title: Segmentation and zooid formation in animals with a posterior growing region: the case for metabolic gradients and Turing waves.
abstract: The discovery of periodic propagation of anteriorly moving pulses/stripes of gene expression in the presomitic mesoderm (PSM) of vertebrates has given new life to the clock and wavefront model, and other models of morphogenesis based on a molecular oscillator where the time periodicity is translated into spatial periodicity. Instead we suggest that segmentation, somitogenesis and metamerism in vertebrates and in invertebrates with a posterior growing region are based on a Turing-Child metabolic gradient that is progressively shifted posteriorly with the PSM as elongation, segmentation and somitogenesis proceed. This gradient corresponds to anteriorly propagating metabolic front in the PSM that drives the anteriorly propagating mRNA synthesis and which, together with mRNA degradation, explains stripe formation and spatial periodicity.The process of segmentation has been compared to zooid formation. We show that for annelids the metabolic profile behaves as a Turing field in the sense that an increase in the length of the system or a decrease of the Turing wavelength results in an additional peak in the posterior growing region as predicted by Turing theory. In particular, it is shown that the metabolic gradient that drives the segmentation is based on a Turing system.
authors.affiliation: Department of Applied Mathematics and Theoretical Physics, Centre for Mathematical Sciences, Wilberforce Road, Cambridge CB3 0WA, UK. y.schiffmann@damtp.cam.ac.uk
authors.forename: Yoram
authors.initials: Y
authors.lastname: Schiffmann
mesh_terms: D000818:Animals; D001683:Biological Clocks / Q000502:physiology*; D019521:Body Patterning; D018507:Gene Expression Regulation, Developmental / Q000502:physiology*; D006801:Humans; D007448:Invertebrates / Q000196:embryology*; D008648:Mesoderm / Q000502:physiology; D008954:Models, Biological; D009024:Morphogenesis / Q000502:physiology*; D010507:Periodicity; D019170:Somites / Q000502:physiology*; D014714:Vertebrates / Q000196:embryology*