Light induced apoptosis is accelerated in transgenic retina overexpressing human EAT/mcl-1, an anti-apoptotic bcl-2 related gene.
OBJECTIVE
EAT/mcl-1 (EAT), an immediate early gene, functions in a similar way to bcl-2 in neutralising Bax mediated cytotoxicity, suggesting that EAT is a blocker of cell death. The aim of this study was to determine the effect of overexpression of the human EAT gene on light induced retinal cell apoptosis.


METHODS
EAT transgenic mice incorporating the EF-1alpha promoter were utilised, and expression of human EAT was detected by RT-PCR. Light damage was induced by raising mice under constant illumination. Two groups of animals, EAT transgenic mice (n=14) and littermates (n=13), were examined by ERG testing and histopathology at regular time points up to 20 weeks of constant light stimulation. Electrophysiological and histopathological findings were evaluated by established systems of arbitrary scoring as scores 0-2 and scores 0-3, respectively.


RESULTS
The mean score (SD) of ERG response was significantly lower in EAT transgenic mice (0.79 (0.89)) than in littermates (1.69 (0.48)) (p<0.01). Although the differences between the two survival curves did not reach statistical significance (p=0.1156), the estimated incidence of electrophysiological retinal damage was higher in EAT mice (0.0495/mouse/week; 95% confidence interval (CI) 0.0347-0.0500) than in littermates (0. 0199/mouse/week; 95% CI 0.0035-0.0364). The mean scores (SD) for histopathological retinal degeneration were 2.31 (0.63) in littermates and 1.43 (1.22) in EAT transgenic mice (p=0.065). However, Kaplan-Meier curves for histopathological failure in two groups of mice showed that retinal photoreceptor cells were preserved significantly against constant light in the littermate compared with transgenic mice (p=0.0241). The estimated incidence of histopathological retinal damage was 0.0042/mouse/week in the littermates (95% CI 0-0.0120) and 0.0419/mouse/week in the EAT mice (95% CI 0.0286-0.0500).


CONCLUSIONS
Retinal photoreceptor cell apoptosis under constant light stimulation is likely to be accelerated in transgenic retina overexpressing EAT.
Shinoda
K
K
Department of Ophthalmology, Keio University School of Medicine, 35 Shinanomachi, Shinjuku-ku, Tokyo 160-8582, Japan.
Nakamura
Y
Y
Matsushita
K
K
Shimoda
K
K
Okita
H
H
Fukuma
M
M
Yamada
T
T
Ohde
H
H
Oguchi
Y
Y
Hata
J
J
Umezawa
A
A
D000818:Animals; D017209:Apoptosis / Q000502:physiology*; D015139:Blotting, Southern; D029742:Caenorhabditis elegans Proteins; D016001:Confidence Intervals; D004596:Electroretinography / Q000379:methods; D005260:Female; D006801:Humans; D008027:Light / Q000009:adverse effects*; D008297:Male; D008565:Membrane Proteins / Q000502:physiology*; D051379:Mice; D008809:Mice, Inbred C3H; D008810:Mice, Inbred C57BL; D008822:Mice, Transgenic; D064549:Myeloid Cell Leukemia Sequence 1 Protein; D009363:Neoplasm Proteins / Q000502:physiology*; D020419:Photoreceptor Cells, Vertebrate / Q000473:pathology* / Q000528:radiation effects; D019253:Proto-Oncogene Proteins c-bcl-2; D020133:Reverse Transcriptase Polymerase Chain Reaction; D016019:Survival Analysis; D015533:Transcriptional Activation / Q000502:physiology*
D029742:Caenorhabditis elegans Proteins; C579094:Mcl1 protein, mouse; D008565:Membrane Proteins; D064549:Myeloid Cell Leukemia Sequence 1 Protein; D009363:Neoplasm Proteins; D019253:Proto-Oncogene Proteins c-bcl-2; C404993:eat-20 protein, C elegans