Evidence that fold change, not absolute level, of b-catenin dictates Wnt signalling

See commentaries on our work:
Signaling motifs and Weber’s Law,  James E. Ferrell,  Molecular Cell 36 (5), 724-727, 2009
It’s All Relative,  Nancy R. Gough, Science Signaling 2 (101), ec397, 2009
Signalling: Sensing a change, Tanita Casci, Nature Reviews Genetics 11, 92-93, 2010