Hitachi Keisuke, Kondow Akiko, Danno Hiroki, Nishimura Yusuke, Okabayashi Koji, Asashima Makoto
Department of Life Sciences (Biology), Graduate School of Arts and Sciences, The University of Tokyo, Meguro-ku, Tokyo, Japan.
Integr Zool. 2009 Dec;4(4):387-94. doi: 10.1111/j.1749-4877.2009.00110.x.
During vertebrate somitogenesis, somites bud off from the anterior end of the presomitic mesoderm (PSM). Mesodermal posterior (Mesp)-related genes play essential roles in somitogenesis, particularly in the definition of the somite boundary position. Among vertebrates, two types of Mesp-related genes have been identified: Mesp1 and Mesp2 in the mouse; Meso-1 and Meso-2 in the chicken; Xl-mespa and Xl-mespb (also known as Thylacine1) in the African clawed frog (Xenopus laevis); and mesp-a and mesp-b in the zebrafish. However, the functional differences between two Mesp-related genes remain unknown. In the present study, we carried out comparative analyses of the Xl-mespa and Xl-mespb genes. The amino acid sequences of the Xl-mespa and Xl-mespb proteins showed a high level of similarity. The expression of Xl-mespa started broadly in the ventrolateral mesoderm and gradually shifted to a striped pattern of expression. In contrast, Xl-mespb showed a striped pattern of expression from the start. These expression profiles completely overlapped at the PSM during somitogenesis. To investigate the functional differences between Xl-mespa and Xl-mespb in terms of target gene regulation, we carried out a luciferase assay using the murine Lunatic fringe (L-fng) promoter. Transcription of the L-fng promoter was activated more strongly by Xl-mespb than by Xl-mespa. This same pattern was observed for the murine Mesp-related proteins. These results suggest that the functional differences between the two types of Mesp-related genes are evolutionally conserved in vertebrates.
在脊椎动物体节发生过程中，体节从前体节中胚层（PSM）的前端芽生出来。中胚层后部（Mesp）相关基因在体节发生中起重要作用，特别是在体节边界位置的界定方面。在脊椎动物中，已鉴定出两种类型的Mesp相关基因：小鼠中的Mesp1和Mesp2；鸡中的Meso-1和Meso-2；非洲爪蟾（非洲爪蟾）中的Xl-mespa和Xl-mespb（也称为袋狼1）；以及斑马鱼中的mesp-a和mesp-b。然而，两种Mesp相关基因之间的功能差异仍然未知。在本研究中，我们对Xl-mespa和Xl-mespb基因进行了比较分析。Xl-mespa和Xl-mespb蛋白的氨基酸序列显示出高度相似性。Xl-mespa的表达最初在腹外侧中胚层广泛开始，然后逐渐转变为条纹状表达模式。相比之下，Xl-mespb从一开始就显示出条纹状表达模式。在体节发生过程中，这些表达谱在PSM处完全重叠。为了研究Xl-mespa和Xl-mespb在靶基因调控方面的功能差异，我们使用小鼠 Lunatic fringe（L-fng）启动子进行了荧光素酶测定。Xl-mespb比Xl-mespa更强烈地激活L-fng启动子的转录。对于小鼠Mesp相关蛋白也观察到相同的模式。这些结果表明，两种类型的Mesp相关基因之间的功能差异在脊椎动物中是进化保守的。
