Anti-human Olig2 antibody as a useful immunohistochemical marker of normal oligodendrocytes and gliomas

Primary diffuse leptomeningeal gliomatosis in 2 dogs

Clinical, neuroimaging, and neuropathological findings of 2 cases of canine primary diffuse leptomeningeal gliomatosis are described. Magnetic resonance imaging and histopathological examination of the brain revealed diffuse leptomeningeal alterations with no parenchymal involvement. These cases share many similarities with the same disease in humans.

Extraventricular neurocytoma in pediatric populations: A case report and review of the literature

Extraventricular neurocytomas (EVNs) are rare neuronal tumors included in the definition of neoplasms in the 2007 World Health Organization classification of tumors of the central nervous system. Although a small case series of EVNs in adults has been previously reported, EVNs in pediatric populations are extremely rare. The current case report presents the clinicopathological features of an EVN in a 2-year-old female who presented with nausea and vomiting that had lasted for five days. In addition, an analysis of the imaging features, histology, treatment and prognosis of these reported rare lesions is presented. Immunohistochemically, EVNs are characterized by the robust expression of synaptophysin, but with a lack of oligodendrocyte transcription factor 2, isocitrate dehydrogenase enzyme isoform 1 (IDH1) R132/IDH2 R172 mutations and p53 immunoexpression. The treatment for EVNs in pediatric and adult populations is gross total resection, with post-operative radiation reserved for subtotal resection or recurrent disease. In addition, drop metastasis must be carefully avoided.

A case of oligodendroglioma with prominent neuronal differentiation

We report a case of oligodendroglioma showing marked neuronal differentiation, which arose in the right frontal lobe of a 46-year-old woman. The resected tumor was composed of a mixture of oligodendroglioma, gangliocytoma, and neurocytoma areas with predominance of gangliocytoma-like areas. The oligodendroglioma areas showed immunoreactivity for Olig2 and mutant isocitrate dehydrogenase 1 protein, whereas the gangliocytoma and neurocytoma areas were positive for synaptophysin and NeuN. Ki-67 labeling index was approximately 5% to 10% in the oligodendroglioma areas. Molecular cytogenetic analyses demonstrated chromosomal losses of 1p and 19q and a mutation of isocitrate dehydrogenase 1 (G395A, R132H) in both the oligodendroglioma and gangliocytoma areas. These data suggest that this tumor is an oligodendroglioma associated with prominent neuronal differentiation. There seems to be a close relationship between oligodendroglial progenitor cells and neuronal cells.

Coexpression of glial and neuronal markers in the neurocytic rosettes of rosette-forming glioneuronal tumors

Rosette-forming glioneuronal tumor of the fourth ventricle (RGNT) is a new entity in the WHO 2007 Classification of Tumors of the Central Nervous System. RGNT has two components: neurocytic rosettes and low-grade gliomas. Neurocytic rosettes are conventionally described as consisting of uniform neurocytes. However, some studies have reported rosette-forming tumor cells that expressed glial markers such as Olig2. We indicated the expression of glial markers including Olig2, cyclinD1, glial fibrillary acidic protein (GFAP), and platelet-derived growth factor receptor alpha (PDGFRα) in the neurocytic rosettes in our previous study, and we suggested that these tumor cells had a heterogeneous nature. In this study, we used double and triple immunostaining to demonstrate that these tumor cells have both glial and neuronal characteristics. We found that rosette-forming tumor cells coexpressed Olig2/cyclinD1 and synaptophysin. Furthermore, the cores of the rosettes coexpressed GFAP/PDGFRα in the peripheral zone and synaptophysin in the central zone. These findings imply that rosette-forming tumor cells have a similar nature to neuronal-glial progenitor cells, and we believe that the nomination "neurocytic rosette" may be unsuitable given their heterogeneous nature. Our study appears to clarify some of the properties of RGNT tumor cells and may help elucidate the histogenesis of RGNT.

