Journal
INVESTIGATIVE OPHTHALMOLOGY & VISUAL SCIENCE
Volume 49, Issue 10, Pages 4631-4640Publisher
ASSOC RESEARCH VISION OPHTHALMOLOGY INC
DOI: 10.1167/iovs.07-1224
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Funding
- American Health Assistance Foundation's Macular Degeneration Program
- National Eye Institute [EY012146]
- National Science Foundation [0351250]
- Direct For Biological Sciences
- Division Of Integrative Organismal Sys [0351250] Funding Source: National Science Foundation
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PURPOSE. Sonic hedgehog (Shh) signaling is essential for photoreceptor differentiation and retinal cell survival in embryonic zebrafish. The study was conducted to determine whether adult heterozygous carriers of mutant alleles for the shh gene display retinal abnormalities. METHODS. Retinal cryosections from young, middle-aged, and senescent wild-type and sonic-you(+/-) (syu(+/-)) zebrafish were probed with retinal cell type-specific markers. Contralateral retinal flatmounts from these fish, and from adult albino zebrafish subjected to light-induced photoreceptor damage followed by regeneration, were hybridized with blue cone opsin cRNA for quantitative analysis of the blue cone pattern. Retinal expression of shh mRNA was measured by quantitative RTPCR. RESULTS. Regions of cone loss and abnormal cone morphology were observed in the oldest syu(+/-) zebrafish, although no other retinal cell type was affected. This phenotype was age-related and genotype-specific. Cone distribution in the oldest syu(+/-) zebrafish was predominantly random, as assessed by measuring the short-range pattern, whereas that of wild-type fish and the younger syu(+/-) zebrafish was statistically regular. A measure of long-range pattern revealed atypical cone aggregation in the oldest syu(+/-) zebrafish. The light-treated albino zebrafish displayed random cone patterns immediately after light toxicity, but showed cone aggregation on regeneration. Retinas from the syu(+/-) fish showed reduced expression of shh mRNA compared with those of wild-type siblings. CONCLUSIONS. The syu(+/-) zebrafish presents a model for the study of hereditary age-related cone abnormalities. The syu(+/-) retinas most likely experience progressive cone photoreceptor loss, accompanied by cone regeneration. Shh signaling may be required to maintain cone viability throughout life.
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