RT Journal Article SR Electronic T1 Fgf/MAPK signalling is a crucial positional cue in somite boundary formation JF Development JO Development FD The Company of Biologists Limited SP 4873 OP 4880 VO 128 IS 23 A1 Sawada, Atsushi A1 Shinya, Minori A1 Jiang, Yun-Jin A1 Kawakami, Atsushi A1 Kuroiwa, Atsushi A1 Takeda, Hiroyuki YR 2001 UL http://dev.biologists.org/content/128/23/4873.abstract AB The temporal and spatial regulation of somitogenesis requires a molecular oscillator, the segmentation clock. Through Notch signalling, the oscillation in cells is coordinated and translated into a cyclic wave of expression of hairy-related and other genes. The wave sweeps caudorostrally through the presomitic mesoderm (PSM) and finally arrests at the future segmentation point in the anterior PSM. By experimental manipulation and analyses in zebrafish somitogenesis mutants, we have found a novel component involved in this process. We report that the level of Fgf/MAPK activation (highest in the posterior PSM) serves as a positional cue within the PSM that regulates progression of the cyclic wave and thereby governs the positions of somite boundary formation.