Identification and quantification of oligodendrocyte precursor cells in multiple system atrophy, progressive supranuclear palsy and Parkinson's disease

Multiple system atrophy is a neurodegenerative disorder characterized pathologically by abnormal accumulations of α-synuclein in the cytoplasm of oligodendrocytes, which are termed glial cytoplasmic inclusions (GCIs). Oligodendrocytes are responsible for myelinating axons and providing neurotrophic support, but in MSA, myelin loss, axonal loss and gliosis are consistent features suggesting that GCIs play a central role in disease pathogenesis. Oligodendroglial, myelin and axonal degeneration are also features of multiple sclerosis (MS) in which recent studies have highlighted the robust remyelination capacity of the central nervous system (CNS). The cells responsible for remyelination are called oligodendroglial precursor cells (OPCs). In this study, we investigated the role of OPCs in the pathogenesis of MSA and progressive supranuclear palsy (PSP), a neurodegenerative disease in which neuropathological changes include oligodendroglial inclusions composed of microtubule-associated protein tau. Despite the lability of OPC-specific antigens, we successfully identified OPCs and demonstrated that tau and α-synuclein do not accumulate in OPCs. We also showed that the density of OPCs was increased in a white matter region of the MSA brain, which is also severely affected by GCIs and myelin degeneration. These findings raise the possibility that OPCs could be available to repair disease-associated damage in MSA, consistent with their biological function.

GFAP-positive neoplastic astrocytes in spontaneous oligodendrogliomas and mixed gliomas of rats

It is generally said that neoplastic cells are immunohistochemically negative for glial fibrillary acidic protein (GFAP) in rat spontaneous astrocytomas, and there are no reports describing the existence of GFAP-positive neoplastic astrocytes in rat spontaneous oligodendrogliomas and mixed gliomas which contain neoplastic astrocytes. In the present study, to clarify whether GFAP-positive neoplastic astrocytes exist in rat spontaneous oligodendrogliomas and mixed gliomas or not, immunohistochemical examination was performed on spontaneous oligodendrogliomas (26 cases) and mixed gliomas (5 cases) collected from the carcinogenicity studies and short-term toxicity studies. The neoplastic cells that constitute oligodendrogliomas and mixed gliomas were morphologically classified into five types: round A, round B, round C, spindle, and bizarre. The cells of round A, B, and C types were thought to be neoplastic oligodendrocytes because of their positive immunostainability for Olig2.  The origin of bizarre cells was obscure because they were negative for Olig2, GFAP, and nestin. The spindle cells were considered to be neoplastic astrocytes, because some of them were positive for GFAP or nestin, and GFAP-positive spindle cells could be morphologically distinguished from reactive astrocytes.  In conclusion, the present study clarified for the first time that GFAP-positive neoplastic astrocytes exist in rat spontaneous gliomas.

A case of unclassified high-grade glioma with polar spongioblastoma pattern

Primitive polar spongioblastoma was first described by Russell and Cairns in 1947. However, the polar spongioblastoma pattern is often seen in many neuroepithelial tumors, and this category was deleted in the previous World Health Organization (WHO) classification. In 2010, Nagaishi et al. reported on a case involving a neuroepithelial tumor with the typical histological pattern of polar spongioblastoma and suggested that this tumor might not be suited to any of the neuroepithelial tumors in the current WHO classification. We report on an autopsy case involving an unclassified high-grade glioma with polar spongioblastoma pattern that was very similar to the case described by Nagaishi et al. A 44-year-old man who presented with a headache exhibited a tumor of the right frontal lobe on MRI. Histological diagnosis of the tumor obtained by gross total resection was high-grade glioma, which was composed of the parallel palisading of spindle tumor cells expressing GFAP, without microvascular proliferation (MVP) and necrosis. Conventional chemoradiotherapy was performed, but the case was complicated by cerebrospinal fluid (CSF) dissemination that resulted in multiple extraneural metastases through systemic diversionary CSF shunting. Finally, the patient died approximately 13 months after the initial treatment. Both the cerebral and Douglas pouch tumors that were obtained at autopsy were diagnosed as typical glioblastomas, and they were composed of the proliferation of atypical astrocytes with MVP and pseudopalisading necrosis without the formation of rhythmic palisading. Although the histological findings were different from that of the first operation, immunohistochemical and genetic profiles demonstrated almost the same results. This tumor was not classified as a typical glioblastoma by the initial findings, but it had the nature of a glioblastoma. These findings suggest that the tumor might be classified as a new subset of glioblastoma called glioblastoma with polar spongioblastoma pattern.

