Quantitative assessment of computational models for retinotopic map   formation
  Molecular and activity-based cues acting together are thought to guide retinal axons to their terminal sites in vertebrate optic tectum or superior colliculus to form an ordered map of connections. The details of mechanisms involved, and the degree to which they might interact, are still not well understood. We have developed a framework within which existing computational models can be assessed in an unbiased and quantitative manner against a set of experimental data curated from the mouse retinocollicular system. Our framework facilitates comparison between models, testing new models against known phenotypes and simulating new phenotypes in existing models. We have used this framework to assess four representative models that combine Eph/ephrin gradients and/or activity-based mechanisms and competition. Two of the models were updated from their original form to fit into our framework. The models were tested against five different phenotypes: wild type, Isl2-EphA3 ki/ki, Isl2-EphA3 ki/+, ephrin-A2,A3,A5 triple knock-out and Math-/- (Atoh7). Only one model could account for the collapse point in Isl2-EphA3 ki/+, and two models successfully reproduced the extent of the Math5-/- anteromedial projection. The models needed a weak anteroposterior gradient in the superior colliculus in order to reproduce the residual order in the ephrin-A2,A3,A5 triple knock-out phenotype, suggesting either an incomplete knock-out or the presence of another guidance molecule. This points to the need for future modelling and experimental work to improve our understanding of the developmental mechanisms involved. 
J. J. Johannes Hjorth, David C. Sterratt, Catherine S. Cutts, David J.   Willshaw, Stephen J. Eglen
q-bio.NC