Fig. 6. Alternate somite boundaries are strengthened in her7 MO-injected embryos. Embryos were examined approximately every 30-40 minutes. The somites that had formed at the beginning of the experiment (A,B,C) are shown in black. Anterior is towards the top and left in A-C, and at the left in D,E. Development at the first time point is shown in red, the second in green, the third in pink, and the fourth in purple. In wild-type embryos (A), a strong somite boundary forms at every time point. Weak boundaries are sometimes seen as somites are forming, but were not observed in this particular embryo. In her7 MO-injected embryos (B,C), somite boundary formation is altered in 3 ways. First, weak boundaries persist much longer than in wild-type embryos and are therefore more frequently observed (dashed lines). Secondly, weak and disorganized attempts form in a segmental fashion but only alternate boundaries are strengthened (solid lines). Finally, large somites sometimes subdivide into 2 normal somites after the formation of many more posterior somites. (D,E) A cartoon summary of somite formation in wild-type (D) and her7 MO-injected embryos (E). In wild-type embryos, somites form in an anterior- to-posterior fashion approximately every 30 minutes. In her7 MO-injected embryos, weak boundaries (dashed lines) form in a segmental fashion. However, only some weak boundaries are strengthened (solid lines).

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