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Supplementary Figure 1 | Characterization of induced mesoderm. (a) Characterization of dissected tissues by RT-PCR. Cerberus is a marker for anterior mesendoderm, Gsc, and Chordin for prechordal mesoderm, Xbra for chordal mesoderm, Sox17 is enriched in the endoderm, but also expressed at lower levels in the mesoderm. Ubiquitously expressed ODC was used as a standard. Quantification is from 3 independent experiments. Error bars are s.d. (b) C-cadherin (red) and β-catenin (green) immunostaining in the gastrula embryo. Nuclei were stained with Hoechst (blue). BCR (Ecto), ectoderm blastocoel roof; AME, anterior mesendoderm; AxM, axial mesoderm. Arrowheads point to the ectoderm-mesoderm boundary. The axial mesoderm is still mostly at the blastopore lip, but starts to participate to the nascent boundary (red arrowhead) and already displays separation activity from ectoderm in vitro 1. |
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Fig. 2. Xenopus ectoderm and mesoderm and their adhesive and contractile properties. a Diagram of the early Xenopus gastrula indicating the regions used as the source for tissue explants. Induced mesoderm was produced by expression of β-catenin (β-cat) and constitutively active Activin receptor (caActR) in the blastocoel roof (BCR). b Distribution of adhesive structures in the ectoderm blastocoel roof (BCR or Ecto), anterior mesendoderm (AME) and axial mesoderm (AxM) visualised by β-catenin immunostaining. The thin yellow dotted line and yellow arrowheads point to the mature (left panel) or nascent (right panel) ectoderm–mesoderm boundary. Scale bar, 20 µm. See also Supplementary Fig. 1b (c–e). Characterisation of adhesive and contractile properties. c Total cadherin levels in dissected tissues determined by immunoblot and expressed as the relative ratio to GAPDH. Graph shows mean values from seven independent experiments. Error bars, s.d. NS: not significantly different from ectoderm, based on one-sided Student’s t-test. d Resistance to dissociation, measured as the number of single-dissociated cells, normalised as the ratio to ectoderm. Mean of four independent experiments. Individual comparisons were made using one-sided Student’s t-test. *P < 0.05; **P < 0.01. Error bars, s.d. e Cortical tension. The elastic modulus of single cells was determined using AFM. The box plots show the interquartile range (box limits), median (centre line and corresponding value), and min and max values without outliers (whiskers). Number of cells/experiments are indicated on top. Individual comparisons were done using Tukey’s HSD test after a significant one-way ANOVA (P = 5.7e−08) |
