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Insulin, insulin-like growth factor-1, insulin receptor, and insulin-like growth factor-1 receptor expression in the chick eye and their regulation with imposed myopic or hyperopic defocus.

Penha AM, Schaeffel F, Feldkaemper M - Mol. Vis. (2011)

Bottom Line: Insulin stimulates eye growth in chicks and this effect is greatly enhanced if the retinal image is degraded by the defocus of either sign.IR mRNA was found in all the studied tissues, although there is evidence of tissue-specific transcript variations.In the retina, no significant gene expression changes were found when defocus was imposed.

View Article: PubMed Central - PubMed

Affiliation: University Eye Hospital, Institute for Ophthalmic Research, Section of Neurobiology of the Eye, Tuebingen, Germany.

ABSTRACT

Purpose: Insulin stimulates eye growth in chicks and this effect is greatly enhanced if the retinal image is degraded by the defocus of either sign. However, it is unclear whether the insulin receptor (IR) is expressed at all in the chicken retina in animals 1-2 weeks post-hatching. We have investigated IR expression and whether IR transcript abundance varies in the fundal layers. To elucidate the possible role of insulin and insulin-like growth factor (IGF)-1 signaling in eye growth regulation, mRNA (mRNA) levels were measured for insulin, IGF-1, IR, and IGF-1 receptor (IGF-1R) during imposed negative or positive defocus.

Methods: Chicks were treated binocularly with positive or negative spectacle lenses for 4 or 24 h, or they remained untreated (n=6, for each treatment group). Northern blot analyses were performed to screen for transcription variants in the different fundal layers of untreated animals. Real-time PCR was used to quantify IR, IGF-1R, IGF-1, and insulin mRNA levels in the different fundal layers of the chick eye in the three treatment groups.

Results: IR mRNA was found in all the studied tissues, although there is evidence of tissue-specific transcript variations. Three major transcripts were detected for IR. The brain, retina, and choroid showed the longest transcript (4.3 kb), which was not present in the liver. Nevertheless, the liver and brain showed a second transcript (2.6 kb) not present in the retina and choroid. A short transcript (1.3 kb) was the predominant form in the liver and choroid, and it seems to be present in the retinal pigment epithelium (RPE) and sclera as well. In the retina, no significant gene expression changes were found when defocus was imposed. Interestingly, in the RPE, both IR and IGF-1R were already downregulated after short periods (4 h) of positive lens wear. In contrast, IR and IGF-1R were upregulated in the choroid and fibrous sclera during treatment with negative, but not positive, lenses.

Conclusions: Differences observed in the IR transcript length in different tissues suggest possibly different functions. The differential regulation of IR and IGF-1R in the RPE, choroid, and fibrous sclera is consistent with their involvement in a signaling cascade for emmetropization.

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Related in: MedlinePlus

Quantification cycle values for all genes in all fundal layers are shown. The mRNA for the insulin receptor and insulin-like growth factor receptors is most abundant in the retina, followed by the RPE, choroid, cartilaginous and fibrous sclera. The sample size is 6 animals per tissues. Error bars represent the standard error of the mean.
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f3: Quantification cycle values for all genes in all fundal layers are shown. The mRNA for the insulin receptor and insulin-like growth factor receptors is most abundant in the retina, followed by the RPE, choroid, cartilaginous and fibrous sclera. The sample size is 6 animals per tissues. Error bars represent the standard error of the mean.

Mentions: The expression levels of IR, IGF-1R, IGF-1, and insulin were measured and compared in all fundal layers of untreated chicks. The results are shown in Figure 3, with a higher quantification cycle threshold corresponding to a lower amount of mRNA. Both receptors and IGF-1 were detected in all tissues, but besides the retina, the amount of IGF-1 mRNA was very low. In addition, insulin mRNA was detected in the retina, but at very low concentrations, and in the choroid with even lower levels than in the retina. Retinal insulin expression was confirmed when an insulin-specific hydrolysis probe was used. The usage of a hydrolysis probe offers a high specificity, because hybridization and fluorescence will only occur if the target DNA sequence exactly matches the hydrolysis probe sequence (for further information, see reference [59]). The results for insulin mRNA quantification are not shown in detail, since the expression level was too low to be precisely quantified.


