Pax–6 and lens regeneration

Abstract

Abstract: : Purpose: Our studies aim to dissect the potential involvement of the transcription factor Pax–6 during lens regeneration in the adult newt. We selected this urodele model because of its ability to regenerate its lens as an adult. Upon lentectomy, the cells of the dorsal iris undergo a transdifferentiation process whereby, they proliferate, dedifferentiate and redifferentiate to form a new lens. Our studies and others have shown that Pax–6 mRNA is expressed in the regenerating dorsal iris and lens vesicle as well in the ventral iris at the early stages of regeneration. These studies have now been extended and we aim to elucidate the role of Pax–6 in this process. Methods: Immunohistochemistry using specific antibodies against Pax–6 were used to correlate Pax–6 expression to proliferation. Proliferation was assayed by BrdU incorporation. In addition, we used valproic acid (VPA) to interfere with Pax–6 in vivo and examine its effects on lens regeneration using standard histological techniques as well as immunohistochemistry. Results: Pax–6 and BrdU co–localization suggest that Pax–6 may control the proliferation of cells in the regenerative lens vesicle, as well as in both dorsal and ventral iris. Functional studies using VPA support the expression studies and show that inhibition of Pax–6 results in the inhibition of the regenerative process. Conclusions: Our results indicate that Pax–6 protein is present in cells that are proliferating during lens regeneration and that Pax–6 may be involved in the re–entering of the cell cycle in both the dorsal and ventral irises. This suggests that the possible regulation of proliferation by Pax–6 is required but not essential for the process of regeneration since the ventral iris cells are also Pax–6/BrdU positive at the initial stages.

Keywords: regeneration • proliferation • immunohistochemistry