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Kristyn VanDerMeulen, Jakub Famulski; Visualizing Periocular Mesenchyme Subpopulation Migratory Behaviors During Zebrafish Ocular Anterior Segment Development. Invest. Ophthalmol. Vis. Sci. 2018;59(9):3523.
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© ARVO (1962-2015); The Authors (2016-present)
The anterior segment (AS) is critical for directing light onto the vertebrate retina and maintaining intraocular pressure. Anterior Segment Dysgenesis (ASD) is a spectrum of developmental disorders effecting the AS and resulting in visual impairment. The neural ectoderm, surface ectoderm, and neural crest-derived Periocular Mesenchyme (POM) cell lineages come together in early development to assist in assembling these structures. Missteps in the processes incorporating the POM into AS tissues may predispose individuals to ASD. We hypothesize that the AS-associated POM population is comprised of several subpopulations, each with unique population sizes and migratory behaviors.
Transgenic zebrafish embryos of four suspected POM subpopulations (FoxC1b:GFP, FoxD3:GFP, Pitx2:GFP, and Lmx1b:GFP) were imaged using 3D confocal and Lightsheet microscopy utilizing fixed and live samples. This two-pronged approach allowed for thorough investigation of AS-related POM distribution and behavior of individual cells/populations. Fixed samples (22-72hpf) were imaged and AS-associated fluorescent POM cells were quantified based on total population size and quadrant of origin. In addition, POM cells were tracked and analyzed for trajectory, average velocity, and total distance traveled using Fiji and Arivis 4D software.
Total subpopulation size was variable as development progressed with significantly more cells expressing FoxC1b, Pitx2, or Lmx1b than FoxD3 within the AS. During key morphological stages, FoxC1b, FoxD3, and Lmx1b expressing cells enter the AS via dorsal regions, while Pitx2 cells enter via temporal regions. Lmx1b expressing cells enter the AS with a wide distribution, but become restricted to a small section of the dorsal nasal region by 48 hpf. No significant difference was seen in distance traveled or velocity within specific eye quadrants, nor between any populations. However, FoxC1b cells exhibited stochastic trajectories while FoxD3 and Pitx2 expressing cells migrated more directly.
Our results support the presence of at least four distinct POM subpopulations within the anterior segment. Future work will examine the possibility of each subpopulation contributing to a unique cell type or structure within the anterior segment.
This is an abstract that was submitted for the 2018 ARVO Annual Meeting, held in Honolulu, Hawaii, April 29 - May 3, 2018.
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