Purpose: The retina is a neural tissue especially differentiated for vision and, thus, the inner blood-retinal barrier (inner BRB) specific molecules may play an essential role in maintaining neural functions in the retina. The purpose of the present study was to identify selectively expressed genes at the inner blood-retinal barrier compared with the blood-brain barrier (BBB).
Methods: A comparison of expressed genes between conditionally immortalized rat retinal (TR-iBRB) cell lines and brain capillary endothelial (TR-BBB) cell lines was performed using mRNA differential display analysis and quantitative real time PCR analysis. The rat M-cadherin gene was cloned by performing 5' RACE, and its protein expression was detected by immunoblot analysis.
Results: Eight clones were identified as highly expressed genes in TR-iBRB cells including GATA-binding protein-3 (GATA-3), cytosolic branched chain amino transferase (BCATc), and M-cadherin (cadherin-15). The rat M-cadherin gene was cloned from TR-iBRB cells, for the first time, and has >86% amino acid sequence identity to the previously cloned mammalian M-cadherins. Rat M-cadherin expression in TR-iBRB cells was much greater than that in TR-BBB cells as far as mRNA and protein levels were concerned.
Conclusions: M-cadherin, GATA-3, and BCATc are highly expressed in TR-iBRB cells compared with TR-BBB cells and may indeed be involved in unique functions at the inner BRB.