Abstract
Abstract: :
Purpose: Optimedin is an olfactomedin domain–containing protein that may interact with myocilin. In the rat eye, optimedin gene is expressed in the neural retina and tissues of the eye angle. In this work we investigated possible biological functions of optimedin. Methods: Rat pheochromocytoma PC12 cells were stably transfected with a tetracycline–inducible vector containing optimedin cDNAs. Stable cell lines, expressing variable amounts of optimedin, were treated with nerve growth factor (NGF) to induce neuronal differentiation. Changes in the gene expression pattern of control versus optimedin in PC 12 cells were assessed using rat Affymetrix arrays. Results: In the presence of NGF under conditions of low serum, control cells differentiated into the neuronal type. More than 48% of single cells produced neurites. In the same conditions, most of the optimedin–expressing cells formed large aggregates. Only 5% of single cells produced neurites. The optimedin–expressing cells were more strongly attached to collagen I or collagen IV extracellular matrix compared with control cells. mRNA levels of about 100 genes were changed by >2 fold in optimedin–expressing cells versus control cells 6 hrs after NGF and doxycycline treatment. Dramatic reductions were observed for the initiation factor 2 gamma chain (13.7X) and delta–like homolog (15.8X) mRNAs. In contrast, significant increases were detected for neuronatin (23.1X), corticotrophin releasing hormone (7.2X) and retinol–binding protein 4 (6.0X). These results were confirmed by real–time RT–PCR. Conclusions: Optimedin is a biologically active secreted protein which may play an important role in the normal function of the retina as well as in the retinal pathology.
Keywords: retina • gene/expression • gene microarray