Self-organised pattern formation in the developing dorsal neural tube by a temporal relay of BMP signalling

Developing tissues interpret dynamic changes in morphogen activity to generate cell type diversity. To quantitatively study BMP signalling dynamicsin the vertebrateneural tube, we developed a new ES cell differentiation systemtailored for growing tissues. Differentiating cellsform strikingself-organised pattern of dorsal neural tube cell typesdriven by sequential phases of BMP signalling that are observed both in vitro and in vivo.Data-driven biophysical modelling showed that thesedynamics result from coupling fast negative feedbackwithslow positive regulation of signalling bythe specification of an endogenousBMP source.Thus, in contrast to relays that propagate morphogen signalling in space, we uncover a BMP signallingrelay that operates intime. This mechanism allows rapid initial concentration-sensitive response that is robustly terminated, thereby regulating balanced sequential cell type generation.Altogether, our study provides an experimental and theoretical framework to understand how signalling dynamicsis exploited indeveloping tissues. Overall design: The differentaition protocol is described in detail in Lehr et al. Cells were treated with bFGF for 48h, followed by bFGF + CHIR for 24h, followed by treatment with RA and the indicated concentration of BMP4. Note that in Lehr et al t=0 denotes the beginning of the treatment with RA+BMP4, which corresponds to 72h after the beginning of the differentiation. Treatment conditions are abbreviated as follows according to the BMP4 concentration that was added: 0ng/ml BMP4 (RA), 0.5ng/ml (RAplus0.5ngB4),1.5ng/ml (RAplus1.5ngB4), 3.0ng/ml (RAplus3ngB4) or 5ng/ml (RAplus5ngB4).