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Ying Chen, David Orlicky, Monica Sandoval, David Thompson, Vasilis Vasiliou; Glutathione is a Critical Regulator of Ocular Morphogenesis. Invest. Ophthalmol. Vis. Sci. 2014;55(13):4465.
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During embryogenesis, the ocular surface tissues are constructed from surface ectoderm (SE). Modulation of signal transduction by the cellular milieu during embryogenesis remains poorly understood; however, evidence indicates that key signaling pathways are redox-sensitive. Glutathione (GSH), the most abundant non-protein thiol, functions as the major redox buffer that maintains cellular redox homeostasis. An essential role of GSH in early mouse development is demonstrated by deaths of E7.5-8.5 embryos deficient in Gclc, the gene that encodes the rate-limiting enzyme in GSH biosynthesis. The presence of GCLC mRNA in the developing mouse eye is suggestive of a possible role of GSH in the process of ocular morphogenesis.
To elucidate such a role, we have developed a mutant (Gclcle/le) mouse line rendered incapable of GSH synthesis in SE-derived ocular structures. This was achieved by crossing Gclc-Floxed mice with Le-Cre mice that express CRE recombinase driven by the promoter of mouse Pax6 gene, the "master control" gene for the development of eyes and some epidermal organs.
Heterozygous (Gclcw/le) and homozygous (Gclcle/le) mutants were born alive with an expected Mendelian frequency. These mutants appear to grow normally and display eye opening around postnatal day 14 (P14). Around weaning (P21), Gclcw/le and Gclcle/le mice show good overall health except that Gclcle/le mice exhibit small eye phenotype. Starting around P35, Gclcle/le mice show growth retardation, develop elevated fasting serum glucose levels (diabetes). Around P63, they become moribund and die of diabetes complications. At this age, small eye becomes apparent in Gclcw/le mice, which appear otherwise healthy. Histological examination of Gclcle/le eyes at P23 and P56 revealed all ocular structures to be present. However, pathologies were observed in multiple tissues, specifically cornea, lens, iris, ciliary body and retina. These included hypercellularity and cytoplasmic vacuolization associated with disorganized cellular proliferation/differentiation/death. Further characterization of the ocular phenotype at embryonic and early postnatal stages in the Gclcle/le mutants is currently underway.
Collectively, our data demonstrate, for the first time, a critical role for GSH in ocular development. Our Gclcle/le mutant line represents a novel model by which the in vivo role of GSH in eye development may be explored.
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