Tfap2: Role in Anterior Segment Development

The vertebrae eye has two main components the anterior segment (AS) and the posterior segment, including the retina, with both being essential to proper vision. The AS includes the cornea, lens, iris, ciliary body, and iridocorneal angle. It functions to properly collect and project light onto the retina. Anterior Segment Dysgenesis (ASD), a potentially blinding disorder, occurs when there is an abnormality in AS formation. The gene family tfap2 is essential for the development of the vertebrae eye. The tfap2 gene family encodes the protein Transcription Factor AP-2. Expression of this protein occurs in Neural Crest Cells (NCC). NCCs are vital for the formation of the Periocular Mesenchyme (POM) cells. AS targeted POM are necessary to form numerous AS structures. In zebrafish there are 5 orthologs of tfap2, tfap2a-e. Tfap2a is required for proper AS development in mammals. Our aim in this study is to determine the function of tfap2 orthologs during zebrafish AS formation. Temporal and spatial expression of tfap2a-e was conducted using wholemount in situ hybridization (WISH) during AS development in 2-5 days post-fertilization embryos. Using cryosectioning we distinguished the spatial expression of tfap2 in the AS. Expression analysis was conducted at time points 2, 3, 4, 5 dpf. The results for 3dpf show that tfap2a, b, e are expressed within the AS. At 2dpf tfap2a, b, e AS expression is reduced. By 4, 5 dpf tfap2a-e AS expression has turned off. Cryosectioning of the 2-5 dpf embryos distinctly separates the expression of each tfap2 gene observed using WISH. With CRISPR established mutant zebrafish lines, tfap2b-e function is being observed at 5, 7 dpf through analysis of AS physiology using Toluidine blue staining (TBS). Overall, we plan to examine the resulting AS physiology, POM cell migratory effects, and NCC/POM gene expression in the absence of tfap2 function