Neurofilament Medium Research Articles

Post-transcriptional regulation mediated by specific neurofilament introns in vivo.

Neurons regulate genes post-transcriptionally to coordinate the supply of cytoskeletal proteins, such as the medium neurofilament (NEFM), with demand for structural materials in response to extracellular cues encountered by developing axons. By using a method for evaluating functionality of cis-regulatory gene elements in vivo through plasmid injection into Xenopus embryos, we discovered that splicing of a specific nefm intron was required for robust transgene expression, regardless of promoter or cell type. Transgenes utilizing the nefm 3'-UTR but substituting other nefm introns expressed little or no protein owing to defects in handling of the messenger (m)RNA as opposed to transcription or splicing. Post-transcriptional events at multiple steps, but mainly during nucleocytoplasmic export, contributed to these varied levels of protein expression. An intron of the β-globin gene was also able to promote expression in a manner identical to that of the nefm intron, implying a more general preference for certain introns in controlling nefm expression. These results expand our knowledge of intron-mediated gene expression to encompass neurofilaments, indicating an additional layer of complexity in the control of a cytoskeletal gene needed for developing and maintaining healthy axons.

α-Internexin and Peripherin: Expression, Assembly, Functions, and Roles in Disease.

α-Internexin and peripherin are neuronal-specific intermediate filament (IF) proteins. α-Internexin is a type IV IF protein like the neurofilament triplet proteins (NFTPs, which include neurofilament light chain, neurofilament medium chain, and neurofilament high chain) that are generally considered to be the primary components of the neuronal IFs. However, α-internexin is often expressed together with the NFTPs and has been proposed as the fourth subunit of the neurofilaments in the central nervous system. α-Internexin is also expressed earlier in the development than the NFTPs and is a maker for neuronal IF inclusion disease. α-Internexin can self-polymerize in vitro and in transfected cells and it is present in the absence of the NFTP in development and in granule cells in the cerebellum. In contrast, peripherin is a type III IF protein. Like α-internexin, peripherin is specific to the nervous system, but it is expressed predominantly in the peripheral nervous system (PNS). Peripherin can also self-assemble both in vitro and in transfected cells. It is as abundant as the NFTPs in the sciatic nerve and can be considered a fourth subunit of the neurofilaments in the PNS. Peripherin has multiple isoforms that arise from intron retention, cryptic intron receptor site or alternative translation initiation. The functional significance of these isoforms is not clear. Peripherin is a major component found in inclusions of patients with amyotrophic lateral sclerosis (ALS) and peripherin expression is upregulated in ALS patients.

Identification of Pathways Mediating Growth Differentiation Factor5-Induced Tenogenic Differentiation in Human Bone Marrow Stromal Cells.

To date, the molecular signalling mechanisms which regulate growth factors-induced MSCs tenogenic differentiation remain largely unknown. Therefore, a study to determine the global gene expression profile of tenogenic differentiation in human bone marrow stromal cells (hMSCs) using growth differentiation factor 5 (GDF5) was conducted. Microarray analyses were conducted on hMSCs cultures supplemented with 100 ng/ml of GDF5 and compared to undifferentiated hMSCs and adult tenocytes. Results of QuantiGene® Plex assay support the use and interpretation of the inferred gene expression profiles and pathways information. From the 27,216 genes assessed, 873 genes (3.21% of the overall human transcriptome) were significantly altered during the tenogenic differentiation process (corrected p<0.05). The genes identified as potentially associated with tenogenic differentiation were ARHGAP29, CCL2, integrin alpha 8 and neurofilament medium polypeptides. These genes, were mainly associated with cytoskeleton reorganization (stress fibers formation) signaling. Pathway analysis demonstrated the potential molecular pathways involved in tenogenic differentiation were: cytoskeleton reorganization related i.e. keratin filament signaling and activin A signaling; cell adhesion related i.e. chemokine and adhesion signaling; and extracellular matrix related i.e. arachidonic acid production signaling. Further investigation using atomic force microscopy and confocal laser scanning microscopy demonstrated apparent cytoskeleton reorganization in GDF5-induced hMSCs suggesting that cytoskeleton reorganization signaling is an important event involved in tenogenic differentiation. Besides, a reduced nucleostemin expression observed suggested a lower cell proliferation rate in hMSCs undergoing tenogenic differentiation. Understanding and elucidating the tenogenic differentiation signalling pathways are important for future optimization of tenogenic hMSCs for functional tendon cell-based therapy and tissue engineering.

