Fig. 2. Bmp(s) and Nog expression pattern and degradation of the basal membrane. Gene expression analysis for the tailbud at HH stage 17. (A,D) cBmp4, (B,E) cBmp7, (C,F) cNog. Arrows indicate expression in the ventrolateral region. Scale bars: 400 µm (A-C); 100 µm (D-F). (G) The kinetics of the cNog expression pattern and basal membrane degradation. The arrow indicates the primitive groove. Note that cNog is expressed in the ventrolateral region of the TVM at HH stage 17-18 (black arrowheads) and that basal membrane degradation occurs where there is a low level of cNog expression (white arrowheads). Until HH stage 24, cNog expression extended to the entire TVM and the basal membrane was formed along the entire ventral ectoderm. Scale bars: 100 µm.