Asashima M, Okada T S
Dept. of Life Science and CREST Project, University of Tokyo, Japan.
Int J Dev Biol. 2001;45(1):57-65.
The discovery of the organizer by H. Spemann and Hilde Mangold, prompted a number of studies of embryonic induction in Japan. C.O. Whitman, N. Yatsu, T. Sato, H. Oka, T. Yamada, and Y.K. Okada were the pioneers in the field of embryonic induction. T. Yamada postulated the double potential theory for embryonic induction. O. Nakamura has modified the fate map of Vogt using newt and Xenopusblastulae. T.S. Okada and G. Eguchi proposed the new concept of "transdifferentiation" based on in vitro experiments in the retina and lens. T.S. Okada is not only an excellent scientist, but he has also nurtured many active developmental biologists. M. Takeichi, from his school, discovered the cell adhesion molecle, cadherin. Nakamura and colleagues tried to determine the origin and formation of the organizer. They performed recombination experiments using the ectoderm, endoderm and mesoderm, and concluded that the phenomenon in which various mesoderm tissues are formed by the recombination of the presumptive ectoderm with endoderm was "regulation of the vegetal-animal gradient". Some groups have also tried to purify specific inducing factors. T. Yamada and colleagues isolated two different types of ribonucleoproteins. I. Kawakami and colleagues showed that the ribosome fraction has neural inducing capacity, and that the extracellular matrix contains mesodermal inducing factors. Finally Asashima and colleagues isolated and identified activin A as a MIF factor. This finding had a great influence not only in the field of developmental biology, but also in molecular biology. Using activin, Asashima's group has successfully generated various organs, tissues, trunk-tail and head structures in vitro using animal caps (undifferentiated cells). Some other important molecules such as BMP, chordin and bFGF are also being studied by young Japanese scientists.
H. 施佩曼和希尔德·曼戈尔德对组织者的发现，促使日本开展了多项胚胎诱导研究。C.O. 惠特曼、N. 矢津、佐藤俊、冈浩、山田常雄和冈田阳一都是胚胎诱导领域的先驱。山田常雄提出了胚胎诱导的双潜能理论。中村修二利用蝾螈和非洲爪蟾囊胚修改了沃格特的命运图谱。冈田节郎和江口圭提出了基于视网膜和晶状体体外实验的“转分化”新概念。冈田节郎不仅是一位杰出的科学家，还培养了许多活跃的发育生物学家。他的学生竹内守发现了细胞黏附分子钙黏蛋白。中村修二及其同事试图确定组织者的起源和形成。他们进行了外胚层、内胚层和中胚层的重组实验，并得出结论，假定外胚层与内胚层重组形成各种中胚层组织的现象是“植物 - 动物梯度调控”。一些研究小组还试图纯化特定的诱导因子。山田常雄及其同事分离出了两种不同类型的核糖核蛋白。川上一及其同事表明核糖体部分具有神经诱导能力，细胞外基质含有中胚层诱导因子。最后，朝岛奈津子及其同事分离并鉴定出激活素A为一种中胚层诱导因子。这一发现不仅在发育生物学领域，而且在分子生物学领域都产生了重大影响。利用激活素，朝岛奈津子的研究小组成功地在体外利用动物帽（未分化细胞）生成了各种器官、组织、躯干 - 尾部和头部结构。一些其他重要分子，如骨形态发生蛋白、脊索蛋白和碱性成纤维细胞生长因子，也受到日本年轻科学家的研究。
