VegT, eFGF and Xbra cause overall posteriorization while Xwnt8 causes eye-level restricted posteriorization in synergy with chordin in early Xenopus development.
We examined several candidate posterior/mesodermal inducing molecules using permanent blastula-type embryos (PBEs) as an assay system. Candidate molecules were injected individually or in combination with the organizer factor chordin mRNA. Injection of chordin alone resulted in a white hemispherical neural tissue surrounded by a large circular cement gland, together with anterior neural gene expression and thus the development of the anterior-most parts of the embryo, without mesodermal tissues. When VegT, eFGF or Xbra mRNAs were injected into a different blastomere of the chordin-injected PBEs, the embryos elongated and formed eye, muscle and pigment cells, and expressed mesodermal and posterior neural genes. These embryos formed the full spectrum of the anteroposterior embryonic axis. In contrast, injection of CSKA-Xwnt8 DNA into PBEs injected with chordin resulted in eye formation and expression of En2, a midbrain/hindbrain marker, and Xnot, a notochord marker, but neither elongation, muscle formation nor more posterior gene expression. Injection of chordin and posteriorizing molecules into the same cell did not result in elongation of the embryo. Thus, by using PBEs as the host test system we show that (i) overall anteroposterior neural development, mesoderm (muscle) formation, together with embryo elongation can occur through the synergistic effect(s) of the organizer molecule chordin, and each of the 'verall posteriorizing molecules'eFGF, VegT and Xbra; (ii) Xwnt8-mediated posteriorization is restricted to the eye level and is independent of mesoderm formation; and (iii) proper anteroposterior patterning requires a separation of the dorsalizing and posteriorizing gene expression domains.
Fujii
Hidefumi
H
Graduate School of Life Science, University of Hyogo, 3-2-1 Kouto, Kamigori Akou, Hyogo 678-1297, Japan. msbhfj88@gmail.com
Sakai
Masao
M
Nishimatsu
Shin-ichiro
S
Nohno
Tsutomu
T
Mochii
Makoto
M
Orii
Hidefumi
H
Watanabe
Kenji
K
D000818:Animals; D001757:Blastomeres / Q000166:cytology / Q000378:metabolism; D036703:Blastula / Q000378:metabolism / Q000648:ultrastructure; D019521:Body Patterning / Q000235:genetics / Q000502:physiology*; D004274:DNA, Recombinant / Q000008:administration & dosage / Q000494:pharmacology; D047108:Embryonic Development / Q000235:genetics / Q000502:physiology*; D005346:Fibroblast Growth Factors / Q000235:genetics / Q000502:physiology*; D018507:Gene Expression Regulation, Developmental; D006023:Glycoproteins / Q000235:genetics / Q000502:physiology*; D018398:Homeodomain Proteins / Q000032:analysis; D036341:Intercellular Signaling Peptides and Proteins / Q000235:genetics / Q000502:physiology*; D008648:Mesoderm / Q000502:physiology; D008845:Microinjections; D009420:Nervous System / Q000196:embryology; D009672:Notochord / Q000502:physiology; D009928:Organ Specificity; D012333:RNA, Messenger / Q000008:administration & dosage / Q000494:pharmacology; D020825:T-Box Domain Proteins / Q000235:genetics / Q000502:physiology*; D015534:Trans-Activators / Q000032:analysis; D051153:Wnt Proteins / Q000235:genetics / Q000502:physiology*; D029867:Xenopus Proteins / Q000032:analysis / Q000235:genetics / Q000502:physiology*; D014982:Xenopus laevis / Q000196:embryology*
D004274:DNA, Recombinant; C528532:FGF4 protein, Xenopus; D006023:Glycoproteins; D018398:Homeodomain Proteins; D036341:Intercellular Signaling Peptides and Proteins; C080209:Not protein, Xenopus; D012333:RNA, Messenger; D020825:T-Box Domain Proteins; C116765:TBXT protein, Xenopus; D015534:Trans-Activators; C103966:VegT protein, Xenopus; D051153:Wnt Proteins; D029867:Xenopus Proteins; C495248:wnt8a protein, Xenopus; D005346:Fibroblast Growth Factors; C054234:chordin