Dynamics of signal transduction in the system of organogenesis and regeneration

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We performed a series of investigations involving systematic and comprehensive studies using model animals, to establish a platform for clarifying the machinery that controls early development consisting of complex cell-to- cell interactions "Early developmental systems" which we call and the relationship among their molecular components. We also carried out functional analyses of components (genes and proteins) identified by the analyses to ask their in vivo role in early embryogenesis. By the coordination of Naoto Ueno, Masanori Taira, and Kosuke Tashiro for using Xenopus laevis as a model system, construction of cDNA libraries, determination of nucleotide sequence of the cDNAs, fabrication of high-density microarray, comprehensive analyses of gene expression by the microarray during early development, spatial and temporal gene expression analysis, and construction of databases containing those information were achieved. Particularly, Ueno and Tashiro optimized the combined methodology of the high-density microarray and overexpression of polypeptide growth factors in embryos. Through the analyses which we established, Ueno and Taira focused on the regulation of gastrulation and head development, respectively, and investigate the function of the identified several genes essential for those developmental events. Satoru Kobayashi established a method of labeling germ cells specifically by expressing GFP under the regulation of a germ cell-specific promoter and germ cells were selected by cell- sorting. The microarray analysis of germ cell specific genes identified a number of genes implicated in germ cell differentiation, maintenance, and migration. It is noteworthy that a large group of genes that are predicted to be involved in one particular function was identified. Taken together these achievements prove that systematic and comprehensive analyses of genes are very effective to clarify the molecular network of early developmental processes.