Anaplastic oligodendroglioma with ganglioglioma-like maturation

Neuronal differentiation of oligodendroglioma has been demonstrated by immunohistochemical and ultrastructural examinations in recent studies. However, oligodendrogliomas displaying a complete neurocytic morphology or even gangliocytic differentiation are rare. We describe a case of anaplastic oligodendroglioma that was characterized by the presence of ganglion cells in a 40-year-old-male. Histologically, the tumor was mainly composed of classical oligodendroglioma cells. The most exceptional finding of this tumor was the presence of ganglion cells and intermediate-sized ganglioid cells. Immunohistochemical analysis revealed that these cells were positive for Olig2 and negative for glial fibrillary acid protein (GFAP). Synaptophysin and microtubule-associated protein 2 (MAP2) were mainly detected in the ganglion cells. Fluorescence in situ hybridization analysis (FISH) revealed the deletion of the 1p and 19q chromosome arms in both the oligodendroglioma cells and ganglion cells. The R132H mutated isocitrate dehydrogenase 1 (IDH1) protein was detected by immunohistochemistry and direct DNA sequencing. The morphological, immunohistochemical, and genetic features of the tumor suggested a diagnosis of anaplastic oligodendroglioma, and this tumor was considered to be a rare form of oligodendroglioma displaying ganglioglioma-like maturation. FISH and mutant IDH1 examinations are useful diagnostic tools for the differential diagnosis of this tumor, i.e., ganglioglioma with anaplastic oligodendroglial features.

NG2 expression in glioblastoma identifies an actively proliferating population with an aggressive molecular signature

Glioblastoma multiforme (GBM) is the most common type of primary brain tumor and a highly malignant and heterogeneous cancer. Current conventional therapies fail to eradicate or curb GBM cell growth. Hence, exploring the cellular and molecular basis of GBM cell growth is vital to develop novel therapeutic approaches. Neuroglia (NG)-2 is a transmembrane proteoglycan expressed by NG2+ progenitors and is strongly linked to cell proliferation in the normal brain. By using NG2 as a biomarker we identify a GBM cell population (GBM NG2+ cells) with robust proliferative, clonogenic, and tumorigenic capacity. We show that a significant proportion (mean 83%) of cells proliferating in the tumor mass express NG2 and that over 50% of GBM NG2+ cells are proliferating. Compared with the GBM NG2- cells from the same tumor, the GBM of NG2+ cells overexpress genes associated with aggressive tumorigenicity, including overexpression of Mitosis and Cell Cycling Module genes (e.g., MELK, CDC, MCM, E2F), which have been previously shown to correlate with poor survival in GBM. We also show that the coexpression pattern of NG2 with other glial progenitor markers in GBM does not recapitulate that described in the normal brain. The expression of NG2 by such an aggressive and actively cycling GBM population combined with its location on the cell surface identifies this cell population as a potential therapeutic target in a subset of patients with GBM.

Clinico-pathological feature of pilomyxoid astrocytomas: three case reports

Pilomyxoid astrocytoma (PMA) is a newly identified variant of pilocytic astrocytoma (PA). We report three cases of PMA with comparison to seven cases of PA in terms of their clinicopathological features. The three cases occurred at the ages of 2, 36 and 6 years, and their tumors were located in the left basal ganglia, the pineal gland, and the cerebellum, respectively. They were diagnosed PMA by surgical specimens that showed a characteristic monomorphous architecture with an angiocentric growth pattern and myxoid background. One patient developed localized relapse at 6 months after the surgery, but the other patients remained alive without tumor progression more than 5 years after treatment. In analysis of the immunohistochemical association in PMA and PA, no specific staining was found to be useful for differential diagnosis of PMA from PA. The expression of biomarkers including O-6-methylguanine-DNA methyltransferase, p53, MIB-1, and EGF receptor neither distinguished PMA from PA nor correlated with outcome. But almost all PMA and PA that demonstrated prominent positivity for nestin showed a high MIB-1 labelling index (LI), and four of these five patients suffered a relapse in the early phase. These results suggest that immunohistochemical expression of nestin and MIB-1 LI may correlate with the aggressiveness of the tumor in PA and PMA.

