title: Involvement of EphB/Ephrin-B signaling in axonal survival in mouse experimental glaucoma.
abstract: OBJECTIVE
  To examine the functional significance of EphB/ephrin-B upregulation in mouse experimental glaucoma.
  
  
  METHODS
  In a loss-of-function approach, mouse mutants lacking EphB2 (EphB2(-/-)) or EphB3 (EphB3(-/-)) protein, and mutants expressing EphB2 truncated in the C-terminus (EphB2(lacZ/lacZ)) were subjected to laser-induced ocular hypertension (LIOH), an experimental mouse model of glaucoma. The number of optic nerve axons was counted in paraphenylenediamine (PPD)-stained sections and compared between EphB mutants and wild type littermates. In a gain-of-function approach, retina/optic nerve explants obtained from LIOH-treated animals were exposed to EphB2-Fc recombinant proteins or Fc control proteins. Tissue sections through the optic nerve head (ONH) were labeled with neuron-specific anti-tubulin β-III antibody to determine axonal integrity.
  
  
  RESULTS
  Both EphB2 and EphB3 null mutant mice exhibited more severe axonal degeneration than wild type littermates after treatment with LIOH. Mutant mice in which the C-terminal portion of EphB2 is truncated had an intermediate phenotype. Application of EphB2-Fc recombinant protein to LIOH-treated optic nerve explants resulted in greater sparing of tubulin β-III-containing retinal ganglion cell (RGC) axons.
  
  
  CONCLUSIONS
  These results provide genetic evidence in mice that both EphB/ephrin-B forward and reverse signaling feed into an endogenous pathway to moderate the effects of glaucomatous insult on RGC axons. LIOH-induced axon loss is maintained in retina/optic nerve explants after removal from an ocular hypertensive environment. Exogenous application of EphB2 protein enhances RGC axon survival in explants, suggesting that modulation of Eph/ephrin signaling may be of therapeutic interest.
authors: Department of Ophthalmology, University of California, San Francisco, San Francisco, California 94143, USA.
authors: Christine T
authors: CT
authors: Fu
authors: David
authors: D
authors: Sretavan
mesh_terms: D000818:Animals; D001369:Axons / Q000502:physiology*; D002470:Cell Survival / Q000502:physiology; D004396:Coloring Agents / Q000378:metabolism; D004195:Disease Models, Animal; D036388:Ephrin-B2 / Q000494:pharmacology / Q000502:physiology*; D036389:Ephrin-B3 / Q000494:pharmacology / Q000502:physiology*; D005901:Glaucoma / Q000378:metabolism / Q000503:physiopathology / Q000517:prevention & control*; D007429:Intraocular Pressure; D051379:Mice; D018345:Mice, Knockout; D018613:Microscopy, Confocal; D009410:Nerve Degeneration; D009798:Ocular Hypertension / Q000378:metabolism / Q000503:physiopathology / Q000517:prevention & control; D009901:Optic Nerve Diseases / Q000378:metabolism / Q000503:physiopathology / Q000517:prevention & control; D009924:Organ Culture Techniques; D010655:Phenylenediamines / Q000378:metabolism; D011993:Recombinant Fusion Proteins / Q000494:pharmacology; D012165:Retinal Ganglion Cells / Q000502:physiology*; D015398:Signal Transduction / Q000502:physiology*; D015854:Up-Regulation
chemical_list: D004396:Coloring Agents; D036388:Ephrin-B2; D036389:Ephrin-B3; D010655:Phenylenediamines; D011993:Recombinant Fusion Proteins; C029728:4-phenylenediamine