Necdin蛋白与神经元的生长分化

在神经系统,Necdin只在成熟神经元的细胞核中表达,可能与成熟神经元分裂静止状态的保持有关.近年的研究表明,Necdin是一种生长抑制蛋白,能与多种因子如SV40大T抗原,腺病毒E1A,转录因子E2F1以及肿瘤抑制蛋白p53等结合,在功能上类似于成视网膜瘤蛋白Rb.necdin基因缺陷时,会引起脑内,特别是下丘脑神经元分化障碍.人类necdin基因位于PWS综合征的基因缺失区,可能与PWS的一些症状有关.本文从Necdin蛋白的基本概况,生物功能以及Necdin与疾病三个方面进行了综述.     

Necdin与神经系统退行性改变

Necdin是黑素瘤相关抗原家族Ⅱ成员之一,主要表达于成熟神经元的细胞核。Necdin作为一种生长抑制蛋白,通过与多种胞核及胞浆中的细胞因子结合,调控细胞周期、细胞分化及细胞凋亡过程。人类Necdin基因位于Prede—Willi综合征（PWS）的基因缺失区,可能与PWS的一些症状有关。Necdin缺失的小鼠表现出运动缺陷,可能参与了神经退行性改变。本文就Necdin的对神经系统的影响做一综述。     

REST和CoREST在神经细胞分化发育过程中的调节作用

正神经元限制性沉默因子(neuron-restrictive silencer factor,NRSF),是一种重要的锌指蛋白转录负调控因子,它与某些基因中相应的神经元限制性沉默元件(neuron restrictive silencer element,NRSE),又称RE-1(repressor element 1,RE-1)相结合,从而对许多与神经元发育及功能相关的基因的表达发挥阻遏作用。REST辅助抑制因子(REST corepressor,CoREST)是一种神经元表型调控因子,CoREST与REST的C端结构域     

下调Homer—1 b／c基因对机械性损伤神经元存活率的影响

目的既往研究表明,Homer-1b／c在神经元损伤后恒定表达,但下调Homer—1b／c能否对损伤的神经元具有保护作用尚不清楚,这也是本实验中待研究的问题。方法采用RNA干涉（RNAi）技术,抑制神经元Homer-1b／c基因及蛋白表达。通过Westernblot法分析神经元转染小干扰RNA（siRNA）后Homer—1b／c基因抑制效果。建立神经元机械性损伤模型,通过细胞存活率、乳酸脱氢酶（LDH）活性测定,研究下调Homer-1b／c基因对神经元损伤的保护作用。结果siRNA转染神经元后36h,Homer-1b／cmRNA和蛋白质表达明显被抑制。siRNA转染组神经元损伤后细胞存活率明显比阴性对照组、空载体组高（P〈0．05）。阴性对照组、空载体组和siRNA转染组神经元损伤前培养液LDH性无统计学差异（P〉0．05）,机械性损伤后24h,与阴性对照组及空载体组比较,siRNA转染组LDH活性明显降低（P〈0．05）。结论Homer—1b／csiRNA转染神经元效率较高,基因抑制效果显著。降低Homer-1b／c蛋白表达能够减少机械性损伤后继发性神经元损害,对神经元具有一定的保护作用。     

阿尔茨海默病主要相关基因及其功能蛋白研究进展

与阿尔茨海默病(AD)相关的基因主要有淀粉样前体蛋白基因、载脂蛋白E基因、早老素基因、α2巨球蛋白基因、Tau蛋白基因等。这些基因表达的功能蛋白以各种方式影响神经元的功能,当其表达异常或蛋白加工异常则患者可能患有以智能衰退为特征的神经退行性疾病。该文就上述基因和其他一些与AD相关基因的基本特征及其所表达的异常蛋白如何影响神经元功能作一综述。     

与缺血性海马CA_1迟发性神经元死亡有关的基因表达改变

短暂脑缺血后海马CA_1区易发生迟发性神经元死亡。缺血后,CA_1神经元线粒体基因、热休克蛋白基因和神经递质系统基因表达改变与迟发性神经元发生有关。CA_1星形细胞基因表达变化也与迟发性神经元死亡有一定的关系。用药物干预后,CA_1部分基因的表达变化,与迟发性神经元死亡率下降的相关性好。     

