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GH Dysfunction in Engrailed-2 Knockout Mice, a Model for Autism Spectrum Disorders.

Provenzano G, Clementi E, Genovesi S, Scali M, Tripathi PP, Sgadò P, Bozzi Y - Front Pediatr (2014)

Bottom Line: IGF-1 levels were found increased in the blood and decreased in the cerebrospinal fluid of ASD children.IGF-1 mRNA was significantly up-regulated in the liver and down-regulated in the En2 (-/-) hippocampus, but no differences were detected in the levels of IGF-1 protein between the two genotypes.Our data strengthen the notion that altered GH levels in the hippocampus may be involved in learning disabilities associated to ASD.

View Article: PubMed Central - PubMed

Affiliation: Laboratory of Molecular Neuropathology, Centre for Integrative Biology (CIBIO), University of Trento , Trento , Italy.

ABSTRACT
Insulin-like growth factor 1 (IGF-1) signaling promotes brain development and plasticity. Altered IGF-1 expression has been associated to autism spectrum disorders (ASD). IGF-1 levels were found increased in the blood and decreased in the cerebrospinal fluid of ASD children. Accordingly, IGF-1 treatment can rescue behavioral deficits in mouse models of ASD, and IGF-1 trials have been proposed for ASD children. IGF-1 is mainly synthesized in the liver, and its synthesis is dependent on growth hormone (GH) produced in the pituitary gland. GH also modulates cognitive functions, and altered levels of GH have been detected in ASD patients. Here, we analyzed the expression of GH, IGF-1, their receptors, and regulatory hormones in the neuroendocrine system of adult male mice lacking the homeobox transcription factor Engrailed-2 (En2 (-/-) mice). En2 (-/-) mice display ASD-like behaviors (social interactions, defective spatial learning, increased seizure susceptibility) accompanied by relevant neuropathological changes (loss of cerebellar and forebrain inhibitory neurons). Recent studies showed that En2 modulates IGF-1 activity during postnatal cerebellar development. We found that GH mRNA expression was markedly deregulated throughout the neuroendocrine axis in En2 (-/-) mice, as compared to wild-type controls. In mutant mice, GH mRNA levels were significantly increased in the pituitary gland, blood, and liver, whereas decreased levels were detected in the hippocampus. These changes were paralleled by decreased levels of GH protein in the hippocampus but not other tissues of En2 (-/-) mice. IGF-1 mRNA was significantly up-regulated in the liver and down-regulated in the En2 (-/-) hippocampus, but no differences were detected in the levels of IGF-1 protein between the two genotypes. Our data strengthen the notion that altered GH levels in the hippocampus may be involved in learning disabilities associated to ASD.

No MeSH data available.


Related in: MedlinePlus

Expression of IGF-1 and IGF-1R mRNAs in the neuroendocrine axis of WT and En2−/− mice. (A,B) Quantitative RT-PCR for IGF-1 class 1 (A) and class 2 (B) transcripts. (C) IGF-1R quantitative RT-PCR. Values are plotted as each gene/L41 comparative quantitation ratios normalized on the expression of WT (mean ± SEM of three replicates from pools of six animals per genotype; *p < 0.05, **p < 0.01; ***p < 0.001; Student’s t-test, En2−/− vs. WT). (D) Representative pictures of in situ hybridization for IGF-1 mRNA (both transcripts) on the dorsal hippocampus from WT and En2−/− mice. Insets show the CA3 subfield. Scale bar: 200 μm (whole hippocampi) and 125 μm (insets). Abbreviations are as in Figure 1.
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Figure 4: Expression of IGF-1 and IGF-1R mRNAs in the neuroendocrine axis of WT and En2−/− mice. (A,B) Quantitative RT-PCR for IGF-1 class 1 (A) and class 2 (B) transcripts. (C) IGF-1R quantitative RT-PCR. Values are plotted as each gene/L41 comparative quantitation ratios normalized on the expression of WT (mean ± SEM of three replicates from pools of six animals per genotype; *p < 0.05, **p < 0.01; ***p < 0.001; Student’s t-test, En2−/− vs. WT). (D) Representative pictures of in situ hybridization for IGF-1 mRNA (both transcripts) on the dorsal hippocampus from WT and En2−/− mice. Insets show the CA3 subfield. Scale bar: 200 μm (whole hippocampi) and 125 μm (insets). Abbreviations are as in Figure 1.

