  Embryonic development involves pattern formation characterized by the
emergence of spatially localized domains characterized by distinct cell fates
resulting from differential gene expression. The boundaries demarcating these
domains are precise and consistent within a species despite stochastic
fluctuations in the morphogen molecular concentration that provides positional
information to the cells, as well as, the intrinsic noise in molecular
processes that interpret this information to guide fate determination. We show
that local interactions between physically adjacent cells mediated by
receptor-ligand binding utilizes the asymmetry between the fate-determining
genes to yield a switch-like response to the global signal provided by the
morphogen. This results in robust developmental outcomes with a consistent
identity of the gene that is dominantly expressed at each cellular location,
thereby substantially reducing the uncertainty in the location of the boundary
between distinct fates.
