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Bahaar Chawla, Brenda L Bohnsack; Retinoic Acid Regulates Neural Crest Migration and Proliferation in Eye Development. Invest. Ophthalmol. Vis. Sci. 2014;55(13):4439.
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© ARVO (1962-2015); The Authors (2016-present)
Retinoic acid (RA) is an essential morphogen that is required for eye development. We previously demonstrated that RA regulates formation of neural crest (NC)-derived ocular structures in zebrafish. In the current studies, we further elucidated the role of RA in regulating NC migration and proliferation.
Morpholino oligonucleotides (MO) were used in combination with exogenous regulators of retinoic acid (RA). Time-lapse imaging of transgenic zebrafish expressing GFP in NC assessed migration. Embryos were harvested for in situ hybridization, immunostaining, TUNEL assay, and histology.
Genetic disruption of RA synthesis (Raldh2 MO) or degradation (Cyp26c1 MO) inhibited early migration from 12-24 hours post fertilization (hpf) of the ventral wave of NC which gives rise to the jaw and periocular mesenchyme. NC passage through the ocular fissures into the developing eye (24-60hpf) was also disrupted in both Raldh2 and Cyp26c1 knockdown embryos. To determine if this later stage of NC migration was inherently dependent on RA or if the lack of early migration disrupted further NC development, pharmacologic treatment with all-trans RA or the aldehdehyde dehydrogenase inhibitor (DEAB) was initiated after completion of early NC migration (24hpf). Neither increased (all-trans RA) nor decreased (DEAB) RA levels inhibited NC migration through the ocular fissures demonstrating that RA was not intrinsically required for this later stage of migration. On the other hand, tight control of RA was necessary for NC organization around the lens and iris stromal formation at 48-60hpf. Since RA was not essential for migration from 24-48hpf, additional studies determined if RA regulated proliferation and survival. All-trans RA significantly decreased NC and retinal proliferation compared to controls while DEAB significantly increased the percent of cells in S-phase. In addition, increased or decreased RA levels resulted in increased NC and retinal apoptosis in the developing eye.
Tight control of RA was essential for specific cellular functions during different stages of eye development including early NC migration, later NC and retinal proliferation and survival, and finally NC organization and differentiation.
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