Regulation of Eye Regrowth in Xenopus laevis

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PROJECT SUMMARY A main challenge in the regeneration field has been to identify the signaling pathways and suitable cell types needed to enable productive tissue repair. For the eye, the successful generation and maintenance of eye-specific stem cells is a key goal. Although the process of vertebrate eye development is well-studied and characterized, the mechanisms that can induce eye stem cell proliferation following injury or disease remain difficult to identify. This is partly because natural stem cell proliferation typically occurs during embryo development whereas studies of retinal regeneration have largely utilized adult (or mature) models – a very different environment. The highly regenerative clawed frog, Xenopus laevis, is an established model for both development and organ regeneration. It is also closely related to humans. We found that Xenopus embryos successfully regrew functional eyes within 5 days. Our studies also showed that successful eye regrowth required increased and extended retinal stem cell proliferation while delaying new eye formation. One candidate pathway to regulate eye regrowth is bioelectrical signaling. Bioelectrical signaling is well-characterized for its role in limb regeneration but its role in eye development and regrowth is unclear. Our data showed that inhibition of bioelectrical signaling blocked eye regrowth, indicating that its function is required. We seek to understand and define the roles of bioelectrical signaling during eye regrowth, as a first step towards establishing a protocol for effectively dissecting the similarities and distinctions between development and repair. This project will: 1) define the expression patterns and key function of bioelectrical signaling components during eye regrowth and development; 2) assess the role of bioelectrical signaling in activating regenerative retinal progenitor cell proliferation and expansion, and 3) identify potential downstream targets. Together, this proposal will leverage the unique biology of Xenopus to establish an efficient strategy to rapidly define key mechanisms that regulate regrowth-induced retinal progenitor cell proliferation in vivo. This protocol will set the foundation for eventually building a blueprint for productive eye repair strategies.