Targeted deletion of AP-2alpha leads to disruption in corneal epithelial cell integrity and defects in the corneal stroma.
OBJECTIVE
The present study was undertaken to create a conditional knockout of AP-2alpha in the corneal epithelium.


METHODS
A line of mice expressing Cre-recombinase specifically in the early lens placode was crossed with mice in which the AP-2alpha allele is flanked by two loxP sites. The resultant Le-AP-2alpha mutants exhibited a targeted deletion of AP-2alpha in lens placode derivatives, including the differentiating corneal epithelium.


RESULTS
The Le-AP-2alpha mutant mice were viable and had a normal lifespan. The adult corneal epithelium exhibited a variation in the number of stratified epithelial layers, ranging from 2 to 10 cell layers. A substantial decrease in expression of the cell-cell adhesion molecule, E-cadherin, was observed in all layers of the Le-AP-2alpha mutant corneal epithelium. The basement membrane, or Bowman's layer, was thinner in the mutant cornea and in many regions was discontinuous. These defects corresponded with altered distribution of laminin and entactin, and to a lesser degree, type IV collagen. The Le-AP-2alpha mutant cornea also exhibited stromal defects, including disrupted organization of the collagen lamellae and accumulation of fibroblasts beneath the epithelium that showed increased immunoreactivity for proliferating cell nuclear antigen (PCNA), alpha-smooth muscle actin (alpha-SMA), p-Smad2, and TGF-beta2.


CONCLUSIONS
In the absence of AP-2alpha, the corneal epithelium exhibits altered cell adhesion and integrity and defects in its underlying basement membrane. These defects likely caused the alterations in the corneal stroma.
Dwivedi
Dhruva J
DJ
Department of Pathology and Molecular Medicine, McMaster University, Hamilton, Ontario, Canada.
Pontoriero
Giuseppe F
GF
Ashery-Padan
Ruth
R
Sullivan
Shelley
S
Williams
Trevor
T
West-Mays
Judith A
JA
D000199:Actins / Q000378:metabolism; D000818:Animals; D001485:Basement Membrane / Q000378:metabolism / Q000473:pathology; D015820:Cadherins / Q000378:metabolism; D002448:Cell Adhesion; D015815:Cell Adhesion Molecules / Q000378:metabolism; D024141:Collagen Type IV / Q000378:metabolism; D003316:Corneal Diseases / Q000378:metabolism / Q000473:pathology*; D003319:Corneal Stroma / Q000378:metabolism / Q000473:pathology*; D019573:Epithelium, Corneal / Q000378:metabolism / Q000473:pathology*; D019084:Fluorescent Antibody Technique, Indirect; D017353:Gene Deletion; D007797:Laminin / Q000378:metabolism; D008562:Membrane Glycoproteins / Q000378:metabolism; D051379:Mice; D018345:Mice, Knockout; D018809:Proliferating Cell Nuclear Antigen / Q000378:metabolism; D016212:Transforming Growth Factor beta / Q000378:metabolism; D053781:Transforming Growth Factor beta2
D000199:Actins; D015820:Cadherins; D015815:Cell Adhesion Molecules; D024141:Collagen Type IV; D007797:Laminin; D008562:Membrane Glycoproteins; D018809:Proliferating Cell Nuclear Antigen; D016212:Transforming Growth Factor beta; D053781:Transforming Growth Factor beta2; C029967:nidogen