Abstract
Purpose:
XIAP (BIRC4) and Survivin (BIRC5) are members of the IAP (inhibitor of apoptosis) family of proteins that inhibit apoptosis by interacting with and regulating caspases. Many retinal diseases, e.g. retinitis pigmentosa and other retinal degenerations, are characterized by retinal cells that degenerate through apoptosis. XIAP and survivin therefore may play a role in the apoptotic cascade, and could potentially serve therapeutically to inhibit cell death and prevent or modulate the rate of retinal degeneration. In order to fully understand the role of IAP proteins in retinal disease or their potential in the treatment thereof, it is important to understand more about their role in the healthy retina. We therefore sought so characterize their expression in the normal retina of multiple mammalian species.
Methods:
Anti-human XIAP and survivin antibodies were used to determine the patterns of expression of these two proteins by fluorescence immunohistochemistry on cryosections from mature retinas of multiple species, including dog, mouse (Balb/c), pig and non-human primate (NHP; Macaque). In the dog, expression also was assessed throughout retinal development (2-12w).
Results:
In the adult dog, survivin labeled the inner segments (IS) and RPE whereas in the NHP, pig and mouse labeling was restricted to the outer segments (OS). XIAP labeled IS of the adult dog and mouse and pig. IS and OS were labeled in NHP and pig, the latter having distinct labeling in cone IS, and rod OS. The pattern of XIAP and survivin labeling in developing normal dog retina was similar to the adult.
Conclusions:
XIAP and Survivin are expressed in the retinas, particularly the photoreceptor cells, of the mammalian species examined. Surprisingly the labeling pattern is quite different between species. The results provide new information to examine the role of these anti apoptotic proteins in retinal diseases, and suggests that these proteins could be particularly important to the normal functioning of a healthy retina.