Towards an understanding of spatial patterning in development

Abstract

A characteristic feature of the way embryos develop is that, by and large, differentiated tissue types preserve topological order Therefore cells must have a means of sensing their (relative) positions in the early embryo. The present article describes two extreme possibilities for the means by which a cell can sense its position. One, positional cues can be provided by the mother by way of morphogenetic determinants laid down in the egg. Two, by means of intercellular interactions whose effect is to set up long-range patterns of external signals, embryonic cells can organise themselves spontaneously.