Comparative DNA methylation among females with neurodevelopmental disorders and seizures identifies TAC1 as a MeCP2 target gene

Background

Several proteins involved in epigenetic regulation cause syndromic neurodevelopmental disorders when human genes are mutated. More general involvement of epigenetic mechanisms in neurodevelopmental phenotypes is unclear.

Methods

In an attempt to determine whether DNA methylation differentiates clinical subgroups, profiling was performed on bisulfite converted DNA from lymphoblastoid cell lines (LCLs) in discovery (n = 20) and replication (n = 40) cohorts of females with Rett syndrome (RTT; n = 18), autism (AUT; n = 17), seizure disorder (SEZ; n = 6), and controls (CTL; n = 19) using Illumina HumanMethylation27 arrays. TAC1 CpGs were validated using a Sequenom EpiTYPER assay and expression was measured in LCLs and postmortem brain. Chromatin immunoprecipitation was performed in HEK cells. Cells were treated with valproic acid and MeCP2 binding was assessed.

Results

Two female-only cohorts were analyzed. DNA methylation profiling in a discovery cohort identified 40 CpGs that exhibited statistically significant differential methylation (≥15%) between clinical groups (P <0.01). Hierarchical clustering and principal components analysis suggested neurodevelopmental groups were distinct from CTL, but not from each other. In a larger and more heterogeneous replication cohort, these 40 CpG sites suggested no clear difference between clinical groups. Pooled analysis of DNA methylation across all 60 samples suggested only four differentially methylated CpG sites (P <0.0005), including TAC1. TAC1 promoter CpG hypermethylation was validated in AUT and SEZ (P <0.005). Analyzed for the first time in postmortem brain, TAC1 expression was reduced in cingulate cortex in RTT and AUT+SEZ (P = 0.003). However, no significant difference in TAC1 promoter CpG methylation was detected in RTT and AUT+SEZ brains. Additional molecular analyses revealed that MeCP2 binds directly to the TAC1 promoter and is sensitive to antiepileptic drug treatment.

Conclusion

These data suggest that DNA methylation is not widely altered in RTT, consistent with subtle changes in gene expression previously observed. However, TAC1 may be an important target for further functional analyses in RTT. Studies of larger sample cohorts using primary cells that also consider shared clinical features and drug treatments may be required to address apparent subtle disruptions of DNA methylation in neurodevelopmental disorders.     

MeCP2 mutation causes distinguishable phases of acute and chronic defects in synaptogenesis and maintenance, respectively

Over 200 mutations in the gene encoding methyl-CpG-binding protein 2 (MeCP2) are known to cause Rett syndrome (RTT), a multiphasic neurodevelopmental disorder that results in motor and cognitive impairments; however, little is known about the neurobiology of RTT. Here, we employ the MeCP2^308/y mouse model of RTT to investigate the course of the neuronal defects imparted by MeCP2 mutation. Using the olfactory system as a neurodevelopmental model, we describe an acute but transient defect in olfactory sensory neuron maturation during synaptogenesis and elaboration of the glomerular neuropil. This defect is overcome through compensatory responses that restore homeostasis. However, a chronic problem in glomerular organization emerges, which eventually leads to increased neuronal apoptosis. This multiphasic course comprising acute developmental and chronic defects in synaptogenesis and maintenance may represent the neurobiological correlates of clinical RTT, and suggests that different therapeutic strategies may be appropriate at different clinical stages of this disease.     

Environmental enrichment ameliorates a motor coordination deficit in a mouse model of Rett syndrome--Mecp2 gene dosage effects and BDNF expression

