Photoreceptor rescue by an abbreviated human RPGR gene in a murine model of X-linked retinitis pigmentosa.
The X-linked RP3 gene codes for the ciliary protein RPGR and accounts for over 10% of inherited retinal degenerations. The critical RPGR-ORF15 splice variant contains a highly repetitive purine-rich linker region that renders it unstable and difficult to adapt for gene therapy. To test the hypothesis that the precise length of the linker region is not critical for function, we evaluated whether adeno-associated virus-mediated replacement gene therapy with a human ORF15 variant containing in-frame shortening of the linker region could reconstitute RPGR function in vivo. We delivered human RPGR-ORF15 replacement genes with deletion of most (314 codons, 'short form') or 1/3 (126 codons, 'long form') of the linker region to Rpgr null mice. Human RPGR-ORF15 expression was detected post treatment with both forms of ORF15 transgenes. However, only the long form correctly localized to the connecting cilia and led to significant functional and morphological rescue of rods and cones. Thus the highly repetitive region of RPGR is functionally important but that moderate shortening of its length, which confers the advantage of added stability, preserves its function. These findings provide a theoretical basis for optimizing replacement gene design in clinical trials for X-linked RP3.
Berman-Gund Laboratory for the Study of Retinal Degenerations, Harvard Medical School, Massachusetts Eye and Ear Infirmary, Boston, MA, USA.
B S
BS
Pawlyk
National Eye Institute, Bethesda, MA, USA.
O V
OV
Bulgakov
National Eye Institute, Bethesda, MA, USA.
X
X
Sun
Berman-Gund Laboratory for the Study of Retinal Degenerations, Harvard Medical School, Massachusetts Eye and Ear Infirmary, Boston, MA, USA.
M
M
Adamian
MRC Human Genetics Unit, University of Edinburgh, Edinburgh, UK.|Department of Life Sciences, Glasgow Caledonian University, Glasgow, UK.
X
http://orcid.org/0000-0003-3760-3019
X
Shu
Department of Genetics, University College London Institute of Ophthalmology, London, UK.
A J
AJ
Smith
Berman-Gund Laboratory for the Study of Retinal Degenerations, Harvard Medical School, Massachusetts Eye and Ear Infirmary, Boston, MA, USA.
E L
EL
Berson
Department of Genetics, University College London Institute of Ophthalmology, London, UK.
R R
RR
Ali
Schepens Eye Research Institute, Harvard Medical School, Massachusetts Eye and Ear Infirmary, Boston, MA, USA.
S
S
Khani
MRC Human Genetics Unit, University of Edinburgh, Edinburgh, UK.
A F
AF
Wright
Berman-Gund Laboratory for the Study of Retinal Degenerations, Harvard Medical School, Massachusetts Eye and Ear Infirmary, Boston, MA, USA.
M A
MA
Sandberg
National Eye Institute, Bethesda, MA, USA.
T
http://orcid.org/0000-0002-9537-2573
T
Li
D017398:Alternative Splicing; D000818:Animals; D000229:Dependovirus / Q000235:genetics*; D004195:Disease Models, Animal; D005136:Eye Proteins / Q000235:genetics*; D051606:G-Protein-Coupled Receptor Kinase 1 / Q000235:genetics; D015316:Genetic Therapy; D006801:Humans; D051379:Mice; D008810:Mice, Inbred C57BL; D011401:Promoter Regions, Genetic; D017949:Retinal Cone Photoreceptor Cells / Q000502:physiology; D017948:Retinal Rod Photoreceptor Cells / Q000502:physiology; D012174:Retinitis Pigmentosa / Q000235:genetics / Q000628:therapy*
D005136:Eye Proteins; C099929:RPGR protein, human; D051606:G-Protein-Coupled Receptor Kinase 1