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Fig. 7. Depletion of Bmp2/Bmp4/Bmp7 causes the formation of head-like structures with a radially patterned CNS in embryos ventralized by β-Catenin MOs. Wild-type, β-Catenin or triple β-Catenin/Bmp4/Bmp7 MO-injected embryos were tested for the expression of CNS markers (n=9 or more per experimental set). (A-C) Expression of Sox2, demarcating the CNS at stage 15 in a control embryo, is abrogated in β-Catenin MO-injected embryos, and greatly expanded in embryos depleted of β-Catenin and Bmp4/Bmp7. (D-F) Expression of N-Tubulin in differentiated neurons in the posterior CNS is abolished in β-Catenin MO-injected embryos, but can be seen radially around the blastopore in embryos lacking β-Catenin and Bmp4/Bmp7. (G-I) Gbx2 expression, which marks rhombomere 1 and otic vesicles (Von Bubnoff et al., 1996), is undetectable in β-Catenin MO-injected embryos but can be visualized in two concentric rings in embryos depleted ofβ -Catenin and Bmp4/Bmp7. (J-L) Engrailed-2 expression, which marks the midbrain-hindbrain boundary, is not present in β-Catenin MO embryos but is expressed as a ring in embryos depleted for β-Catenin and Bmp4/Bmp7. (M-O) Expression of the forebrain/midbrain marker Otx2 is absent in embryos injected with β-Catenin MOs but is expressed circumferentially in embryos depleted of β-Catenin and Bmp4/Bmp7. (P) Histological section through a β-Catenin MO-ventralized embryo. ae, atypical ectoderm; en, endodermal tissue; m, mesothelium. (Q) Co-injection ofβ -Catenin and Bmp4/Bmp7 MOs revealed enhanced cell proliferation in ectoderm with neural tissue (ne) differentiation and radial cement gland formation (cg). (R) Schematic depiction of the anteroposterior polarity of the radial CNS formed in β-Catenin and Bmp4/Bmp7-deficient embryos deduced from in situ hybridization studies. |
