Nogo A, B and C expression in schizophrenia, depression and bipolar frontal cortex, and correlation of Nogo expression with CAA/TATC polymorphism in 3'-UTR

Schizophrenia may result from altered gene expression leading to abnormal neurodevelopment. In a search for genes with altered expression in schizophrenia, our previous work on human frontal cerebral cortex found the mRNA of Nogo, a myelin-associated protein which inhibits the outgrowth of neurites and nerve terminals, to be overexpressed in schizophrenia. Because those earlier results did not examine tissues for the separate Nogo A, B and C isoforms from age- and sex-matched individuals, we repeated the study for all three isoforms, using a new set of tissues from matched individuals, and using the more accurate method of quantitative real-time PCR (polymerase chain reaction). We found Nogo C to be overexpressed by 26% in the schizophrenia tissues, which is in accordance with our earlier results. The expression of Nogo B was statistically significantly reduced by 17% in the frontal cortices from individuals who had been diagnosed as having had severe depression. Furthermore, we show that there is a direct correlation between the expression of Nogo A and C and the presence of alleles with a CAA insert, irrespective of disease status. While upregulation of Nogo C expression may play a role in schizophrenia, altered Nogo B may contribute to the clinical condition of depression. Nogo A showed a statistically non-significant increase in expression in schizophrenia.     

Reticulons RTN3 and RTN4-B/C interact with BACE1 and inhibit its ability to produce amyloid beta-protein

Beta-secretase beta-site APP cleaving enzyme 1 (BACE1), is a membrane-bound aspartyl protease necessary for the generation of amyloid beta-protein (Abeta), which accumulates in the brains of individuals with Alzheimer's disease (AD). To gain insight into the mechanisms by which BACE1 activity is regulated, we used proteomic methods to search for BACE1-interacting proteins in human neuroblastoma SH-SY5Y cells, which overexpress BACE1. We identified reticulon 4-B (RTN4-B; Nogo-B) as a BACE1-associated membrane protein. Co-immunoprecipitation experiments confirmed a physical association between BACE1 and RTN4-B, RTN4-C (the shortest isoform of RTN-4), and their homologue reticulon 3 (RTN3), both in SH-SY5Y cells and in transfected human embryonic kidney (HEK) 293 cells. Overexpression of these reticulons (RTNs) resulted in a 30-50% reduction in the secretion of both Abeta40 and Abeta42 from HEK293 cells expressing the AD-associated Swedish mutant amyloid precursor protein (APP), but did not affect Abeta secretion from cells expressing the APP beta-C-terminal fragment (beta-CTF), indicating that these RTNs can inhibit BACE1 activity. Furthermore, a BACE1 mutant lacking most of the N-terminal ectodomain also interacted with these RTNs, suggesting that the transmembrane region of BACE1 is critical for the interaction. We also observed a similar interaction between these RTNs and the BACE1 homologue BACE2. Because RTN3 and RTN4-B/C are substantially expressed in neural tissues, our findings suggest that they play important roles in the regulation of BACE1 function and Abeta production in the brain.     

Deficits of visuospatial working memory and executive function in single- versus multiple-domain amnestic mild cognitive impairment: A combined ERP and sLORETA study

ObjectiveAccording to recent criteria of classification, amnestic mild cognitive impairment (aMCI) could be divided into two categories: single-domain aMCI (sd-aMCI) and multiple-domain aMCI (md-aMCI). The difference between sd-aMCI and md-aMCI needs further exploration. The present study aimed to compare deficits in visuospatial working memory (VSWM) and executive function between sd-aMCI versus md-aMCI patients by use of event-related potentials (ERP) and standardized low-resolution brain electromagnetic tomography analysis (sLORETA).MethodsThe ERP data were measured and analyzed in 26 sd-aMCI, 13 md-aMCI patients and 46 healthy elderly controls (HEC) during VSWM and Go/Nogo processes.ResultsDuring VSWM task, md-aMCI patients showed decreased P300 amplitude compared to HEC and sd-aMCI patients (All p < 0.05). As compared to sd-aMCI, md-aMCI showed a hypoactivation in the right middle frontal gyrus in 1-back task during the P300 time range. During the Go/Nogo task, sd-aMCI and md-aMCI patients showed reduced N200 amplitude, compared to HEC (All p < 0.05). However, md-aMCI patients had decreased N200 amplitude, with respect to sd-aMCI patients. Further, as compared to sd-aMCI patients, md-aMCI patients showed a hypoactivation in the right superior frontal gyrus during the N200 time range.ConclusionsThese findings with a combined ERP and sLORETA study showed more severe deficits in updating operations of WM, detections of the target stimulus and conflict processes in md-aMCI, compared to sd-aMCI patients.SignificanceThe present study showed that a combined ERP and sLORETA study during the VSWM and Go/Nogo tasks could distinguish md-aMCI from sd-aMCI.     

Decreased occipital alpha oscillation in children who stutter during a visual Go/Nogo task

Objective

Our goal was to discover attention- and inhibitory control-related differences in the main oscillations of the brain of children who stutter (CWS) compared to typically developed children (TDC).

Nogos and the Nogo-66 receptor: factors inhibiting CNS neuron regeneration

The recently cloned gene Nogo, whose alternative splice products correspond to the antigenic target of the central nervous system (CNS) regeneration enhancing monoclonal antibody IN-1, codes for membrane proteins enriched in brain, particularly in oligodendrocytes. The 66-amino acid extracellular domain of Nogo (Nogo-66) interacts with a high-affinity receptor (NgR), a glycosylphosphatidylinositol (GPI)-linked protein with multiple leucine-rich repeats. The amino terminal cytoplasmic domain of Nogo appears to have a general cellular growth inhibitory effect. Nogo-66, on the other hand, specifically retards neurite outgrowth and induces growth cone collapse, possibly through its interaction with NgR and as yet unidentified transmembrane coreceptors. Recent results also suggest that Nogo expression may induce apoptosis in tumor cells. Together, these proteins provide new molecular handles for the design of therapeutic interventions for CNS injuries and neurodegenerative diseases, as well as possible leads to anticancer strategies.     

