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Céline Portal, Qing Liu, Peter Y Lwigale, Carlo Iomini; Disruption of primary cilium in neural crest cells leads to Anterior Segment Dysgenesis (ASD). Invest. Ophthalmol. Vis. Sci. 2018;59(9):3449. doi: https://doi.org/.
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© ARVO (1962-2015); The Authors (2016-present)
Anterior segment dysgenesis (ASD) represents one of the main causes of congenital opacity, and leads to glaucoma in ~50% of the cases. Several ciliopathies display conditions affecting tissues of the anterior segment (AS). Here we test the hypothesis that assembly of primary cilia in neural crest (NC) cells are required for normal anterior segment development.
To investigate the role of cilia in AS development, we used Ift88-/- mice and a conditional knock-out mouse Wnt1-Cre;Ift88fx/fx (cKO). cKO were crossed with the Rosa26mT/mG reporter line and the Gli1LacZ mouse to monitor the Cre activity and assess hedgehog (Hh) signaling activation, respectively. Phenotypic analysis of AS in ciliary mutants was performed using microscopy. Cell proliferation of periocular mesenchyme (POM) cells was assessed by bromodeoxyuridine labeling and nerves and blood vessels were immunostained. Hh and ASD-causing gene expression was assessed by RT-qPCR on Wnt1Cre-positive cells after cell sorting.
In Ift88-/- embryos, the optic vesicle, although defective, is present. However, the mice died at E10.5 before AS development. Thus, we obtained cKO mice by excision of Ift88 in POM cells of NC origin. cKO mice display strong craniofacial defects and die at birth. In late stages of embryonic development, cKO mice display significant reduction of the anterior chamber, a thinner stromal extracellular matrix and corneal endothelial malformations. Although migration of NC cells appears normal, we detected a reduction of mesenchymal cells at the angle between the stroma and the optic cup at E17.5. In addition, cKO embryos have abnormal innervation and vascularization of the cornea, and their stromal keratocytes exhibit an increased number of cellular protrusions. Using a reporter mouse for the Hh pathway (Gli1LacZ) we found a dramatic reduction of the Hh signaling activity and cell proliferation in a subpopulation of POM cells surrounding the optic nerve and the retinal pigmented epithelium up to the iridocorneal angle of cKO mice. Importantly, Wnt1Cre-positive POM sorted cells from cKO mice displayed significant lower levels of Gli1, Gli2, Ptch1, CyclinD1 and ASD-causing genes.
Primary cilia play a pivotal role in AS development by promoting the Hh signaling in a subset of POM cells and are involved in the etiology of ocular disorders derived from ASD.
This is an abstract that was submitted for the 2018 ARVO Annual Meeting, held in Honolulu, Hawaii, April 29 - May 3, 2018.
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