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Updated: Aug 26, 2026
Quantification of Immunostained Caspase-9 in Retinal Tissue
Published on: July 25, 2022
Caspase-3 in postnatal retinal development and degeneration
Caroline J Zeiss1, Jason Neal, Elizabeth A Johnson
1Section of Comparative Medicine, Yale School of Medicine, New Haven, Connecticut 06520, USA. caroline.zeiss@yale.edu
Purpose:
The primary purpose of this study was to evaluate the impact of caspase-3 ablation on photoreceptor degeneration in the rd-1 mouse. Concurrently, the role of caspase-3 in postnatal retinal development was evaluated. Caspase-3 is an important effector caspase that mediates many of the terminal proteolytic events of apoptosis. Its activation has been demonstrated in rodent models of photoreceptor degeneration and its ablation results in exencephaly and neonatal death.
Methods:
Retinal morphometry was performed at the light microscopic level in caspase-3 mutant mice from PN0 through PN23, and in rd-1/caspase-3 double mutant mice at PN14, -16, and -18. This was supplemented by terminal dUTP transferase nick end labeling (TUNEL) and immunohistochemical staining for activated caspase-3, rhodopsin, factor VII-related antigen and proliferating cell nuclear antigen (PCNA).
Results:
Caspase-3-deficient animals display marginal microphthalmia, peripapillary retinal dysplasia, delayed regression of vitreal vasculature, and retarded apoptotic kinetics of the inner nuclear layer. Ablation of caspase-3 provided transient photoreceptor protection in rd-1, but TUNEL-positive rod death proceeded, despite the absence of caspase-3 activation.
Conclusions:
In vivo, caspase-3 is not critical for rod photoreceptor development, nor does it play a significant role in mediating pathologic rod death. Peripapillary dysplastic lesions suggest that there is delayed fusion of the optic fissure, and inner nuclear layer abnormalities indicate a cell-specific dependency on the mitochondria-caspase axis during development. The temporal nature of apoptotic retardation in the absence of caspase-3 implies the presence of caspase-independent mechanisms of developmental and pathologic cell death.
Insights
Caspase-3 ablation offers limited protection against photoreceptor degeneration in rd-1 mice and is not essential for normal retinal development or pathologic cell death, suggesting caspase-independent pathways are involved.
Area of Science:
- Ophthalmology
- Cell Biology
- Developmental Biology
Background:
- Caspase-3 is a key enzyme in apoptosis, with its activation observed in photoreceptor degeneration models.
- Previous studies suggest caspase-3's role in apoptosis, but its specific function in retinal development and degeneration remains unclear.
Purpose of the Study:
- To investigate the impact of caspase-3 deficiency on photoreceptor degeneration in the rd-1 mouse model.
- To assess the role of caspase-3 in normal postnatal retinal development.
Main Methods:
- Retinal morphometry was conducted on caspase-3 mutant and rd-1/caspase-3 double mutant mice.
- Terminal deoxynucleotidyl transferase dUTP nick end labeling (TUNEL) and immunohistochemistry were employed.
Main Results:
- Caspase-3 deficient mice exhibited microphthalmia, retinal dysplasia, and delayed vascular regression.
- Ablation of caspase-3 provided only transient photoreceptor protection in rd-1 mice, with ongoing rod cell death observed.
Conclusions:
- Caspase-3 is not critical for rod photoreceptor development or mediating pathologic rod death in vivo.
- Abnormalities suggest a cell-specific reliance on the mitochondria-caspase pathway and highlight caspase-independent mechanisms in cell death.