Rett syndrome, commonly associated with mutations of the methyl CpG-binding protein 2 ( MECP2 ) gene, is characterised by an apparently normal early postnatal development followed by deterioration of acquired cognitive and motor coordination skills in early childhood. To evaluate whether environmental factors may influence the disease outcome of Rett syndrome, we tested the effect of environmental enrichment from 4 weeks of age on the behavioural competence of mutant mice harboring a Mecp2 ^tm1Tam-null allele. Our findings show that enrichment improves motor coordination in heterozygous Mecp2 ^+/− females but not Mecp2 ^−/y males. Standard-housed Mecp2 ^+/− mice had an initial motor coordination deficit on the accelerating rotarod, which improved with training then deteriorated in subsequent weeks. Enrichment resulted in a significant reduction in this coordination deficit in Mecp2 ^+/− mice, returning the performance to wild-type levels. Brain-derived neurotrophic factor (BDNF) protein levels were 75 and 85% of wild-type controls in standard-housed and environmentally enriched Mecp2 ^+/− cerebellum, respectively. Mecp2 ^−/y mice showed identical deficits of cerebellar BDNF (67% of wild-type controls) irrespective of their housing environment. Our findings demonstrate a positive impact of environmental enrichment in a Rett syndrome model; this impact may be dependent on the existence of one functional copy of Mecp2 .     

中枢神经系统肿瘤CDKN2基因的丢失

目的探讨中枢神经系统肿瘤CDKN2基因的丢失情况。方法采用聚合酶链反应(PCR)对81例脑、脊髓肿瘤手术标本中CDKN2基因的丢失情况进行了检测。结果胶质瘤CDKN2基因丢失率为60％,且高级别胶质瘤基因丢失率显著高于低级别肿瘤;脑膜瘤、神经鞘瘤、垂体腺瘤及转移瘤亦存在不同程度CDKN2基因的丢失。结论CDKN2基因的丢失与中枢神经系统肿瘤的发生、发展有一定的关系。     

Nogo-A在神经细胞分子调控中的研究现状

视神经是中枢神经系统的一部分,其损伤后再生能力有限.眼外伤等因素引起视神经损伤,往往给伤者带来不可逆转的视功能损害,导致患者视力严重受损.因此,探讨中枢神经再生困难的原因对视神经再生以及视功能的恢复有重要借鉴意义.成年哺乳动物中枢神经损伤后再生困难,研究认为这可能和中枢神经髓磷脂中某种蛋白的抑制作用有关.     

Role of MeCP2, DNA methylation, and HDACs in regulating synapse function

Over the past several years there has been intense effort to delineate the role of epigenetic factors, including methyl-CpG-binding protein 2, histone deacetylases, and DNA methyltransferases, in synaptic function. Studies from our group as well as others have shown that these key epigenetic mechanisms are critical regulators of synapse formation, maturation, as well as function. Although most studies have identified selective deficits in excitatory neurotransmission, the latest work has also uncovered deficits in inhibitory neurotransmission as well. Despite the rapid pace of advances, the exact synaptic mechanisms and gene targets that mediate these effects on neurotransmission remain unclear. Nevertheless, these findings not only open new avenues for understanding neuronal circuit abnormalities associated with neurodevelopmental disorders but also elucidate potential targets for addressing the pathophysiology of several intractable neuropsychiatric disorders.     

中枢神经系统基因治疗的病毒载体

重组病毒载体因其自然感染途径而成为有效的基因转移手段。迄今为止，许多病毒载体，包括逆转录病毒、腺病毒、单纯疱疹病毒、腺相关病毒、慢病毒及多种杂交型病毒载体等，已应用于中枢神经系统基因治疗的基础和临床研究。本对其主要研究进展进行了综述。     

Anatomical localisation of preproatrial natriuretic peptide mRNA in the rat brain by in situ hybridisation histochemistry: Novel identification in olfactory regions

