Retinoschisin expression and localization in rodent and human pineal and consequences of mouse RS1 gene knockout.

PURPOSE The pineal gland shares a common neuroectoderm origin with the retina, and like the retina, regulates circadian rhythms through melatonin secretion. Recent expressed tag sequence (EST) analysis showed that several gene mutations, including RS1, which cause retinal degeneration, are also expressed in the pineal gland. Mutations in RS1 result in structural delamination of the neural retinal layers, leading to formation of schisis cavities in men affected with "X-linked retinoschisis" (XLRS). In this study, we evaluated RS1 expression in the rat and mouse as well as in human pineal and looked for morphological changes in the pineal of the RS1 knockout (RS1(-/Y)) mouse. METHODS We analyzed rat and mouse pineal for RS1 expression by Northern blot and in situ hybridization. RS protein, synaptophysin, S-100, and GFAP localization in the pineal of rat and mouse and RS protein in human pineal were evaluated immunohistochemically. Morphological studies were performed using transmission electron microscopy and light microscopy comparing wild-type to the RS1(-/Y) mouse. RESULTS RS1 expression was detected in RNA isolated from both the pineal and retina as a single major band migrating at about 5.5 kbp in Northern blots. RS1 riboprobe in situ hybridization demonstrated message in rat and mouse pineal, and immunohistochemistry showed RS protein in pinealocytes expressing synaptophysin but not in interstitial GFAP- and S100-positive glial cells. RS protein was present in many pinealocytes in human pineal. In light and electron microscopic examination of the pineal gland from RS1(-/Y) mice none of the structural changes found in the retina, such as cavity formation and loosening of the tissue, were seen. CONCLUSIONS This study demonstrates that RS protein is expressed in the pinealocytes but not in interstitial glial cells. The lack of structural abnormalities in the RS1(-/Y) mice suggests that RS serves a different function in the pineal gland than in the retina.