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Carlo Iomini, Grisanti Laura, Ekaterina Revenkova; A role of primary cilia in Anterior Segment Dysgenesis disorders. Invest. Ophthalmol. Vis. Sci. 2016;57(12):3860.
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© ARVO (1962-2015); The Authors (2016-present)
The development of the anterior segment (AS) of the mammalian eye involves tightly coordinated cellular interactions between tissues of different embryonic origins. Defects in this process lead to severe ocular disorders including aniridia, microcornea and primary congenital glaucoma of unclear pathophysiology. Interestingly, dysgenesis of the AS was reported in patients affected by ciliopathies. Here we investigate the role of cilia during development of the AS in mice.
Phenotypic analysis of the AS was performed using light and transmission electron microscopy. Expression of ciliary-mediated pathways target genes or transcription factors implicated in AS morphogenesis were assessed using qRT-PCR and immunostaining approaches. Cell proliferation of periocular mesenchyme was assessed by BrdU incorporation and immunostaining.
Null mutations that prevent cilia assembly such as Ift88-/- are lethal at E9.5-10.5. In Ift88-/- embryos the optic vesicle, although defective, is present. In contrast, at E10.5 the optic cup do not form as observed in wild-type embryos. To overcome mid-gestation lethality generated a conditional KO mouse Wnt1-Cre;IFT88flox/- (Ift88 cKO) in which the Ift88 gene is excised in all migrating mesenchymal cells of neural crest origin. cKO mice display strong craniofacial defects and die at postnatal day P0. Early eye patterning appears normal. However, later in development cKO mice display significant reduction of the anterior chamber with occasional fusion of the endothelium to the lens epithelium, a thinner stromal ECM and corneal endothelial malformations. Interestingly, although migration of neural crest-derived cells appears normal, we detected reduction of mesenchymal cells at the angle between the stroma and the optic cup at E17.5. Gene expression analysis revealed reduction of Hedgehog pathway target genes and Ptx2 but not Foxc1, both encoding for transcription factors linked to the Axenfeld-Rieger Syndrome. Immunofluorescence analysis confirmed reduction of PTX2 expression at the iridocorneal angle and detected mislocalization of cells expressing FOXC1.
We have uncovered a pivotal role of primary cilia in the development of the AS and highlighted their involvement in the etiology of ocular disorders derived from AS dysgenesis. We have also provided an accessible paradigm to address the role of primary cilia in complex tissue morphogenesis.
This is an abstract that was submitted for the 2016 ARVO Annual Meeting, held in Seattle, Wash., May 1-5, 2016.
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