Fig. 2

a Representative elongation vs time curves for in vivo embryos, and explants that are free to elongate or embedded inside agarose gel. b Elongation rates extracted from elongation vs time curves, such as shown in (a) (N = 4, n = 9 embryos, N = 4, n = 13 free explants, N = 3, n = 10 embedded explants). c Average period of somitogenesis in intact embryos (N = 4, n = 10), free tail explants (N = 4, n = 16), and embedded tail explants (N = 2, n = 7). d Average period of Her1-YFP oscillations in intact embryos (N = 4, n = 10), free tail explants (N = 4, n = 14), and embedded tail explants (N = 2, n = 7). e Representative plots showing the intensity of Her1-YFP signal over time. The signal is recorded in the anterior part of the intact embryos, free tail explant and embedded tail explants. f Schematic showing the tail explant embedded in 2% LMPA (low melting point agarose). Embedding leads to structural defects in the somites and the notochord (A: anterior, P: posterior). g, h Representative time-lapse BF images of a tail explant under confinement. Orange arrows indicate the location of buckling of the notochord. (g) shows the length measurement based on the anterior and posterior ends of the tail explant, termed tail elongation. h The length measurement based on the notochord of the tail explant, termed notochord elongation. i Elongation rates of the embedded tail explant (emb. tail) (N = 3, n = 10), notochord of the embedded tail explant (emb. Noto) (N = 3, n = 10), and the elongation rate of the notochord of the free explant (free Noto) (N = 4, n = 13). j Representative time-lapse fluorescence images of tail explants expressing H2B-mCherry. Orange arrows indicate the location and progression of buckling of the notochord. Scale bars, 100 μm. Box plots in panels (b), (c), (d) and (i) indicate the median (mid-line), 25th and 75th percentiles (box), and 1.5× the interquartile range (whiskers). All statistical comparisons are performed with one way ANOVA test, ***P < 0.001, n.s. indicates not significant.