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Figure 2. Maternal xNorrin activates the canonical Wnt signaling pathway.
(A) RT-PCR analysis of mRNAs from equatorially bisected oocytes (Egg). xNorrin mRNA is present in the animal half (Ani) of fully grown oocytes, while Xcat-2 mRNA is present in the vegetal half (Veg). -RT: no reverse transcription. (B) Both xNorrin mRNA and Wnt11 mRNA are enriched in the dorsal cells of 16-cell embryos. Embryos are evenly bisected into dorsal and ventral halves. D, dorsal half; V, ventral half; WE, whole embryo. (C) Spatial and temporal expression patterns of xNorrin mRNA from fertilized eggs to the late blastula stage (stage 9) revealed by whole-mount in situ hybridization. (D) xNorrin mRNA (500 pg) injection into the animal region of UV-ventralized embryos at one-cell stage reactivates the expression of Siamois, Chordin, Noggin, and Xnr3 at the late blastula stage. (E) xNorrin injection enhanced Chordin expression (detected by in situ hybridization) at stage 9 (81%, n = 36) and stage 10 (80%, n = 35) compared to wild-type embryos. UV, UV-irradiated embryos; WT, wild-type embryos; xNorrin, wild-type embryos injected with xNorrin (500 pg) into the dorsal-animal region at the four- to eight-cell stage. |
