Abstract
Purpose: :
Genetic factors play significant roles in normal aging and age-dependent diseases in the retina. However, genetic factors involved in these conditions are not fully understood. For the discovery of these genetic factors, it is of great value to characterize the detailed phenotype associated with aging and its variation between mouse strains with different genetic backgrounds. In this study, our aim is to test whether the age-dependent synaptic phenotype is influenced by the genetic background in the mouse retina.
Methods: :
We characterized the morphological changes of the synaptic interaction between photoreceptor cells and postsynaptic neurons (bipolar and horizontal cells) in young (2-3 months), adult (7-8 months), and old (17-20 months) A/J and C57BL/6J mice using synaptic and cell-specific makers. We also measured the thickness of the outer and inner nuclear layers in order to assess age-dependent retinal degeneration.
Results: :
In both A/J and C57BL/6J mice, ectopic localization of the photoreceptor cell presynapse and elongation of neurites from postsynaptic neurons were observed as mice aged. We found that the severity of the ectopic synapse phenotype is greater in A/J mice compared to C57BL/6J mice. We also observed temporal and spatial correlation between the synaptic abnormality and retinal degeneration associated with aging. Both phenotypes were first observed only in the peripheral retina and later in the central retina as well.
Conclusions: :
Our results suggest that age-dependent synaptic abnormality is affected by the genetic background. Additionally, we found that retinal phenotypes associated with aging advance from the peripheral to the central area.
Keywords: aging • retina • synapse