Related Experiment Video
Updated: Aug 25, 2026
A Novel Light Damage Paradigm for Use in Retinal Regeneration Studies in Adult Zebrafish
Published on: October 24, 2013
Light-induced apoptosis in the neonatal mouse retina and superior colliculus
1Department of Ophthalmology, Chiba University School of Medicine, Japan. kozosasa@green.ocn.ne.jp
Unlabelled:
PURPOSE. Apoptosis occurs naturally in the rodent retina and superior colliculus (SC) during the neonatal period. The authors used mice to demonstrate the dependency of this apoptosis on the light stimulation and the developmental period.
Methods:
A number of apoptotic cells were counted in the retina and SC from a group of newborn mice reared in constant darkness (DD group), a group reared in normal light and dark conditions (LD group), and a group reared in constant darkness up to P7 and then transferred to normal condition (DD-to-LD group). Terminal deoxynucleotidyl transferase-mediated biotin-dUTP nick end labeling (TUNEL) was used for visualization of the apoptotic cells.
Results:
In the LD group, apoptotic cells significantly increased in the retinal nuclear layers, including both the outer and inner nuclear layers, the retinal ganglion cell layer, and SC at postnatal day 1 (P1) and postnatal day 2 (P2). The number of apoptotic cells in the ganglion cell layer and SC reached the maximum level at P1. In contrast, in the DD group, an increase in the number of apoptotic cells was not observed. At P9, no significant increase in the number of apoptotic cells was observed in the outer nuclear layer, ganglion cell layer, and SC either in the LD, DD, or DD-to-LD groups, but the LD and DD-to-LD groups showed a significant increase in the inner nuclear layer compared to the DD group.
Conclusions:
Apoptosis during the neonatal period in the mouse visual system is induced by a light stimulus. This apoptosis was not induced after P7 in the retinal ganglion cell layer and SC, even if excessive cells survived.
Insights
Light exposure triggers natural apoptosis in the neonatal mouse visual system, specifically the retina and superior colliculus (SC). This light-dependent cell death is crucial during early development but ceases after postnatal day 7.
Area of Science:
- Neuroscience
- Developmental Biology
- Cell Biology
Background:
- Apoptosis, or programmed cell death, is a natural process during neonatal development in rodents.
- The retina and superior colliculus (SC) are key components of the visual system that undergo developmental changes.
Purpose of the Study:
- To investigate the role of light stimulation in neonatal apoptosis within the mouse retina and superior colliculus (SC).
- To determine the developmental window during which light-induced apoptosis occurs in these visual structures.
Main Methods:
- Mice were reared under different light conditions: constant darkness (DD), normal light-dark cycles (LD), and a switch from DD to LD (DD-to-LD).
- Apoptotic cells in the retina and SC were quantified using Terminal deoxynucleotidyl transferase-mediated biotin-dUTP nick end labeling (TUNEL) assay.
- Cell counts were analyzed at specific postnatal days (P1, P2, P9).
Main Results:
- Light exposure (LD) significantly increased apoptotic cells in the retina (nuclear layers, ganglion cell layer) and SC at P1 and P2.
- Constant darkness (DD) prevented this light-induced increase in apoptosis.
- By P9, light-induced apoptosis was no longer observed in the retinal ganglion cell layer and SC, although the inner nuclear layer still showed increased apoptosis in LD and DD-to-LD groups compared to DD.
Conclusions:
- Neonatal apoptosis in the mouse visual system is primarily induced by light stimulation.
- The critical period for light-induced apoptosis in the retinal ganglion cell layer and SC is before postnatal day 7.
- Light-dependent developmental processes, including cell death, are time-sensitive during early life.
