Abstract
Purpose: :
To expand the usefulness of Tilapia (Oreochromis niloticus) as a model organism to investigate refractive development. Here we examine the phylogenetic relationships and gene expression patterns of tilapia retinal annexin max2, a protein identified using a novel proteomics screening protocol.
Methods: :
Translucent goggles were directly sutured over the right eye for 2 weeks to induce form deprivation myopia while the left eye served as an untreated contralateral control. 2–D Differential in Gel Electrophoresis (DIGE) was used in conjunction with Mass Spectrometry (MS) to identify proteins that were differentially expressed in the retina/choroid complex. Annexin max 2, a protein showing significant expression changes, was PCR cloned from Tilapia retinal tissue. Targeted gene expression studies were carried out using semi–quantitative Real–time PCR on separated retinal and choroidal tissue. In addition to those above, sham–surgery and sham–untreated contralateral controls were included in the gene transcription analysis.
Results: :
Annexin max 2 was one of four proteins identified by DIGE showing significant changes in protein expression in form deprived eyes. A 293 bp fragment of tilapia annexin max 2 was cloned from retinal tissue and is 80.5 % identical to the Japanese medaka (Oryzias latipes) homolog. Phylogenetic analysis with other known annexins confirmed the closest known homolog as the medaka annexin max2. While this protein was significantly down regulated (47%) in form–deprived eyes at the protein level, no differences were detected in gene expression between treatment groups at the same 2–week time point. Transcription levels were noted to be significantly higher in the choroid relative to the retina (p<.0001).
Conclusions: :
The use of a proteomic screening protocol followed by a targeted gene expression study has identified a novel potential myopia related target and provided insight into the molecular mechanisms of myopia. The identified annexin max2 is of key interest based upon its connection to retinoic acid and its participation in exocytotic pathways. Further characterization is currently in progress.
Keywords: myopia • gene/expression • proteomics