Zebrafish as a model system for studying hair-cell regeneration

People worldwide are suffering from hearing loss due to death of hair cells, which cannot regenerate in mammals but can, by transdifferentiation of supporting cells in non-mammals such as fish. Several lines of evidence suggest that accumulation of E-cad, a component of adherens junction, during maturation of mammals might be accountable for the inability to regenerate hair cells. My previous research shows that weakening adherens junctions leads to death of mammalian supporting cells. Therefore, verifying whether adherens junctions hinder hair-cell regeneration by overexpressing E-cad in zebrafish neuromasts comes as an alternative approach to testing the hypothesis. E-cad overexpression is harmful for zebrafish embryos and might hinder neuromast development, so agents must be delivered into mature neuromasts to overexpress E-cad. This project shows that the distribution of neuromasts on 2-month fish tail fins follows a consistent and organized pattern, which allows for delivery of agents and enables tail-fin comparisons between treated and control fish. A protocol is developed in this project for delivering agents into neuromast cells. Results show that agents delivered using this protocol were retained in cells that were likely to be neuromast cells, 48 h after treatment. Optimization experiments show that higher local doses of agent significantly enhance agent delivery. With this protocol, the proposed hypothesis can be verified, and other manipulations of gene expression can be done in mature neuromasts for hair-cell regeneration studies