Formation of Vertebral Precursors: Past Models and Future Predictions

Abstract

Disruption of normal vertebral development results from abnormal formation and segmentation of the vertebral precursors, called somites. Somitogenesis, the sequential formation of a periodic pattern along the antero-posterior axis of vertebrate embryos, is one of the most obvious examples of the segmental patterning processes that take place during embryogenesis and also one of the major unresolved events in developmental biology. We review the most popular models of somite formation: Cooke and Zeeman's clock and wavefront model, Meinhardt's reaction -diffusion model and the cell cycle model of Stern and co-workers, and discuss the consistency of each in the light of recent experimental findings concerning FGF-8 signalling in the presomitic mesoderm (PSM). We present an extension of the cell cycle model to take account of this new experimental evidence, which shows the existence of a determination front whose position in the PSM is controlled by FGF-8 signalling, and which controls the ability of cells to become competent to segment. We conclude that it is, at this stage, perhaps erroneous to favour one of these models over the others.

Waves and patterning in developmental biology: vertebrate segmentation and feather bud formation as case studies

“…If cells are initially all in state p , the positional information gradient can be used to control the initial switch of cells to state a . The mathematical basis of Meinhardt's model is reviewed in (Baker, 2005, Baker et al , 2003). …”

“…There have been several models for somite formation and these have previously been reviewed by the authors (Baker et al , 2003, Baker et al , 2006a, Baker et al , 2008). In all but a single case (Schnell et al , 2002), the models specify only a pre-pattern for somitogenesis.…”

From segment to somite: Segmentation to epithelialization analyzed within quantitative frameworks

“…Maini and coworkers proposed a mathematical formulation of the clock and wavefront model (Baker et al, 2003(Baker et al, , 2006a, using the signaling basis of the cell cycle model (Collier et al, 2000;McInerney et al, 2004). The mathematical formulation concentrates on modeling the role of the FGF signaling gradient, and the resulting developmental anomalies that are observed when the gradient is perturbed.…”

Mathematical Models for Somite Formation

“…Likewise, it is simply assumed that a generic FGF8 molecule makes up the gradient controlling the position of the determination front. Whilst this approach has many benefits-we can make simplifications and predictions regarding the effects of many experimental perturbations (Baker et al, 2003(Baker et al, , 2006a(Baker et al, , 2006b)-we are unable to infer exactly how each biological perturbation affects somite formation. For example, vitamin A deficient embryos have somites which are reduced in size (Diez del Corral et al, 2003;Molotkova et al, 2005;Moreno and Kinter, 2004).…”

“…Our mathematical model is based on the signaling model for somite formation, originally proposed by Primmett and co-workers (Primmett et al, 1988(Primmett et al, , 1989, and then developed by Maini and co-workers (Baker et al, 2003;Collier et al, 2000;McInerney et al, 2004;Schnell et al, 2002). In this model (see Fig.…”