Identifying functional interactors of the retinal transcription factor, Vsx2, during early retinal development

Abstract

Eye development is a delicate process requiring a balance of genes and proteins expressed over the correct time course. Disruptions in the expression of essential genes are detrimental to vision. The transcription factor Vsx2 is one such essential gene for proper eye development. Mutations in Vsx2 cause recessive microphthalmia and congenital blindness in both humans and mice, further highlighting its conservation and importance. The objective of this thesis was to identify genetic interactors of Vsx2 in the early retina. This objective was tackled through a comprehensive approach combining genetic mouse mutants, immunohistology, RNA sequencing, and pharmacological inhibitors while following the logic of epistasis. These methods led to the discovery of genetic interactors of Vsx2 in the early retina. Mitf was a known interactor of Vsx2. The positive epistatic relationship was used to identify candidate interactors based on corrective gene expression in double mutant retinas. A small cohort of genes regulated by both Vsx2 and Mitf was identified. Rxrg emerged as a highly differentiated gene in the Vsx2 loss of function mutant (orJ), only to be found as a minor genetic interactor of Vsx2. Negative epistasis was observed between Vsx2 and gamma secretase, as gamma secretase arose as a factor of critical importance to cell proliferation in the early retina. The data presented in this thesis demonstrate a framework to uncover genetic interactors, using the importance of Vsx2 to retinal development to explore interactors that contribute to retinal lineage fidelity, RPC proliferation and neurogenesis.