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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 ß-Catenin MOs.
Wild-type, ß-Catenin or triple ß-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 ß-Catenin MO-injected
embryos, and greatly expanded in embryos depleted of ß-Catenin and
Bmp4/Bmp7. (D-F) Expression of N-Tubulin in differentiated neurons in
the posterior CNS is abolished in ß-Catenin MO-injected embryos, but can
be seen radially around the blastopore in embryos lacking ß-Catenin and
Bmp4/Bmp7. (G-I) Gbx2 expression, which marks rhombomere 1 and otic
vesicles (Von Bubnoff et al.,
1996), is undetectable in ß-Catenin MO-injected embryos but
can be visualized in two concentric rings in embryos depleted of
ß-Catenin and Bmp4/Bmp7. (J-L) Engrailed-2 expression, which
marks the midbrain-hindbrain boundary, is not present in ß-Catenin MO
embryos but is expressed as a ring in embryos depleted for ß-Catenin and
Bmp4/Bmp7. (M-O) Expression of the forebrain/midbrain marker Otx2 is
absent in embryos injected with ß-Catenin MOs but is expressed
circumferentially in embryos depleted of ß-Catenin and Bmp4/Bmp7. (P)
Histological section through a ß-Catenin MO-ventralized embryo. ae,
atypical ectoderm; en, endodermal tissue; m, mesothelium. (Q) Co-injection of
ß-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 ß-Catenin and Bmp4/Bmp7-deficient embryos deduced
from in situ hybridization studies.
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