Mentions: We next analyzed mRNA expression of IGF-1 and its receptor in the brain–pituitary–liver axis of WT and En2−/− adult mice. IGF-1 mRNA exists in two major forms (class 1 and class 2), class 2 mRNA transcription being directly regulated by GH (33, 34). We found that levels of IGF-1 class 1 mRNA were significantly reduced in the hippocampus but not other tissues of En2−/− mice, as compared to WT (−18%, p < 0.05 for all comparisons) (Figure 4A). In keeping with GH mRNA expression data (Figure 2), IGF-1 class 2 mRNA was significantly up-regulated in the liver (+43%, p < 0.001) and down-regulated in the hypothalamus (−19%, p < 0.001) of En2−/− mice, as compared to WT littermates; increased levels of IGF-1 class 2 mRNA were also detected in En2−/− pituitary gland (+16%, p < 0.01) and blood (+312%, p < 0.001) (Figure 4B). In situ hybridization with a riboprobe specific for both class 1 and class 2 IGF-1 mRNAs confirmed that IGF-1 mRNA levels are decreased in the En2−/− hippocampus (Figure 4D). Finally, IGF-1R mRNA levels did not differ between genotypes in hypothalamus, hippocampus, and pituitary gland, while a significant increase was found in blood (+84%, p < 0.01) and liver (+52%, p < 0.05) from En2−/− mice compared to WT controls (Figure 4C). Table 3 summarizes mRNA expression data for all the analyzed genes in the brain–pituitary–liver axis of WT and En2−/− adult mice.


GH Dysfunction in Engrailed-2 Knockout Mice, a Model for Autism Spectrum Disorders.

Provenzano G, Clementi E, Genovesi S, Scali M, Tripathi PP, Sgadò P, Bozzi Y - Front Pediatr (2014)

Expression of IGF-1 and IGF-1R mRNAs in the neuroendocrine axis of WT and En2−/− mice. (A,B) Quantitative RT-PCR for IGF-1 class 1 (A) and class 2 (B) transcripts. (C) IGF-1R quantitative RT-PCR. Values are plotted as each gene/L41 comparative quantitation ratios normalized on the expression of WT (mean ± SEM of three replicates from pools of six animals per genotype; *p < 0.05, **p < 0.01; ***p < 0.001; Student’s t-test, En2−/− vs. WT). (D) Representative pictures of in situ hybridization for IGF-1 mRNA (both transcripts) on the dorsal hippocampus from WT and En2−/− mice. Insets show the CA3 subfield. Scale bar: 200 μm (whole hippocampi) and 125 μm (insets). Abbreviations are as in Figure 1.
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Related In: Results  -  Collection