Utility of in situ demonstration of 1p loss and p53 overexpression in pathologic diagnosis of oligodendroglial tumors

To improve the diagnostic accuracy of oligodendroglial tumors and to find more convenient parameters that could predict the cytogenetic status, oligodendroglial and astrocytic tumors were cytogenetically and immunohistochemically investigated. Materials included 22 oligodendroglial tumors (15 oligodendrogliomas and 7 oligoastrocytomas) and 20 astrocytic tumors. 1p loss was examined with the fluorescence in situ hybridization (FISH) method. Expression of GFAP, Olig2 and p53 was immunohistochemically investigated and co-localization of GFAP and Olig2 was evaluated on double-immunostained sections. Furthermore, TP53 mutation analyses were carried out on three oligodendroglial tumors showing p53 protein overexpression with a direct sequence analysis. Our FISH studies demonstrated 1p loss in 73% of oligodendroglial tumors (80% oligodendrogliomas and 57% oligoastrocytomas) and in only 10% of astrocytic tumors. There were no clear-cut morphologic differences between 1p-deleted and 1p-intact oligodendroglial tumors. GFAP and Olig2 were expressed in most oligodendroglial and astrocytic tumors, and their cellular localization was almost independent of each other. Overexpression of p53 was observed in five oligodendroglial tumors, all of which were 1p-intact. In comparison, 16 oligodendroglial tumors with 1p deletion showed no overexpression of p53. TP53 missense mutations were detected in three of the p53 overexpressed oligodendroglial tumors studied. Our results suggest that 1p loss is almost specific to oligodendroglial tumors. Although the prediction of 1p status based solely on the morphologic features seems to be difficult, the immunohistochemistry for p53 is a useful tool in that p53 overexpression is closely related to the 1p-intact status in oligodendroglial tumors.

Olig2 is useful in the differential diagnosis of oligodendrogliomas and extraventricular neurocytomas

A 42-year-old woman had suffered from headaches since April 2009. Computed tomography revealed a tumor with marked calcification in the left frontal lobe adjacent to the left anterior horn of the lateral ventricle. T1-weighted gadolinium-enhanced magnetic resonance imaging showed a well-enhanced tumor at the lesion. Dynamic methionine positron emission tomography showed no delayed methionine attenuation. Initial preoperative diagnosis was extraventricular neurocytoma (EVN). However, oligodendroglioma was determined upon a second diagnosis. The patient underwent total tumor removal. Hematoxylin and eosin staining showed the characteristic fried egg-like cells, round nuclei, and immunohistochemically, the tumor cells were positive for glial fibrillary acidic protein, synaptophysin, neuronal nuclear antigen, microtubule-associated protein 2 and Olig2. The MIB-1 labeling index was 20%, which suggested malignancy. Although these findings demonstrated that the tumor had glioneuronal character, it was difficult to differentiate between EVN and oligodendroglioma. There have been reports that Olig2 immunohistochemistry is generally positive in cases of oligodendroglioma, but not in cases of neurocytoma. We completed the diagnosis as oligodendroglioma. Subsequent electron microscopy results presented oligodendroglial but not neuronal characteristics. We concluded that Olig2 is useful in the differential diagnosis of oligodendrogliomas and EVNs.

Quantification of oligodendrocyte progenitor cells in human and cat optic nerve: implications for endogenous repair in multiple sclerosis

In multiple sclerosis (MS), one strategy to reduce disability is enhancement of endogenous repair by remyelinating oligodendrocytes derived from oligodendrocyte progenitor cells (OP). An important prerequisite is determining the abundance of OP relative to oligodendrocytes in normal human central nervous system (CNS), which, in turn, requires reliable OP identification. To achieve this, cat and human optic nerves (ON) were subjected to varied preparation protocols, and the resultant neuroglial staining profiles correlated to generate an antigenic phenotype for OP applicable to human autopsy specimens. OP, interchangeably called NG2cells due to universal NG2 expression, were shown to comprise a separate class of neuroglial cells, related to oligodendrocytes by expression of the oligodendrocyte lineage transcription factors, Olig1 and Olig2. Despite their morphological complexity, including contact with axons and other neuroglia, NG2cells all appear capable of responding as OP to counter local oligodendrocyte loss. However, quantification revealed that NG2cells comprised less than 5% of the neuroglia and had a ratio to oligodendrocytes of about 1:10, not only in human and cat ON but also in white and gray-matter regions of cat spinal cord. The finding that NG2cells are not abundant, particularly relative to oligodendrocytes, may have implications for efforts to enhance endogenous repair in MS.