Differentiation of rat adipose tissue-derived stem cells into neuron-like cells by valproic acid, a histone deacetylase inhibitor.

Valproic acid (VPA) is a widely used antiepileptic drug, which has recently been reported to modulate the neuronal differentiation of adipose tissue-derived stem cells (ASCs) in humans and dogs. However, controversy exists as to whether VPA really acts as an inducer of neuronal differentiation of ASCs. The present study aimed to elucidate the effect of VPA in neuronal differentiation of rat ASCs. One or three days of pretreatment with VPA (2 mM) followed by neuronal induction enhanced the ratio of immature neuron marker βIII-tubulin-positive cells in a time-dependent manner, where the majority of cells also had a positive signal for neurofilament medium polypeptide (NEFM), a mature neuron marker. RT-PCR analysis revealed increases in the mRNA expression of microtubule-associated protein 2 (MAP2) and NEFM mature neuron markers, even without neuronal induction. Three-days pretreatment of VPA increased acetylation of histone H3 of ASCs as revealed by immunofluorescence staining. Chromatin immunoprecipitation assay also showed that the status of histone acetylation at H3K9 correlated with the gene expression of TUBB3 in ASCs by VPA. These results indicate that VPA significantly promotes the differentiation of rat ASCs into neuron-like cells through acetylation of histone H3, which suggests that VPA may serve as a useful tool for producing transplantable cells for future applications in clinical treatments.

Mass spectrometric phosphoproteome analysis of HIV-infected brain reveals novel phosphorylation sites and differential phosphorylation patterns.

To map the phosphoproteome and identify changes in the phosphorylation patterns in the HIV-infected and uninfected brain. Parietal cortex from individuals with and without HIV infection were lysed and trypsinized. The peptides were labeled with iTRAQ reagents, combined, phospho-enriched by titanium dioxide chromatography, and analyzed by LC-MS/MS with high resolution. Our phosphoproteomic workflow resulted in the identification of 112 phosphorylated proteins and 17 novel phosphorylation sites in all the samples that were analyzed. The phosphopeptide sequences were searched for kinase substrate motifs, which revealed potential kinases involved in important signaling pathways. The site-specific phosphopeptide quantification showed that peptides from neurofilament medium polypeptide, myelin basic protein, and 2'-3'-cyclic nucleotide-3' phosphodiesterase have relatively higher phosphorylation levels during HIV infection. This study has enriched the global phosphoproteome knowledge of the human brain by detecting novel phosphorylation sites on neuronal proteins and identifying differentially phosphorylated brain proteins during HIV infection. Kinases that lead to unusual phosphorylations could be therapeutic targets for the treatment of HIV-associated neurocognitive disorders.

Targeted neural differentiation of murine mesenchymal stem cells by a protocol simulating the inflammatory site of neural injury.

Damaged neural tissue is regenerated by neural stem cells (NSCs), which represent a rare and difficult-to-culture cell population. Therefore, alternative sources of stem cells are being tested to replace a shortage of NSCs. Here we show that mouse adipose tissue-derived mesenchymal stem cells (MSCs) can be effectively differentiated into cells expressing neuronal cell markers. The differentiation protocol, simulating the inflammatory site of neural injury, involved brain tissue extract, fibroblast growth factor, epidermal growth factor, supernatant from activated splenocytes and electrical stimulation under physiological conditions. MSCs differentiated using this protocol displayed neuronal cell morphology and expressed genes for neuronal cell markers, such as neurofilament light (Nf-L), medium (Nf-M) and heavy (Nf-H) polypeptides, synaptophysin (SYP), neural cell adhesion molecule (NCAM), glutamic acid decarboxylase (GAD), neuron-specific nuclear protein (NeuN), βIII-tubulin (Tubb3) and microtubule-associated protein 2 (Mtap2), which are absent (Nf-L, Nf-H, SYP, GAD, NeuN and Mtap2) or only slightly expressed (NCAM, Tubb3 and Nf-M) in undifferentiated cells. The differentiation was further enhanced when the cells were cultured on nanofibre scaffolds. The neural differentiation of MSCs, which was detected at the level of gene expression, was confirmed by positive immunostaining for Nf-L protein. The results thus show that the simulation of conditions in an injured neural tissue and inflammatory environment, supplemented with electrical stimulation under physiological conditions and cultivation of cells on a three-dimensional (3D) nanofibre scaffold, form an effective protocol for the differentiation of MSCs into cells with neuronal markers. Copyright © 2015 John Wiley & Sons, Ltd.

