Development

Signal Stability

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Science  03 Oct 2008:
Vol. 322, Issue 5898, pp. 16
DOI: 10.1126/science.322.5898.16c

Chordin and BMP signaling develop opposing trends across the Xenopus embryo, defining between them the axis from dorsal to ventral and destinations in between. The interactions between these and other factors involve complex regulatory interactions, including both negative and positive feedback loops. Although predictions from some combinations of the known regulatory loops might suggest that axis establishment is rather tenuous, instead, observations of real embryos indicate that dorsal-ventral axis establishment in Xenopus is robust to perturbation. Inomata et al. identify the protein ONT1 as a stabilizing factor in the signaling networks defining the dorsal-ventral axis. The protein is expressed first in late blastula stages and is generally found in the more dorsal regions as the embryo develops; diminished ONT1 function results in dorsalization of the embryo. ONT1 binds to chordin and also to a protease known to degrade chordin, and seems to function as a scaffold enticing chordin to its demise. The biphasic outcome of this interaction ensures that enough, but not too much, chordin survives to define the developing dorsal axis. — PJH

Cell 134, 854 (2008).

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