Parkin蛋白与帕金森病

分子遗传学研究证明parkin基因是常染色体隐性遗传性少年型帕金森综合征(AR-JP)的致病基因,其表达产物parkin蛋白具有E3泛素-蛋白连接酶活性.Parkin蛋白可能在维持多巴胺能神经元的正常功能中发挥重要作用,而parkin蛋白功能障碍可能与帕金森病的发病有关.目前已经鉴定了几种parkin蛋白的底物蛋白,使我们能够初步了解帕金森病发病的分子和细胞学机理,这对于我们最终搞清帕金森病的发病机制、开发相应的治疗药物具有极其重要的意义.本文综述了parkin蛋白最新研究进展.     

神经疾病风险基因肌细胞增强因子2研究进展

肌细胞增强因子 2（MEF2）在神经系统中广泛分布，MEF2 蛋白及其相关信号通路在人体生 理和病理过程中都起着重要的作用。作为参与神经元分化、突触连接和传递以及神经元存活的关键神 经发育因子，上调 MEF2 活性能起到神经保护作用，同时一定程度上防止神经元凋亡。近年 MEF2 成为 多种神经类疾病尤其是神经退行类疾病的风险基因。现就 MEF2 的结构、生物学功能及其与神经疾病 关系的研究现状进行综述，以期寻找此类疾病治疗新靶点。     

血管内皮活性肠肽介导的高活性神经保护肽的研究进展

神经营养因子(neurotrophic factors，NTFs)是一类能支持神经元存活、促进其生长、分化及维持其功能的化学因子，它既是神经元之间或与其它细胞建立功能性联系的依赖因子，又是发育成熟神经元功能的调控因子，甚至在神经元损伤后或老年退行性变时是保护其存活和促进其再生的必需因子。自Levi—Montalcini首次发现神经生长因子(nerve     

常氧及低氧条件下胶质源性神经营养因子体外诱导中脑神经干细胞向多巴胺能神经元的分化

背景：神经干细胞的定向诱导分化和扩增受细胞自身基因和外来信号的调控。 目的：观察中脑源性神经干细胞在常氧、低氧和胶质源性神经营养因子诱导下向多巴胺能神经元的分化情况。 方法：无菌条件下分离E12小鼠胚胎腹侧中脑组织,胰酶消化和机械吹打制成单细胞悬液,在无血清培养基中培养扩增;Nestin免疫细胞化学染色方法鉴定神经干细胞。在有血清培养基中对纯化神经干细胞自然分化;神经元特异性烯醇化酶和胶质纤维酸性蛋白免疫细胞化学染色方法分别鉴定神经元和星形胶质细胞。建立常氧和低氧环境,设置常氧组、常氧+胶质源性神经营养因子组、低氧组、低氧+胶质源性神经营养因子组,按实验分组在有血清条件下诱导分化。 结果与结论：在低氧条件下,中脑神经干细胞向多巴胺能神经元分化均高于常氧组;尤其是低氧环境和胶质源性神经营养因子诱导下向多巴胺能神经元分化比例更高,表型更成熟。说明低氧环境下胶质源性神经营养因子可明显促进中脑神经干细胞分化为数量足够、形态及功能成熟的多巴胺能神经元。     

Expression of necdin, an embryonal carcinoma-derived nuclear protein, in developing mouse brain.

Necdin is a polypeptide sequence encoded by neural differentiation-specific mRNA derived from embryonal carcinoma cells. We have examined the expression of necdin and its mRNA in cultured cells and mouse brain by Northern blot analysis and immunohistochemistry. Among various established cell lines including neuroblastoma and glioma cells, only differentiated embryonal carcinoma cells (P19 and F9) expressed necdin mRNA. Necdin immunoreactivity was localized in the nuclei of differentiated neurons derived from P19 cells. Necdin mRNA was detected throughout brain regions of adult mouse; the relative abundances in the hypothalamus and midbrain were the highest, whereas those in the olfactory bulb and cerebellum were the lowest. In developing mouse brain, necdin mRNA was expressed during early periods of neuronal generation and differentiation, and the peak levels were attained during postnatal days 1-4. Necdin immunoreactivity was not detected in the neural stem cells on embryonic day 10, but was concentrated in the nuclei of brain cells, mostly neurons, at advanced stages of differentiation. The majority of differentiated neurons in the brain had necdin-immunoreactive nuclei on postnatal day 33. Thus, necdin may represent a valuable molecular marker for differentiated neurons both in vitro and in vivo.     

