis was investigated and compared to evaluate the evolutionary dynamics of the T2-MITE subfamilies. The subfamilies showed differences in chromosomal distribution, uniformity of insertion density on scaffolds, ratios of upstream to downstream insertions with respect to genes, and their distance from genes. Among these, the T2-C subfamily was interesting because it was frequently inserted upstream and close to genes and because genes with close insertions of this subfamily showed high correlations in spatial expression patterns. This unique distribution and long-lived transposition activity may reflect a mutual relationship evolved between this subfamily and the host.
微型反向重复转座元件T2家族（T2-MITE）是在热带爪蟾（Silurana）和非洲爪蟾中均发现的一个普遍存在的MITE家族。一些亚家族，特别是T2-A1和T2-C，可能在这两种爪蟾谱系分化之前就已起源，并且目前在热带爪蟾中包含活跃成员，而另一个亚家族T2-E可能更早地失去了转座活性。研究并比较了每个T2-MITE亚家族在热带爪蟾中的分布情况，以评估T2-MITE亚家族的进化动态。这些亚家族在染色体分布、支架上插入密度的均匀性、相对于基因的上下游插入比例以及它们与基因的距离等方面存在差异。其中，T2-C亚家族很有趣，因为它经常插入到基因上游且靠近基因，并且该亚家族紧密插入的基因在空间表达模式上显示出高度相关性。这种独特的分布和长期的转座活性可能反映了该亚家族与宿主之间进化出的相互关系。
