Adam9-deficient retinal pigment epithelium pseudopods maintain photoreceptor outer segment renewal despite subretinal space expansion
Tylor R. Lewis, Carson M. Castillo, Sebastien Phan, Camilla R. Shores, Kylie K. Hayase, Keun-Young Kim, Mark H. Ellisman, Oleg Alekseev, Marie E. Burns, Vadim Y. Arshavsky
Tylor R. Lewis, Carson M. Castillo, Sebastien Phan, Camilla R. Shores, Kylie K. Hayase, Keun-Young Kim, Mark H. Ellisman, Oleg Alekseev, Marie E. Burns, Vadim Y. Arshavsky
View: Text | PDF
Research Article Cell biology Neuroscience Ophthalmology

Adam9-deficient retinal pigment epithelium pseudopods maintain photoreceptor outer segment renewal despite subretinal space expansion

Abstract

Vision begins in the outer segment compartment of photoreceptor cells, which is constantly renewed through the addition of membrane material at its base and ingestion of mature membranes at its tip by the retinal pigment epithelium (RPE). The close apposition of outer segments to the RPE is believed to be critical for maintaining this renewal process. Yet, in several retinal diseases, expansion of the subretinal space separating photoreceptors from the RPE does not immediately impact photoreceptor functionality. Here, we analyzed outer segment function and renewal in the Adam9-knockout mouse characterized by a major expansion of the subretinal space. Surprisingly, photoreceptor-RPE separation affected neither the sensitivity of photoreceptor light responses nor the normal rate of outer segment renewal in this mouse prior to the onset of photoreceptor degeneration. The latter is achieved through the formation of elongated RPE pseudopods extending across the enlarged subretinal space to ingest outer segment tips. This work suggests that pseudopod formation may underlie the persistence of photoreceptor function in human diseases accompanied by photoreceptor-RPE separation, such as vitelliform macular dystrophy or age-related macular degeneration associated with subretinal drusenoid deposits.

Authors

Tylor R. Lewis, Carson M. Castillo, Sebastien Phan, Camilla R. Shores, Kylie K. Hayase, Keun-Young Kim, Mark H. Ellisman, Oleg Alekseev, Marie E. Burns, Vadim Y. Arshavsky

×

Figure 9

Ablation of subretinal mononuclear phagocytes does not affect the pathology associated with loss of ADAM9.

Options: View larger image (or click on image) Download as PowerPoint
Ablation of subretinal mononuclear phagocytes does not affect the pathol...
(A) Representative immunofluorescence images of RPE flatmounts stained with IBA1 to label subretinal mononuclear phagocytes from P90 Adam9–/– mice fed a diet with or without PLX3397 (PLX) beginning at P60. For each group, 3 mice were analyzed. Scale bar: 100 μm. (B) Representative light microscopy images of Adam9–/– retinas treated with control or PLX diet from P30 through P180. For each condition, 4 mice were analyzed. OS, outer segment; ONL, outer nuclear layer. Scale bar: 10 μm. (C) Quantification of the number of photoreceptor nuclei. ON, optic nerve. For each condition, 4 mice were analyzed. Two-way ANOVA was used to determine that there was a statistically significant increase in photoreceptor numbers in PLX-treated retinas compared with control retinas (P = 0.0090). (D) Representative TEM images of control and PLX-treated Adam9–/– retinas. For each condition, 4 mice were analyzed. Scale bar: 5 μm. (E) ERG scotopic a-wave response of dark-adapted control and PLX-treated Adam9–/–. For control diet, 18 eyes were analyzed. For PLX diet, 14 eyes were analyzed. Two-way ANOVA showed no statistically significant difference in genotype/light intensity (P = 0.1049). (F) ERG scotopic b-wave response of dark-adapted control and PLX-treated Adam9–/– mice. For control diet, 18 eyes were analyzed. For PLX diet, 14 eyes were analyzed. Two-way ANOVA was used to determine that there was a statistically significant difference in genotype/light intensity (****P < 0.0001). (G) ERG scotopic b-wave response of dark-adapted control and PLX-treated WT mice. For control diet, 12 eyes were analyzed. For PLX diet, 16 eyes were analyzed. Two-way ANOVA showed a statistically significant difference in genotype/light intensity (****P < 0.0001). Data are presented as mean ± SEM.