The retinal pigment epithelium (RPE) is a multifunctional and indispensable component of the vertebrate retina. Its asymmetry, specialized membrane structures, and membrane motility, which are essential for many of its functions, rely heavily on a highly ordered cytoskeleton. At present, relatively little is known about the machinery and the molecular mechanism regulating cytoskelton-mediated RPE functions. Our lab found that CLIC4, a recently identified actin-associated protein, was abundantly expressed in apical RPE microvilli. In cultured RPE cells, CLIC4 appears to be a key component in the phagocytic cup, the structure that engulfs the photoreceptor outer segment. To study CLIC4's role in RPE in vivo, we performed CLIC4 silencing by transfecting siRNA (small interfering RNA) into RPE of rodent eyes. The CLIC4-suppressed RPE cells developed several morphological changes including shortening of microvilli and breakdown of cell- cell contacts. Moreover, these animals developed profound retinal detachment and photoreceptor atrophy, resembling those phenotypes previously described for proliferative vitroretinopathy.
Three specific aims are proposed.
Aim 1 will identify the direct involvement of CLIC4 in the genesis of the microvillar and junctional structure of RPE and RPE-photoreceptor interdigitation.
Aim 2 will investigate the molecular interactions between CLIC4 and Ezrin, an actin-plasma membrane linker protein, and the importance of such interactions in CLIC4-mediated RPE morphogenesis in vivo.
Aim 3. will obtain functional evidence for CLIC4's involvement in outer segment phagocytosis by RPE and dissect the specific step(s) in which CLIC4 is involved. It is our belief that these studies will provide novel insights into the pivotal role of cytoskeletal organization and regulation in both normal and diseased RPE. These are not only important cell biological questions but also highly relevant for our understanding of the etiology of proliferative vitroretinopathy and perhaps also other degenerative retinal diseases.

Agency
National Institute of Health (NIH)
Institute
National Eye Institute (NEI)
Type
Research Project (R01)
Project #
5R01EY016805-05
Application #
7922004
Study Section
Special Emphasis Panel (ZRG1-CB-G (90))
Program Officer
Mariani, Andrew P
Project Start
2006-08-01
Project End
2012-01-31
Budget Start
2010-08-01
Budget End
2012-01-31
Support Year
5
Fiscal Year
2010
Total Cost
$322,993
Indirect Cost
Name
Weill Medical College of Cornell University
Department
Ophthalmology
Type
Schools of Medicine
DUNS #
060217502
City
New York
State
NY
Country
United States
Zip Code
10065
Hsu, Kuo-Shun; Chuang, Jen-Zen; Sung, Ching-Hwa (2017) The Biology of Ciliary Dynamics. Cold Spring Harb Perspect Biol 9:
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Hsu, Ya-Chu; Chuang, Jen-Zen; Sung, Ching-Hwa (2015) Light regulates the ciliary protein transport and outer segment disc renewal of mammalian photoreceptors. Dev Cell 32:731-42
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Yeh, Celine; Li, Aiqun; Chuang, Jen-Zen et al. (2013) IGF-1 activates a cilium-localized noncanonical G?? signaling pathway that regulates cell-cycle progression. Dev Cell 26:358-68

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