Fig. 1

Disruption of the segmentation clock in tbx6, her1;her7 and her1;her7;tbx6 mutants.

(A–D’) In situ hybridization for segmentation clock marker her7. (B and B') her7 oscillates in the posterior PSM of tbx6^−/−, but does not oscillate in her1^−/−;her7^−/− (C and C´) or her1^−/−;her7^−/−;tbx6^−/− (D and D`). (E–H) In situ hybridization for segmental output marker mespb. mespb is not expressed in tbx6^−/− (F) or her1^−/−;her7^−/−;tbx6^−/− (H), but is weakly expressed in her1^−/−;her7^−/−, albeit not in segmental stripes (G). (I–L’) Somite boundaries in the paraxial mesoderm. In tbx6^−/− (J), her1^−/−;her7^−/− (K) and her1^−/−;her7^−/−;tbx6^−/− (L) mutants, boundaries lose periodic order. (M–P’) Spatial distribution of muscle pioneers marked by in situ hybridization with en2a. In tbx6^−/− (N), her1^−/−;her7^−/− (O) and her1^−/−;her7^−/−;tbx6^−/− (P) muscle pioneers lose segmental pattern. A-H’ are dorsal views of 13.5 hpf (10 somites) embryos, I-P' are lateral views of 18–19.5 hpf (18–20 somites) embryos. a – anterior, p – posterior. Scale bar in A is 100 µm and applies to A-G. Scale bar in I is 150 µm, applies to I-L and in I’ is 100 µm, applies to I’-L’. Scale bars in M and M’ are 150 µm and 100 µm respectively, and apply to M-P and M’-P’ respectively.