John Flannery
Professor (Vision Science, Molecular & Cell Biology)
Email: flannery@berkeley.edu
Web site: http://mcb.berkeley.edu/labs/flannery
Research areas: Cellular and Molecular Neuroscience, Cellular and Molecular Neuroscience
Molecular & Cell Biology Faculty page
The retina is a complex tissue in the back of the eye that contains the rod and cone photoreceptor cells. The photoreceptors connect to a network of retinal interneurons. The adjacent retinal pigment epithelium (RPE) supports many of the retina's metabolic functions. The retina is susceptible to a number of blinding diseases, such as age-related macular degeneration, diabetic retinopathy and other inherited retinal degenerations. The inherited retinal degenerations are typified by retinitis pigmentosa (RP), which results in blindness from destruction of photoreceptor cells, and the RPE. This group of conditions affects approximately 100,000 people in the United States. To date, more than 130 genes causing inherited retinopathies in humans have been identified. This makes it possible to identify the cause of RP in approximately 50 percent of patients and the cause of Usher syndrome in 75 percent of patients.
Gene identifications in humans have allowed us to examine the biochemical pathways in these diseases. In addition, gene identification in patients permits us to identify naturally occurring animal models or create new transgenic or knockout animal models with retinal degeneration due to defects in the gene homologs. In particular, we have the examined retinal degeneration in the naturally arising rd mouse strains (defects in the β-subunit of phosphodiesterase). We have also developed transgenic rats, expressing dominant rhodopsin mutations. Most recently we have developed a knockout mouse model of Usher syndrome type 3, which caused progressive blindness and deafness in patients. These animal models are the subject of study to determine the pathophysiological mechanisms whereby these gene defects lead to photoreceptor degeneration and hopefully will lead to pilot studies of novel therapies for retinal degeneration.
Development of effective treatments for retinal diseases.
With increasing insight into the molecular etiologies of several inherited retinal and macular dystrophies, studies from ours and many laboratories have defined several promising therapeutic strategies.
Current projects in our lab involve development of retinal cell specific viral vectors based upon lentivirus and adeno-associated viruses. In previous work, we have demonstrated significant slowing of photoreceptor degeneration in several animal models following gene transfer of neurotrophic agents. Another promising strategy for dominantly inherited retinal diseases involves directly targeting the mutant mRNA product using ribozymes, and siRNA. For recessive null diseases, gene replacement is an option.
We find that gene therapy has vast potential for treating and potentially curing a number of inherited photoreceptor diseases. However, gene delivery technologies require significant improvements in cellular targeting, efficiency, and safety before promising findings in animal studies are translated to the clinic. In particular, for retinal gene therapy it would be highly advantageous to transduce a single cell type that spans the entire retina after an intravitreal injection of a gene delivery vehicle for the subsequent secretion of a general neuroprotective factor throughout the retina. Unfortunately, there is no vector capable of efficiently infecting the cell type that meets these needs, Müller cells. Vectors based on adeno-associated virus (AAV) have proven themselves to be highly promising in numerous retinal disease models, but they are also incapable of Müller cell infection. Recently, we have developed novel lentiviral vectors with new properties, including altered receptor binding, which are capable of efficient Müller cell transduction. In parallel, the basic mechanisms of AAV transduction of Müller cells will be explored in order to develop new AAV pseudotypes capable of Müller cell transduction. The novel approaches developed in this work will have general impact for the molecular engineering of enhanced viral gene delivery vehicles, and future work will focus on testing these vectors in an animal model of retinal disease.
Selected Publications
Green, E.S., et al. 2000. Characterization of rhodopsin mis-sorting and constitutive activation in a transgenic rat model of retinitis pigmentosa Investigative Ophthalmology and Visual Science 41(6): 1546-53.
Lewin, A.S., et al. 1998. Ribozyme rescue of photoreceptor cells in a transgenic rat model of autosomal dominant retinitis pigmentosa Nature Medicine 4(8): 967-71.
Flannery, J.G., et al. 1997. Efficient photoreceptor-targeted gene expression in vivo by recombinant adeno-associated virus Proceedings of the National Academy of Sciences of the United States of America V94(N13): 6916-6921.
Lau, D. and Flannery, J. 2003. Viral-mediated FGF-2 treatment of the constant light damage model of photoreceptor degeneration Doc Ophthalmol 106: 89-98.
Adato, A. et al. 2002. USH3A transcripts encode clarin-1, a four-transmembrane-domain protein with a possible role in sensory synapses Eur J Hum Genet 10: 339-50.
McGee Sanftner, L.H. et al. 2001. Recombinant AAV-mediated delivery of a tet-inducible reporter gene to the rat retina Mol Ther 3: 688-96.
McGee Sanftner, L.H., Abel, H., Hauswirth, W.W. and Flannery, J.G. 2001. Glial cell line derived neurotrophic factor delays photoreceptor degeneration in a transgenic rat model of retinitis pigmentosa Mol Ther 4: 622-9.
Green, E.S. et al. 2001. Two animal models of retinal degeneration are rescued by recombinant adeno-associated virus-mediated production of FGF-5 and FGF-18 Mol Ther 3: 507-15.
Ogueta, S.B., Di Polo, A., Flannery, J.G., Yamashita, C.K. and Farber, D.B. 2000. The human cGMP-PDE beta-subunit promoter region directs expression of the gene to mouse photoreceptors Investigative Ophthalmology and Visual Science 41: 4059-63.
LaVail, M.M. et al. 2000. Ribozyme rescue of photoreceptor cells in P23H transgenic rats: long-term survival and late-stage therapy Proc Natl Acad Sci USA 97: 11488-93.
Lau, D. et al. 2000. Retinal degeneration is slowed in transgenic rats by AAV-mediated delivery of FGF-2 Investigative Ophthalmology and Visual Science 41: 3622-33.
Hauswirth, W.W., LaVail, M.M., Flannery, J.G. and Lewin, A.S. 2000. Ribozyme gene therapy for autosomal dominant retinal disease Clin Chem Lab Med 38: 147-53.
Lee, E., Burnside, B. and Flannery, J. (in press). Characterization of Peripherin/rds and Rom-1 Transport in Photoreceptors of Transgenic and Knockout Animals Investigative Ophthalmology and Visual Science.
Flannery, J., Geller, S. and Chen, J. (in press). Structure And Function Of Rod Photoreceptors Retina.
Kenneth P. Greenberg, Scott F. Geller, David V. Schaffer and John G. Flannery (in press). Targeted transgene expression in Müller glia of normal and diseased retinas using lentiviral vectors Investigative Ophthalmology and Visual Science.
