Evolving mechanisms of morphogenesis: on the interplay between differential adhesion and cell differentiation

Differential cell adhesion, mediated by e.g. integrin and cadherins/catenin es, plays an important role in morphogenesis and it has been shown that the re is intimate cross-talk between their expression and modification, and in ter-cellular signalling, cell differentiation, cell growth and apoptosis. I n this paper, we introduce and use a formal model to explore the morphogene tic potential of the interplay between these processes. We demonstrate the formation of interesting morphologies. Initiated by cell differentiation, d ifferential cell adhesion leads to a long transient of cell migrations, e.g . engulfing and intercalation of cells and cell layers. This transient can be sustained dynamically by further cell differentiation, and by cell growt h/division and cell death which are triggered by the (also long range) forc es (stretching and squeezing) generated by the cell adhesion. We study the interrelation between modes of cell differentiation and modes of morphogene sis. We use an evolutionary process to zoom in on gene-regulation networks which lead to cell differentiation. Morphogenesis is not selected for but a ppears as a side-effect. The evolutionary dynamics shows the hallmarks of e volution on a rugged landscape, including long neutral paths. We show that a combinatorially large set of morphologies occurs in the vicinity of a neu tral path which sustains cell differentiation. Thus, an almost linear molec ular phylogeny gives rise to mosaic evolution on the morphological level. ( C) 2000 Academic Press.