Neuronal differentiation distinguishes supratentorial and infratentorial childhood ependymomas

Ependymomas are glial neoplasms occurring in any location throughout the central nervous system and supposedly are derived from radial glia cells. Recent data suggest that these tumors may have different biological and clinical behaviors according to their location. Pediatric supratentorial and infratentorial ependymoma (SE and IE) were compared with respect to clinical and radiological parameters and immunohistochemistry (IHC). Neuronal markers were specifically assessed by IHC and quantitative PCR (qPCR). No single morphological or radiological characteristic was associated with location or any neuronal marker. However, there was a significant overexpression of neuronal markers in SE compared with IE: neurofilament light polypeptide 70 (NEFL)-positive tumor cells were found in 23 of 34 SE and in only 4 of 32 IE (P < .001). Among SE, 10 of 34 exhibited high expression of NEFL, defined as more than 5% positive cells. qPCR confirmed the upregulation of neuronal markers (NEFL, LHX2, FOXG1, TLX1, and NPTXR) in SE compared with IE. In addition, strong NEFL expression in SE was correlated with better progression-free survival (P = .007). Our results support the distinction of SE and IE. SEs are characterized by neuronal differentiation, which seems to be associated with better prognosis.

Differential distribution of erbB receptors in human glioblastoma multiforme: expression of erbB3 in CD133-positive putative cancer stem cells

Glioblastomas are the most common primary central nervous system tumors in adults, and they remain resistant to current treatments. erbB1 signaling is frequently altered in glioblastomas, suggesting thaterbB receptor family members may represent targets for molecular therapy. We performed a comprehensive analysis of erbB receptor and ligand expression profiles in a panel of 9 glioblastomas andcompared them to nonneoplastic cerebral tissue containing neocortex and adjacent white matter. Quantitative reverse transcription-polymerase chain reaction and Western blot analysis showed that erbB1signaling and erbB2 receptors exhibited highly variable deregulation profiles in the tumors, with patterns ranging from underexpression to overexpression; in contrast, erbB3 and erbB4 were downregulated. We next performed immunohistochemistry to determinethe distribution patterns of erbB receptors among the main neuralcell types in the tumors with special reference to the putative tumor stem cell population. Results revealed intertumoral and intratumoral heterogeneity in all 4 erbB expression profiles, but each receptor exhibited a distinct distribution pattern among glial fibrillary acidic protein-, Olig2-, NeuN-, and CD133-positive populations. Although erbB1 immunoreactivity was detected in only small subsets of CD133-positive putative tumor stem cells, erbB3 immunoreactivity was prominent in this population, suggesting that erbB3 may represent a new potential therapeutic target.

Polar spongioblastoma: A high-grade glioma that does not contain the IDH1 mutation or 1p/19q LOH

We report a case of an unusual glioma termed "primitive polar spongioblastoma" that displayed characteristic palisading tumor cells at the light microscopic level. The patient was a 52-year-old woman who underwent subtotal removal for a left frontotemporal tumor. The palisading pattern was present throughout the tumor. Several glial markers were revealed by immunohistochemical examination, but no neuronal markers were observed. Genetic studies showed O-6-methylguanine-DNA methyltransferase (MGMT) methylation, wild type IDH1, and the absence of 1p/19q loss of heterozygosity (LOH) in the tumor genes. Based on histological and genetic features, this tumor might not be suited to any of neuroepithelial tumor in the recent WHO classification. We consider that cases such as this should be temporarily set under a separate heading and be entrusted to future investigation after more cases have been accumulated.

Rosette-forming glioneuronal tumor: report of an unusual case with intraventricular dissemination

A rosette-forming glioneuronal tumor (RGNT) was encountered in a 16-year-old Chinese girl. She experienced seizures with loss of consciousness for 1 month prior to diagnosis. A brain MRI revealed multifocal masses occupying all of the ventricular system associated with marked hydrocephalus. A biopsy was performed on the right lateral ventricle using a neuroendoscope and the patient was given postoperative radiotherapy. She was followed for 7 months, and there was no radiological or clinical evidence of tumor progression. Histological examination demonstrated two regions characterized by predominant neurocytic rosettes and scant low grade astrocytoma. No histological anaplasia was present. Immunohistological studies showed that the small round tumor cells forming rosettes were strongly positive for Olig2. A chromosome 1p/19q co-deletion was not detected by FISH analysis. While the pathological features of our case closely resembled those reported in the original description, the diffuse intraventricular growth pattern of the tumor was different from previous examples. Further long-term follow-up studies are required to assess the biological behavior and clinical outcome of the RGNT entity.

