Mesoderm induction in Xenopus is a zygotic event regulated by maternal VegT via TGFbeta growth factors.
The maternal transcription factor VegT is important for establishing the primary germ layers in Xenopus. In previous work, we showed that the vegetal masses of embryos lacking maternal VegT do not produce mesoderm-inducing signals and that mesoderm formation in these embryos occurred ectopically, from the vegetal area rather than the equatorial zone of the blastula. Here we have increased the efficiency of the depletion of maternal VegT mRNA and have studied the effects on mesoderm formation. We find that maternal VegT is required for the formation of 90% of mesodermal tissue, as measured by the expression of mesodermal markers MyoD, cardiac actin, Xbra, Xwnt8 and alphaT4 globin. Furthermore, the transcription of FGFs and TGFbetas, Xnr1, Xnr2, Xnr4 and derrière does not occur in VegT-depleted embryos. We test whether these growth factors may be endogenous factors in mesoderm induction, by studying their ability to rescue the phenotype of VegT-depleted embryos, when their expression is restricted to the vegetal mass. We find that Xnr1, Xnr2, Xnr4 and derrière mRNA all rescue mesoderm formation, as well as the formation of blastopores and the wild-type body axis. Derrière rescues trunk and tail while nr1, nr2 and nr4 rescue head, trunk and tail. We conclude that mesoderm induction in Xenopus depends on a maternal transcription factor regulating these zygotic growth factors.
Kofron
M
M
Department of Genetics, Cell Biology and Development, University of Minnesota, 321 Church Street SE, Minneapolis, MN 55455, USA.
Demel
T
T
Xanthos
J
J
Lohr
J
J
Sun
B
B
Sive
H
H
Osada
S
S
Wright
C
C
Wylie
C
C
Heasman
J
J
D000818:Animals; D001483:Base Sequence; D004627:Embryonic Induction / Q000235:genetics / Q000502:physiology*; D051518:Fibroblast Growth Factor 3; D051524:Fibroblast Growth Factor 8; D005346:Fibroblast Growth Factors / Q000235:genetics / Q000502:physiology; D006133:Growth Substances / Q000235:genetics / Q000502:physiology; D036341:Intercellular Signaling Peptides and Proteins; D008648:Mesoderm / Q000502:physiology*; D008969:Molecular Sequence Data; D055456:Nodal Signaling Ligands; D010641:Phenotype; D011506:Proteins / Q000235:genetics / Q000502:physiology; D011518:Proto-Oncogene Proteins / Q000235:genetics / Q000502:physiology; D018125:Receptors, Transforming Growth Factor beta / Q000235:genetics / Q000502:physiology; D020825:T-Box Domain Proteins / Q000235:genetics / Q000502:physiology*; D016212:Transforming Growth Factor beta / Q000235:genetics / Q000502:physiology*; D029867:Xenopus Proteins; D014982:Xenopus laevis / Q000235:genetics / Q000502:physiology; D015053:Zygote
C489198:FGF3 protein, Xenopus; D051518:Fibroblast Growth Factor 3; C118849:GDF3 protein, Xenopus; D006133:Growth Substances; D036341:Intercellular Signaling Peptides and Proteins; C105817:NODAL protein, Xenopus; C113775:Ndr2 protein, vertebrate; D055456:Nodal Signaling Ligands; D011506:Proteins; D011518:Proto-Oncogene Proteins; D018125:Receptors, Transforming Growth Factor beta; C485173:STK38L protein, Xenopus; D020825:T-Box Domain Proteins; D016212:Transforming Growth Factor beta; C103966:VegT protein, Xenopus; D029867:Xenopus Proteins; C512833:nodal1 protein, Xenopus; C094620:nodal3.1 protein, Xenopus; D051524:Fibroblast Growth Factor 8; D005346:Fibroblast Growth Factors