Figure 3.

Staggered Endodermal Expression of Hox Genes and NvGbx Is Regulated by BMP Signaling

(A–DD) Expression of NvHoxB (A–F), NvHoxD (G–L), NvHoxE (M–R), NvHoxF (S–X), and NvGrm (Y–DD) in StdMO-, BMP5-8MO-, DppMO-, GDF5lMO-, ChdMO-, and GrmMO-injected embryos at early planula stage. Lateral views; oral end to the left. Embryos on (Y) and (DD) are rotated 90° compared to other stained embryos to make bilateral expression of NvGbx visible.

(EE–HH) Ectopic expression of BMPRI_{Q209 > D}-EGFP in patches of ectodermal cells in 2-day planula results in ectopic activation of NvHoxE protein. (EE) Ectopic pSMAD1/5-positive nuclei in the ectoderm of early planula in addition to endogenous staining in the endoderm (blue dots). (FF) In addition to endogenous αNvHoxE staining (blue dots), ectopic expression is observed in pSMAD1/5-positive ectodermal nuclei. Apart from specific nuclear NvHoxE signal, the secondary anti-rat antibody cross-reacts with mouse anti-GFP antibody staining the BMPRI_{Q209 > D}-EGFP fusion protein in the cell membranes. (GG) Anti-GFP antibody detects BMPRI_{Q209 > D}-EGFP in cell membranes. Anti-mouse antibody does not cross-react with the rat αNvHoxE, thus no nuclear staining is observed, showing that nuclear staining on (FF) is specific for NvHoxE. (HH) Merged image of (EE–GG). White dots indicate the border between ectoderm and endoderm. White arrows point at two strongly pSMAD1/5-positive ectodermal nuclei in transgenic cells, which also ectopically express NvHoxE. Yellow arrows point at a weakly pSMAD1/5-positive ectodermal nucleus in a transgenic cell, which does not express detectable amounts of NvHoxE. Scale bars represent 50 μm.

See also Figure S3.