Clusterin protein diversity in the primate eye

Purpose: The clusterin gene encodes a multi-functional protein that has bee n identified in different tissues, including a number of different eye tiss ues, primarily in the mouse and to a much lesser extent in humans. Clusteri n has been implicated in a number of cellular processes such as lipid trans port, membrane integrity, apoptosis, and neurodegeneration, all of which co uld be important to the biology of the eye. In the current communication, w e provide data that confirms the expression of clusterin in a number of dif ferent human eye tissues and establishes the expression profile of this gen e in monkey derived eye tissues. The issue that we sought to examine is whe ther a broad profile of clusterin expression in the eye is consistent in pr imates (monkey and human). Methods: The majority of our study was done using monkey eye tissues. Where possible, we have used human tissues in order to confirm published finding s. Northern and western analysis was performed using tissues derived from m onkey eyes. In situ hybridization and immunochemistry were carried out on h uman eye sections. Results: Clusterin mRNA is expressed in primate lens, cornea, limbus, scler a, orbital muscle, ciliary body, retina, RPE/ choroid, and RPE cells in cul ture. Western analysis revealed that two major groups of clusterin exist in the eye, a high molecular weight group (>100 kDa) and a second group consi sting of at least five clusterin species that are all approximately 80 kDa. Analysis of conditioned media from RPE cells cultured on permeable support s suggests that different forms of clusterin display alternative patterns o f secretion. Conclusions: Clusterin is expressed in a broad range of eye tissues in both human and monkey, suggesting that this is a characteristic feature in prim ates. We demonstrate for the first time that a diverse number of clusterin isoforms were observed in monkey eye tissues by western analysis. Meanwhile , the molecular size of clusterin mRNA detected in the array of tissues are identical in size, suggesting that the nature of the diversity in clusteri n forms is due to post-translational modifications. In addition, new insigh ts were made in defining clusterin expression in ciliary body, cornea, and the retinal pigment epithelium.