Abstract
Purpose :
We have recently discovered that proper corneal epithelial development is reliant on expression of transcription factor activating protein 2β (AP-2β). We have developed a mouse model lacking AP-2β expression in neural crest cell (NCC) derived tissues utilizing Wnt1Cre recombinase. These mutant mice (AP-2β NCC KO) lack proper corneal epithelial stratification. A possible mechanism for the lack of stratification may be altered Wnt/β-catenin signaling between the corneal stroma and epithelium. The purpose of this study was to investigate changes in Wnt/β-catenin signaling markers in the absence of stromal AP-2β expression.
Methods :
To generate AP-2β NCC KO mice, male mice heterozygous for the Wnt1Cre transgene (Wnt1Cre+/-) and Tfap2b (Tfap2b+/-) were bred with female mice homozygous for floxed Tfap2b (Tfap2blox/lox). Wild-type littermates were used as controls. Mice were euthanized at postnatal day (P) 7, P14, and P30 and their eyes and eyelids were extracted, processed and sectioned. Immunohistochemistry was performed using primary antibodies for active β-catenin (p489), Axin2, BMP4, and ABCB5.
Results :
At an early postnatal stage, P7, active β-catenin (n=4; control=32; mutant=35) and Axin2 (n=4; control=41; mutant=46) expression was observed to be similar between groups in the corneal stroma. However, at P14, we observed a significant decrease in the expression of β-catenin (n=8; control=21; mutant=35; p<0.05) and Axin2 (n=8; control=27; mutant=37; p<0.001) in the corneal stroma of controls compared to mutants. A further reduction in β-catenin (n=6; control=3; mutant=20; p<0.001) and Axin2 (n=6; control=4; mutant=25; p<0.00001) was observed in the stroma of the controls at P30 compared to that of stroma of the mutants. Furthermore, at older ages, minimal BMP4 expression was observed in the epithelium of the mutant when compared to that of control mice. In addition, ABCB5 expression was absent in the central cornea of mutant mice across all age groups when compared to their respective controls.
Conclusions :
The observed changes in expression of Wnt/β-catenin signaling markers indicate a shift in corneal stromal signaling resulting in a defective corneal epithelium in our mutant mice. The absence of ABCB5 expression from mutant corneal epithelium suggests altered stem cell populations. These findings suggest that AP-2β may have a role in corneal epithelium stratification via Wnt/β-catenin signaling.
This abstract was presented at the 2024 ARVO Annual Meeting, held in Seattle, WA, May 5-9, 2024.