Purchase this article with an account.
Bahaar Chawla, Antionette L Williams, Brenda L Bohnsack; Pitx2 Regulates Early Neural Crest Migration in Periocular Mesenchyme. Invest. Ophthalmol. Vis. Sci. 2015;56(7 ):5480.
Download citation file:
© ARVO (1962-2015); The Authors (2016-present)
Mutations in the PITX2 gene are associated with the congenital eye disease, Axenfeld-Rieger Syndrome (ARS). Pitx2, which is expressed in the neural crest-derived periocular mesenchyme, is regulated by the essential morphogen, retinoic acid (RA). In these studies, we used zebrafish to further elucidate the role of RA and pitx2 in neural crest and eye development.
Morpholino oligonucleotides (MO) and mRNA injections were used in combination with exogenous regulators of RA. Time-lapse imaging of transgenic zebrafish expressing GFP in neural crest assessed migration. Embryos were harvested for in situ hybridization, immunostaining, TUNEL assay, and histology.
Time-lapse imaging demonstrated that the neural crest migrated in waves that were dorsal and ventral to the developing eye. Both MO knockdown and overexpression of Pitx2 completely suppressed the ventral wave of neural crest migration. Alterations in Pitx2 levels also disrupted the dorsal wave, causing the neural crest cells to improperly migrate and undergo apoptosis. These findings were mirrored in embryos where RA synthesis was genetically decreased (Raldh2 MO) or increased (raldh2 mRNA). Further, improper early neural crest migration into the craniofacial region and periocular mesenchyme inhibited later neural crest migration into the eye. RA induced pitx2 expression in the neural crest via RA receptor (RAR) A2A, A2B, and GA and together RA and Pitx2 regulated retinal and neural crest cell proliferation in the developing eye. Alterations in RA or Pitx2 levels prevented the cells from exiting the cell cycle leading to a higher proportion of retinal and neural crest cells in S-phase. Disruption in cellular migration and proliferation resulted in increased apoptosis throughout the developing eye.
RA regulation of Pitx2 in the neural crest-derived periocular mesenchyme was essential for early neural crest migration into the craniofacial region and later NC and retinal proliferation and survival.
This PDF is available to Subscribers Only