Epigenetic silencing of neurofilament genes promotes an aggressive phenotype in breast cancer

Neurofilament heavy polypeptide (NEFH) has recently been identified as a candidate DNA hypermethylated gene within the functional breast cancer hypermethylome. NEFH exists in a complex with neurofilament medium polypeptide (NEFM) and neurofilament light polypeptide (NEFL) to form neurofilaments, which are structural components of the cytoskeleton in mature neurons. Recent studies reported the deregulation of these proteins in several malignancies, suggesting that neurofilaments may have a role in other cell types as well. Using a comprehensive approach, we studied the epigenetic inactivation of neurofilament genes in breast cancer and the functional significance of this event. We report that DNA methylation-associated silencing of NEFH, NEFL, and NEFM in breast cancer is frequent, cancer-specific, and correlates with clinical features of disease progression. DNA methylation-mediated inactivation of these genes occurs also in multiple other cancer histologies including pancreas, gastric, and colon. Restoration of NEFH function, the major subunit of the neurofilament complex, reduces proliferation and growth of breast cancer cells and arrests them in Go/G1 phase of the cell cycle along with a reduction in migration and invasion. These findings suggest that DNA methylation-mediated silencing of the neurofilament genes NEFH, NEFM, and NEFL are frequent events that may contribute to the progression of breast cancer and possibly other malignancies.

CD4+ T cells display increased cross reactivity when primed with peptides of lower affinity for MHC (BA8P.165)

Abstract Studies propose the degree of T cell cross reactivity for peptide antigens is associated with similarities in the amino acid residues contacting TCR. Here we advance this concept by assessing how the stability of peptide for MHC contributes to cross reactivity in demyelinating autoimmune disease by evaluating two CNS antigens MOG35-55 (myelin oligodendrocyte glycoprotein) and NFM15-35 (neurofilament medium protein). These peptides share identical TCR contact residues yet vary at 3 MHC anchors such that MOG exhibits greater stability than NFM for I-Ab. This difference dictates encephalitogenic potential as well because MOG promotes demyelination and NFM does not. Polyclonal CD4+ T cells primed with MOG or NFM were probed for affinity and cross reactivity using MHC monomers presenting the priming peptides or the encephalitogenic peptides MOG(42P) and MOG(47A), which vary from wild type MOG at TCR contact residues. The 2D micropipette adhesion frequency assay used to assess these parameters showed that NFM and MOG expanded splenic CD4+ T cells that recognized 47A and 42P with similar frequencies and low affinities ~1.8 x10-6 μm4. Interestingly though, NFM specific cells had a greater capacity to recognize multiple peptides than MOG specific cells and this potential was unique to individual clones. Thus, peptide stability for MHC influences the degree of cross reactivity in peripheral tissues and provides a unique point of comparison for studying cross reactivity in the CNS.

Phosphorylation State Modulates the Interaction Between Neurofilament Medium and Spinophilin

In Parkinson's Disease (PD) there is both a structural and functional loss of dendritic spines on striatal medium spiny neurons (MSNs). However, the full mechanisms underlying functional and structural changes in striatal MSNs are not completely clear. Spine morphology and striatal MSN physiology are regulated by an array of structural and scaffolding proteins. Two such proteins are spinophilin, a protein phosphatase 1 and F-actin binding protein, and the intermediate filament protein, neurofilament medium (NFM). Here we show that these two proteins interact in brain tissue and when overexpressed in a heterologous cell system. Interestingly, in a preliminary proteomics screen, the interaction of spinophilin with NFM was reduced in 6-hydroxydopamine-lesioned mice, a model of PD. It is known that there is a misregulation of multiple protein kinases in many neurodegenerative diseases, including PD. Interestingly, we have found that overexpression of the catalytic subunit of protein kinase A (PKA) along with spinophilin and NFM in a heterologous cell system increases the interaction between spinophilin and NF-M. The implications of this altered association and modulation of spinophilin and NFM phosphorylation in PD will be discussed.