Atrial natriuretic peptide (ANP) is one of three structurally homologous natriuretic peptides present in heart and brain, which is thought to be involved in the regulation of water and salt intake, blood pressure, and hormone secretion. In the present study, the distribution of preproatrial natriuretic peptide (ppANP) mRNA in the central nervous system of the rat was examined by in situ hybridisation histochemistry by using [³⁵S]-labelled oligonucleotides. Cells expressing ppANP mRNA were apparent in several major neuronal systems, being present in hypothalamic, limbic, pontine and forebrain olfactory regions. Relatively high densities of ppANP mRNA-positive neurones were found in the anterior medial preoptic hypothalamic nucleus, medial habenular nucleus, and in Barrington's nucleus in the pons. Moderate numbers of ppANP mRNA-positive cells were present in a number of amygdaloid nuclei, including the posterolateral and anterior cortical nuclei, in the zona incerta, and the pedunculopontine tegmental nucleus. Other areas, including the ventromedial hypothalamic nucleus and the laterodorsal tegmental nucleus, displayed only low densities of ppANP mRNA-positive neurones. A number of structures in which ppANP mRNA (or ANP-like immunoreactivity) has not previously been reported were found to contain moderate to high numbers of ppANP mRNA-positive neurones including several nuclei associated with the olfactory system, such as the anterior olfactory nucleus and neurones of the tenia tecta and ventrolateral orbital cortex. Although ppANP mRNA in CA1 pyramidal cells of the hippocampus has been described, we also detected labelling in CA2 and ventral CA3 regions of the hippocampus. Conversely, nuclei such as the bed nucleus of the stria terminalis and the nucleus of the solitary tract, which are reported to possess ANP-like immunoreactivity, were found not to contain ppANP mRNA. Overall, these results demonstrate the presence of ANP gene expression in discrete neuronal populations of the rat central nervous system and provide additional evidence to support a putative role for this peptide in regulating and integrating hypothalamic, olfactory, limbic, and neuroendocrine systems. © 1995 Wiley-Liss, Inc.     

IL-33及其在中枢神经系统中作用的研究进展(英文)

白介素-33(interleukin-33,IL-33)是IL-1家族的新成员,在多种细胞和组织中表达。IL-33能与常染色体结合,因此被认为具有抑制核内转录的作用。当受到炎性刺激时,IL-33可作为危险信号的警报释放到细胞外发挥细胞因子的作用。IL-33的受体是由ST2和IL-1受体结合蛋白组成的异物二聚体,其中IL-1受体结合蛋白是所有白介素家族受体共有的部分。IL-33/ST2信号通路通过调节细胞因子的生成,不仅对炎症、免疫性疾病发挥关键作用,还参与了许多其他疾病如中枢神经系统疾病。近年来有关IL-33尤其是它在中枢神经系统中表达及功能的研究不断增多,本文对IL-33及其在中枢神经系统中的作用进行了综述。     

重症肌无力中枢损害模型大脑基因表达差异

目的　探讨 SD大鼠重症肌无力 ( myasthenia gravis,MG)中枢神经系统 ( CNS)损害模型大脑皮质基因表达的差异 ,为深入研究 MG的 CNS损害机制提供实验依据。方法　将从 MG患者和非 MG患者血清中提取的免疫球蛋白分别注入实验组和对照组 SD大鼠侧脑室 ,3周后取新鲜脑组织提取 m RNA并分析基因表达的差异 ,将所得的差异表达基因在 Gene Bank中分析。结果　在 2 0 0 0条目的基因中共发现差异表达基因 46条 ,包括全长表达基因 1 7条 ,表达序列标识 2 9条。其中 42条表达减少 ,4条表达增加。差异表达基因包括信号转导相关基因、氨基酸及微量元素代谢相关基因、蛋白转运相关基因、细胞周期相关基因、细胞骨架和运动蛋白基因、免疫相关基因、蛋白质修饰相关基因、DNA结合蛋白及转录起始因子基因、离子通道相关基因等。结论　多种基因与 MG CNS损害相关 ,差异基因表达的检测结果可为深入研究 MG的发病机制提供新思路。     

Gene therapy in the central nervous system: Direct versus indirect gene delivery

Over the last decade, the combination of molecular biology and cell transplantation techniques has given rise to a powerful method for gene therapy. The implantation of genetically modified cultured cells has been extensively used in the central nervous system (CNS) in various experimental models of neurologic disorders. More recently, viral and chemical methods have been developed to further efforts to shuttle transgenes into the relatively inaccessible brain. Adenoviral and liposomal synthetic vectors carry transgenes into neural tissue in situ and are beginning to show promise as new methods for CNS therapy. © 1995 Wiley-Liss, Inc.