Abstract
Purpose: :
To examine the spatial and temporal expression of Sp1 and Krüppel–like factor 6 (KLF6) in the human cornea in the developing and adult eyes. Sp1 and KLF6 are transcription factors that contain three zinc fingers and interact with GC boxes in the promoter elements of various genes. Both factors, especially Sp1, have been implicated in keratoconus, a cornea–thinning disease.
Methods: :
Eyes from human fetus (F) of 7, 9, 10, 11, 13, and 27 weeks (w), as well as corneas from 11 and 56–day (d)–old children and donors 2, 6, 16, 25, 40, 51, 69 and 83 years (y) of age were obtained from the University of Seattle tissue bank, University of Illinois at Chicago, Illinois Eye Bank or National Disease Research Interchange. All specimens were fixed in 4% paraformaldehyde and processed for paraffin sections. Immunohistochemistry was performed using polyclonal antibodies for Sp1 and KLF6.
Results: :
Staining for Sp1 was evident at the earliest F7w embryonic time point in the cornea. From F7w to F27w, the moderate to strong Sp1 immunostaining was seen in the nuclei of epithelial and endothelial cells. Staining in keratocytes was also observed. The intensity of Sp1 staining in all layers of the cornea was substantially decreased at 11d after birth and remained low afterwards. Positive KLF6 staining was also noted at F7w in all corneal layers. In the epithelium and endothelium, the staining was mostly cytoplasmic throughout the fetal stages. After birth, the KLF6 staining appeared in the nuclei of corneal epithelial cells along with that in the cytoplasm. The intensity of KLF6 staining in the epithelium and endothelium remained relatively constant from E47d to the 83y–old donor cornea. The KLF6 staining in the stroma however was reduced after F27w.
Conclusions: :
The expression of Sp1 in the human cornea appears to be temporally regulated while that of KLF6 in the corneal epithelium is spatially regulated. The observed expression patterns of Sp1 and KLF6 in humans are consistent with those reported previously in the developing mouse cornea.
Keywords: cornea: basic science • transcription factors • gene/expression