[Abnormalities in signal transduction of Purkinje cells in spinocerebellar ataxias: a review].

Spinocerebellar ataxias (SCAs) are a group of autosomal dominant neurodegenerative diseases that have been currently identified with numerous subtypes exhibiting genetic heterogeneity and clinical variability. Purkinje neuronal degeneration and cerebellar atrophy are common pathological features among most SCA subtypes. The physiological functions of Purkinje cells are regulated by multiple factors, and their dysfunction in signal transduction may lead to abnormal cerebellar motor control. This review summarizes the abnormalities in voltage-gated ionic channels, intracellular calcium signaling, and glutamate signaling transduction of Purkinje cells in SCAs, aiming to provide a theoretical basis for further understanding the common pathogenesis of SCAs and developing specific treatments.

Tyrosine kinase receptor ErbB4 in Advillin-positive neurons contributes to inflammatory pain hypersensitivity in mouse DRG.

Inflammatory pain is a common type of pathological pain. Although the dorsal root ganglion (DRG) is key to pathogenesis of inflammatory pain, the underlying specific molecular and cellular mechanisms remain unclear. In this study, we used mouse models of acute or chronic inflammatory pain, induced by formalin or complete Freund' s adjuvant (CFA), respectively, to explore whether tyrosine kinase receptor ErbB4 participates in the pathogenesis of inflammatory pain. Firstly, we found that both the expression of Neuregulin 1 (Nrg1) and phosphorylation of ErbB4 receptor were upregulated in DRG after inflammatory pain, implying the activation of ErbB4 in DRG. Using ErbB4-mutant mice, we found reduced pain sensitivity of mice when ErbB4 gene expression was largely ablated; furthermore, ErbB4 deletion decreased the inflammatory pain hypersensitivity of either formalin- or CFA-induced mouse models. Moreover, the pain sensitivity was reduced in mice with specific deletion of ErbB4 on advillin-positive neurons within DRG. Importantly, pain hypersensitivity also decreased in Advillin-Cre;ErbB4-/- cKO mice after formalin- or CFA-induced inflammatory pain. Finally, gene quantification differential expression analysis, using RNAseq technology in combination with GO and KEGG enrichment analysis, suggested that calcium signaling pathway possibly mediated the roles of ErbB4 on DRG sensory neurons in inflammatory pain models. Together, these results indicate that ErbB4 on advillin-positive sensory neurons enhances inflammatory pain sensitivity, providing new clues towards the pathogenic mechanisms of inflammatory pain.

Enzymatic reaction modulated DNA assembly on graphitic carbon nitride nanosheets for sensitive fluorescence detection of acetylcholinesterase activity and inhibition.

A novel fluorescent strategy has been developed by using an enzymatic reaction modulated DNA assembly on graphitic carbon nitride nanosheets (CNNS) for the detection of acetylcholinesterase (AChE) activity and its inhibitors. The two-dimensional and ultrathin-layer CNNS-material was successfully synthesized through a chemical oxidation and ultrasound exfoliation method. Because of its excellent adsorption selectivity to ssDNA over dsDNA and superior quenching ability toward the fluorophore labels, CNNS were employed to construct a sensitive fluorescence sensing platform for the detection of AChE activity and inhibition. The detection was based on enzymatic reaction modulated DNA assembly on CNNS, which involved the specific AChE-catalyzed reaction-mediated DNA/Hg2+ conformational change and subsequent signal transduction and amplification via hybridization chain reaction (HCR). Under the excitation at 485 nm, the fluorescence signal from 500 to 650 nm (λmax = 518 nm) of the developed sensing system was gradually increased with increasing concentration of AChE. The quantitative determination range of AChE is from 0.02 to 1 mU/mL and the detection limit was 0.006 mU/mL. The developed strategy was successfully applied to the assay of AChE in human serum samples, and can also be used to effectively screen AChE inhibitors, showing great promise providing a robust and effective platform for AChE-related diagnosis, drug screening, and therapy.

Which Factors Influence Healthy Aging? A Lesson from the Longevity Village of Bama in China.

