Fig. 6

Ectopic Mnx2a-Expressing Cells Form a Sharp Ventral Domain Similar to the pMN Domain (A) The 24 hpf neural tube phenotypes after injection of mem-mCherry α mnx2a mRNAs in one blastomere at 8- to 16-cell stage are shown. Phenotypes are classified according to the distribution of mCherry+ cells (brackets): class I embryos contain cells only in the ventral third of the neural tube, class II embryos contain cells in the ventral two-thirds, and “random” contains injected cells throughout. Green indicates mnx1:gfp. Scale bars, 10 μm. See also Figure S6A.(B) Summary of mosaic injection experiments. Early defect embryos failed to form neurula. Cyclopamine treatment started at 7 hpf. (C) Sample time course of Mnx2a domain formation. This Mnx2a embryo became class II type. Dashed-line circles indicate position of the notochord. Green shows mnx1:gfp. Red designates mem-mCherry. Scale bar, 10 μm. See also Figure S6B. (D) Mnx2a-expressing cells replace “normal” pMNs. Imaging and counting of MNs as Figure 3C. p = 0.09, p = 0.00004, p = 0.0001, and p = 0.03 (Student’s t test).