Neurofilament medium polypeptide (NFM) protein concentration is increased in CSF and serum samples from patients with brain injury.

Brain injury is a medical emergency that needs to be diagnosed and treated promptly. Several proteins have been studied as biomarkers of this medical condition. The aims of this study were to: 1) evaluate the selectivity and precision of a commercial ELISA kit for neurofilament medium polypeptide (NFM) protein; and 2) evaluate the concentration in cerebrospinal fluid (CSF) and serum of healthy individuals and patients with brain damage. An ELISA from Elabscience was used. The selectivity was evaluated using size-exclusion chromatography and mass spectrometry. Intra- and inter-batch coefficients of variation (CV) were also studied. Fifty-one CSF samples from 36 age-matched patients with hemorrhagic stroke (HS) (n=30), ischemic stroke (IS) (n=11) and healthy individuals (n=10) were assayed. In addition, serum samples from healthy volunteers (n=47), 68 serum samples from seven patients with HS, 106 serum samples from 12 patients with traumatic brain injury (TBI) and 68 serum samples from 68 patients with mild traumatic brain injury (mTBI) were also analyzed. NFM was identified in the chromatographic fraction with highest immunoreactivity. The intra- and inter-batch CVs were ≤10% and ≤13%, respectively. The CSF-NFM concentration in HS was significantly higher (p<0.0001) than in IS and controls. Serum NFM concentration ranged from 0.26 to 8.57 ng/mL in healthy individuals (median=2.29), from 0.97 to 42.4 ng/mL in HS (median=10.8) and from 3.48 to 45.4 ng/mL in TBI (median=14.7). Finally, 44% of patients with mTBI had increased NFM concentration, with significantly higher levels (p=0.01) in patients with polytrauma. To our knowledge this is the first study describing increased NFM levels in CSF and serum from patients with brain damage.

Sectoral variations in the distribution of axonal cytoskeleton proteins in the human optic nerve head

Axonal cytoskeleton proteins are intrinsically related to retinal ganglion cell (RGC) health and disease. This study quantifies and documents the sectoral distribution of axonal cytoskeleton proteins in the different laminar compartments of the normal human optic nerve head (ONH). Nine human eyes were used (mean age of 46.9 ± 3.7 years). Coronal sections of the prelaminar, anterior lamina cribrosa, posterior lamina cribrosa and retrolaminar regions were examined using immunohistochemical and confocal microscopy techniques. The axonal cytoskeleton was studied using antibodies to neurofilament light (NFL), neurofilament medium (NFM), neurofilament heavy (NFH), phosphorylated NFH (NFHp), microtubule associated protein-1 (MAP-1) and tubulin. Axonal cytoskeleton intensity was quantified in a standardized manner and comparisons were made within and between laminar regions. The intensity of NFM, NFH and NFHp is significantly greater in the nasal and peripheral sectors of the prelaminar, anterior lamina cribrosa and posterior lamina cribrosa regions. There is no significant difference in the distribution of NFL, tubulin and MAP-1 proteins between sectors in any laminar region. The intensity of all axonal cytoskeleton proteins in unmyelinated laminar regions is greater than the retrolaminar region. The distribution of all cytoskeleton proteins in the myelinated, retrolaminar region of the optic nerve appears to be relatively even. The distribution of axonal cytoskeleton proteins may have relevance for understanding the vulnerability of distinct ONH sectors to intraocular pressure- and ischaemia-mediated damage. The findings in this study may be important for understanding patho-physiological mechanisms involved in glaucomatous and ischaemic optic neuropathy.

Bispecificity for myelin and neuronal self-antigens is a common feature of CD4 T cells in C57BL/6 mice.