A growing aging population is associated with increasing incidences of aging-related diseases and socioeconomic burdens. Hence, research into healthy longevity and aging is urgently needed. Longevity is an important phenomenon in healthy aging. The present review summarizes the characteristics of longevity in the elderly population in Bama, China, where the proportion of centenarians is 5.7-fold greater than the international standard. We examined the impact of genetic and environmental factors on longevity from multiple perspectives. We proposed that the phenomenon of longevity in this region is of high value for future investigations in healthy aging and aging-related disease and may provide guidance for fostering the establishment and maintenance of a healthy aging society.

Involvement of nitrergic neurons in colonic motility in a rat model of ulcerative colitis.

BACKGROUND: The mechanisms underlying gastrointestinal (GI) dysmotility with ulcerative colitis (UC) have not been fully elucidated. The enteric nervous system (ENS) plays an essential role in the GI motility. As a vital neurotransmitter in the ENS, the gas neurotransmitter nitric oxide (NO) may impact the colonic motility. In this study, dextran sulfate sodium (DSS)-induced UC rat model was used for investigating the effects of NO by examining the effects of rate-limiting enzyme nitric oxide synthase (NOS) changes on the colonic motility as well as the role of the ENS in the colonic motility during UC. AIM: To reveal the relationship between the effects of NOS expression changes in NOS-containing nitrergic neurons and the colonic motility in a rat UC model. METHODS: Male rats (n = 8/each group) were randomly divided into a control (CG), a UC group (EG1), a UC + thrombin derived polypeptide 508 trifluoroacetic acid (TP508TFA; an NOS agonist) group (EG2), and a UC + NG-monomethyl-L-arginine monoacetate (L-NMMA; an NOS inhibitor) group (EG3). UC was induced by administering 5.5% DSS in drinking water without any other treatment (EG1), while the EG2 and EG3 were gavaged with TP508 TFA and L-NMMA, respectively. The disease activity index (DAI) and histological assessment were recorded for each group, whereas the changes in the proportion of colonic nitrergic neurons were counted using immunofluorescence histochemical staining, Western blot, and enzyme linked immunosorbent assay, respectively. In addition, the contractile tension changes in the circular and longitudinal muscles of the rat colon were investigated in vitro using an organ bath system. RESULTS: The proportion of NOS-positive neurons within the colonic myenteric plexus (MP), the relative expression of NOS, and the NOS concentration in serum and colonic tissues were significantly elevated in EG1, EG2, and EG3 compared with CG rats. In UC rats, stimulation with agonists and inhibitors led to variable degrees of increase or decrease for each indicator in the EG2 and EG3. When the rats in EGs developed UC, the mean contraction tension of the colonic smooth muscle detected in vitro was higher in the EG1, EG2, and EG3 than in the CG group. Compared with the EG1, the contraction amplitude and mean contraction tension of the circular and longitudinal muscles of the colon in the EG2 and EG3 were enhanced and attenuated, respectively. Thus, during UC, regulation of the expression of NOS within the MP improved the intestinal motility, thereby favoring the recovery of intestinal functions. CONCLUSION: In UC rats, an increased number of nitrergic neurons in the colonic MP leads to the attenuation of colonic motor function. To intervene NOS activity might modulate the function of nitrergic neurons in the colonic MP and prevent colonic motor dysfunction. These results might provide clues for a novel approach to alleviate diarrhea symptoms of UC patients.

MacroH2A1.2 deficiency leads to neural stem cell differentiation defects and autism-like behaviors.

