Purpose: To examine the expression of transcription factor Sp1 in the cornea of the mouse eye throughout developmental stages. The environmental effect of light on Sp1 expression was also assessed.
Methods: C57BL/6 mice were set up for timed mating. Embryos on embryonic day (E)10.5, E12.5, E15.5, and E18.5 and eyes from mice on postnatal day (P)0, P7, P11, P15, P30, and P60 were collected for immunohistochemical staining and in situ hybridization. One group of mice was bred strictly in the dark between E18.5 and P15, and the eyes were collected at P0, P7, P11, and P15 time points.
Results: Sp1 expression was observed in the ectoderm and lens vesicle as early as E10.5. Both Sp1 protein and mRNA were abundant in the corneal basal epithelium and keratocytes until P11. Their levels were markedly reduced at P15, right after eyelid opening, and declined further between P15 and P60. In those mice bred in the dark, Sp1 was evident in the cornea at P0. The Sp1 level gradually increased until P11 and was decreased at P15. This expression pattern was nearly identical in mice bred either in a light/dark cycle or in the dark. The Sp1 level in the central lens epithelium was much lower than that in the cornea from E15.5 to late stages.
Conclusions: The present study indicates that Sp1 expression is developmentally regulated, providing a basis for further investigations on the regulation of the Sp1 gene during the course of corneal development and in diseases such as keratoconus.