Receptor Degeneration is a Normal Part of Retinal Development
The degeneration of photoreceptors is regarded as pathological, for the tangible reason that it causes blindness. The causes of such degeneration include genetic defects specific to photoreceptors, many specific to the rhodopsin molecule, and genetic defects in the retinal pigment epithelium (reviewed in ref. 5 and this volume). The death of affected photoreceptors involves DNA fragmentation (2, 7, 8,18) characteristic of apoptosis or programmed cell death (3). This paper presents evidence from the rat and rabbit that DNA fragmentation occurs in committed photoreceptors in normally developing retina; that the affected cells undergo death; that this physiological death of photoreceptors occurs during a discrete period in retinal development, which coincides with the growth of inner and outer segments; and that, in the res strain of rat in which photoreceptors degenerate pathologically, the onset of their degeneration coincides with the onset of physiological degeneration.
KeywordsRetinal Pigment Epithelium Retinitis Pigmentosa Outer Segment Ganglion Cell Layer Outer Nuclear Layer
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