The development of the nervous system requires precise regulation. Any disturbance in the regulation process can lead to neurological developmental diseases, such as autism and schizophrenia. Histone variants are important components of epigenetic regulation. The function and mechanisms of the macroH2A (mH2A) histone variant during brain development are unknown. Here, we show that deletion of the mH2A isoform mH2A1.2 interferes with neural stem cell differentiation in mice. Deletion of mH2A1.2 affects neurodevelopment, enhances neural progenitor cell (NPC) proliferation, and reduces NPC differentiation in the developing mouse brain. mH2A1.2-deficient mice exhibit autism-like behaviors, such as deficits in social behavior and exploratory abilities. We identify NKX2.2 as an important downstream effector gene and show that NKX2.2 expression is reduced after mH2A1.2 deletion and that overexpression of NKX2.2 rescues neuronal abnormalities caused by mH2A1.2 loss. Our study reveals that mH2A1.2 reduces the proliferation of neural progenitors and enhances neuronal differentiation during embryonic neurogenesis and that these effects are at least in part mediated by NKX2.2. These findings provide a basis for studying the relationship between mH2A1.2 and neurological disorders.

Intracerebral Transplantation of Neural Stem Cells Restores Manganese-Induced Cognitive Deficits in Mice.

Manganese (Mn) is a potent neurotoxin known to cause long-lasting structural damage and progressive cognitive deficits in the brain. However, new therapeutic approaches are urgently needed since current treatments only target symptoms of Mn exposure. Recent studies have suggested a potential role for multipotent neural stem cells (NSCs) in the etiology of Mn-induced cognitive deficits. In this study, we evaluated the effect of direct intracerebral transplantation of NSCs on cognitive function of mice chronically exposed to MnCl2, and further explored the distribution of transplanted NSCs in brain tissues. NSCs were isolated and bilaterally injected into the hippocampal regions or lateral ventricles of Mn-exposed mice. The results showed that many transplanted cells migrated far away from the injection sites and survived in vivo in the Mn-exposed mouse brain, implying enhanced neurogenesis in the host brain. We found that NSCs transplanted into either the hippocampal regions or the lateral ventricles significantly improved spatial learning and memory function of the Mn-exposed mice in the Morris water maze. Immunofluorescence analyses indicated that some surviving NSCs differentiated into neurons or glial cells, which may have become functionally integrated into the impaired local circuits, providing a possible cellular basis for the improvement of cognitive function in NSC-transplanted mice. Taken together, our findings confirm the Mn-induced impairment of neurogenesis in the brain and underscore the potential of treating Mn exposure by NSC transplantation, providing a practical therapeutic strategy against this type of neurotoxicity.

[The role of Bmal1 in neuronal radial migration and axonal projection of the embryonic mouse cerebral cortex].

Normal development of the cerebral cortex is a basis for the formation and function of mammalian brains. During this process, the radial migration of cortical neurons, as well as the axon projection into specific layers, are the most important steps regulated by some transcription factors, but the underlying molecular mechanisms are still obscure. BMAL1 (brain and muscle Arnt-like protein 1) is a newly identified transcription factor that plays important roles in the circadian rhythms. It was recently found to regulate the proliferation of hippocampal neuronal progenitor/precursor cells (NPCs), implicating Bmal1 in the brain development. Here we employed both RT-RCR and real-time PCR to explore the expression pattern of the Bmal1 gene in the developing brain. We found BMAl1 is enriched in the brain cortex during the perinatal stages and peaked in P3 mouse brains. Combined with in utero electroporation and interference with RNAi, we found that reducing the expression level of Bmal1 in neurons, the radial migration of embryonic cortical neurons was largely delayed, in a gene dose-effect pattern. Moreover, reducing the level of Bmal1 expression in mouse brains, the axonal projection in the corpus callosum was also disrupted from ipsilateral to the lateral cerebral hemisphere. These findings indicate that BMAL1 is essential for the radial migration of neurons in the cerebral cortex and the axonal projection of the corpus callosum, providing insights into the molecular mechanisms of cerebral cortex development.

Autism-associated CHD8 deficiency impairs axon development and migration of cortical neurons.

