Regulation of ERK activity duration by Sprouty contributes to dorsoventral patterning.

Distinct modes of ERK activation, sustained or transient, are essential for cell fate decision in cultured cells. Here we show that Xenopus laevis Sprouty2 (XSpry2) controls the duration of ERK activity and thereby contributes to the establishment of dorsoventral patterning during mesoderm formation. Furthermore, Xenopus Fos (XFos) can function as a molecular sensor of the ERK signalling duration in Xenopus embryos. This work provides the first evidence that regulating the duration of ERK activity contributes to cell fate decisions in the context of the whole organism.