Mexican tetra (Astyanax mexicanus) as a model to understand the development and regeneration of the epithelial appendages

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Cave dwelling animals are classic examples of regressive evolution; however, they also have evolved constructive features to compensate for life in perpetual darkness. The small fresh water fish, Mexican tetra (Astyanax mexicanus), is a novel animal model and exists as two morphological types: an eyed, pigmented surface-dwelling form (surface fish /SF) and an eyeless, unpigmented cave-dwelling form (cavefish /CF). The CF have evolved with morphological, sensory and behavioural traits for better adaptation to a subterranean environment. CF have enhanced epithelial structures, including teeth, taste buds (TBs) and neuromast cells (NMC). The long-term goal of this NSERC DG program is to identify the mechanisms underlying the development and regeneration of the epithelial appendages of vertebrates using Mexican tetra as an animal model. In Mexican tetra, we found different eye phenotypes have variation in tooth number, morphology, patterning and removal of the lens on one side of the head of SF altered the gene expression in the craniofacial region. Based on these findings, I hypothesize CF has advanced cellular and molecular mechanisms for the development and regeneration of epithelial appendages. My short-term objectives to address this hypothesis are: 1)To understand the effect of eye degeneration on the development and regeneration of epithelial appendages in the craniofacial region. We will use histological and embryo manipulation techniques to identify the genetic basis for changes associated with epithelial appendage development and regeneration. Further, this data will highlight any possible gradient effect of Shh (Sonic Hedgehog) overexpression on epithelial appendage development in this species. 2)To characterise the influence of neural crest cell (NCC) migration on CF epithelial appendage development. Cell labeling and NCC transplantation techniques will be used to compare the migratory pattern of the NCC of SF and CF at different developmental stages. This data will demonstrate the altered migratory behaviour of the NCC and its effect on craniofacial development. 3)To investigate the adaptive significance of germ layer origin in patterning the epithelial appendages. Using cell labeling techniques and gene expression analysis we will compare the ectodermal derived epithelial appendages with endodermal derived appendages. This data will provide insight to the microevolutionary mechanisms of epithelial appendage development of this species. Significance: With my HQP we will advance the understanding of the development and regenerative mechanisms of the epithelial appendages while giving HQP valuable skill set in developmental and molecular cell biology techniques. These are needed for the biological research in tissue engineering, veterinary and aquaculture applications. In summary, the proposed program will increase our understanding of the fundamental developmental mechanisms of epithelial appendages in vertebrates.