Deriving structure from evolution: metazoan segmentation.
Segmentation is a common feature of disparate clades of metazoans, and its evolution is a central problem of evolutionary developmental biology. We evolved in silico regulatory networks by a mutation/selection process that just rewards the number of segment boundaries. For segmentation controlled by a static gradient, as in long-germ band insects, a cascade of adjacent repressors reminiscent of gap genes evolves. For sequential segmentation controlled by a moving gradient, similar to vertebrate somitogenesis, we invariably observe a very constrained evolutionary path or funnel. The evolved state is a cell autonomous 'clock and wavefront' model, with the new attribute of a separate bistable system driven by an autonomous clock. Early stages in the evolution of both modes of segmentation are functionally similar, and simulations suggest a possible path for their interconversion. Our computation illustrates how complex traits can evolve by the incremental addition of new functions on top of pre-existing traits.
François
Paul
P
Center for Studies in Physics and Biology, The Rockefeller University, New York, NY 10065, USA.
Hakim
Vincent
V
Siggia
Eric D
ED
D000465:Algorithms; D000818:Animals; D005075:Biological Evolution; D019521:Body Patterning / Q000235:genetics; D003198:Computer Simulation; D004331:Drosophila melanogaster / Q000033:anatomy & histology / Q000196:embryology* / Q000235:genetics; D053263:Gene Regulatory Networks; D006863:Hydrogen-Ion Concentration; D019476:Insect Proteins / Q000502:physiology; D007313:Insecta / Q000033:anatomy & histology / Q000196:embryology / Q000235:genetics; D008954:Models, Biological; D008957:Models, Genetic; D009154:Mutation; D019170:Somites / Q000033:anatomy & histology*; D014157:Transcription Factors; D014714:Vertebrates / Q000033:anatomy & histology / Q000196:embryology* / Q000235:genetics
D019476:Insect Proteins; D014157:Transcription Factors