Background: Mutations in CHD8, chromodomain helicase DNA-binding protein 8, are among the most replicated and common findings in genetic studies of autism spectrum disorder (ASD). The CHD8 protein is believed to act as a transcriptional regulator by remodeling chromatin structure and recruiting histone H1 to target genes. The mechanism by which deficiency of CHD8 causes ASD has not been fully elucidated. Methods: We examined the expression of CHD8 in human and mouse brains using both immunohistochemistry and RNA in situ hybridization. We performed in utero electroporation, neuronal culture, and biochemical analysis using RNAi to examine the functional consequences of CHD8 deficiency. Results: We discovered that CHD8 is expressed highly in neurons and at low levels in glia cells in both humans and mice. Specifically, CHD8 is localized predominately in the nucleus of both MAP2 and parvalbumin-positive neurons. In the developing mouse brain, expression of Chd8 peaks from E16 to E18 and then decreases significantly at P14 to adulthood. Knockdown of Chd8 results in reduced axon and dendritic growth, disruption of axon projections to the contralateral cortex, and delayed neuronal migration at E18.5 which recovers by P3 and P7. Conclusion: Our findings indicate an important role for CHD8 in dendritic and axon development and neuronal migration and thus offer novel insights to further dissect the underlying molecular and circuit mechanisms of ASD caused by CHD8 deficiency.

PRRT2 deficiency induces paroxysmal kinesigenic dyskinesia by regulating synaptic transmission in cerebellum.

Mutations in the proline-rich transmembrane protein 2 (PRRT2) are associated with paroxysmal kinesigenic dyskinesia (PKD) and several other paroxysmal neurological diseases, but the PRRT2 function and pathogenic mechanisms remain largely obscure. Here we show that PRRT2 is a presynaptic protein that interacts with components of the SNARE complex and downregulates its formation. Loss-of-function mutant mice showed PKD-like phenotypes triggered by generalized seizures, hyperthermia, or optogenetic stimulation of the cerebellum. Mutant mice with specific PRRT2 deletion in cerebellar granule cells (GCs) recapitulate the behavioral phenotypes seen in Prrt2-null mice. Furthermore, recording made in cerebellar slices showed that optogenetic stimulation of GCs results in transient elevation followed by suppression of Purkinje cell firing. The anticonvulsant drug carbamazepine used in PKD treatment also relieved PKD-like behaviors in mutant mice. Together, our findings identify PRRT2 as a novel regulator of the SNARE complex and provide a circuit mechanism underlying the PRRT2-related behaviors.

Identify mutation in amyotrophic lateral sclerosis cases using HaloPlex target enrichment system.

To date, at least 18 causative genes have been identified in amyotrophic lateral sclerosis (ALS). Because of the clinical and genetic heterogeneity, molecular diagnosis for ALS faces great challenges. HaloPlex target enrichment system is a new targeted sequencing approach, which can detect already known mutations or candidate genes. We performed this approach to screen 18 causative genes of ALS, including SOD1, SETX, FUS, ANG, TARDBP, ALS2, FIG4, VAPB, OPTN, DAO, VCP, UBQLN2, SPG11, SIGMAR1, DCTN1, SQSTM1, PFN1, and CHMP2B in 8 ALS probands. Using this approach, we got an average of 9.5 synonymous or missense mutations per sample. After validation by Sanger sequencing, we identified 3 documented SOD1 mutations (p.F21C, p.G148D, and p.C147R) and 1 novel DCTN1 p.G59R mutation in 4 probands. The novel DCTN1 mutation appeared to segregate with the disease in the pedigree and was absent in 200 control subjects. The high throughput and efficiency of this approach indicated that it could be applied to diagnose ALS and other inherited diseases with multiple causative genes in clinical practice.

X-linked microtubule-associated protein, Mid1, regulates axon development.

Opitz syndrome (OS) is a genetic neurological disorder. The gene responsible for the X-linked form of OS, Midline-1 (MID1), encodes an E3 ubiquitin ligase that regulates the degradation of the catalytic subunit of protein phosphatase 2A (PP2Ac). However, how Mid1 functions during neural development is largely unknown. In this study, we provide data from in vitro and in vivo experiments suggesting that silencing Mid1 in developing neurons promotes axon growth and branch formation, resulting in a disruption of callosal axon projections in the contralateral cortex. In addition, a similar phenotype of axonal development was observed in the Mid1 knockout mouse. This defect was largely due to the accumulation of PP2Ac in Mid1-depleted cells as further down-regulation of PP2Ac rescued the axonal phenotype. Together, these data demonstrate that Mid1-dependent PP2Ac turnover is important for normal axonal development and that dysregulation of this process may contribute to the underlying cause of OS.

