Neurogranin regulates sensorimotor gating through cortico-striatal circuitry.

Glutamate dysregulation is known to contribute to many psychiatric disorders including schizophrenia. Aberrant cortico-striatal activity and therefore glutamate levels might be relevant to this disease characterized by reduced prepulse inhibition (PPI), however, the molecular and behavioral mechanism of the pathophysiology of schizophrenia remains unclear. The focus of this study was to contribute to the current understanding of the glutamate and neurogranin (Ng) pathway, in relation to the cortico-striatal pathology of schizophrenia using a mouse model. A variant of the Ng gene has been detected in people with schizophrenia, implicating maladaptation of cortical glutamate signaling and sensorimotor gating. To test Ng-mediated PPI regulation in the mouse model, we utilized Ng null mice, viral-mediated Ng expression, and genetics approaches. Our results demonstrate that lack of Ng in mice decreases PPI. Ng over-expression in the prefrontal cortex (PFC) increases PPI, while Ng expression in either the nucleus accumbens (NAc) or hippocampus induces no change in PPI. Using optogenetics and chemogenetics, we identified that cortico-striatal activation is involved in PPI regulation. Finally, pharmacological regulation of Ng using glutamate receptor inhibitors demonstrated altered PPI between genotypes. In this study, we have investigated the impact of Ng expression on sensorimotor gating. This study contributes to a better understanding of the glutamatergic theory of schizophrenia, opening novel therapeutic avenues that may lead to glutamatergic treatments to ameliorate the symptoms of schizophrenia.

Effects of myeloid sirtuin 1 deficiency on hypothalamic neurogranin in mice fed a high-fat diet.

Hypothalamic inflammation has been known as a contributor to high-fat diet (HFD)-induced insulin resistance and obesity. Myeloid-specific sirtuin 1 (SIRT1) deletion aggravates insulin resistance and hypothalamic inflammation in HFD-fed mice. Neurogranin, a calmodulin-binding protein, is expressed in the hypothalamus. However, the effects of myeloid SIRT1 deletion on hypothalamic neurogranin has not been fully clarified. To investigate the effect of myeloid SIRT1 deletion on food intake and hypothalamic neurogranin expression, mice were fed a HFD for 20 weeks. Myeloid SIRT1 knockout (KO) mice exhibited higher food intake, weight gain, and lower expression of anorexigenic proopiomelanocortin in the arcuate nucleus than WT mice. In particular, KO mice had lower ventromedial hypothalamus (VMH)-specific neurogranin expression. However, SIRT1 deletion reduced HFD-induced hypothalamic neurogranin. Furthermore, hypothalamic phosphorylated AMPK and parvalbumin protein levels were also lower in HFD-fed KO mice than in HFD-fed WT mice. Thus, these findings suggest that myeloid SIRT1 deletion affects food intake through VMH-specific neurogranin-mediated AMPK signaling and hypothalamic inflammation in mice fed a HFD.

Effects of the neurogranin variant rs12807809 on thalamocortical morphology in schizophrenia.

Although the genome wide supported psychosis susceptibility neurogranin (NRGN) gene is expressed in human brains, it is unclear how it impacts brain morphology in schizophrenia. We investigated the influence of NRGN rs12807809 on cortical thickness, subcortical volumes and shapes in patients with schizophrenia. One hundred and fifty six subjects (91 patients with schizophrenia and 65 healthy controls) underwent structural MRI scans and their blood samples were genotyped. A brain mapping algorithm, large deformation diffeomorphic metric mapping, was used to perform group analysis of subcortical shapes and cortical thickness. Patients with risk TT genotype were associated with widespread cortical thinning involving frontal, parietal and temporal cortices compared with controls with TT genotype. No volumetric difference in subcortical structures (hippocampus, thalamus, amygdala, basal ganglia) was observed between risk TT genotype in patients and controls. However, patients with risk TT genotype were associated with thalamic shape abnormalities involving regions related to pulvinar and medial dorsal nuclei. Our results revealed the influence of the NRGN gene on thalamocortical morphology in schizophrenia involving widespread cortical thinning and thalamic shape abnormalities. These findings help to clarify underlying NRGN mediated pathophysiological mechanisms involving cortical-subcortical brain networks in schizophrenia.

A high-fat diet induces lower expression of retinoid receptors and their target genes GAP-43/neuromodulin and RC3/neurogranin in the rat brain.

