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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 mGRF and SST mRNAs in the neuroendocrine axis of WT and En2−/− mice. (A,B) mRNA expression levels of mGRF (A) and SST (B), obtained by 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; Student’s t-test, En2−/− vs. WT). (C) mGRF in situ hybridization and SST immunohistochemistry. Representative pictures show mGRF mRNA and SST protein staining in the dorsomedial and ventromedial paraventricular nuclei of the hypothalamus. Scale bar: 200 μm. Abbreviations are as in Figure 1.
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Figure 3: Expression of mGRF and SST mRNAs in the neuroendocrine axis of WT and En2−/− mice. (A,B) mRNA expression levels of mGRF (A) and SST (B), obtained by 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; Student’s t-test, En2−/− vs. WT). (C) mGRF in situ hybridization and SST immunohistochemistry. Representative pictures show mGRF mRNA and SST protein staining in the dorsomedial and ventromedial paraventricular nuclei of the hypothalamus. Scale bar: 200 μm. Abbreviations are as in Figure 1.

Mentions: We then investigated the expression of mGRF (also known as growth hormone releasing hormone, GHRH) and SST, the two hypothalamic hormones regulating GH synthesis, in the brain–pituitary–liver axis of WT and En2−/− adult mice. As compared to WT controls, a marked increase of mGRF mRNA (+53%, p < 0.05; Figure 3A) and a significant decrease of SST mRNA (−13%, p < 0.01; Figure 3B) was found in the En2−/− hypothalamus. Significantly higher mRNA levels for the two hormones were also found in blood (mGRF: +125%, p < 0.05) and liver (mGRF: +129%, p < 0.01; SST: +147%, p < 0.001) from En2−/− mice (Figures 3A,B). According to our previous study (27), lower levels of SST mRNA were found in the En2−/− hippocampus, as compared to WT (−10%, p < 0.05; Figure 3B). In situ hybridization and immunohistochemistry experiments, respectively, confirmed the increased expression of mGRF mRNA and decreased levels of SST protein in the dorsomedial/ventromedial paraventricular nuclei of the En2−/− hypothalamus, as compared to WT (Figure 3C).


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 mGRF and SST mRNAs in the neuroendocrine axis of WT and En2−/− mice. (A,B) mRNA expression levels of mGRF (A) and SST (B), obtained by 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; Student’s t-test, En2−/− vs. WT). (C) mGRF in situ hybridization and SST immunohistochemistry. Representative pictures show mGRF mRNA and SST protein staining in the dorsomedial and ventromedial paraventricular nuclei of the hypothalamus. Scale bar: 200 μm. Abbreviations are as in Figure 1.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4150208&req=5

Figure 3: Expression of mGRF and SST mRNAs in the neuroendocrine axis of WT and En2−/− mice. (A,B) mRNA expression levels of mGRF (A) and SST (B), obtained by 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; Student’s t-test, En2−/− vs. WT). (C) mGRF in situ hybridization and SST immunohistochemistry. Representative pictures show mGRF mRNA and SST protein staining in the dorsomedial and ventromedial paraventricular nuclei of the hypothalamus. Scale bar: 200 μm. Abbreviations are as in Figure 1.
Mentions: We then investigated the expression of mGRF (also known as growth hormone releasing hormone, GHRH) and SST, the two hypothalamic hormones regulating GH synthesis, in the brain–pituitary–liver axis of WT and En2−/− adult mice. As compared to WT controls, a marked increase of mGRF mRNA (+53%, p < 0.05; Figure 3A) and a significant decrease of SST mRNA (−13%, p < 0.01; Figure 3B) was found in the En2−/− hypothalamus. Significantly higher mRNA levels for the two hormones were also found in blood (mGRF: +125%, p < 0.05) and liver (mGRF: +129%, p < 0.01; SST: +147%, p < 0.001) from En2−/− mice (Figures 3A,B). According to our previous study (27), lower levels of SST mRNA were found in the En2−/− hippocampus, as compared to WT (−10%, p < 0.05; Figure 3B). In situ hybridization and immunohistochemistry experiments, respectively, confirmed the increased expression of mGRF mRNA and decreased levels of SST protein in the dorsomedial/ventromedial paraventricular nuclei of the En2−/− hypothalamus, as compared to WT (Figure 3C).

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