Absence of functional and structural abnormalities associated with expression of EGFP in the retina.
OBJECTIVE
The present study was undertaken to evaluate the effect of uniform EGFP expression on retinal morphology and function.


METHODS
Electroretinography (ERG) was used to evaluate the recovery of scotopic a- and b-wave amplitudes after a single 137-cd.sec/m2 flash exposure. The cellular distribution of enhanced green fluorescent protein (EGFP) in the retina and its effect on retinal morphology were evaluated by fluorescence microscopy and histology, respectively. To evaluate its effect on retinal sensitivity to light, EGFP-expressing and control mice were exposed to constant light for 76 hours (3500 lux), and eyes were assessed functionally and structurally at 3 weeks after light exposure.


RESULTS
Fluorescence microscopy showed a pronounced EGFP expression in the photoreceptor cell bodies and inner segments. ERG analysis revealed no significant differences in either a- or b-wave amplitudes or recovery between EGFP(+/-) and control mice under dark- or light-adapted conditions. Histologic assessment at as late as 4 months of age showed no difference in retinal morphology or photoreceptor nuclei count in EGFP(+/-) mice when compared with nontransgenic littermates. In addition, evaluation of animals, 3 weeks after constant light exposure, showed no difference between ERG amplitudes, recovery of the scotopic ERG response, or retinal morphology between EGFP(+/-) mice and control animals.


CONCLUSIONS
Functional and morphologic evidence shows that long-term, high, uniform levels of EGFP expression have no deleterious effect on the mouse retina. This data demonstrates the safety of EGFP use as an indicator of viral transduction in retinal gene therapy.
Nour
May
M
Oklahoma Center for Neuroscience, Oklahoma City, Oklahoma, USA.
Quiambao
Alexander B
AB
Al-Ubaidi
Muayyad R
MR
Naash
Muna I
MI
D000818:Animals; D003623:Dark Adaptation; D004596:Electroretinography; D005786:Gene Expression Regulation / Q000502:physiology*; D049452:Green Fluorescent Proteins; D007202:Indicators and Reagents / Q000378:metabolism; D008164:Luminescent Proteins / Q000235:genetics* / Q000378:metabolism; D051379:Mice; D008810:Mice, Inbred C57BL; D008817:Mice, Mutant Strains; D008822:Mice, Transgenic; D008856:Microscopy, Fluorescence; D010775:Photic Stimulation; D020419:Photoreceptor Cells, Vertebrate / Q000166:cytology / Q000502:physiology; D012160:Retina / Q000166:cytology* / Q000502:physiology*; D012449:Safety; D014785:Vision, Ocular / Q000502:physiology
D007202:Indicators and Reagents; D008164:Luminescent Proteins; D049452:Green Fluorescent Proteins