Numerous studies have reported an association between cognitive impairment in old age and nutritional factors, including dietary fat. Retinoic acid (RA) plays a central role in the maintenance of cognitive processes via its nuclear receptors (NR), retinoic acid receptor (RAR) and retinoid X receptor (RXR), and the control of target genes, e.g. the synaptic plasticity markers GAP-43/neuromodulin and RC3/neurogranin. Given the relationship between RA and the fatty acid signalling pathways mediated by their respective NR (RAR/RXR and PPAR), we investigated the effect of a high-fat diet (HFD) on (1) PUFA status in the plasma and brain, and (2) the expression of RA and fatty acid NR (RARbeta, RXRbetagamma and PPARdelta), and synaptic plasticity genes (GAP-43 and RC3), in young male Wistar rats. In the striatum of rats given a HFD for 8 weeks, real-time PCR (RT-PCR) revealed a decrease in mRNA levels of RARbeta ( - 14 %) and PPARdelta ( - 13 %) along with an increase in RXRbetagamma (+52 %). Concomitantly, RT-PCR and Western blot analysis revealed (1) a clear reduction in striatal mRNA and protein levels of RC3 ( - 24 and - 26 %, respectively) and GAP-43 ( - 10 and - 42 %, respectively), which was confirmed by in situ hybridisation, and (2) decreased hippocampal RC3 and GAP-43 protein levels (approximately 25 %). Additionally, HFD rats exhibited a significant decrease in plasma ( - 59 %) and brain ( - 6 %) n-3 PUFA content, mainly due to the loss of DHA. These results suggest that dietary fat induces neurobiological alterations by modulating the brain RA signalling pathway and n-3 PUFA content, which have been previously correlated with cognitive impairment.

Peony root extract upregulates transthyretin and phosphoglycerate mutase in mouse cobalt focus seizure.

Cobalt focus is a seizure focus model in which cerebral neurons exhibit long-lasting severe spike discharges, followed by neuronal death. However, the neuronal death is prevented when peony root extract (PR) is administered prior to cobalt application. We tested the hypothesis that PR modulates the expression of neuroprotective proteins in the cerebrum of mouse cobalt focus by proteomic analysis using two-dimensional polyacrylamide gel electrophoresis and mass spectrometry to screen for differentially expressed proteins. Analyses revealed that transthyretin, a carrier protein for thyroid hormones and retinoids, and the brain form of phosphoglycerate mutase, a glycolytic enzyme, were upregulated in the cobalt-treated mouse cerebrum and further increased by PR administration in association with upregulation of neurogranin/RC3, a target of the transcriptional activation by thyroid hormones and retinoids. These findings suggest that PR-induced protection of mouse cerebral neurons involves neurotrophic events caused by thyroid hormones and/or retinoids and enhanced glycolysis.

Neuron-specific phosphorylation of c-Jun N-terminal kinase increased in the brain of hypoxic preconditioned mice.

Accumulated studies have suggested that mitogen-activated protein kinase (MAPK) play a pivotal role in the development of cerebral hypoxic preconditioning (HPC). By using our "auto-hypoxia"-induced HPC mouse model, we have reported increased phosphorylation level of p38 MAPK, and decreased phosphorylation and protein expression levels of extracellular signal regulated kinases 1/2 (ERK1/2) in the brain of HPC mice. In the current study, we investigated the involvement of c-Jun N-terminal kinase (JNK) in the brain of HPC mice. By using Western blot analysis, we found that the phosphorylation levels of JNK at Thr183 and Tyr185 sites (phospho-Thr183/Tyr185 JNK), but not its protein expression, increased significantly (p<0.05, n=6 for each group) both in the hippocampus and frontal cortex of early (H1-H4) and delayed (H5 and H6) HPC mice than that of the normoxic group (H0, n=6). Similarly, enhanced phospho-Thr183/Tyr185 JNK was also observed by immunostaining in the hippocampus and frontal cortex of mice following series of hypoxic exposures (H3 and H6). In addition, we found that phospho-Thr183/Tyr185 JNK predominantly co-localized with a neuron-specific protein, neurogranin, in both the hippocampus and frontal cortex of HPC mice (H3) by using double-labeled immunofluorescence. These results suggest that the increased neuron-specific phosphorylation of JNK at Thr183/Tyr185, not protein expression, might be involved in the development of cerebral HPC of mice.

[Effects of early intervention on learning and memory in young rats of marginal vitamin A deficiency and it's mechanism].