The recognition of multiple ligands by a single TCR is an intrinsic feature of T cell biology, with important consequences for physiological and pathological processes. Polyspecific T cells targeting distinct self-antigens have been identified in healthy individuals as well as in the context of autoimmunity. We have previously shown that the 2D2 TCR recognizes the myelin oligodendrocyte glycoprotein epitope (MOG)35-55 as well as an epitope within the axonal protein neurofilament medium (NF-M15-35) in H-2(b) mice. In this study, we assess whether this cross-reactivity is a common feature of the MOG35-55-specific T cell response. To this end, we analyzed the CD4 T cell response of MOG35-55-immunized C57BL/6 mice for cross-reactivity with NF-M15-35. Using Ag recall responses, we established that an important proportion of MOG35-55-specific CD4 T cells also responded to NF-M15-35 in all mice tested. To study the clonality of this response, we analyzed 22 MOG35-55-specific T cell hybridomas expressing distinct TCR. Seven hybridomas were found to cross-react with NF-M15-35. Using an alanine scan of NF-M18-30 and an in silico predictive model, we dissected the molecular basis of cross-reactivity between MOG35-55 and NF-M15-35. We established that NF-M F24, R26, and V27 proved important TCR contacts. Strikingly, the identified TCR contacts are conserved within MOG38-50. Our data indicate that due to linear sequence homology, part of the MOG35-55-specific T cell repertoire of all C57BL/6 mice also recognizes NF-M15-35, with potential implications for CNS autoimmunity.

P.6.c.013 Adolescent mice are more vulnerable than adults to the rewarding effects of ecstasy

In our previous study in rats acutely exposed to As, we observed an effect of As on neurofilaments in the sciatic nerve. This study deals with the effects of inorganic As in Wistar rats on the cytoskeletal protein composition of the sciatic nerve after subchronic intoxication. Sodium meta-arsenite (NaAsO2) dissolved in phosphate-buffered saline (PBS) was administered daily in doses of 0, 3 and 10 mg/kg body weight/day (n = 9 rats/group) by intragastric route for 4, 8 and 12 week periods. Toxicokinetic measurements revealed a saturation of blood As in the 3- and 10-mg/kg dose groups at approximately 14 μg/ml, with an increase in renal clearance of As at increasing doses. After exsanguination, sciatic nerves were excised and the protein composition was analyzed. Analysis of the sciatic nerves showed compositional changes in their proteins. Protein expression of neurofilament Medium (NF-M) and High (NF-H) was unchanged. Neurofilament protein Low (NF-L) expression was reduced, while μ- and m-calpain protein expression was increased, both in a dose/time pattern. Furthermore, NF-H protein was hypophosphorylated, while NF-L and microtubule-associated protein tau (MAP-tau) proteins were (hyper)-phosphorylated. In conclusion, we show that expression of μ- and m-calpain protein is increased by exposure to As, possibly leading to increased NF-L degradation. In addition, hyperphosphorylation of NF-L and MAP-tau by As also contribute to destabilization and disruption of the cytoskeletal framework, which eventually may lead to axonal degeneration.

Extracellular matrix (ECM) and cell adhesion molecules (CAMs) gene expression in brain GD-10, hippocampal cell (mHT-22 Cell Line), human glioblastoma-astrocytoma (hLN-405), and rat glioma cell (rF98) using real time PCR.

The aim of this study is to compare ECM and CAMs gene expression in hippocampal cell, glioblastoma-astrocytoma and glioma cell using real time PCR at gestation day of 10 (GD-10) Result of real time PCR showed that expression level of extracelluler matrix of vimentin was higher than the expression of fibronectin, Neural cell Adhesion molecule (Ncam), neurofilament high (Nfh), neurofilament medium (NFm), neurofilament low (Nfl) and tenascin. The expression of vimentin in the brain also shows the highest when compare to the expression in the human glioblastoma-astrocytoma (hLN-405), rat glioma cell (rF98) and mouse hippocampal cell line (mHT-22). The number of vimentin gene copy was 538.554, whereas in the culture of hLN-405 was 2.246.309, in culture of rF98 was 974.368 and mHT-22 was 1.542.529. These findings suggested that vimentin most dominant expressed compare to the another gen. Expression of vimentin was gradually lower from astrocyte cell (hLN-405 or human glioblastoma-astrocytoma), then in hippocampus cell, glioma cell and embryonic brain cell. ________________________________________GRAPHICAL ABSTRACT

Plasma profiling reveals three proteins associated to amyotrophic lateral sclerosis.

