Reconstituting tissue patterning: A synthetic morphogen reveals quantitative principles of tissue patterning

Multicellular organisms develop through a sequence of patterning events, in which cells adopt distinct cell fates. In many instances, patterns are established by morphogen gradients that determine cell fates according to the position of cells within a uniform field. On pages 327 and 321 of this issue, Toda et al. (1) and Stapornwongkul et al. (2), respectively, use synthetic approaches to study morphogen gradients. Why are synthetic approaches helpful? Patterning systems operate in complex biological settings, and synthetic reconstitution isolates and defines the key players. Because the features of such systems depend directly on quantitative parameters, synthetic approaches allow reconstituting systems in which parameters can be precisely tuned and their effects measured with precision. Additionally, the regulation of patterning systems relies on different feedback loops, and synthetic rewiring highlights the logic of the critical circuits. Overall, the key parameters and players can be examined from different angles.