The Angelman syndrome protein Ube3a is required for polarized dendrite morphogenesis in pyramidal neurons.

Pyramidal neurons have a highly polarized dendritic morphology, characterized by one long apical dendrite and multiple short basal dendrites. They function as the primary excitatory cells of the mammalian prefrontal cortex and the corticospinal tract. However, the molecular mechanisms underlying the development of polarized dendrite morphology in pyramidal neurons remain poorly understood. Here, we report that the Angelman syndrome (AS) protein ubiquitin-protein ligase E3A (Ube3a) plays an important role in specifying the polarization of pyramidal neuron dendritic arbors in mice. shRNA-mediated downregulation of Ube3a selectively inhibited apical dendrite outgrowth and resulted in impaired dendrite polarity, which could be rescued by coexpressing mouse Ube3a isoform 2, but not isoform 1 or 3. Ube3a knockdown also disrupted the polarized distribution of the Golgi apparatus, a well established cellular mechanism for asymmetric dendritic growth in pyramidal neurons. Furthermore, downregulation of Ube3a completely blocked Reelin-induced rapid deployment of Golgi into dendrite. Consistently, we also observed selective inhibition of apical dendrite outgrowth in pyramidal neurons in a mouse model of AS. Overall, these results show that Ube3a is required for the specification of the apical dendrites and dendrite polarization in pyramidal neurons, and suggest a novel pathological mechanism for AS.

Serum inducible kinase is a positive regulator of cortical dendrite development and is required for BDNF-promoted dendritic arborization.

Serum inducible kinase (SNK), also known as polo-like kinase 2 (PLK2), is a known regulator of mitosis, synaptogenesis and synaptic homeostasis. However, its role in early cortical development is unknown. Herein, we show that snk is expressed in the cortical plate from embryonic day 14, but not in the ventricular/subventricular zones (VZ/SVZ), and SNK protein localizes to the soma and dendrites of cultured immature cortical neurons. Loss of SNK impaired dendritic but not axonal arborization in a dose-dependent manner and overexpression had opposite effects, both in vitro and in vivo. Overexpression of SNK also caused abnormal branching of the leading process of migrating cortical neurons in electroporated cortices. The kinase activity was necessary for these effects. Extracellular signal-regulated kinase (ERK) pathway activity downstream of brain-derived neurotrophic factor (BDNF) stimulation led to increases in SNK protein expression via transcriptional regulation, and this upregulation was necessary for the growth-promoting effect of BDNF on dendritic arborization. Taken together, our results indicate that SNK is essential for dendrite morphogenesis in cortical neurons.

Neuregulin 1 represses limbic epileptogenesis through ErbB4 in parvalbumin-expressing interneurons.

Epilepsy is a common and refractory neurological disorder, but the neuronal regulatory mechanisms of epileptogenesis remain largely unclear. Activity-dependent transcription of genes for neurotrophins such as brain-derived neurotrophic factor (BDNF) has been shown to promote epileptogenesis; however, little is known about factors that may act as intrinsic, homeostatic or counterbalancing mechanisms. Using rodent models, here we show that limbic seizure activity upregulated NRG1-ErbB4 signaling and that epileptogenesis was inhibited by infusing NRG1 intracerebrally but exacerbated by neutralizing endogenous NRG1 with soluble ErbB4 extracellular domain, by inhibiting ErbB4 activation or by deleting the Erbb4 gene. Furthermore, specific depletion of ErbB4 in parvalbumin-expressing interneurons abolished NRG1-mediated inhibition of epileptogenesis and promoted kindling progression, resulting in increased spontaneous seizures and exuberant mossy fiber sprouting. In contrast, depleting ErbB4 in CaMKIIα-positive pyramidal neurons had no effect. Thus, NRG1-induced activation of ErbB4 in parvalbumin-expressing inhibitory interneurons may serve as a critical endogenous negative-feedback mechanism to suppress limbic epileptogenesis.

