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Fig. 5. Model integrating the Vmem signal into eye development and depicting the effects of its change on endogenous and ectopic eye development. (A) Neural induction is crucial in the process of eye development. Bilateral hyperpolarization of a cluster of cells in the anterior neural field regulates the expression pattern of eye development markers (EFTFs) such as Rx1 and Pax6. Note that there is a positive-feedback loop between factors such as Pax6 and local hyperpolarization. (B) Eye development factor expression in relation to changes in Vmem. Normal eye development involves regulation of bilateral patterning of EFTFs by the bilateral Vmem signal (hyperpolarization). Underlying mesodermal inhibitory signal also plays an important role in this bilateral regionalization of EFTFs. Disruption of the bilateral Vmem signal results in diminished or lost EFTF signal, resulting in disrupted endogenous eye development. Induction of ectopic Vmem changes results in de novo EFTF expression and formation of ectopic eyes. (C) Hyperpolarization within a window of Vmem is important for the proper formation and development of eyes. Perturbation (depolarization, 1) of endogenous Vmem signal takes the cells outside this window and results in improper eye development. Perturbation (depolarization, 2) of Vmem of non-eye cells, such that their Vmem now lies within the window of eye formation, results in the formation of ectopic eye tissue by these cells. Perturbation (depolarization, 3 and 4) of Vmem in non-eye cells, such that their Vmem still does not fall within the eye formation window, does not result in ectopic eye tissue formation from these cells. Image published in: Pai VP et al. (2012) Copyright © 2012. Image reproduced with permission of the publisher and the copyright holder. This is an Open Access article distributed under the terms of the Creative Commons Attribution License. Larger Image Printer Friendly View

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