Figure 2.

Time-Space Translation [8] A BMP dependent timer (clock) running in a high BMP tissue (Xenopus NOM mesoderm) determines potential A-P axial values as a function of time (A early-P late). The clock is stoppped sequentially by anti- BMP organizer signals as NOM cells migrate to the dorsal side of the embryo in an early to late sequence to yield an A-P sequence of stable A-P identities. The sequence is extended forward from the postereior Hox expressing trunk-tail prt of the axis to imclude the anterior head nd (most anterior) EAD [37].