Limits...
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.

Show MeSH

Related in: MedlinePlus

Quantification cycle values for two different regions of the insulin receptor sequence in different tissues are shown. All tissues expressed the insulin receptor tyrosine kinase domain mRNA as well as the insulin receptor L2-rich binding domain mRNA. The sample size is 4 animals per tissues. Error bars represent the standard error of the mean.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
getmorefigures.php?uid=PMC3108898&req=5

f2: Quantification cycle values for two different regions of the insulin receptor sequence in different tissues are shown. All tissues expressed the insulin receptor tyrosine kinase domain mRNA as well as the insulin receptor L2-rich binding domain mRNA. The sample size is 4 animals per tissues. Error bars represent the standard error of the mean.

Mentions: Three pairs of primers were designed to amplify different parts of the IR sequence. The first primer pair, called insulin receptor ligand-binding domain (IR-LD), amplified a part of the sequence corresponding to the L2 domain in the receptor protein. The leucine-rich L2 domain is involved in the ligand binding and is encoded by exon numbers 4 and 5. The second primer pair, IR-tyrosine kinase (TK), was designed to amplify a fragment that after translation belongs to the tyrosine-kinase domain, which is a catalytic domain with phosphotransferase activity, and comprises exons 16 and 17. The mentioned exons are localized on the longest transcript sequence for the IR mRNA based on the Ensembl database. Based on the results (Figure 2), all tissues expressed mRNA for the tyrosine-kinase domain and the L2 (binding domain), although in different amounts. For both the IR-TK and IR-LD, the retina and brain showed the highest amounts, followed by the choroid, RPE, liver, and cartilaginous and fibrous sclera. The third primer pair also amplified a part of the tyrosine-kinase domain and comprised exons 17 and 18. Concerning the IR-TK2 region, no specific PCR product was obtained in most tissues; only the retina and liver showed a very low expression (data not shown).


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 two different regions of the insulin receptor sequence in different tissues are shown. All tissues expressed the insulin receptor tyrosine kinase domain mRNA as well as the insulin receptor L2-rich binding domain mRNA. The sample size is 4 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

f2: Quantification cycle values for two different regions of the insulin receptor sequence in different tissues are shown. All tissues expressed the insulin receptor tyrosine kinase domain mRNA as well as the insulin receptor L2-rich binding domain mRNA. The sample size is 4 animals per tissues. Error bars represent the standard error of the mean.
Mentions: Three pairs of primers were designed to amplify different parts of the IR sequence. The first primer pair, called insulin receptor ligand-binding domain (IR-LD), amplified a part of the sequence corresponding to the L2 domain in the receptor protein. The leucine-rich L2 domain is involved in the ligand binding and is encoded by exon numbers 4 and 5. The second primer pair, IR-tyrosine kinase (TK), was designed to amplify a fragment that after translation belongs to the tyrosine-kinase domain, which is a catalytic domain with phosphotransferase activity, and comprises exons 16 and 17. The mentioned exons are localized on the longest transcript sequence for the IR mRNA based on the Ensembl database. Based on the results (Figure 2), all tissues expressed mRNA for the tyrosine-kinase domain and the L2 (binding domain), although in different amounts. For both the IR-TK and IR-LD, the retina and brain showed the highest amounts, followed by the choroid, RPE, liver, and cartilaginous and fibrous sclera. The third primer pair also amplified a part of the tyrosine-kinase domain and comprised exons 17 and 18. Concerning the IR-TK2 region, no specific PCR product was obtained in most tissues; only the retina and liver showed a very low expression (data not shown).

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