In the third experiment that was done for the paper, FTIR spectra of reconstituted and eluted rhodopsin protein were measured. The experiment indicated that there is a decrease in alpha-helix and an increase in beta-pleated sheets in both mutations but the differences were stronger in P23H. The N15S mutation protein is more folded compared to P23H mutation. This indicates that there is a decreased amount of alpha-helix in misfolded fraction compared to wt. Circular dichroism spectra were recorded with samples of rhodopsin and clathrin e 6. There is a loss of alpha-helix structure from wt to the mutants with a further loss in P23H. Clathrin e6 stabilizes the alpha helix of the wt and the P23H but not N15S. This indicates that clathrin e6 causes stability in the alpha helix of the P23H mutated proteins. The whole paper impacts the disease by indicating why the mutation of P23H has a more impact compared to patients with a mutation in S15N, and suggest a possible therapy for the mutation P23H.
The mutation affects the stability of the cone structure causing the protein to aggregate and to be instable. This, in turn, causes degeneration of cone cells, which directly leads to a decrease in vision. There are phenotypic differences between individuals with the same genotype; however, this is not well studied since many different genes cause retinitis pigmentosa, and P23H mutation in RHO gene is relatively rare in an already rare disease. The variability is due to the different mutation types that are present as over 40 different mutations can result in retinitis pigmentosa. It is also possible that there are modifiers. However, this is not studied very well.
The mutation in the gene affects the physiology of the cell in the tissue by causing degeneration of the rod photoreceptors, which in turn causes changes in the surrounding cell tissue. Without rod cells in the retina is unable to process vision completely. In this experiment, the researchers investigate the evolution of microglial changes during retinal degeneration in P23H rats. The cell density and morphology of the retinal degeneration were studied at different ages in normal and diseased retinas through immunocytochemical localization of GFAP. Astrocyte quantification showed that astrocyte density increased astrocyte density was lower in adults there was a significant increase in astrocyte numbers in P23H rat at P120 in all regions examined. In P23H rats the retina also showed a progressive disruption of blood vessels and there were tangles of blood vessels. There was also astrocyte hyperplasia and hypertrophy accompanied by increased GFAP activity. When the retina is undergoing a dramatic remodeling due to retinal degeneration, there is a major change in the astrocyte number the numbers change less when the degeneration process slows down.