OBJECTIVE: In recent years, some experiments on vitamin A-deprived animals reveal a progressive and ultimately profound impairment of hippocampal CA1 area's long-term potentiation and these losses are fully reversible by dietary vitamin A replenishment in vivo. Our previous study revealed that marginal vitamin A deficiency (MVAD) beginning from embryonic period impairs learning, memory and long-term potentiation (LTP) in young rats. But the losses might not be reversible if the vitamin A supplementation is late, especially when the critical period of hippocampus development is missed. The present study aimed to observe the recovery of learning and memory in vitamin A marginally deficient young rats after early intervention with vitamin A supplementation and begin to study the mechanism. METHODS: Rats were divided into control, MVAD, vitamin A intervention 1 (VAI1) and VAI2 groups in this study. In control group (10 young rats) the dams and pups were fed with normal diet (VA 6500 U/kg). In MVAD group (19 young rats) the dams and pups were fed with MVAD diet (VA 400 U/kg). In VAI1 group (10 young rats) the dams were fed with MVAD diet till day 14 of pregnancy, then were fed with normal diet and the pups were fed with normal diet. In VAI2 group (13 young rats) the dams were fed with MVAD diet till delivery, then were fed with normal diet and the pups were fed with normal diet too. All the young rats were killed at the age of 7 weeks. During the last week of the experiment, the shuttle box active avoidance reaction tests were carried out. At week 7, the hippocampal CA1 LTP was detected by electrophysiological technique. The expression of RAR-alpha, RAR-beta, RXR-beta, RXR-gamma, RC3 and tTG mRNA was detected by using semi-quantified RT-PCR in hippocampus. RESULTS: (1) The times to reach the learning standard in MVAD group (45.6 +/- 12.1) were more than those in control group (17.1 +/- 4.4) (P < 0.01), in both VAI1 group (20.8 +/- 3.1) and VAI2 group (22.1 +/- 4.0) were more than those in group MVAD (P < 0.01), and there were no significant differences among groups VAI1, VAI2 and control (P > 0.05) in active avoidance reaction tests. (2) The changes of field excitatory postsynaptic potentials (fEPSP) slope for MVAD group [(22.9 +/- 9.4)%] and VAI2 group [(39.1 +/- 4.33)%] were less than that of control group [(57.5 +/- 27.3)%], respectively (P < 0.05). No significant difference was found between VAI1 and control group (P > 0.05). (3) The expression of RAR-beta and RXR-beta mRNA decreased by 48.72% and 37.84% respectively (P < 0.05) compared with control, but the expression of RAR-beta mRNA in group VAI1 was higher than that in group MVAD (P = 0.065). The expression of RC3 mRNA in MVAD group was lower than that in control (P = 0.061) and RAR-alpha mRNA in MVAD group was higher than that in control (P = 0.061). The expression of RXR-gamma and tTG mRNA had no significant difference among different groups as determined with semi-quantified RT-PCR in hippocampus. CONCLUSION: Early vitamin A intervention may make the impaired learning and memory behavior due to marginal vitamin A deficiency recover to the normal level in young rats, but lip losses in group VAI2 might not be reversible. Vitamin A may modulate the expression of RC3 mRNA by affecting RAR-alpha, RAR-beta and RXR-beta to influence the LTP, learning and memory.

RC3/neurogranin is expressed in pyramidal neurons of motor and somatosensory cortex in normal and denervated monkeys.

RC3/neurogranin is a neuron-specific calpacitin located in the cytoplasm and, especially, in dendrites and dendritic spines of cortical neurons, involved in many aspects of excitatory transmission and long-term potentiation. We investigated RC3 expression in pyramidal cortical neurons and interneurons of the motor and somatosensory cortex of normal Macaca fascicularis by means of double immunofluorescence and with techniques that combine immunohistochemistry and radioactive in situ hybridization. We show that RC3 is expressed in virtually all pyramidal neurons and spiny stellate neurons of neocortical areas 4, 3b, 1, 2, 5, 7, and SII, but not in the majority of cortical interneurons. RC3 protein and mRNA are tightly colocalized with the alpha subunit of CaM kinase II and the 200-kD, nonphosphorylated neurofilament, whereas they are absent from cells expressing the 27-kD, vitamin D-dependent calbindin and parvalbumin. In order to investigate possible activity-dependent regulation of the expression of RC3, we compared these results with those obtained from monkeys subjected to chronic peripheral cutaneous denervation of the first finger. We found that the pattern of distribution of RC3 in motor and somatosensory cortices after nerve cut did not differ from normal.