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Fig. 4 Overexpression of gadd45β genes affects somite segmentation. Synthetic RNA (gadd45β, 75 pg) together with EGFP RNA (300 pg; tracer) was injected into one blastomere of two-cell-stage embryos. The injection side was identified by EGFP before in situ hybridization. Dorsal view, anterior is up (A–F, J–L, and P–R). Posterior view, dorsal is up (G–I and M–O). (A–C) Morphology of developing somites in live embryos at 8- or 10-somite stages. (D–F) GFP expression at the corresponding embryos. Injection of zebrafish gadd45β1, but not a gadd45β1 mutant lacking middle- and C-terminal domain, caused defects in somite segmentation (A–C). (G–R) Whole-mount in situ hybridization with probes shown at the upper right. Expression of segmentation genes (mesp-a, her1, and MyoD) was severely reduced in the injected side (G–O), whereas ntl expression was not changed (P–R).