Quox 1 homeobox protein is expressed in postmitotic sensory neurons of dorsal root ganglia

The expression of vertebrate homeoproteins has been extensively studied in a variety of normal and cancerous tissues, but little is known on the role of vertebrate homeoproteins in the proliferation and differentiation of cells from these tissues. In the present study, we investigate the relationship between Quox 1 protein (a quail homeodomain containing protein) expression and the proliferation and differentiation of quail dorsal root ganglia (DRG) and neural crest cells. In vivo [³H]TdR labeling experiments demonstrate that the postmitotic sensory neuroblasts appear before the formation of the ganglion, and that more than half of sensory neuroblasts from DRG have already terminated their proliferation in embryos of 2 days of incubation (E2). All DRG neurons have completely ceased to proliferate from E6.5 onwards. By means of immunocytochemistry, we observe that Quox 1 protein is accumulated exclusively in all bipolar neurons in culture of DRG from E9–E11, and in all postmitotic sensory-like neuroblasts during in vitro cell differentiation of the neural crest. The Quox 1 immunoreactive neurons express simultaneously neurofilaments or substance P, and they are never labeled by anti-bromodeoxyuridine. These observations together with the morphology of Quox 1 positive cells, demonstrate that Quox1 protein is expressed in the postmitotic sensory neurons of DRG. Our previous experiments have shown that between E4 and E6, the accumulation of Quox 1 protein increases in DRG in vivo, but decreases in the central nervous system in which cell proliferation decreases (Xue et al., (1993) Mech. Dev. 43, 149–158). Taken together, our results show that the accumulation of Quox 1 protein in DRG is tightly linked to the increase in the number of postmitotic neurons, whereas in the central nervous system the level of expression of Quox 1 seems concomitant with the extent of cell proliferation.     

Activation of calpain in cultured neurons overexpressing Alzheimer amyloid precursor protein

We have previously reported that overexpression of wild-type amyloid precursor protein (APP) in postmitotic neurons induces cleavage-dependent activation of caspase-3 both in vivo and in vitro. In this study, we investigated the mechanism underlying APP-induced caspase-3 activation using adenovirus-mediated gene transfer into postmitotic neurons derived from human embryonal carcinoma NT2 cells. Overexpression of wild-type APP significantly increased intracellular (45)Ca(2+) content prior to the activation of caspase-3 in NT2-derived neurons. Chelation of intracellular Ca(2+) markedly suppressed APP-induced activation of caspase-3. Furthermore, calpain, a Ca(2+)-dependent cysteine protease, was activated in neurons overexpressing APP as assessed by increased levels of calpain-cleaved alpha-fodrin and autolytic mu-calpain fragments. Neither calpain nor caspase-3 was activated in neurons expressing an APP mutant defective in the Abeta(1-20) domain. Calpain inhibitors almost completely suppressed APP-induced activation of neuronal caspase-3. E64d, a membrane permeable inhibitor of calpain, significantly suppressed APP-induced neuronal death. These results suggest that overexpression of wild-type APP activates calpain that mediates caspase-3 activation in postmitotic neurons.     

BRCA1–BARD1 Regulates Axon Regeneration in Concert with the Gqα–DAG Signaling Network

