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Fig. 4. Section in situ hybridization analysis. (1) A stage 10.5 section, oriented with the animal pole at the top and the vegetal pole at the bottom, shows Mespo expression in the lateral mesoderm cells at the endomesodermal border. Note that the blastopore lip is out of the plane of this section. (2) A stage 13 section, oriented with dorsal at the top and ventral at the bottom, with anterior to the left and posterior to the right. Mespo expression is excluded from the involuted dorsal mesoderm but dorsallateral, ventral-lateral, and ventral expression is seen in the mesodermal cells around the yolk plug. The cavity at the top is the archenteron and the cavity at the left is the blastocoel. (3) A stage 17 transverse section, oriented with dorsal at the top and ventral at the bottom, shows Mespo expression in the presomitic mesoderm; expression is not seen in the notochord or archenteron roof cells. (4) A stage 22 transverse section shows expression in the tail region. The cavity shown is the hindgut. (5) A sense control of a stage 10.5 embryo section. |
