Fig. 9. The AP polarity in the supernumerary somites. (A,A') When an ectopic fissure was induced to form by NotchE-producing cells (asterisk), the small somite located anterior to the fissure expressed Delta1 mRNA at its posterior margin (arrow). (B) NotchE-producing cells themselves showed an intense signal even when they were located outside the somite. (C,C') Notch LNG did not affect the AP polarity of the host somite. (D) When a large graft of level –1 was placed into level –1.5 (the same transplantation as Fig. 2A), the resulting miniature somites, after 5 hours of incubation, expressed Delta1 mRNA in the posterior margin of each somite. DiI was used to mark the grafted level along the AP axis of a host (pink in the control side). (E,F) QCPN staining of horizontal sections. Embryos with the same manipulation that were incubated for another 2 days formed supernumerary DRGs in the anterior part of each segment (E), whereas a control isotopic transplantation had no effect on DRG (F).

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