The fate of ultraviolet receptors in the retina of the atlantic salmon (Salmo salar)

Kunz, Yvette W.; Wildenburg, Gabriele; Goodrich, Lisa V.; Callaghan, Eric

doi:10.1016/0042-6989(94)90136-8

Cited by 57 publications

(46 citation statements)

References 21 publications

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“…Thus, in ovo exposure of rainbow trout embryos to elevated T4 content in the yolk appears to have increased the responsiveness of the retina to exogenous T4 treatment and influenced subsequent UVS cone loss. TH-induced UVS cone loss has been shown to occur via programmed cell death, suggesting that early TH exposure may sensitize photoreceptors to later TH-related cell death signaling events (Kunz et al, 1994;Allison et al, 2006).…”

Section: Discussionmentioning

confidence: 99%

“…Knockout studies demonstrate that TH binding to TR2 is necessary for proper cone subtype specification, and a recent study suggests a role for type 3 deiodinase (D3), an enzyme that inactivates TH, in cone survival and maintenance (Ng et TH signaling also regulates retinal changes during later development, including changes in opsin expression and cone distribution associated with metamorphosis in diverse fish species (Browman and Hawryshyn, 1992;Browman and Hawryshyn, 1994;Allison et al, 2003;Allison et al, 2006;Mader and Cameron, 2006;Cheng et al, 2009). Natural loss of ultraviolet-sensitive (UVS) cones from the retina in the salmon and trout (salmonid) family of fishes occurs during a developmental transition phase called smoltification (Browman and Hawryshyn, 1992;Browman and Hawryshyn, 1994;Kunz et al, 1994;Deutschlander et al, 2001;Allison et al, 2003;Allison et al, 2006). Smoltification is characterized by behavioral, physiological and morphological changes that transform juvenile fish (parr) living in freshwater streams into seaward-migrating smolts that spend much of their life in the ocean (Hoar, 1988).…”

Section: Introductionmentioning

confidence: 99%

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In ovo thyroxine exposure alters later UVS cone loss in juvenile rainbow trout

Raine

Coffin

Hawryshyn

2011

Journal of Experimental Biology

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a thyroid hormone) induces precocious SWS1 downregulation and UVS cone degeneration, whereas TH attenuation via propylthiouracil (PTU) delays SWS1 downregulation and UVS cone loss, suggesting that endogenous T4 initiates these processes naturally during development (Browman and Hawryshyn, 1992;Browman and Hawryshyn, 1994 Accepted 17 March 2011 SUMMARY Thyroid hormones (THs) play a vital role in vertebrate neural development, and, together with the beta isoform of the thyroid hormone receptor (TR), the development and differentiation of cone photoreceptors in the vertebrate retina. Rainbow trout undergo a natural process of cone cell degeneration during development and this change in photoreceptor distribution is regulated by thyroxine (T4; a thyroid hormone). In an effort to further understand the role of T4 in photoreceptor ontogeny and later developmental changes in photoreceptor subtype distribution, the influence of enhanced in ovo T4 content on the onset of opsin expression and cone development was examined. Juvenile trout reared from the initial in ovo-treated embryos were challenged with exogenous T4 at the parr stage of development to determine if altered embryonic exposure to yolk THs would affect later T4-induced short-wavelength-sensitive (SWS1) opsin transcript downregulation and ultraviolet-sensitive (UVS) cone loss. In ovo TH manipulation led to upregulation of both SWS1 and long-wavelength-sensitive (LWS) opsin transcripts in the prehatch rainbow trout retina and to changes in the relative expression of TR. After 7days of exposure to T4, juveniles that were also treated with T4 in ovo had greatly reduced SWS1 expression levels and premature loss of UVS cones relative to T4-treated juveniles raised from untreated eggs. These results suggest that changes in egg TH levels can have significant consequences much later in development, particularly in the retina.

