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HW Greenlee, DS Sakaguchi, MC Wilson; High Levels of SNAP-25 Are Required for Normal photoreceptor Differentiation and Development . Invest. Ophthalmol. Vis. Sci. 2002;43(13):2687.
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© ARVO (1962-2015); The Authors (2016-present)
Purpose: During development of the retina, high levels of SNAP-25 are expressed in the outer retina in the region of developing photoreceptors (PR). The high level of SNAP-25 in these cells, relative to what is observed in most other retinal neurons, is maintained throughout development and is observed in PR of the adult retina, not only in synaptic regions and cell bodies, but also in the region of the inner segments. Methods: To test the hypothesis that high levels of SNAP-25 are important for PR development we have used mice with a null mutation (Snap25 -/-), or an exon replacement mutation (Snap25 3a/3a) which disrupts expression of SNAP-25 by causing termination of transcription 55 amino acids into the coding region. Animals that are homozygous null (-/-) express no SNAP-25, while animals heterozygous for the mutations (-/+) express approximately 50% of SNAP-25 when compared to wild-type (wt) animals. There are no overt abnormalities in brain development or structure and the neuromuscular junctions form in the diaphragm, although the null mutation is lethal at birth, likely due to respiratory failure. We examined PR development in these animals using immuno-staining for the proteins recoverin and rhodopsin. Results: At early stages, PR number is significantly different in -/- and -/+ when compared to wt. In juveniles and adults subtle differences in rhodopsin localization and inner segment length are observable. Conclusion: hese results suggest that PR differentiation is sensitive to the level of SNAP-25 expression during retinal development. Further, our observations suggest that high levels of SNAP-25 expression may be important for normal photoreceptor morphology in mature animals.
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