Limits...
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 GH and GH receptor mRNAs in the neuroendocrine axis of WT and En2−/− mice. (A) GH mRNA quantitative RT-PCR. (B) GHR 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 < 0.001; Student’s t-test, En2−/− vs. WT). (C) Representative pictures of GH mRNA in situ hybridization 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.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
getmorefigures.php?uid=PMC4150208&req=5

Figure 2: Expression of GH and GH receptor mRNAs in the neuroendocrine axis of WT and En2−/− mice. (A) GH mRNA quantitative RT-PCR. (B) GHR 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 < 0.001; Student’s t-test, En2−/− vs. WT). (C) Representative pictures of GH mRNA in situ hybridization 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: Before investigating GH, GHR, mGRF, SST, IGF-1, and IGF-1R mRNA expression in the neuroendocrine axis of En2−/− mice, we first verified whether En2 might directly regulate their transcription. Indeed, bioinformatic analysis revealed that En2 binding sites are present in the promoters of all these genes (Table 2). We next studied GH and GHR mRNA expression in the neuroendocrine axis of WT and En2−/− adult mice. We found that GH mRNA expression was markedly deregulated throughout the neuroendocrine axis in En2−/− mice. A statistically significant increase of GH mRNA levels was detected in the pituitary gland (+72%, p < 0.001), liver (+376%, p < 0.001), and blood (+87%, p < 0.05) of En2−/− mice, as compared to WT littermates (Figure 2A). GH mRNA levels were instead significantly lower in the En2−/− hypothalamus (−97%, p < 0.001) and hippocampus (−98%, p < 0.001), as compared to WT (Figure 2A). In situ hybridization confirmed GH mRNA decrease in the En2−/− hippocampus, mainly in the CA3 subfield (Figure 2C). No significant differences in GHR mRNA levels were detected between genotypes in the analyzed tissues, with the exception of blood, where a marked increase was detected in mutant mice compared to controls (+312%, p < 0.05) (Figure 2B).


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 GH and GH receptor mRNAs in the neuroendocrine axis of WT and En2−/− mice. (A) GH mRNA quantitative RT-PCR. (B) GHR 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 < 0.001; Student’s t-test, En2−/− vs. WT). (C) Representative pictures of GH mRNA in situ hybridization 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.
© Copyright Policy - open-access
Related In: Results  -  Collection

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

Figure 2: Expression of GH and GH receptor mRNAs in the neuroendocrine axis of WT and En2−/− mice. (A) GH mRNA quantitative RT-PCR. (B) GHR 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 < 0.001; Student’s t-test, En2−/− vs. WT). (C) Representative pictures of GH mRNA in situ hybridization 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: Before investigating GH, GHR, mGRF, SST, IGF-1, and IGF-1R mRNA expression in the neuroendocrine axis of En2−/− mice, we first verified whether En2 might directly regulate their transcription. Indeed, bioinformatic analysis revealed that En2 binding sites are present in the promoters of all these genes (Table 2). We next studied GH and GHR mRNA expression in the neuroendocrine axis of WT and En2−/− adult mice. We found that GH mRNA expression was markedly deregulated throughout the neuroendocrine axis in En2−/− mice. A statistically significant increase of GH mRNA levels was detected in the pituitary gland (+72%, p < 0.001), liver (+376%, p < 0.001), and blood (+87%, p < 0.05) of En2−/− mice, as compared to WT littermates (Figure 2A). GH mRNA levels were instead significantly lower in the En2−/− hypothalamus (−97%, p < 0.001) and hippocampus (−98%, p < 0.001), as compared to WT (Figure 2A). In situ hybridization confirmed GH mRNA decrease in the En2−/− hippocampus, mainly in the CA3 subfield (Figure 2C). No significant differences in GHR mRNA levels were detected between genotypes in the analyzed tissues, with the exception of blood, where a marked increase was detected in mutant mice compared to controls (+312%, p < 0.05) (Figure 2B).

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