Insulin, insulin-like growth factor-1, insulin receptor, and insulin-like growth factor-1 receptor expression in the chick eye and their regulation with imposed myopic or hyperopic defocus.

Penha AM, Schaeffel F, Feldkaemper M - Mol. Vis. (2011)

Quantification cycle values for all genes in all fundal layers are shown. The mRNA for the insulin receptor and insulin-like growth factor receptors is most abundant in the retina, followed by the RPE, choroid, cartilaginous and fibrous sclera. The sample size is 6 animals per tissues. Error bars represent the standard error of the mean.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC3108898&req=5

f3: Quantification cycle values for all genes in all fundal layers are shown. The mRNA for the insulin receptor and insulin-like growth factor receptors is most abundant in the retina, followed by the RPE, choroid, cartilaginous and fibrous sclera. The sample size is 6 animals per tissues. Error bars represent the standard error of the mean.
Mentions: The expression levels of IR, IGF-1R, IGF-1, and insulin were measured and compared in all fundal layers of untreated chicks. The results are shown in Figure 3, with a higher quantification cycle threshold corresponding to a lower amount of mRNA. Both receptors and IGF-1 were detected in all tissues, but besides the retina, the amount of IGF-1 mRNA was very low. In addition, insulin mRNA was detected in the retina, but at very low concentrations, and in the choroid with even lower levels than in the retina. Retinal insulin expression was confirmed when an insulin-specific hydrolysis probe was used. The usage of a hydrolysis probe offers a high specificity, because hybridization and fluorescence will only occur if the target DNA sequence exactly matches the hydrolysis probe sequence (for further information, see reference [59]). The results for insulin mRNA quantification are not shown in detail, since the expression level was too low to be precisely quantified.

Bottom Line: Insulin stimulates eye growth in chicks and this effect is greatly enhanced if the retinal image is degraded by the defocus of either sign.IR mRNA was found in all the studied tissues, although there is evidence of tissue-specific transcript variations.In the retina, no significant gene expression changes were found when defocus was imposed.

View Article: PubMed Central - PubMed

Affiliation: University Eye Hospital, Institute for Ophthalmic Research, Section of Neurobiology of the Eye, Tuebingen, Germany.

ABSTRACT

Purpose: Insulin stimulates eye growth in chicks and this effect is greatly enhanced if the retinal image is degraded by the defocus of either sign. However, it is unclear whether the insulin receptor (IR) is expressed at all in the chicken retina in animals 1-2 weeks post-hatching. We have investigated IR expression and whether IR transcript abundance varies in the fundal layers. To elucidate the possible role of insulin and insulin-like growth factor (IGF)-1 signaling in eye growth regulation, mRNA (mRNA) levels were measured for insulin, IGF-1, IR, and IGF-1 receptor (IGF-1R) during imposed negative or positive defocus.

Methods: Chicks were treated binocularly with positive or negative spectacle lenses for 4 or 24 h, or they remained untreated (n=6, for each treatment group). Northern blot analyses were performed to screen for transcription variants in the different fundal layers of untreated animals. Real-time PCR was used to quantify IR, IGF-1R, IGF-1, and insulin mRNA levels in the different fundal layers of the chick eye in the three treatment groups.

Results: IR mRNA was found in all the studied tissues, although there is evidence of tissue-specific transcript variations. Three major transcripts were detected for IR. The brain, retina, and choroid showed the longest transcript (4.3 kb), which was not present in the liver. Nevertheless, the liver and brain showed a second transcript (2.6 kb) not present in the retina and choroid. A short transcript (1.3 kb) was the predominant form in the liver and choroid, and it seems to be present in the retinal pigment epithelium (RPE) and sclera as well. In the retina, no significant gene expression changes were found when defocus was imposed. Interestingly, in the RPE, both IR and IGF-1R were already downregulated after short periods (4 h) of positive lens wear. In contrast, IR and IGF-1R were upregulated in the choroid and fibrous sclera during treatment with negative, but not positive, lenses.

Conclusions: Differences observed in the IR transcript length in different tissues suggest possibly different functions. The differential regulation of IR and IGF-1R in the RPE, choroid, and fibrous sclera is consistent with their involvement in a signaling cascade for emmetropization.

Show MeSH
Related in: MedlinePlus