We studied the localization of calcineurin by immunoblotting analysis and immunohistochemistry as a first step in clarifying the role of calcineurin in the retina. Rat, bovine, and human retinal tissues were examined with subtype-nonspecific and subtype-specific antibodies for the Aα and Aβ isoforms of its catalytic subunit. In mature retinas of the three species, calcineurin was localized mainly in the cell bodies of ganglion cells and the cells in the inner nuclear layer, in which amacrine cells were distinctively positive. The calcineurin Aα and Aβ isoforms were differentially localized in the nucleus and the cytoplasm of the ganglion cell, respectively. Calcineurin was also present in developing rat retinas, in which the ganglion cells were consistently positive for it. The presence of calcineurin across mammalian species and regardless of age shown in the present study may reflect its importance in visual function and retinal development, although its function in the retina has not yet been clarified.
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