Ocular phenotypic consequences of a single copy deletion of the Yap1 gene (Yap1+/−) in mice

Purpose: To identify the effects of a single copy deletion of Yap1 (Yap1+/−) in the mouse eye, the ocular phenotypic consequences of Yap1+/− were determined in detail. Methods: Complete ophthalmic examinations, as well as corneal esthesiometry, the phenol red thread test, intraocular pressure, and Fourier-domain optical coherence tomography were performed on Yap1+/− and age-matched wild-type (WT) mice between eyelid opening (2 weeks after birth) and adulthood (2 months and 1 year after birth). Following euthanasia, enucleated eyes were characterized histologically. Results: Microphthalmia with small palpebral fissures, corneal fibrosis, and reduced corneal sensation were common findings in the Yap1+/− mice. Generalized corneal fibrosis precluded clinical examination of the posterior structures. Histologically, thinning and keratinization of the corneal epithelium were observed in the Yap1+/− mice in comparison with the WT mice. Distorted collagen fiber arrangement and hypercellularity of keratocytes were observed in the stroma. Descemet’s membrane was extremely thin and lacked an endothelial layer in the Yap1+/− mice. The iris was adherent to the posterior cornea along most of its surface creating a distorted contour. Most of the Yap1+/− eyes were microphakic with swollen fibers and bladder cells. The retinas of the Yap1+/− mice were normal at 2 weeks and 2 months of age, but the presence of retinal abnormalities, including retinoschisis and detachment, was markedly increased in the Yap1+/− mice at 1 year of age. Conclusions: The results show that the heterozygous deletion of the Yap1 gene in mice leads to complex ocular abnormalities, including microphthalmia, corneal fibrosis, anterior segment dysgenesis, and cataract.