Abstract
Purpose::
Lens development is tightly regulated by the internal cell cycle regulator machinery and by extrinsic factors, such as pro- and anti- apoptotic factors. Survivin, also called Birc5, is the smallest member of the Inhibitor of apoptosis protein (IAP) family. Survivin functions at a pivotal junction of the cell cycle/apoptosis balance and is vital in maintaining normal tissue homeostasis. The aim of this study was to investigate Survivin expression in the embryonic chick lens and to correlate this with proliferation and apoptosis.Our previous microarray studies revealed differential expression of Survivin in the maturing and cataractous lens.
Methods::
A thorough spatio-temporal analysis of Survivin expression in the developing lens was carried out. Embryonic chicken lenses were collected from embryonic day (ED) 4 to ED 20 (H & H stages 29-46). RT-PCR, Western Blot and immunocytochemistry were used to study the expression of Survivin during lens development. Proliferation (PCNA) and apoptosis (TUNEL) staining were correlated with dynamic changes in the pattern of expression of Survivin during lens development.
Results::
Using RT-PCR, Survivin was highly expressed in the chick embryo lens from ED 6 until ED 12 (H & H stages 29-38), while from stage 38 onwards; the expression of survivin was downregulated, coinciding with formation of the organelle free zone. Immunostaining revealed Survivin expression in lens epithelial cells (associated with proliferation) and in lens fibre cells (associated with differentiation).
Conclusions::
The results suggest an important pro-survival role for survivin in the regulation of cell proliferation and apoptosis signalling pathways during embryonic lens development.
Keywords: cell survival • apoptosis/cell death • development