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Kristen Kwan, Chase Bryan; Migratory neural crest cells provide crucial extracellular matrix factors to regulate optic cup morphogenesis. Invest. Ophthalmol. Vis. Sci. 2017;58(8):1728.
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© ARVO (1962-2015); The Authors (2016-present)
Although migratory neural crest contributes to mature eye structures such as cornea and iris, its role in controlling early stages of eye development, specifically optic cup morphogenesis, is poorly understood. In mouse, optic cup defects have been described in a neural crest mutant, but the cellular and molecular mechanisms underlying aberrant early eye development are unknown. Using zebrafish 4-dimensional live imaging and molecular genetics, we set out to ask exactly when and how do optic cup defects arise? When does neural crest start to contact the optic vesicle? Importantly, what molecule(s) is the neural crest providing to control optic cup morphogenesis?
4D imaging datasets of eye morphogenesis are acquired via confocal microscopy. To test the role of neural crest, we use zebrafish tfap2a;foxd3 double mutants, which exhibit a complete loss of neural crest. Neural crest migration is visualized using transgenic embryos (sox10:mRFP or sox10:GFP). Optic cup patterning is assayed via antibody staining for pSmad3 or Pax2a.
Zebrafish neural crest mutants display defective optic cup invagination. Neural crest cells contact the optic vesicle at the earliest stages of morphogenesis, migrating to enwrap the developing optic cup, except for the distal, lens-facing side. Somewhat surprisingly, RPE development and TGF-β signaling appear unaffected, however, expression of the optic stalk marker Pax2a is expanded into the RPE layer. Nidogen, a laminin-collagen crosslinking protein expressed by neural crest and essential for optic cup morphogenesis in ES cells, appears to be a crucial factor: dominant negative nidogen disrupts wild type optic cup morphogenesis without affecting neural crest migration, whereas wild type nidogen rescues optic cup morphogenesis in neural crest mutants.
Our data indicate that during early eye formation, neural crest cells provide crucial cues regulating optic cup morphogenesis: the laminin-collagen crosslinking protein nidogen is deposited in a spatially restricted manner reflective of neural crest migration patterns. We hypothesize that nidogen alters extracellular matrix superstructure to facilitate specific morphogenetic movements underlying optic cup invagination. We are currently acquiring 4D imaging datasets of optic cup morphogenesis to pinpoint specific cell movements impaired by loss of neural crest.
This is an abstract that was submitted for the 2017 ARVO Annual Meeting, held in Baltimore, MD, May 7-11, 2017.
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