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Section: Discussionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

In ovo thyroxine exposure alters later UVS cone loss in juvenile rainbow trout

Raine

Coffin

Hawryshyn

2011

Journal of Experimental Biology

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“…Documented mechanisms include apoptosis of UV-sensitive cones in existing retina (Kunz et al, 1994), production of new retina at the CGZ that does not contain UV-sensitive cones (Flamarique, 2001), and production of new retina at the CGZ in which UV-sensitive cones are present only transiently (Allison et al, 2003). There is also some evidence that as some salmonids reach reproductive maturity, UV-sensitive vision is reestablished, and UV-sensitive cones reappear in the retina (Beaudet et al, 1997).…”

Section: Smoltification In Salmonids-mentioning

confidence: 99%

Neurogenesis in the Fish Retina

Stenkamp

2007

International Review of Cytology

123

136

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The retinas of teleost fish have long been of interest to developmental neurobiologists for their persistent plasticity during growth, life history changes, and response to injury. Because the vertebrate retina is a highly conserved tissue, the study of persistent plasticity in teleosts has provided insights into mechanisms for postembryonic retinal neurogenesis in mammals. In addition, in the past 10 years there has been an explosion in the use of teleost fish-zebrafish (Danio rerio) in particular-to understand the mechanisms of embryonic retinal neurogenesis in a model vertebrate with genetic resources. This review summarizes the key features of teleost retinal neurogenesis that make it a productive and interesting experimental system, and focuses on the contributions to our knowledge of retinal neurogenesis that uniquely required or significantly benefited from the use of a fish model system.

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“…Smoltification is most dramatic in anadromous species, but rainbow trout (Oncorynchus mykiss), which are a landlocked freshwater species, demonstrate some of these same changes, and, in particular, comparable changes occur in their visual system . During smoltification, both anadromous and land-locked species undergo downregulation of SWS1 opsin expression and depopulation of UVS cones in the retina through apoptosis; this corresponds to a decrease in UV sensitivity (Browman and Hawryshyn, 1992;Browman and Hawryshyn, 1994;Kunz et al, 1994;Deutschlander et al, 2001;Allison et al, 2003;Allison et al, 2006;Hawryshyn et al, 2003;Kunz, 2006;Veldhoen et al, 2006). Natural smoltification is accompanied by the elevation of several hormones, and exogenous treatment with one of these elevated hormones, thyroxine (T4; a thyroid hormone), can induce some of the changes that occur during natural smoltification, such as body silvering and a change in condition factor (Hoar, 1988).…”

Section: Introductionmentioning

confidence: 99%

Changes in thyroid hormone reception precede SWS1 opsin downregulation in trout retina

Raine

Hawryshyn

2009

Journal of Experimental Biology

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SUMMARYRainbow trout undergo natural cone degeneration and thus are interesting models for examining mechanisms of neural degeneration. They have ultraviolet-sensitive (UVS) cones that are lost over most of the retina during development; only a small functional population remains in the dorsal retina. How this spatial distribution of UVS cones is maintained is unclear. Thyroxine (T4) induces UVS cone loss, and local thyroid hormone regulation was hypothesized to control UVS cone distribution. Thyroid hormone receptor alpha (TRα), thyroid hormone receptor beta (TRβ) and Type 2 deiodinase (D2) regulate thyroid hormone exposure to target cells. Regional retinal expression of these genes was investigated during exogenous T4 treatment and natural smoltification of rainbow trout. Each retina from dark-adapted parr, T4-treated parr and natural smolts was divided into four quadrants, and total RNA was isolated. Quantitative real-time RT-PCR analysis demonstrated that all retinal quadrants had increased accumulation of TRβ transcripts 2 days post-T4 treatment, corresponding to initiation of SWS1 opsin downregulation. Smolts exhibited decreased accumulation of TRα and TRβ transcripts in all quadrants, but this effect was most pronounced in the dorso-temporal (DT) retinal quadrant where UVS cones persist. By contrast, in 2 day T4-treated parr, the DT quadrant showed increased expression of TRα and TRβ. Furthermore, D2 transcripts decreased in the DT quadrant of T4-treated parr but increased in the DT quadrant of smolts. These results suggest that T4 upregulates TRβ expression to initiate SWS1 opsin downregulation, while TRα and TRβ downregulation occurs to prevent natural loss of UVS cones from the DT retina.

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The fate of ultraviolet receptors in the retina of the atlantic salmon (Salmo salar)

Cited by 57 publications

References 21 publications

In ovo thyroxine exposure alters later UVS cone loss in juvenile rainbow trout

In ovo thyroxine exposure alters later UVS cone loss in juvenile rainbow trout

Neurogenesis in the Fish Retina

Changes in thyroid hormone reception precede SWS1 opsin downregulation in trout retina

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