p190RhoGAP May be Required to Regulate Eye Size in Zebrafish


Jessica Pollart

Faculty Advisor

Andrea James

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During eye development the retina protrudes from the brain subsequently surrounding the invaginating lens. During this process a transient cavity initiates, the choroid fissure (CF). Closure of the CF initiates in the central CF and proceeds toward the distal and proximal CF locations. If the CF does not close completely the eye is at risk for developing a coloboma which can result in blindness. It is thought CF fusion occurs via cadherin proteins and the strength of the adhesion is regulated by p190RhoGAP. Previous work in our lab demonstrated that p190RhoGAP mutants have an adhesive/fusion seal throughout the CF ~10 hours longer than siblings. In neural tissue, this extended adhesion can lead to apoptosis. We hypothesize that p190RhoGAP may be required for proper eye formation and that the extended closure process may lead to reduction in eye size in p190RhoGAP mutants compared to siblings. Embryos were collected from p190RhoGAP+/- in-crosses. At 5 days post fertilization (5dpf), images were collected and eye length/width ratios utilized to determine the overall eye size/shape. In 3 separate trials, ~25% of embryos had a smaller length/width ratio in p190RhoGAP-/- embryos, L/W ratio of 1.05, whereas siblings had a L/W ratio of 1.26. When this experiment was performed in a WT background, a ratio average of 1.17 was calculated, which is similar to our sibling measurements. We are currently genotyping embryos using restriction fragment length polymorphism (RFLP) analysis will validate the phenotype with the genotype. Further work is needed to determine if this reduction in eye size may be due to increased apoptosis, reduced proliferation and/or both.

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