ObjectiveAmyotrophic lateral sclerosis (ALS) is the most common adult motor neuron disease leading to muscular paralysis and death within 3–5 years from onset. Currently, there are no reliable and sensitive markers able to substantially shorten the diagnosis delay. The objective of the study was to analyze a large number of proteins in plasma from patients with various clinical phenotypes of ALS in search for novel proteins or protein profiles that could serve as potential indicators of disease.MethodsAffinity proteomics in the form of antibody suspension bead arrays were applied to profile plasma samples from 367 ALS patients and 101 controls. The plasma protein content was directly labeled and protein profiles obtained using 352 antibodies from the Human Protein Atlas targeting 278 proteins. A focused bead array was then built to further profile eight selected protein targets in all available samples.ResultsDisease-associated significant differences were observed and replicated for profiles from antibodies targeting the proteins: neurofilament medium polypeptide (NEFM), solute carrier family 25 (SLC25A20), and regulator of G-protein signaling 18 (RGS18).InterpretationUpon further validation in several independent cohorts with inclusion of a broad range of other neurological disorders as controls, the alterations of these three protein profiles in plasma could potentially provide new molecular markers of disease that contribute to the quest of understanding ALS pathology.

Damage to enteric neurons occurs in mice that develop fatty liver disease but not diabetes in response to a high-fat diet.

Disorders of gastrointestinal functions that are controlled by enteric neurons commonly accompany fatty liver disease. Established fatty liver disease is associated with diabetes, which itself induces enteric neuron damage. Here, we investigate the relationship between fatty liver disease and enteric neuropathy, in animals fed a high-fat, high-cholesterol diet in the absence of diabetes. Mice were fed a high-fat, high-cholesterol diet (21% fat, 2% cholesterol) or normal chow for 33weeks. Liver injury was assessed by hematoxylin and eosin, picrosirius red staining, and measurement of plasma alanine aminotransaminase (ALT). Quantitative immunohistochemistry was performed for different types of enteric neurons. The mice developed steatosis, steatohepatitis, fibrosis, and a 10-fold increase in plasma ALT, indicative of liver disease. Oral glucose tolerance was unchanged. Loss and damage to enteric neurons occurred in the myenteric plexus of ileum, cecum, and colon. Total numbers of neurons were reduced by 15-30% and neurons expressing nitric oxide synthase were reduced by 20-40%. The RNA regulating protein, Hu, became more concentrated in the nuclei of enteric neurons after high-fat feeding, which is an indication of stress on the enteric nervous system. There was also disruption of the neuronal cytoskeletal protein, neurofilament medium. Enteric neuron loss and damage occurs in animals with fatty liver disease in the absence of glucose intolerance. The enteric neuron damage may contribute to the gastrointestinal complications of fatty liver disease.

The affinity of MOG specific CD4 + T cells does not predict cross-recognition to NFM in demyelinating autoimmune disease (BA2P.127)

Abstract TCRs can recognize and cross-react to multiple antigens, but little is known of how cross-reactivity might contribute to the etiology of demyelinating autoimmune disease. Here we extend the analysis of monoclonal 2D2 TCR cross-reactivity for MOG38-49 (myelin oligodendrocyte glycoprotein) and NFM18-30 (neurofilament medium protein) to polyclonal T cells. Utilization of the 2D micropipette adhesion frequency assay allows definition of antigen specificity and affinity of individual T cells for peptide:MHC ex vivo. We show that the frequency of CD4+ T cells from the CNS recognizing MOG, NFM, or both fluctuate during the course of MOG35-55 induced experimental autoimmune encephalomyelitis. Higher affinity T cells are maintained as a rare population within the repertoire yet the frequency of higher affinity, MOG specific T cells increase to a greater extent than NFM specific T cells during disease and MOG specific T cells exhibit higher affinities (10-4 to 10-3) than NFM specific T cells (&amp;lt;10-4). Importantly, cross-recognition is not limited to higher or lower affinity clones. We have cloned an encephalitogenic T cell that is high affinity for MOG and low affinity for NFM, which contrasts the 2D2 TCR exhibiting a medium affinity for NFM and a very low MOG affinity. On a population level, TCR recognition of one or more CNS antigens is dynamic within the chronic autoimmune repertoire warranting future research to understand their individual contributions to disease.

