Fig. 1. BMP signaling controls G1/S transition in the neural tube in an axial-specific manner. Neural tube sections opposite dissociating somites (A-C) or segmental plate mesoderm (D,E). Hoechst+ nuclei are blue and BrdU+ nuclei are pink. CHO pellets are delineated by white dots and asterisks (^*). In A, there is an intact area showing the neural tube with emigrating NC cells (arrowheads); B represents a nearby section from the same embryo at a level where CHO-noggin cells were implanted (^*). No NC cells emigrate and BrdU incorporation is partially inhibited. (C) Implanted CHO-control cells (^*) have no effect on NC delamination (arrowheads) and BrdU incorporation. (D,E) Noggin overexpression (E) has no effect on neuroepithelial cell proliferation at segmental plate levels of the axis when compared with control CHO (D). (F) Percentage of BrdU+/total nuclei (±s.d) at dissociating and segmental plate levels of the axis in embryos grafted with CHO-noggin cells or electroporated (EP) with a noggin-expressing vector. Numbers in parenthesis represent the embryos quantified. Scale bar: 25 µm in A-C; 40 µm in D,E.