We investigate a mechanism for the robust identification of the center of a developing biological system. We assume the existence of two morphogen gradients, an activator emanating from the anterior, and a corepressor from the posterior. The corepressor inhibits the action of the activator in switching on target genes. We apply this system to Drosophila embryos, where we predict the existence of a hitherto undetected posterior corepressor. Using mathematical modeling, we show that a symmetric activator-corepressor model can quantitatively explain the precise midembryo expression boundary of the hunchback gene, and the scaling of this pattern with embryo size.

Phys. Rev. Lett.
Biochemical Networks

Howard, M, & ten Wolde, P.R. (2005). Finding the center reliably: robust patterns of developmental gene expression. Phys.Rev.Lett., 95(20, Article number: 208103), 1–4. doi:10.1103/physrevlett.95.208103