title: Comparison between axonal and retinal ganglion cell gene expression in various optic nerve injuries including glaucoma.
abstract: OBJECTIVE
  The pathogenesis of retinal ganglion cell loss in glaucoma remains incompletely understood. Current evidence suggests that the optic nerve (ON) head and axons are the main site of injury in glaucoma. This study compares changes in prosurvival and proapoptotic gene expression in ONs with those in retinas in three models of ocular injury, specifically ON transection (ONTX), N-methyl-D-aspartate (NMDA) retinal toxicity, and experimental glaucoma.
  
  
  METHODS
  Rats (n=240) were divided into three models (ONTX, NMDA retinal toxicity, and experimental glaucoma). The experimental model was induced unilaterally and the contralateral eye served as control. Rats were sacrificed at 4-5 different time points specific for each model. ONs and retinas were isolated for real-time PCR investigation of expression of selected genes. Immunohistochemistry localized changes in inhibitor of apoptosis (IAP)-1 and X-linked IAP (XIAP) proteins in retinas and ONs. Colocalization was measured using Imaris colocalization software (three-dimensional analysis).
  
  
  RESULTS
  The earliest changes in gene expression occurred in ONs in the ONTX model and in retinas in the NMDA model, as expected. However, some gene changes occurred first in ONs, while others occurred first in retinas in the glaucoma model. The expression patterns of the prosurvival genes IAP-1 and XIAP differed between retinas and ONs of glaucomatous eyes: Both were upregulated in the retinas, but XIAP was downregulated in the ONs, while IAP-1 stayed unchanged. Colocalization of IAP-1, XIAP, glial fibrillary acidic protein, and Thymus cell antigen-1 (Thy-1) suggested that IAP-1 was colocalized mostly with Thy-1 and XIAP with glial fibrillary acidic protein in the ONs. Members of the B-cell lymphoma 2 (BCL-2) family were similarly involved in the ONs and retinas of glaucomatous, transected, and NMDA-injected eyes. The expression of the prosurvival genes, Bcl-2 and Bcl-xl, decreased significantly in both the ONs and retinas of injured eyes. The proapoptotic genes, BCL2-associated X protein (BAX) and Bcl-2-associated death promoter (BAD), were significantly upregulated in both injured retinas and ONs.
  
  
  CONCLUSIONS
  The overexpression of XIAP and IAP-1 genes in the retinas was not associated with similar changes in the ONs of glaucomatous eyes. The lack of activation of these prosurvival genes in the ONs may explain the increased vulnerability of ONs to elevated intraocular pressure.
authors.affiliation: Sam Rothberg Ophthalmic Molecular Biology Laboratory, Goldschleger Eye Institute, Sheba Medical Center, Tel-Hashomer, Sackler Faculty of Medicine, Tel-Aviv University, Israel.
authors.forename: Hani
authors.initials: H
authors.lastname: Levkovitch-Verbin
authors.affiliation: Sam Rothberg Ophthalmic Molecular Biology Laboratory, Goldschleger Eye Institute, Sheba Medical Center, Tel-Hashomer, Sackler Faculty of Medicine, Tel-Aviv University, Israel.
authors.forename: Daria
authors.initials: D
authors.lastname: Makarovsky
authors.affiliation: Sam Rothberg Ophthalmic Molecular Biology Laboratory, Goldschleger Eye Institute, Sheba Medical Center, Tel-Hashomer, Sackler Faculty of Medicine, Tel-Aviv University, Israel.
authors.forename: Shelly
authors.initials: S
authors.lastname: Vander
mesh_terms: D000818:Animals; D001369:Axons / Q000378:metabolism* / Q000473:pathology; D004195:Disease Models, Animal; D005786:Gene Expression Regulation; D005901:Glaucoma / Q000235:genetics* / Q000378:metabolism / Q000473:pathology; D005904:Glial Fibrillary Acidic Protein / Q000235:genetics / Q000378:metabolism; D007150:Immunohistochemistry; D051034:Inhibitor of Apoptosis Proteins / Q000235:genetics* / Q000378:metabolism; D009900:Optic Nerve / Q000378:metabolism* / Q000473:pathology; D020221:Optic Nerve Injuries / Q000235:genetics* / Q000378:metabolism / Q000473:pathology; D019253:Proto-Oncogene Proteins c-bcl-2 / Q000235:genetics / Q000378:metabolism; D051381:Rats; D017208:Rats, Wistar; D060888:Real-Time Polymerase Chain Reaction; D012165:Retinal Ganglion Cells / Q000378:metabolism* / Q000473:pathology; D015398:Signal Transduction; D018800:Thy-1 Antigens / Q000235:genetics / Q000378:metabolism; D013997:Time Factors; D044767:Ubiquitin-Protein Ligases; D051636:X-Linked Inhibitor of Apoptosis Protein / Q000235:genetics* / Q000378:metabolism
chemical_list: D005904:Glial Fibrillary Acidic Protein; D051034:Inhibitor of Apoptosis Proteins; D019253:Proto-Oncogene Proteins c-bcl-2; D018800:Thy-1 Antigens; D051636:X-Linked Inhibitor of Apoptosis Protein; C494834:Birc2 protein, mouse; D044767:Ubiquitin-Protein Ligases