Bearer E L
Division of Biology and Medicine, Brown University, Providence, RI 02912.
Eur J Cell Biol. 1994 Apr;63(2):255-68.
In Drosophila embryos, the dorsal gene, a member of the rel family of transcription factors, is a maternal gene required for dorsal/ventral axis specification and mesoderm and neural migration and differentiation. In this report, the presence and distribution of Xrel-1 protein, a Xenopus homologue of the rel family of transcription factors, is described during early embryogenesis. Antiserum to v-rel, an avian homologue of dorsal, was used in immunoblot to detect rel proteins in Xenopus embryos. Anti-v-rel serum recognized a single band of approximately 57 kDa in Western blots of extracts of Xenopus embryos. Antiserum was also generated against bacterially expressed Xrel-1 fusion protein, a Xenopus rel homologue expressed during oogenesis. Anti-Xrel-1 antiserum recognized the same approximately 57 kDa band in Western blots as anti-v-rel. In developmental Westerns, this 57 kDa protein was present throughout early embryogenesis. Whole mounts and histologic sections of staged embryos were stained with anti-rel antiserum. Asymmetric staining of the cytoplasm of the animal cap became apparent by the eight-cell stage, with little or no staining of the vegetal hemisphere. Staining of nuclei in cells of the animal cap down to the equatorial zone became apparent between Stage 7 and 8, while vegetal nuclei never stained. Unlike Drosophila dorsal, no dorsal-ventral gradient of Xrel-1 could be detected. Anti-actin antibodies stained embryos uniformly, while preimmune serum or anti-v-rel antiserum immunoabsorbed against bacterially expressed Xrel-1 protein failed to stain. Nuclear staining diminished during gastrulation, but reappeared during neurulation. In conclusion, Xrel-1 protein is enriched in the cytoplasm of the animal pole of early Xenopus embryos, and enters the nuclei of the cells of the animal cap and presumptive mesoderm at Stage 7-1/2. The presence of this putative transcription factor in the nuclei of these cells prior to mid-blastula transition suggests that Xrel-1 may be involved in programming animal cells to respond to vegetal-inducing factors.
在果蝇胚胎中,背侧基因是转录因子rel家族的成员,是背腹轴特化以及中胚层和神经迁移与分化所需的母体基因。在本报告中,描述了转录因子rel家族的非洲爪蟾同源物Xrel-1蛋白在早期胚胎发生过程中的存在和分布情况。使用针对背侧的禽类同源物v-rel的抗血清进行免疫印迹,以检测非洲爪蟾胚胎中的rel蛋白。抗v-rel血清在非洲爪蟾胚胎提取物的蛋白质印迹中识别出一条约57 kDa的单一条带。还针对在卵子发生过程中表达的非洲爪蟾rel同源物细菌表达的Xrel-1融合蛋白产生了抗血清。抗Xrel-1抗血清在蛋白质印迹中识别出与抗v-rel相同的约57 kDa条带。在发育性蛋白质印迹中,这种57 kDa的蛋白质在整个早期胚胎发生过程中都存在。用抗rel抗血清对分期胚胎的整体标本和组织切片进行染色。在八细胞期,动物帽细胞质的不对称染色变得明显,植物半球几乎没有染色或没有染色。在7至8期之间,动物帽细胞直至赤道区的细胞核染色变得明显,而植物细胞核从未染色。与果蝇背侧不同,未检测到Xrel-1的背腹梯度。抗肌动蛋白抗体对胚胎进行均匀染色,而针对细菌表达的Xrel-1蛋白免疫吸附的免疫前血清或抗v-rel抗血清未能染色。原肠胚形成期间核染色减少,但在神经胚形成期间重新出现。总之,Xrel-1蛋白在早期非洲爪蟾胚胎的动物极细胞质中富集,并在7-1/2期进入动物帽和预定中胚层细胞的细胞核。在囊胚中期转变之前,这些细胞的细胞核中存在这种假定的转录因子,这表明Xrel-1可能参与使动物细胞编程以响应植物诱导因子。