Glaucoma is a major debilitating eye disease affecting some 3 million individuals in this country. Of these, an estimated 100,000 patients each year lose some vision despite medical treatment for the normalization of intraocular pressure. As the incidence of glaucoma for the 65 yo.+ population segment is as high as 1 in 20, there is a great need to better understand disease mechanisms underlying optic nerve axon loss and to identify potential therapeutic strategies. A rapidly progressing area of research is th disease-linked up-regulation of intercellular signaling involving the EphB family of receptor tyrosine kinases and their ligands the ephrin-B proteins. Up-regulation of EphB/ephrin-B signaling occurs specificaly at the optic nerve head, an unmyelinated region of the optic nerve that clinical observations and experimental data both point to as a major site contributing to disease. In addition, increased activation of EphB/ephrin-B signaling occurs in two separate mouse models of glaucoma, in primates with experimental glaucoma, and in ONH tissues/cells from human patients, thereby implicating this signaling pathway as a potential key component of pathology. Recent work from our laboratory utilizing animals with genetic deletions and mutant alleles of specific EphB proteins has further demonstrated that animals with deficient EphB/ephrin-B signaling have more severe optic nerve axon loss compared to their wild-type littermates, indicating that EphB and ephrin-B proteins participate in an endogenous axon protective mechanism triggered by as yet incompletely characterized signals at the ONH. The up-regulation of EphB/ephrin-B signaling as an endogenous response in glaucoma is reminiscent of previous work implicating this signaling pathway in modulating axon survival and re-growth after spinal cord and optic nerve injury. Endogenous mechanisms that act to limit axon loss in glaucoma present intriguing targets for therapy. The current proposed research is based on preliminary evidence that the augmentation of EphB/ephrin-B signaling triggered by the application of biologically active EphB2 protein fragments results in a moderation of optic axon loss in an ex vivo tissue model of glaucomatous disease. Here we seek to build upon this finding and determine whether increased EphB and ephrin-B forward as well as reverse signaling in vivo can salvage optic axon loss in a laser-induced mouse model of glaucoma. Augmentation of EphB and B- ephrin signaling will be accomplished using an inducible Tet-on strategy in laser treated mice and optic nerve axon survival compared between animals receiving Doxycycline and those that do not. The results from this work potentially provide support for a novel therapeutic target and encourage additional discovery efforts.

Public Health Relevance

The proposed research is directed at investigating the efficacy of augmented Eph and ephrin signaling in salvaging optic nerve axon survival in the blinding disease, glaucoma. Results from these studies may potentially lead to a new therapeutic avenue to mitigate and delay vision loss in the approximately 3 million patients affected by this disability.

Agency
National Institute of Health (NIH)
Institute
National Eye Institute (NEI)
Type
Research Project (R01)
Project #
5R01EY010688-18
Application #
8515411
Study Section
Special Emphasis Panel (DPVS)
Program Officer
Chin, Hemin R
Project Start
1994-07-01
Project End
2016-06-30
Budget Start
2013-07-01
Budget End
2014-06-30
Support Year
18
Fiscal Year
2013
Total Cost
$372,875
Indirect Cost
$135,375
Name
University of California San Francisco
Department
Ophthalmology
Type
Schools of Medicine
DUNS #
094878337
City
San Francisco
State
CA
Country
United States
Zip Code
94143
Song, Yuanquan; Sretavan, David; Salegio, Ernesto A et al. (2015) Regulation of axon regeneration by the RNA repair and splicing pathway. Nat Neurosci 18:817-25
Fu, Christine T; Sretavan, David (2012) Involvement of EphB/Ephrin-B signaling in axonal survival in mouse experimental glaucoma. Invest Ophthalmol Vis Sci 53:76-84
Fu, Christine T; Sretavan, David W (2012) Ectopic vesicular glutamate release at the optic nerve head and axon loss in mouse experimental glaucoma. J Neurosci 32:15859-76
Du, Juan; Tran, Tony; Fu, Christine et al. (2007) Upregulation of EphB2 and ephrin-B2 at the optic nerve head of DBA/2J glaucomatous mice coincides with axon loss. Invest Ophthalmol Vis Sci 48:5567-81
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Birgbauer, E; Cowan, C A; Sretavan, D W et al. (2000) Kinase independent function of EphB receptors in retinal axon pathfinding to the optic disc from dorsal but not ventral retina. Development 127:1231-41
Zhang, F; Lu, C; Severin, C et al. (2000) GAP-43 mediates retinal axon interaction with lateral diencephalon cells during optic tract formation. Development 127:969-80
Marcus, R C; Shimamura, K; Sretavan, D et al. (1999) Domains of regulatory gene expression and the developing optic chiasm: correspondence with retinal axon paths and candidate signaling cells. J Comp Neurol 403:346-58
Deiner, M S; Sretavan, D W (1999) Altered midline axon pathways and ectopic neurons in the developing hypothalamus of netrin-1- and DCC-deficient mice. J Neurosci 19:9900-12

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