Successful closure of the choroid fissure (CF) is essential for proper development of the vertebrate eye. The impermanent structure forms as the optic cup surrounds the invaginating lens allowing hyaloid vasculature to enter the developing eye. If the choroid fissure closure (CFC) fails to close, a coloboma develops associated with approximately 3-11% of childhood blindness worldwide. The CF cells are distinct prior to fusion as they remain undifferentiated until fusion of the opposing sides and have unique N-cadherin expression. During CFC, cells must breakdown basement membrane to allow fusion between both sides producing a seamless ventral retina. Both breakdown and fusion of the apposing sides of the CF initiate from the central region and proceeds bi-directionally. It is unknown however where or if the CF cells migrate away from an aligned fusion point. in vivo confocal microscopy of transgenic Hsp701:Gal4;UAS:Kaede zebrafish embryos during CFC allows distinctive contrast of photoconverted cells to give insight to their spatial temporal movement. We partitioned our analysis into three distinct regions along the proximal/distal axis of the CF to determine if cellular movement at the choroid fissure edges maintained distinct cellular migration patterns prior to differentiation. Preliminary analysis from 44 to 48 hpf in the proximal and distal regions demonstrate movement distinct from those within the central region. In both proximal and distal CF, upper (dorsal) CF cells move towards the central CF changing their proximal/distal axis in the opposite direction of fusion. Lower (ventral) CF cells move further ventrally towards the apposing side in order to fuse the CF. This contrasts with the central CF upper and lower cells that move directly towards the apposed sides. These results further support the hypothesis that cells at the CF edge are regulated differentially from the remaining differentiating retina.
Selz, Brandon and James, Andrea, "Migration Pattern Dynamics during Choroid Fissure Closure in Zebrafish" (2020). 2020 Undergraduate Presentations. 38.