The breast cancer susceptibility protein BRCA1 and its partner BRCA1-associated RING domain protein 1 (BARD1) form an E3-ubiquitin (Ub) ligase complex that acts as a tumor suppressor in mitotic cells. However, the roles of BRCA1–BARD1 in postmitotic cells, such as neurons, remain poorly defined. Here, we report that BRC-1 and BRD-1, the Caenorhabditis elegans orthologs of BRCA1 and BARD1, are required for adult-specific axon regeneration, which is positively regulated by the EGL-30 Gqα–diacylglycerol (DAG) signaling pathway. This pathway is downregulated by DAG kinase (DGK), which converts DAG to phosphatidic acid (PA). We demonstrate that inactivation of DGK-3 suppresses the brc-1 brd-1 defect in axon regeneration, suggesting that BRC-1–BRD-1 inhibits DGK-3 function. Indeed, we show that BRC-1–BRD-1 poly-ubiquitylates DGK-3 in a manner dependent on its E3 ligase activity, causing DGK-3 degradation. Furthermore, we find that axon injury causes the translocation of BRC-1 from the nucleus to the cytoplasm, where DGK-3 is localized. These results suggest that the BRC-1–BRD-1 complex regulates axon regeneration in concert with the Gqα–DAG signaling network. Thus, this study describes a new role for breast cancer proteins in fully differentiated neurons and the molecular mechanism underlying the regulation of axon regeneration in response to nerve injury.SIGNIFICANCE STATEMENT BRCA1–BRCA1-associated RING domain protein 1 (BARD1) is an E3-ubiquitin (Ub) ligase complex acting as a tumor suppressor in mitotic cells. The roles of BRCA1–BARD1 in postmitotic cells, such as neurons, remain poorly defined. We show here that Caenorhabditis elegans BRC-1/BRCA1 and BRD-1/BARD1 are required for adult-specific axon regeneration, a process that requires high diacylglycerol (DAG) levels in injured neurons. The DAG kinase (DGK)-3 inhibits axon regeneration by reducing DAG levels. We find that BRC-1–BRD-1 poly-ubiquitylates and degrades DGK-3, thereby keeping DAG levels elevated and promoting axon regeneration. Furthermore, we demonstrate that axon injury causes the translocation of BRC-1 from the nucleus to the cytoplasm, where DGK-3 is localized. Thus, this study describes a new role for BRCA1–BARD1 in fully-differentiated neurons.     

Clathrin assembly proteins AP180 and CALM in the embryonic rat brain

Clathrin‐coated vesicles are known to play diverse and pivotal roles in cells. The proper formation of clathrin‐coated vesicles is dependent on, and highly regulated by, a large number of clathrin assembly proteins. These assembly proteins likely determine the functional specificity of clathrin‐coated vesicles, and together they control a multitude of intracellular trafficking pathways, including those involved in embryonic development. In this study, we focus on two closely related clathrin assembly proteins, AP180 and CALM (clathrin assembly lymphoid myeloid leukemia protein), in the developing embryonic rat brain. We find that AP180 begins to be expressed at embryonic day 14 (E14), but only in postmitotic cells that have acquired a neuronal fate. CALM, on the other hand, is expressed as early as E12, by both neural stem cells and postmitotic neurons. In vitro loss‐of‐function studies using RNA interference (RNAi) indicate that AP180 and CALM are dispensable for some aspects of embryonic neurogenesis but are required for the growth of postmitotic neurons. These results identify the developmental stage of AP180 and CALM expression and suggest that each protein has distinct functions in neural development. J. Comp. Neurol. 518:3803–3818, 2010. © 2010 Wiley‐Liss, Inc.     

Early postmitotic neurons transiently express TOAD-64, a neural specific protein

To identify proteins involved in the early development of the mammalian cerebral cortex, we previously used two-dimensional gels to compare proteins synthesized at different stages in corticogenesis in the embryonic rat at embryonic day 14 (E14), E17, and E21. During this period, the cortex develops from a morphologically homogeneous population of proliferative precursor cells into a complex structure containing a diverse array of terminally differentiated neurons. Several proteins are up-regulated coincident with the generation of postmitotic neurons. Here we describe the purification, partial amino acid sequencing, and characterization of one of these proteins, TOAD-64 (Turned On After Division; 64 kDa), using polyclonal antisera to two synthetic peptides from the protein. This analysis reveals that TOAD-64 is a 64,000 Da protein that increases in abundance over the period of corticogenesis and then subsequently decreases to very low levels in the adult. The protein is neural specific and is expressed by postmitotic neurons as they begin their migration out of the ventricular zone into the developing cortical plate. It is expressed in advance of most other neuronal proteins. Progenitor cells do not express TOAD-64. Therefore, this protein is a marker for postmitotic cells that have made a commitment to a neuronal phenotype. The extremely early expression, the relative abundance in newly born neurons, as well as the restriction in expression to the period of initial neuronal differentiation suggest that TOAD-64 may be a key structural protein for early neuronal function.