Immunohistochemical localization of cyclic AMP-responsive element binding protein (CREB)-binding protein in the pig retina during postnatal development

This study evaluated the cellular localization of cyclic AMP-responsive element binding protein-binding protein (CBP) expression in pig retinas during postnatal development. Immunohistochemistry and Western blot analysis were performed on retinal tissue from 2-day-old, 5-week-old, and 6-month-old pigs. Western blot analysis detected the expression of CBP in the retinas of 2-day-old piglets and showed that it was significantly decreased in the retinas of 5-week-old and 6-month-old pigs. Immunohistochemically, CBP was intensely immunostained in protein kinase C alpha (PKC alpha)-positive-bipolar cells, glutamine synthetase-positive Muller cells, and in ganglion cells in 2-day-old piglets. CBP was detected weakly in the inner plexiform, outer nuclear, and rod and cone layers. CBP immunoreactivity in the ganglion cell layer was decreased in the retinas of 5-week-old and 6-month-old pigs, while clear CBP expression detected in the neurite of PKC alpha-positive bipolar cells in the inner nuclear layer. In addition, CBP immunoreactivity in Muller cells and glial fibrillary acidic protein-positive glial processes was particularly noteworthy in pig retinas, but not in rat retinas. The results indicate that CBP is expressed differentially in the retinal neurons and glial cells according to growth and animal species, and may play an important role in homeostasis in Muller cells, neurite extention in bipolar cells, and signal transduction in photoreceptor cells in the porcine retina.