Abstract
Purpose: :
Synucleins, including α–, ß– and γ– synuclein, and synoretin, are soluble proteins found primarily in neural tissues. They have been implicated in the development of neurodegenerative diseases including Parkinson's, Alzheimer's, and dementia with Lewy body. Synuclein expression is strongly upregulated in breast and ovarian tumors. We and others previously documented the expression patterns of synucleins in mouse and human retina. In this study, synuclein expression in the anterior segment structures of the eye was investigated.
Methods: :
The anterior part of the mouse eyes were dissected into cornea, iris and lens. Human lenses were obtained from Mid–Missouri Eye Bank. Ocular tissues were homogenized to extract total RNA using TriReagent from Sigma. Synuclein expression was determined by reverse transcriptase–polymerase chain reaction (RT–PCR) using isoform specific primers. Individual PCR fragment was cloned into a plasmid vector and used as a DNA template to prepare riboprobes for in situ hybridization. The expression patterns of synuclein transcripts and proteins in the anterior segments were determined by in situ hybridization, immunohistochemistry and western blot techniques.
Results: :
In mouse eye, ß– and γ–synuclein transcripts were detected in the cornea and lens by RT–PCR. This result was confirmed by immunohistochemical staining using an antibody recognizing all synuclein isoforms. Synuclein immuno–reactivity was found in the corneal epithelial and endothelial cells, lens epithelial and cortical fiber cells, and in iris muscle fibers. In contrast to mouse lens, a high level of α–synuclein was detected in human lens by RT–PCR. The γ–synuclein transcripts were, however, in low abundance in human lens. Immunohistochemical staining showed that synuclein was mainly localized in the human lens epithelia and outermost cortical region.
Conclusions: :
Expression of synuclein isoforms in multiple tissues of the anterior segments is observed. The mouse and human lens show distinct expression pattern for α– and ß– synulcleins. Since synuclieins are implicated in the pathophysiology of other tissues, further studies on ocular synucleins may provide new insights to their role in lens and cornea aging.
Keywords: gene/expression • anterior segment • aging