Determining The Window Of Rhodopsin Degradation By RPE Cells

Research paper

Honors Project Abstract: Macular Telangiectasia (MacTel) is a rare, late onset, degenerative eye disease whereby the photoreceptors (cones and rods) of the macula become diseased and slowly degenerate, thus reducing vision. These photoreceptors are subjected to harsh stresses, which cause them to shed the outer 10% of each cell on a nightly basis. This results in the build up of debris which another cell type, the retinal pigment epithelium (RPE) removes and recycles every night to reveal a fresh photoreceptor free of debris4. Excessive debris accumulated between the retina and RPE cells has been consistently observed in post mortem retinal samples from patients with MacTel .3 We hypothesize that patients with MacTel may have RPE cells with reduced functionality, which ultimately reduces their efficacy of clearing debris and contributes to debris accumulation over time, leading to photoreceptor death and loss of vision.2 To test this hypothesis, iPS cells will be collected from MacTel patients and differentiated into RPE cells. These cells will then be compared with iPS-derived RPE from normal (non-diseased), age-matched controls for the efficiency of rhodopsin degradation, a function of normal operating RPE cells. We will describe efforts to create and optimize a phagocytosis assay whereby photoreceptor outer segments are ‘fed’ to normal RPE and then the time-course for degradation of internalized rhodopsin is assayed using western blot analyses. This work will 1) provide a key functional assay that is optimized for future use with the more precious iPS-derived RPE, and 2) establish a baseline of normal RPE phagocytosis and debris processing.


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