Lef J, Clement J H, Oschwald R, Köster M, Knöchel W
Abteilung Biochemie, Universität Ulm, FRG.
Mech Dev. 1994 Feb;45(2):117-26. doi: 10.1016/0925-4773(94)90025-6.
Two novel fork head related cDNA sequences, termed XFD-2 and XFD-2', have been isolated from a Xenopus laevis gastrula stage cDNA library. XFD-2 and XFD-2' proteins share 88% sequence identity; a comparison of their fork head domains yields 96% identity. Such close homology suggests that the two genes represent pseudo-allelic variants of a common ancestor and probably arose by the ancient tetraploidization event in this species. Both genes are activated at midblastula transition. Main transcriptional activity is found during blastula and gastrula stages of development; thereafter, there is a gradual decrease of transcripts until somite segregation stages. Whole mount in situ hybridisation of blastula stage embryos reveals that the genes are initially transcribed within the animal hemisphere. Subsequently, we observe their transcription in a circumferential mode along the marginal zone, i.e., within the forming mesoderm. During gastrulation, these cells enter the blastoporus at the ventral, lateral and dorsal sites. At the end of gastrula and during neural stages transcripts are localized within somitogenic mesoderm, notochord, lateral and ventral mesoderm, neural floor plate, spinal cords and in the developing brain.
从非洲爪蟾原肠胚期cDNA文库中分离出两个新的叉头相关cDNA序列，分别命名为XFD - 2和XFD - 2'。XFD - 2和XFD - 2'蛋白的序列一致性为88%；对它们的叉头结构域进行比较，一致性为96%。如此高的同源性表明这两个基因代表了一个共同祖先的拟等位基因变体，可能是由该物种古老的四倍体化事件产生的。两个基因在囊胚中期转变时被激活。主要转录活性出现在囊胚期和原肠胚期的发育阶段；此后，转录本逐渐减少，直到体节分离阶段。囊胚期胚胎的整体原位杂交显示，这些基因最初在动物半球内转录。随后，我们观察到它们沿着边缘区以圆周模式转录，即在形成中的中胚层内。在原肠胚形成过程中，这些细胞从腹侧、外侧和背侧进入胚孔。在原肠胚末期和神经发育阶段，转录本定位于体节中胚层、脊索、外侧和腹侧中胚层、神经底板、脊髓以及发育中的大脑中。
