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Expression of glial fibrillary acidic protein by Müller cells in rd chick retina
1Department of Neuroscience, University of Florida College of Medicine, Gainesville 32610-0244.
Abstract:
Accumulation of glial fibrillary acidic protein (GFAP) in Müller cells has been observed in retinas of several mammalian species secondary to genetically induced degeneration and neuronal injury. In the present series of experiments, I have examined the effects of the rd (retinal degeneration) mutation on the expression of GFAP in retinas of chicks homozygous for the mutation (rd/rd) prior to and following the onset of photoreceptor degeneration, which first appears approximately 7 days posthatch (7 dph). Carrier (+/rd) and wild-type (+/+) retinas served as controls. Retinas taken from 1, 7, 21, and 33 dph rd/rd, +/rd, and +/+ chicks were analyzed for the presence of GFAP by immunocytochemical and SDS-PAGE/Western blot techniques. The following immunocytochemical observations were made: (1) GFAP immunostaining was limited to and located throughout the Müller cells. (2) The intensity of GFAP immunostaining increased with age in all three retina types in tissue sections, as well as on immunoblots. (3) The distribution of GFAP staining within rd/rd Müller cells following the onset of degeneration was slightly different from that observed in +/+ and +/rd retinas and was distinguished by increased staining of the cell bodies and the cell processes forming the outer limiting membrane. The results of these experiments show that Müller cells in chick retina contain GFAP. In addition, they suggest that, in contrast to Müller cells in degenerating mammalian retina, Müller cells in rd chick retina do not accumulate large amounts of GFAP in response to degeneration.
Insights
Glial fibrillary acidic protein (GFAP) is present in chick Müller cells. Unlike in mammals, GFAP does not accumulate in chick retinas with the retinal degeneration (rd) mutation.
Area of Science:
- Ophthalmology
- Neuroscience
- Cell Biology
Background:
- Glial fibrillary acidic protein (GFAP) accumulates in Müller cells in mammalian retinas with genetic degeneration or neuronal injury.
- The role of GFAP in avian retinal degeneration is not well understood.
Purpose of the Study:
- To investigate the effect of the retinal degeneration (rd) mutation on GFAP expression in chick retinas.
- To compare GFAP accumulation in chick Müller cells with that observed in mammalian models.
Main Methods:
- Immunocytochemistry and SDS-PAGE/Western blot techniques were used to analyze GFAP presence.
- Retinas from chicks with the rd mutation (rd/rd), carriers (+/rd), and wild-type (+/+) were examined at 1, 7, 21, and 33 days posthatch.
Main Results:
- GFAP was detected throughout Müller cells in all examined chick retinas.
- GFAP immunostaining intensity increased with age in all groups.
- While GFAP distribution differed slightly in rd/rd retinas post-degeneration, significant accumulation was not observed, unlike in mammalian models.
Conclusions:
- Chick Müller cells express GFAP.
- The retinal degeneration (rd) mutation in chicks does not lead to the substantial Müller cell GFAP accumulation seen in degenerating mammalian retinas.