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Andrea Hartsock, Jeffrey Gross; Cell-ECM interactions during formation of the zebrafish hyaloid vasculature. Invest. Ophthalmol. Vis. Sci. 2013;54(15):3037.
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© ARVO (1962-2015); The Authors (2016-present)
Vasculature formation requires an orchestrated series of morphogenetic changes to generate an integrated vessel system. Virtually nothing is known about how hyaloid vasculature morphogenesis occurs, despite its importance in the developing eye. Thus, the purpose of this study was to identify the cellular underpinnings of hyaloid morphogenesis and test the hypothesis that cell-ECM interactions play an integral role in building the hyaloid.
Fixed sample and in vivo time lapse imaging of fli1a:GFP and flk:mCherry transgenics were utilized to image and quantify dynamic aspects of hyaloid morphogenesis in wild-type, fibronectin1 (fn1) and integrin-α5 (itga5) mutant embryos. Lens transplantation was utilized to determine if lens-derived Fn was required for hyaloid formation.
Hyaloid formation can be divided into five distinct morphogenetic stages: During Stage I (48hpf) vascular precursor cells arrive at the posterior of the lens. Throughout Stage II (48-72hpf) hyaloid precursor cells increase in number, forming a meshwork that covers the posterior lens. During Stage III (72-96hpf), remodeling of this meshwork initiates; here, Stage II hyaloid cells reorganize into a highly branched web that surrounds the lens. An anterior ring is also observed at this time. At Stage IV (96hpf), the anterior ring is no longer present. Throughout Stage V (108-120hpf), disorganized hyaloid precursor cells mature into connected lumenal vessels. The hyaloid in fn1 mutants possessed “clumps” of vascular precursor cells on their lenses that did not reorganize into mature vessels. The hyaloid in itga5 mutants extends anteriorly, but vessel thickening, maturation, and organization are disrupted.
Fixed sample and in vivo time-lapse imaging of hyaloid formation revealed that hyaloid morphogenesis involves a series of dynamic cell migration events and morphogenetic changes in order to build the functional hyaloid. Analyses of two mutations that affect cell-ECM interactions, fn1 and itga5, reveal specific requirements for these factors during hyaloid development. Analyses of the roles of additional cell-ECM proteins, as well as other morphogenetic regulators, during hyaloid formation will generate a comprehensive understanding of the cellular underpinnings of hyaloid morphogenesis during embryonic eye development.
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