Epitope-tagged recombinant AAV vectors for expressing neurturin and its receptor in retinal cells.
OBJECTIVE
Neurturin (NTN) is a potent neuronal survival factor in the central and peripheral nervous systems. We previously described altered expression of mRNAs for NTN and one of its receptor components, GFRa-2 in degenerative retinas of rd/rd mice. Towards assessing the potential for transfer of these genes to counteract retinal degeneration, we examined recombinant adeno-associated virus (rAAV) constructs for expression of NTN and GFRa-2 transgenes in retinal cells in vitro and for the effect of transgene expression on retinal function following intraocular delivery in rd/rd mice.


METHODS
The rAAV constructs incorporated epitope tags to facilitate discrimination between transgenic and endogenous expression. Expression of murine NTN was driven by a CMV promoter and a partial murine opsin promoter was used to drive expression of human GFRa-2. rAAV preparations were used to infect mouse retinal cell cultures and for intraocular injection of predegenerative rd/rd mice. Endogenous and transgene expression was analyzed by immunofluorescence. Photoreceptor function in treated mice was assessed by electroretinography.


RESULTS
Both vectors delivered and expressed their transgenes in vitro and in vivo. Differential targeting was achieved in vivo through the use of alternative promoters. Under the conditions examined, no functional rescue of rd photoreceptors was observed.


CONCLUSIONS
Therapeutic treatment of the rd model of retinal degeneration does not appear to be effected by simple modulation of the expression of NTN or GFRa-2, and may therefore depend on additional synergistic factors. Our AAV constructs will facilitate the development of combinatorial approaches to the treatment of central and peripheral neurodegenerations.
Retinitis Pigmentosa Research Unit, The Rayne Institute, Division of Pharmacology and Therapeutics, Guy's, King's and St Thomas' School of Biomedical Sciences, King's College London, St Thomas' Hospital, London, UK. cjomary@hgmp.mrc.ac.uk
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C
Jomary
J
J
Grist
J
J
Milbrandt
M J
MJ
Neal
S E
SE
Jones
D000818:Animals; D002478:Cells, Cultured; D000229:Dependovirus / Q000235:genetics*; D029721:Drosophila Proteins; D004596:Electroretinography; D000939:Epitopes; D019084:Fluorescent Antibody Technique, Indirect; D015870:Gene Expression; D005822:Genetic Vectors; D051379:Mice; D008817:Mice, Mutant Strains; D009414:Nerve Growth Factors / Q000235:genetics* / Q000378:metabolism; D051101:Neurturin; D011518:Proto-Oncogene Proteins / Q000235:genetics* / Q000378:metabolism; D051096:Proto-Oncogene Proteins c-ret; D012333:RNA, Messenger / Q000096:biosynthesis; D020794:Receptor Protein-Tyrosine Kinases / Q000235:genetics* / Q000378:metabolism; D012160:Retina / Q000378:metabolism* / Q000503:physiopathology / Q000821:virology; D012162:Retinal Degeneration / Q000378:metabolism* / Q000503:physiopathology / Q000821:virology; D016324:Sequence Tagged Sites; D014162:Transfection; D019076:Transgenes
D029721:Drosophila Proteins; D000939:Epitopes; D009414:Nerve Growth Factors; D051101:Neurturin; C495056:Nrtn protein, mouse; D011518:Proto-Oncogene Proteins; D012333:RNA, Messenger; D051096:Proto-Oncogene Proteins c-ret; D020794:Receptor Protein-Tyrosine Kinases; C416649:Ret protein, Drosophila