Elevated levels of autoantibodies targeting the M1 muscarinic acetylcholine receptor and neurofilament medium in sera from subgroups of patients with schizophrenia

Schizophrenia is a severe debilitating brain disorder with a poorly understood aetiology. Among the diverse aetiological clues lies evidence for immune abnormalities in some individuals. The aim of this study was to investigate the frequency and specificity of autoantibodies directed against the brain in people with schizophrenia. Sera were screened for reactivity against human brain tissue (hippocampus and prefrontal cortex). Neuronal cell body and filamentous patterns of brain tissue staining were observed significantly more frequently in sera from schizophrenia patients (n=30) compared to controls (n=24). Sera that showed a neuronal cell body pattern of staining on hippocampus reacted strongly to an extracellular epitope of the M1 muscarinic acetylcholine receptor (m1AChR) in ELISA. Both cell body staining and elevated m1AChR reactivity correlated with higher symptom scores for poverty of speech. Sera showing a filamentous staining pattern predominantly targeted microfilaments, intermediate filaments or neurofilaments, particularly neurofilament medium (NFM), which is a dopamine receptor interacting protein. By ELISA, there was strongly elevated reactivity against NFM in a subset (15%) of schizophrenia patients (n=101) compared to healthy controls (n=55) or patients with multiple sclerosis (n=32). These results support the hypothesis that neurotransmitter receptors or molecules involved in regulation of neurotransmission are targets of autoantibodies in some people with schizophrenia.

Diazoxon Disrupts the Expression and Distribution of βIII‐Tubulin and MAP 1B in Differentiating N2a Cells

This study aimed at assessing the effects of diazoxon (DZO), a major metabolite of the insecticide diazinon (DZ), on key cytoskeletal proteins in differentiating N2a neuroblastoma cells. Initial experiments established that sublethal concentrations of 1, 5 and 10 μM DZO produced profound inhibition of neurite outgrowth. Densitometric scanning of probed immunoblots of N2a cell lysates demonstrated that DZO had no effect on total β-tubulin levels. However, probing with a monoclonal antibody that recognised specifically the βIII-tubulin isotype revealed that 10 μM DZO induced a significant reduction in the levels of this particular form. Levels of polyglutamylated tubulin were not altered. Exposure to 10 μM DZO also decreased the expression of microtubule-associated protein 1B (MAP 1B). However, DZO had no effect on the expression of MAP tau. DZO also failed to affect the levels neurofilament light (NFL) and neurofilament medium (NFM) chain levels. Indirect immunofluorescence demonstrated that the staining of neurites in treated cells was weaker than in the controls for βIII-tubulin. In conclusion, DZO disrupts the microtubule (MT) network affecting the expression and distribution of two specific MT proteins known to be important in neuritogenesis. DZO may contribute to the developmental neurotoxicity seen following exposure to DZ.

Neurofilaments are the major neuronal target of hydroxynonenal-mediated protein cross-links

Lipid peroxidation generates reactive aldehydes, most notably hydroxynonenal (HNE), which covalently binds amino acid residue side chains leading to protein inactivation and insolubility. Specific adducts of lipid peroxidation have been demonstrated to be intimately associated with pathological lesions of Alzheimer's disease (AD), suggesting that oxidative stress is a major component in the disease. Here, we examined the HNE-cross-linking modifications by using an antibody specific for a lysine–lysine cross-link. Since in a prior study we noted no immunolabeling of neuritic plaques or neurofibrillary tangles but instead found strong labeling of axons, we focused this study on axons. Axonal labeling was examined in mouse sciatic nerve, and immunoblotting showed the cross-link was restricted to neurofilament heavy and medium subunits, which while altering migration, did not indicate larger NF aggregates, indicative of intermolecular cross-links. Examination of mice at various ages showed the extent of modification remaining relatively constant through the life span. These findings demonstrate lipid-cross-linking peroxidation primarily involves lysine-rich neurofilaments and is restricted to intramolecular cross-links.