Induced ER-xSmad6 localizes to cytoplasmic speckles in cultured cells or embryos. (A-D) HepG2 cells were transfected with 3 μg pEGFP-ER-xSmad6 and shown prior to addition of E2 (A-B) or after addition of E2 for 90 minutes (C-D). In panels A and C, cells are double-labeled with Hoechst 33342 (blue stain) to identify nuclei. Panels B and D are phase images for panels A and C, respectively. (E-H) Embryos were injected at the 2-cell stage with 300 pg pEGFP-C1 DNA (E-F) or 400 pg pEGFP-ER-xSmad6 DNA (G-H). Panels E and G are from embryos cultured in the absence of E2. Panels F and H are from embryos induced with E2 at stage 8. All embryos in panels E-H were photographed between stages 24 and 26. White arrows indicate speckles. (A-D) Bar equals 10 μm. (E-H) Original magnification × 100.