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Clic6 Deficiency Triggers Aberrant Apical Microvilli in RPE
Sangwan Park1, Naran Suvarnpradip2, Niusha Kasiri2
1Department of Surgical and Radiological Sciences, School of Veterinary Medicine, University of California-Davis, Davis, California, United States.
Purpose:
We sought to demonstrate the impact of Clic6 deficiency in the retina and RPE of C57BL/6N mice that are homozygous for the Crb1rd8 mutation.
Methods:
Six Clic6-/- and six age-matched wild-type mice were used. Ophthalmic examination, ERG, and retinal optical coherence tomography were performed for clinical phenotyping. The mice were euthanized, and the eyes were processed for hematoxylin and eosin stain, immunohistochemistry, and transmission electron microscopy. Additionally, adult nonhuman primate and fetal human retinas were used for immunohistochemistry.
Results:
Both Clic6-/- and wild-type mice showed retinal lamination defects on optical coherence tomography and hematoxylin and eosin staining with a significantly greater number of lesions identified in Clic6-/- mice. No significant differences in ERG parameters were identified between genotypes. The expression of ezrin/radixin/moesin seemed to be flat and blunted at the apical RPE surface in Clic6-/- vs. wild-type mice. On transmission electron microscopy, Clic6-/- mice showed broadened and stout RPE microvilli with a significantly decreased apical microvilli height and significantly increased width of each RPE microvillus. Although the height of the RPE cells and basal infoldings and pigment granule density did not differ significantly, phagosome density was significantly greater in Clic6-/- mice. Both CLIC6 and ezrin/radixin/moesin were expressed in the RPE of adult nonhuman primate and fetal human tissues.
Conclusions:
Clic6 deficiency induced aberrant RPE microvilli leading to a decreased intimacy between the RPE and photoreceptors and worsened the Crb1rd8 mutation phenotype that was inherent in C57BL/6N mice. CLIC6 may have a potential role in RPE dysfunction across species, including humans.
Insights
Chloride intracellular channel 6 (CLIC6) deficiency in mice worsened retinal defects and altered retinal pigment epithelium (RPE) microvilli. CLIC6 may play a role in RPE dysfunction across species.
Area of Science:
- Ophthalmology
- Cell Biology
- Genetics
Background:
- The retinal pigment epithelium (RPE) is crucial for photoreceptor health and function.
- CLIC6 is a protein involved in cellular processes, but its role in the retina is not fully understood.
- The Crb1rd8 mutation in C57BL/6N mice causes retinal degeneration.
Purpose of the Study:
- To investigate the impact of Chloride intracellular channel 6 (CLIC6) deficiency on the retina and RPE.
- To examine how CLIC6 deficiency affects the phenotype of the Crb1rd8 mutation in mice.
- To explore the potential role of CLIC6 in RPE dysfunction across species.
Main Methods:
- Comparative analysis of Clic6-/- and wild-type C57BL/6N mice (n=6 per group).
- Ophthalmic examination, ERG, and OCT for retinal phenotyping.
- Histological analysis including H&E staining, immunohistochemistry, and TEM of retinal tissues.
- Immunohistochemistry on nonhuman primate and human fetal retinas.
Main Results:
- Clic6 deficiency exacerbated retinal lamination defects and increased lesion numbers in mice.
- Electron microscopy revealed broadened RPE microvilli with decreased height and increased width in Clic6-/- mice.
- Phagosome density was significantly higher in Clic6-/- mice, suggesting impaired phagocytosis.
- CLIC6 and ezrin/radixin/moesin expression was observed in RPE cells of primates and humans.
Conclusions:
- CLIC6 deficiency leads to aberrant RPE microvilli, reducing RPE-photoreceptor intimacy.
- CLIC6 deficiency worsens the Crb1rd8 mutation phenotype in mice.
- CLIC6 may have a conserved role in RPE function and dysfunction across species, including humans.
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