Single - Embryo Metabolomics and Systematic Prediction of Developmental Stage in

Early development is a dynamic process in higher organisms. A single fertilized egg gives rise to complex, standardized tissues, organs, and body plan. The genome sequence of several organisms has been determined, and the functions of individual genes associated with embryogenesis have been demonstrated in many studies (Stanford et al., 2001). The systematic analyses of the transcriptome and the proteome have been instrumental in understanding various developmental processes in zebrafi sh embryos (Mathavan et al., 2005; Link et al., 2006). However the mechanisms of early development are not yet completely understood. Metabolomics can be understood as a comprehensive, simultaneous, and systematic determination of metabolite levels in cells, tissues, and/or organisms (Oliver et al., 1998; Nicholson et al., 1999; Lindon et al., 2007). The metabolome represents the fi nal downstream product of gene expression (Dunn et al., 2005; Maharjan and Ferenci, 2005; Kell, 2006), thus the change in the metabolome could be regarded as the ultimate response of biological systems (Fiehn, 2002). Transcriptomics and proteomics are both considered to be intermediates in the fl ow of genetic information. In contrast, metabolomics should be thought of as being more proximate to the phenotype (Raamsdonk et al., 2001; Fukusaki and Kobayashi, 2005) and expressed at various stages after transcriptional control of mRNA, posttranslational modifi cation of proteins, localization of gene products, and so on. Metabolomics might be the sole technology capable of detecting complex, biologically essential changes. Zebrafi sh (Danio rerio) is a common and powerful model organism used to understand vertebrate embryogenesis and organ development (Hsu et al., 2007). Metabolites are known to play an important role in embryogenesis, and they enhance our understanding of this dynamic Single-Embryo Metabolomics and Systematic Prediction of Developmental Stage in Zebrafi sh Shunsuke Hayashi, Mako Yoshida, Toshinobu Fujiwara, Shingo Maegawa, and Eiichiro Fukusaki*