GAP-43 overexpression in adult mouse Purkinje cells overrides myelin-derived inhibition of neurite growth

Up-regulation of growth-associated proteins in adult neurons promotes axon regeneration and neuritic elongation onto nonpermissive substrates. To investigate the interaction between these molecules and myelin-related inhibitory factors, we examined transgenic mice in which overexpression of the growth-associated protein GAP-43 is driven by the Purkinje cell-specific promoter L7. Contrary to their wild-type counterparts, which have extremely poor regenerative capabilities, axotomized transgenic Purkinje cells exhibit profuse sprouting along the intracortical neurite and at the severed stump [Buffo et al. (1997) J. Neurosci., 17, 8778-8791]. Here, we investigated the relationship between such sprouting axons and oligodendroglia to ask whether GAP-43 overexpression enables Purkinje neurites to overcome myelin-derived inhibition. Intact transgenic Purkinje axons display normal morphology and myelination. Following injury, however, many GAP-43-overexpressing neurite stumps are devoid of myelin cover and sprout into white matter regions containing densely packed myelin and Nogo-A- or MAG-immunopositive oligodendrocytes. The intracortical segments of these neurites show focal accumulations of GAP-43, which are associated with disrupted or retracted myelin sheaths. Numerous sprouts originate from such demyelinated segments and spread into the granular layer. Some myelin loss, though not axon sprouting, is also evident in wild-type mice, but this phenomenon is definitely more rapid and extensive in transgenic cerebella. Thus, GAP-43-overexpressing Purkinje axons are endowed with enhanced capabilities for growing into nonpermissive territories and show a pronounced tendency to lose myelin. Our observations suggest that accumulation of GAP-43 along precise axon segments disrupts the normal axon-glia interaction and enhances the retraction of oligodendrocytic processes to facilitate the outgrowth of neuritic sprouts.     

Cortical potentials related to the nogo decision

The go/nogo reaction time task has been frequently used to assess volitional inhibition. Psychophysiological studies of the correlates of the go/nogo decision have almost exclusively been concerned with N2 and P3 potentials of the event-related potentials (ERPs). However, in studies where the EMG onset latency was available, it was obvious that this latency was shorter than or at least equal to the latencies of the studied cerebral potentials. In this study, by concurrent recording of the EEG and EMG activity we aimed to better define the temporal relationship between cortical activity and motor response. Particularly, we wanted to identify the early (i.e. pre EMG-onset) electrophysiological correlates of the nogo decision. We used a modified S1-S2 paradigm that involved a two-stage go/nogo decision. In this task both S1 and S2 were informative and required the subject to make a decision, but the nature of the decision differed. The decision at S1 involved whether to prepare a movement, whereas the decision at S2 involved whether to initiate or inhibit an already prepared response. To better visualise the nogo decision related components of the ERPs, the go ERPs were subtracted from the corresponding nogo ERPs and difference ERPs were formed. Before EMG onset, a small negative component common to both go/nogo difference traces and corresponding roughly with the N1 wave was detected. It is suggested that this early negativity may be a more specific electrophysiological reflection of the nogo decision proper.     

体外高苯丙氨酸作用下少突胶质细胞Nogo A蛋白及mRNA的检测

目的了解高苯丙氨酸(Phe)对中枢神经系统少突胶质细胞(OLG)Nogo A表达的影响。方法采用水平摇床和差数贴壁方法获取OLG前体细胞,并在化学限定液中培养诱导成OLG。用细胞免疫荧光和免疫组化方法进行OLG的鉴定和Nogo A蛋白的定位。体外模拟高Phe(0.9μmol/L)环境,实时荧光定量PCR和Western blot方法分别检测高Phe作用0(对照组)、12、24和48 h的OLG Nogo A mRNA和蛋白的表达情况。结果高Phe作用12、24和48 h的OLG Nogo A mRNA与alpha-tubolin(DM1A)的相对Ct值无明显改变,其相对表达量轻度上升,分别为0.98、1.09和1.20。高Phe作用12、24和48 h的OLG Nogo A蛋白的相对表达量与对照组相比明显增加,分别为对照组的1.5、5.3和6.7倍。结论高Phe作用下,OLG产生的轴突生长抑制因子Nogo A表达增加,可能为高Phe导致脑损伤的机制之一。     

兔视神经损伤后Nogo受体在视神经及视网膜的表达变化

目的研究免视神经损伤后Nogo受体在视神经及视网膜的表达变化。方法采用兔球后视神经钳夹伤模型，动物分别于损伤后3，7，14d处死。免疫组织化学染色观察Nogo受体在视神经及视网膜的表达变化。结果视神经损伤后3d，Nogo表达上调，视神经和视网膜均可见Nogo-A表达，其吸光度值分别为（45．3±1．3）×10^-3，（10．7±1．6）×10^-3，至损伤后7d，阳性反应达最高峰，吸光度值分别为（138．3±2．1）×10^-3，（29．4±3．3）×10^-3，至损伤后14d，视神经阳性反应下降，视网膜未见明显阳性表达。结论视神经损伤后，视神经及视网膜均可见Nogo-A阳性表达，且阳性表达随时间后延呈上升趋势，说明Nogo-A在抑制视．神经损伤后轴突再生的机制中可能起重要作用.