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Antionette L Williams, Bahaar Chawla, Brenda L Bohnsack; Cyp1b1 regulates retinal and ocular neural crest development through retinoic acid-dependent and RA-independent pathways. Invest. Ophthalmol. Vis. Sci. 2015;56(7 ):1481.
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© ARVO (1962-2015); The Authors (2016-present)
CYP1B1 gene mutations are the most common genetic causes of congenital glaucoma. Despite this disease association, the role of CYP1B1 in eye development and its in vivo substrate remains unknown. In these studies, we used zebrafish to elucidate the mechanism by which CYP1B1 regulates eye development.
Zebrafish eye and neural crest development was analyzed using antisense morpholino oligonucleotides (MO) or mRNA injections and exogenous treatment with all-trans retinoic acid (RA) or pharmacological regulators of RA. Live imaging of transgenic zebrafish embryos, in situ hybridization, immunostaining, TUNEL assay, and RT-PCR were used to assess migration, proliferation, survival and downstream targets in the developing eye.
Herein, we observed the specific spatio-temporal expression of cyp1b1 in the ocular fissures of the developing zebrafish retina. Cyp1b1 regulated RA activity in the periocular mesenchyme. Further, similar to RA, Cyp1b1 inhibited retinal proliferation and regulated neural crest-derived periocular mesenchyme migration into the developing anterior segment. Cyp1b1 overexpression inhibited inferior ocular fissure closure, resulting in prominent coloboma formation and ocular neural crest disorganization. Importantly, embryos injected with human wild type, but not mutant, CYP1B1 mRNA also showed colobomas, and these effects were rescued by knockdown of endogenous zebrafish Cyp1b1. Although increasing endogenous RA levels rescued anterior segment defects due to Cy1b1 knockdown, Cyp1b1-regulated ocular fissure closure was independent of RA. Cyp1b1 negatively regulated the expression of both retinal pax6a and pax6b. Consistently, knockdown of Pax6a or Pax6b resulted in coloboma formation, which was partially rescued through concurrent Cyp1b1 knockdown.
Cyp1b1 function in eye development is mediated through 2 pathways: a RA-dependent pathway, which regulates ocular neural crest migration and retinal proliferation, and a Pax6-mediated pathway, which regulates ocular fissure closure. These studies provide insight into the role of Cyp1b1 in eye development and further elucidate the pathogenesis of congenital glaucoma.
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