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Figure 6. The Pro-BMP Function of CV2 Is Revealed in Epistatic Experiments with Chordin or Tolloid(A) Expression of the eye field marker Rx2a in uninjected Xenopus late neurula embryo (n = 45), anterior view.(B) Chordin protein injection (2 μM, 60 nl) into the blastocoele at late blastula (stage 9.5) caused dorsalization and an increase in Rx2a expression (n = 54).(C) CV2-depleted hosts were more sensitive to the anti-BMP effects of Chordin, as indicated by the expansion in the Rx2a domain (n = 48).(D) Uninjected early neurula (stage 13, side view) showing Otx2 expression in the future forebrain and midbrain regions (n = 19).(E) Chordin protein injection expands Otx2 in wild-type embryos (n = 25).(F) CV2 depletion sensitizes the embryo to the effects of Chordin on Otx2 (n = 23). Note that the border of Otx2 expression expands posteriorly.(G–I) qRT-PCR analysis of the D-V markers Chd, CV2, and Szl after Chordin protein injection into wild-type and CV2-depleted embryos at late blastula. The bars indicate standard deviation between two groups of seven embryos each.(J and K) Anterior views of uninjected control or embryo microinjected four times with 250 pg of DN-Xlr mRNA, which inhibits the proteolytic degradation of Chordin. Note that the Otx2-positive forebrain (fb), midbrain, and cement gland (cg) regions are expanded, consistent with the anti-BMP effects of Tolloid inhibition (n = 27).(L) In CV2-depleted embryos, Otx2 expression is greatly expanded by DN-Xlr mRNA (n = 27). The dotted line indicates the eye field (eye), which is more weakly stained by Otx2. |