Exome sequencing identifies truncating mutations in PRRT2 that cause paroxysmal kinesigenic dyskinesia.

Paroxysmal kinesigenic dyskinesia is the most common type of paroxysmal movement disorder and is often misdiagnosed clinically as epilepsy. Using whole-exome sequencing followed by Sanger sequencing, we identified three truncating mutations within PRRT2 (NM_145239.2) in eight Han Chinese families with histories of paroxysmal kinesigenic dyskinesia: c.514_517delTCTG (p.Ser172Argfs*3) in one family, c.649dupC (p.Arg217Profs*8) in six families and c.972delA (p.Val325Serfs*12) in one family. These truncating mutations co-segregated exactly with the disease in these families and were not observed in 1,000 control subjects of matched ancestry. PRRT2 is a newly discovered gene consisting of four exons encoding the proline-rich transmembrane protein 2, which encompasses 340 amino acids and contains two predicted transmembrane domains. PRRT2 is highly expressed in the developing nervous system, and a truncating mutation alters the subcellular localization of the PRRT2 protein. The function of PRRT2 and its role in paroxysmal kinesigenic dyskinesia should be further investigated.

Conditional deletion of NRSF in forebrain neurons accelerates epileptogenesis in the kindling model.

Neuron-restrictive silencer factor (NRSF), also known as repressor element-1 silencing transcription factor, is a transcriptional repressor that plays important roles in embryonic development and neurogenesis. Recent findings show that NRSF is upregulated after seizures activity however, the link between NRSF and epileptogenesis remains poorly understood. To investigate the role of NRSF in epilepsy, we employed a Cre-loxp system to specifically delete NRSF in excitatory neurons of the postnatal mouse forebrain. In the kindling model of epileptogenesis, conditional NRSF knockout (NRSF-cKO) mice exhibited dramatically accelerated seizure progression and prolonged afterdischarge duration compared with control mice. Moreover, seizures activity-induced mossy fiber sprouting was enhanced in the NRSF-cKO mice. The degree of upregulation of Fibroblast growth factor 14 and Brain-derived neurotrophic factor (BDNF) following kainic acid-induced status epilepticus was significantly increased in the cortex of NRSF-cKO mice compared with control mice. Furthermore, the derepression of BDNF was associated by activation of PLCγ and PI(3)K signaling pathways. These findings indicate that NRSF functions as an intrinsic repressor of limbic epileptogenesis.

[Effects of manganismus on proliferation of neural stem cells in mice's hippocampus].

OBJECTIVE: To explore the effects of manganese poisoning on the proliferation of neural stem cells (NSCs) in mice's hippocampus. METHODS: The mice (weight 8 approximately 10 g) were divided into control group(CG) low-dose group(LDG) middle-dose group(MDG) and high-dose group(HDG)by intraperitoneal injection of 0, 5, 20, 50 mg x kg(-1) x d(-1) of manganese chloride dissolved in physiological saline. The ability of learning and memory was detected by Morris Water Maze, and the proliferation of NSCs in subgranular zone (SGZ) in these mice's hippocampus was also detected by immunohistochemistry. RESULTS: 1) Compared with the CG, the ability of learning and memory in all manganism group decreased significantly (P < 0.01) and this phenomenon in HDG was most notable (P < 0.01). Meanwhile, the ability of memory was negatively correlated with the dose of manganese chloride (r(s) = -0.598, P < 0.01), but the difference of swimming speed in every group was of no statistic significance. (2) The numbers of NSCs in proliferation period in SGZ of all manganism groups was much lower than that of CG (P < 0.01) negatively correlated with the dose of manganese chloride (r(s) = -0.666, P < 0.01). (3) The reduction of NSCs had a positive correlation to the depression of learning and memory (r(s) = 0.734, P < 0.01). CONCLUSIONS: Manganismus can affect the ability of learning and memory, which is probably caused by the inhalation of manganese on NSCs in hippocampus.