Related Experiment Videos
Apoptosis: final common pathway of photoreceptor death in rd, rds, and rhodopsin mutant mice
1Department of Ophthalmology, Duke University School of Medicine, Durham, North Carolina 27710.
Abstract:
Mutations in the retinal degeneration, retinal degeneration slow(/peripherin) and rhodopsin genes cause photoreceptor degeneration in humans and mice. Although the phenotypes arising from these mutations are different, suggesting different mechanisms of pathogenesis, we present evidence that apoptosis may be the final common pathway of the disease process linking genotype to phenotype. We observed internucleosomal cleavage of retinal DNA by gel electrophoresis and fragmented DNA at the single cell level by labeling the nicked DNA ends with biotinylated poly(dU). In retinal degeneration mice, DNA fragmentation occurred during the period of photoreceptor degeneration. In retinal degeneration slow mice and in transgenic mice expressing a mutant (Pro347Ser) rhodopsin gene, DNA fragmentation occurred after normal histogenetic cell death (also apoptosis) had ceased. Since DNA fragmentation by internucleosomal cleavage is a cardinal feature of apoptosis, our data suggest that all three of these genetic mutations lead to apoptosis.
Insights
Genetic mutations causing photoreceptor degeneration in retinal degeneration (rd) and retinal degeneration slow (rds) mice, and in rhodopsin gene mutations, ultimately lead to cell death via apoptosis. This study reveals apoptosis as a common pathway linking these genetic defects to disease.
Area of Science:
- Genetics
- Molecular Biology
- Ophthalmology
Background:
- Mutations in retinal degeneration (rd), retinal degeneration slow (rds), and rhodopsin genes cause photoreceptor degeneration.
- These mutations present distinct phenotypes, suggesting varied pathogenic mechanisms.
Purpose of the Study:
- To investigate if apoptosis serves as a common final pathway in photoreceptor degeneration caused by these genetic mutations.
- To link specific genetic mutations (genotype) to the observed disease outcomes (phenotype) through a shared mechanism.
Main Methods:
- DNA fragmentation analysis using gel electrophoresis to detect internucleosomal cleavage.
- Single-cell DNA fragmentation assessment via biotinylated poly(dU) labeling of nicked DNA ends.
Main Results:
- DNA fragmentation, a hallmark of apoptosis, was observed in rd mice during photoreceptor degeneration.
- In rds mice and transgenic mice with mutant rhodopsin (Pro347Ser), DNA fragmentation occurred after normal apoptotic cell death had concluded.
- Internucleosomal DNA cleavage, indicative of apoptosis, was identified across all three mutation models.
Conclusions:
- The findings strongly suggest that apoptosis is the final common pathway for photoreceptor degeneration in rd, rds, and mutant rhodopsin-induced retinal diseases.
- This unifying mechanism helps explain how diverse genetic mutations converge to cause similar disease processes at the cellular level.