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Show All Figures
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Figure 4: Expression of IGF-1 and IGF-1R mRNAs in the neuroendocrine axis of WT and En2−/− mice. (A,B) Quantitative RT-PCR for IGF-1 class 1 (A) and class 2 (B) transcripts. (C) IGF-1R quantitative RT-PCR. Values are plotted as each gene/L41 comparative quantitation ratios normalized on the expression of WT (mean ± SEM of three replicates from pools of six animals per genotype; *p < 0.05, **p < 0.01; ***p < 0.001; Student’s t-test, En2−/− vs. WT). (D) Representative pictures of in situ hybridization for IGF-1 mRNA (both transcripts) on the dorsal hippocampus from WT and En2−/− mice. Insets show the CA3 subfield. Scale bar: 200 μm (whole hippocampi) and 125 μm (insets). Abbreviations are as in Figure 1.
Mentions: We next analyzed mRNA expression of IGF-1 and its receptor in the brain–pituitary–liver axis of WT and En2−/− adult mice. IGF-1 mRNA exists in two major forms (class 1 and class 2), class 2 mRNA transcription being directly regulated by GH (33, 34). We found that levels of IGF-1 class 1 mRNA were significantly reduced in the hippocampus but not other tissues of En2−/− mice, as compared to WT (−18%, p < 0.05 for all comparisons) (Figure 4A). In keeping with GH mRNA expression data (Figure 2), IGF-1 class 2 mRNA was significantly up-regulated in the liver (+43%, p < 0.001) and down-regulated in the hypothalamus (−19%, p < 0.001) of En2−/− mice, as compared to WT littermates; increased levels of IGF-1 class 2 mRNA were also detected in En2−/− pituitary gland (+16%, p < 0.01) and blood (+312%, p < 0.001) (Figure 4B). In situ hybridization with a riboprobe specific for both class 1 and class 2 IGF-1 mRNAs confirmed that IGF-1 mRNA levels are decreased in the En2−/− hippocampus (Figure 4D). Finally, IGF-1R mRNA levels did not differ between genotypes in hypothalamus, hippocampus, and pituitary gland, while a significant increase was found in blood (+84%, p < 0.01) and liver (+52%, p < 0.05) from En2−/− mice compared to WT controls (Figure 4C). Table 3 summarizes mRNA expression data for all the analyzed genes in the brain–pituitary–liver axis of WT and En2−/− adult mice.

Bottom Line: IGF-1 levels were found increased in the blood and decreased in the cerebrospinal fluid of ASD children.IGF-1 mRNA was significantly up-regulated in the liver and down-regulated in the En2 (-/-) hippocampus, but no differences were detected in the levels of IGF-1 protein between the two genotypes.Our data strengthen the notion that altered GH levels in the hippocampus may be involved in learning disabilities associated to ASD.

View Article: PubMed Central - PubMed

Affiliation: Laboratory of Molecular Neuropathology, Centre for Integrative Biology (CIBIO), University of Trento , Trento , Italy.

ABSTRACT
Insulin-like growth factor 1 (IGF-1) signaling promotes brain development and plasticity. Altered IGF-1 expression has been associated to autism spectrum disorders (ASD). IGF-1 levels were found increased in the blood and decreased in the cerebrospinal fluid of ASD children. Accordingly, IGF-1 treatment can rescue behavioral deficits in mouse models of ASD, and IGF-1 trials have been proposed for ASD children. IGF-1 is mainly synthesized in the liver, and its synthesis is dependent on growth hormone (GH) produced in the pituitary gland. GH also modulates cognitive functions, and altered levels of GH have been detected in ASD patients. Here, we analyzed the expression of GH, IGF-1, their receptors, and regulatory hormones in the neuroendocrine system of adult male mice lacking the homeobox transcription factor Engrailed-2 (En2 (-/-) mice). En2 (-/-) mice display ASD-like behaviors (social interactions, defective spatial learning, increased seizure susceptibility) accompanied by relevant neuropathological changes (loss of cerebellar and forebrain inhibitory neurons). Recent studies showed that En2 modulates IGF-1 activity during postnatal cerebellar development. We found that GH mRNA expression was markedly deregulated throughout the neuroendocrine axis in En2 (-/-) mice, as compared to wild-type controls. In mutant mice, GH mRNA levels were significantly increased in the pituitary gland, blood, and liver, whereas decreased levels were detected in the hippocampus. These changes were paralleled by decreased levels of GH protein in the hippocampus but not other tissues of En2 (-/-) mice. IGF-1 mRNA was significantly up-regulated in the liver and down-regulated in the En2 (-/-) hippocampus, but no differences were detected in the levels of IGF-1 protein between the two genotypes. Our data strengthen the notion that altered GH levels in the hippocampus may be involved in learning disabilities associated to ASD.

No MeSH data available.


Related in: MedlinePlus