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Figure 5. AXPC is specifically required for specification of axial mesoderm but not general mesoderm induction. A: Embryos were injected bilaterally in the dorsal marginal zone at the 2-cell stage with 40 ng of either control (CtlMO) or AXPC morpholino (AXPCMO), then cultured until stage 12.5 and prepared for in situ hybridization with either chordin or MyoD. A': Embryos were scored by using the categories of “normal,” “reduced,” and “absent” to describe the staining intensity. Examples of normal and reduced are depicted (a,c or b,d, respectively) (n > 30). Anterior is up. B: Embryos were prepared as described above for the detection of chordin at stage 10.5. B': The categories “strong,” “mid,” and “weak” represent the degree of chordin staining used to score the control and AXPC MO–injected embryos. The bottom image is a higher magnification of the dorsal lip (boxed region) (n>30). C: RT-PCR analysis of animal caps from embryos injected with either control or AXPC MO and treated with or without 100 ng activin to induce mesodermal gene expression. Data were normalized to histone 4 (×H4). D: Mesoderm is not respecified to nueroectoderm or endoderm due to loss of AXPC. Embryos were injected as described in A and probed for Xbra, Sox17 (endoderm), or Sox2 (neuroectoderm). Asterisks denote the blastopore. Arrowhead indicates dorsal lip. Scale bar in A and B = 250 μm.Download figure to PowerPoint |
