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Fig. 2. Effect of BMP signaling on XSip1 activity. (A–I) Animal caps derived from embryos injected at the four cell-stage (250 pg/blastomere) with Geminin RNA (A), XSip1 RNA (B, C, E–I) or XSip1δSBD mRNA (D) with or without CA-Alk3 RNA (100 pg) analyzed at neurula stage by in situ hybridization with the indicated probes. For each marker, control non-injected animal caps are shown on the left. Non-injected control embryos and CA-Alk3 RNA-injected (100 pg) embryos at neurula stage (dorsal view, anterior right) are shown on the right. Note that CA-Alk3 blocks XSip1's ability to induce the neuronal markers Sox2 and NCAM (B and C) and the repression of Gata2 expression (E). In contrast, CA-Alk3 does not affect XSip1's ability to block several other epidermal genes like epidermal keratin, TA-2, Hya-1 and Vgl-4 (E–I). (J) Lateral views of embryos injected with XSip1 RNA alone or together with CA-Alk3 RNA and stained for epidermal keratin. Co-expression of CA-Alk3 does not affect XSip1 repression of epidermal keratin. Respective inductions/inhibitions in “+CA-Alk3 caps and embryos”: (A) all positive, n = 35; (B) all inhibited, n = 18; (C) all inhibited, n = 52; (D) all inhibited, n = 36; (E) none inhibited, n = 40; (F) all inhibited, n = 22; (G) all inhibited, n = 25; (H) all inhibited, n = 28; (J) all inhibited, n = 33. Arrows in panels E–J indicate the injected area. |
