Abstract
Purpose: :
The pineal gland shares a common neuroectoderm origin with the retina, and regulates circadian rhythm through melatonin secretion. The pinealocytes and the retinal photoreceptors also originate from a common ancestral cell and during development pinealocytes show morphological photoreceptor features. Recent EST analysis showed that several genes that cause retinal degeneration are also expressed in the pineal gland, including RS1. Mutations in RS1 result in structural delamination and the formation of schisis cavities in the neural retinal layers in men with "X–linked retinoschisis" (XLRS). In this study, we explored RS1 expression in the pineal gland and evaluate morphological change in RS1 knockout mouse pineal gland.
Methods: :
We analyzed rat and mouse pineal for RS1 expression by Northern blot and in situ hybridization. RS protein, synapstophysin and GFAP localization in the pineal was evaluated immunohistochemically. Morphological studies were performed using transmission electron microscopy and light microscopy comparing wild type to the RS1 knockout mouse (KO).
Results: :
RS1 expression was detected in Northern blots as a single major band migrating at about 5.5 kbp in RNA isolated from both the pineal and retina. Riboprobe demonstrated message in the rat and mouse pineal, and immunohistochemistry showed retinoschisin protein is associated with pinealocytes expressing synaptophysin but not with the interstitial GFAP positive glial cells. Light and electron microscopic examinations showed that, unlike the retina, no structural changes, cavity formation or loosening of the tissue was present in the pineal gland of the RS1 KO mouse.
Conclusions: :
This demonstrates that RS1 is expressed in the pinealocytes but not in interstitial glial cells. The lack of structural abnormalities in the RS KO mouse suggests that RS1 may serve a different function in the pineal gland than in the retina.
Keywords: anatomy • microscopy: light/fluorescence/immunohistochemistry • retinal degenerations: cell biology