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Activation of GH signaling and GH-independent stimulation of growth in zebrafish by introduction of a constitutively activated GHR construct

Activation of GH signaling and GH-independent stimulation of growth in zebrafish by introduction of a constitutively activated GHR construct,10.1007/s

Activation of GH signaling and GH-independent stimulation of growth in zebrafish by introduction of a constitutively activated GHR construct   (Citations: 1)
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Growth hormone (GH) gene transfer can markedly increase growth in transgenic fish. In the present study we have developed a transcriptional assay to evaluate GH-signal activation (GHSA) in zebrafish embryos. By analyzing the transcription of c-fos and igf1, and the promoter activity of spi2.1, in zebrafish embryos injected with different constructs, we found that overexpression of either GH or growth hormone receptor (GHR) resulted in GHSA, while a synergetic overexpression of GH and GHR gave greater activation. Conversely, overexpression of a C-terminal truncated dominant-negative GHR (ΔC-GHR) efficiently blocked GHSA epistatic to GH overexpression, demonstrating the requirement for a full GHR homodimer in signaling. In view of the importance of signal-competent GHR dimerization by extracellular GH, we introduced into zebrafish embryos a constitutively activated GHR (CA-GHR) construct, which protein products constitutively dimerize the GHR productively by Jun-zippers to activate downstream signaling in vitro. Importantly, overexpression of CA-GHR led to markedly higher level of GHSA than the synergetic overexpression of GH and GHR. CA-GHR transgenic zebrafish were then studied in a growth trial. The transgenic zebrafish showed higher growth rate than the control fish, which was not achievable by GH transgenesis in these zebrafish. Our study demonstrates GH-independent growth by CA-GHR in vivo which bypasses normal IGF-1 feedback control of GH secretion. This provides a novel means of producing growth enhanced transgenic animals based on molecular protein design.
Journal: Transgenic Research - TRANSGENIC RES , vol. 20, no. 3, pp. 557-567, 2011
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    • ...In a similar study, Ishtiaq Ahmed et al. (2011) observed accelerated growth in transgenic zebrafish overexpressing GHR that had been constitutively activated due to the introduction of leucine zippers in the molecule’s structure...
    • ...Perhaps, as proposed by Ishtiaq Ahmed et al. (2011), an interesting alternative could be to associate transgenics to a molecular design of constitutively activated proteins in specific tissues...

    Marcio Azevedo Figueiredoet al. Muscle-specific growth hormone receptor (GHR) overexpression induces h...

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