title: Calcineurin activation causes retinal ganglion cell degeneration.
abstract: OBJECTIVE
  We previously reported that calcineurin, a Ca(2+)/calmodulin-dependent serine/threonine phosphatase, is activated and proposed that it participates in retinal ganglion cell (RGC) apoptosis in two rodent ocular hypertension models. In this study, we tested whether calcineurin activation by itself, even in the absence of ocular hypertension, is sufficient to cause RGC degeneration.
  
  
  METHODS
  We compared RGC and optic nerve morphology after adeno-associated virus serotype 2 (AAV2)-mediated transduction of RGCs with constitutively active calcineurin (CaNCA) or unactivated, wild-type calcineurin (CaNwt). Retinas and optic nerves were harvested 7-16 weeks after injection of the AAV into mouse vitreous. In flatmounted retinas, the transduced RGCs were identified with immunohistochemistry. The morphology of the RGCs was revealed by immunostaining for neurofilament SMI32 or by using GFP-M transgenic mice. A modified Sholl analysis was applied to analyze the RGC dendritic morphology. Optic nerve damage was assessed with optic nerve grading according to the Morrison standard.
  
  
  RESULTS
  CaNwt and CaNCA were highly expressed in the injected eyes. Compared to the CaNwt-expressing RGCs, the CaNCA-expressing RGCs had smaller somas, smaller dendritic field areas, shorter total dendrite lengths, and simpler dendritic branching patterns. At 16 weeks, the CaNCA-expressing eyes had greater optic nerve damage than the CaNwt-expressing eyes.
  
  
  CONCLUSIONS
  Calcineurin activation is sufficient to cause RGC dendritic degeneration and optic nerve damage. These data support the hypothesis that calcineurin activation is an important mediator of RGC degeneration, and are consistent with the hypothesis that calcineurin activation may contribute to RGC neurodegeneration in glaucoma.
authors.affiliation: Massachusetts Eye and Ear Infirmary, Department of Ophthalmology, Harvard Medical School, Boston, MA 02114, USA.
authors.forename: Juan
authors.initials: J
authors.lastname: Qu
authors.forename: Roland
authors.initials: R
authors.lastname: Matsouaka
authors.forename: Rebecca A
authors.initials: RA
authors.lastname: Betensky
authors.forename: Bradley T
authors.initials: BT
authors.lastname: Hyman
authors.forename: Cynthia L
authors.initials: CL
authors.lastname: Grosskreutz
mesh_terms: D000818:Animals; D001369:Axons / Q000201:enzymology* / Q000473:pathology; D019703:Calcineurin / Q000235:genetics* / Q000378:metabolism; D003712:Dendrites / Q000201:enzymology* / Q000473:pathology; D000229:Dependovirus / Q000235:genetics; D004789:Enzyme Activation; D005822:Genetic Vectors; D049452:Green Fluorescent Proteins; D007150:Immunohistochemistry; D058449:Intravitreal Injections; D051379:Mice; D008822:Mice, Transgenic; D009410:Nerve Degeneration / Q000201:enzymology* / Q000473:pathology; D009900:Optic Nerve / Q000201:enzymology* / Q000473:pathology; D012162:Retinal Degeneration / Q000201:enzymology* / Q000473:pathology; D012165:Retinal Ganglion Cells / Q000201:enzymology* / Q000473:pathology; D014161:Transduction, Genetic; D019076:Transgenes
chemical_list: D049452:Green Fluorescent Proteins; D019703:Calcineurin