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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

mRNA expression of En2 and genes involved in the GH/IGF-1 pathway in the neuroendocrine axis of WT mice. En2(A), GH (B), GHR (C), mGRF (D), SST (E), IGF-1 (F,G), and IGF-1R (H) mRNA expression levels in the hippocampus, hypothalamus, pituitary gland, liver, and blood, obtained by quantitative RT-PCR. For each mRNA, relative expression levels (normalized to L41) are reported on a log scale. Two different transcripts (class 1 and class 2) were analyzed for IGF-1. Values are plotted as mean ± SEM of three independent experiments. Abbreviations: hi, hippocampus; hy, hypothalamus; pit, pituitary gland; liv, liver; bld, blood (cell fraction). Other abbreviations are as in the text.
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Figure 1: mRNA expression of En2 and genes involved in the GH/IGF-1 pathway in the neuroendocrine axis of WT mice. En2(A), GH (B), GHR (C), mGRF (D), SST (E), IGF-1 (F,G), and IGF-1R (H) mRNA expression levels in the hippocampus, hypothalamus, pituitary gland, liver, and blood, obtained by quantitative RT-PCR. For each mRNA, relative expression levels (normalized to L41) are reported on a log scale. Two different transcripts (class 1 and class 2) were analyzed for IGF-1. Values are plotted as mean ± SEM of three independent experiments. Abbreviations: hi, hippocampus; hy, hypothalamus; pit, pituitary gland; liv, liver; bld, blood (cell fraction). Other abbreviations are as in the text.

Mentions: By using quantitative RT-PCR, we first investigated mRNA expression of En2, GH, GH receptor (GHR), mGRF, SST, IGF-1, and IGF-1 receptor (IGF-1R) in the neuroendocrine axis of WT adult male mice from our colony. mRNA expression was studied in the hypothalamus, pituitary gland, and liver (the crucial tissues involved in GH and IGF-1 synthesis), as well as hippocampus and blood cell fraction. In agreement with previous findings, we confirmed that En2 mRNA is expressed in the hypothalamus and hippocampus (23, 25, 27). En2 mRNA was also expressed at detectable levels in blood, pituitary gland, and liver (Figure 1A). As expected, GH mRNA was mainly detected in the pituitary gland, while much lower levels were present in the hippocampus, hypothalamus, liver, and blood (Figure 1B). Consistent with the notion that liver is the main target of GH action, we found GHR mRNA predominantly expressed in the liver, and at lower levels in the other tissues analyzed (Figure 1C). mRNA expression of mGRF and SST, the two hypothalamic hormones controlling GH synthesis, was mainly detected in the hypothalamus (Figures 1D,E). High levels of SST mRNA were also present in the hippocampus, as previously described (27). Two major different transcripts have been described for IGF-1 [class 1 and class 2; (32, 33)]. Both IGF-1 class 1 and class 2 mRNAs were predominantly expressed in the liver (Figures 1F,G), as expected (32). Finally, IGF-1R mRNA was mainly expressed in the pituitary gland (the target for IGF-1 negative feedback for GH production) (Figure 1H), but also throughout the neuroendocrine axis, consistent with the widespread action of IGF-1 on multiple tissues. These results clearly indicate that our RT-PCR protocol can detect the expression of genes belonging to the GH/IGF-1 pathway in the appropriate tissues throughout the brain–pituitary–liver axis.


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)

mRNA expression of En2 and genes involved in the GH/IGF-1 pathway in the neuroendocrine axis of WT mice. En2(A), GH (B), GHR (C), mGRF (D), SST (E), IGF-1 (F,G), and IGF-1R (H) mRNA expression levels in the hippocampus, hypothalamus, pituitary gland, liver, and blood, obtained by quantitative RT-PCR. For each mRNA, relative expression levels (normalized to L41) are reported on a log scale. Two different transcripts (class 1 and class 2) were analyzed for IGF-1. Values are plotted as mean ± SEM of three independent experiments. Abbreviations: hi, hippocampus; hy, hypothalamus; pit, pituitary gland; liv, liver; bld, blood (cell fraction). Other abbreviations are as in the text.
© Copyright Policy - open-access
Related In: Results  -  Collection

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

Figure 1: mRNA expression of En2 and genes involved in the GH/IGF-1 pathway in the neuroendocrine axis of WT mice. En2(A), GH (B), GHR (C), mGRF (D), SST (E), IGF-1 (F,G), and IGF-1R (H) mRNA expression levels in the hippocampus, hypothalamus, pituitary gland, liver, and blood, obtained by quantitative RT-PCR. For each mRNA, relative expression levels (normalized to L41) are reported on a log scale. Two different transcripts (class 1 and class 2) were analyzed for IGF-1. Values are plotted as mean ± SEM of three independent experiments. Abbreviations: hi, hippocampus; hy, hypothalamus; pit, pituitary gland; liv, liver; bld, blood (cell fraction). Other abbreviations are as in the text.
Mentions: By using quantitative RT-PCR, we first investigated mRNA expression of En2, GH, GH receptor (GHR), mGRF, SST, IGF-1, and IGF-1 receptor (IGF-1R) in the neuroendocrine axis of WT adult male mice from our colony. mRNA expression was studied in the hypothalamus, pituitary gland, and liver (the crucial tissues involved in GH and IGF-1 synthesis), as well as hippocampus and blood cell fraction. In agreement with previous findings, we confirmed that En2 mRNA is expressed in the hypothalamus and hippocampus (23, 25, 27). En2 mRNA was also expressed at detectable levels in blood, pituitary gland, and liver (Figure 1A). As expected, GH mRNA was mainly detected in the pituitary gland, while much lower levels were present in the hippocampus, hypothalamus, liver, and blood (Figure 1B). Consistent with the notion that liver is the main target of GH action, we found GHR mRNA predominantly expressed in the liver, and at lower levels in the other tissues analyzed (Figure 1C). mRNA expression of mGRF and SST, the two hypothalamic hormones controlling GH synthesis, was mainly detected in the hypothalamus (Figures 1D,E). High levels of SST mRNA were also present in the hippocampus, as previously described (27). Two major different transcripts have been described for IGF-1 [class 1 and class 2; (32, 33)]. Both IGF-1 class 1 and class 2 mRNAs were predominantly expressed in the liver (Figures 1F,G), as expected (32). Finally, IGF-1R mRNA was mainly expressed in the pituitary gland (the target for IGF-1 negative feedback for GH production) (Figure 1H), but also throughout the neuroendocrine axis, consistent with the widespread action of IGF-1 on multiple tissues. These results clearly indicate that our RT-PCR protocol can detect the expression of genes belonging to the GH/IGF-1 pathway in the appropriate tissues throughout the brain–pituitary–liver axis.

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