NG2+/Olig2+ cells are the major cycle-related cell population of the adult human normal brain

A persistent cycling cell population in the normal adult human brain is well established. Neural stem cells or neural progenitors have been identified in the subventricular zone and the dentate gyrus subgranular layer (SGL), two areas of persistent neurogenesis. Cycling cells in other human normal brain areas, however, remains to be established. Here, we determined the distribution and identity of these cells in the cortex, the white matter and the hippocampal formation of adult patients with and without chronic temporal lobe epilepsy using immunohistochemistry for the cell cycle markers Ki-67 (Mib-1) and minichromosome maintenance protein 2. Rare proliferative neuronal precursors expressing the neuronal antigen neuronal nuclei were restricted to the SGL. In contrast, the oligodendrocyte progenitor cell markers Olig2 and the surface antigen NG2 were expressed by the vast majority of cycling cells scattered throughout the cortex and white matter of both control and epileptic patients. Most of these cycling cells were in early G1 phase, and were significantly more numerous in epileptic than in non-epileptic patients. These results provide evidence for a persistent gliogenesis in the human cortex and white matter that is enhanced in an epileptic environment.

Quantitative analysis of mitotic Olig2 cells in adult human brain and gliomas: implications for glioma histogenesis and biology

The capacity of adult human glial progenitor cells (AGPs), to proliferate and undergo multipotent differentiation, positions them as ideal candidate cells of origin for human gliomas. To investigate this potential role we identified AGPs as mitotically active Olig2 cells in nonneoplastic adult human brain and gliomas. We conservatively estimated that one in 5,000 human temporal lobe neocortical gray or subcortical white matter cells is mitotic. Extrapolating from a mean Olig2/Mib-1 labeling index (LI) of 52% and total cell number of 100 billion, we estimated the overall prevalence of mitotic Olig2 AGPs in nonneoplastic human brain parenchyma at 10 million. These data identify a large reservoir of Olig2 AGPs which could be potential targets for human gliomagenesis. The vast majority of mitotic cells in Grade II and Grade III gliomas of all histologic subtypes expressed Olig2 (mean LI 75%) but rarely S100B (LI 0.6%), identifying the Olig2 cell as a distinct contributor to the proliferating cell population of human gliomas of both oligodendroglial and astrocytic lineages. In the most malignant Grade IV glioma, or glioblastoma multiforme (GBM), the prevalence of Olig2/Mib-1 cells was significantly decreased (24.5%). The significantly lower Olig2/Mib-1 LI in GBMs suggests that a decrease in the prevalence of Olig2 cells to the total mitotic cell pool accompanies increasing malignancy. The novel framework provided by this quantitative and comparative analysis supports future studies to examine the histogenetic role of Olig2 AGPs in adult gliomas, their potential contribution to the tumor stroma and the molecular role of Olig2 in glioma pathogenesis.

Extraneural metastases of anaplastic oligodendroglial tumors

Extraneural metastases of malignant gliomas are rare. According to the literature, they tend to appear in glioblastoma patients, but are exceptionally rare in anaplastic oligodendroglioma. We report on an anaplastic oligodendroglioma and an anaplastic oligoastrocytoma that metastasized to cervical lymph nodes and bones. Both patients were women aged 54 and 30 years, and the metastases appeared following craniotomy. In the first patient, metastases to cervical lymph nodes developed one year after surgery, and, despite adjuvant therapy, recurred in the same location several times. Fine needle aspiration biopsy (FNAB) of the cervical lymph node prior to neck dissection suggested a possible metastatic primitive neuroepithelial tumor. In the second case, metastases to the sacrum and femur developed after surgery for a recurrent anaplastic oligoastrocytoma. Our two cases reconfirm a rare but definite ability not only of glioblastoma but also of anaplastic oligodendroglioma, namely to metastasize to extraneural sites. It is important to bear this in mind, particularly in cases when the history of primary brain tumor is unavailable. In such instances, the correct diagnosis of the metastatic lesion may be extremely difficult if not impossible.

Selective adenosine A2a receptor antagonism reduces JNK activation in oligodendrocytes after cerebral ischaemia

Adenosine is a potent biological mediator, the concentration of which increases dramatically following brain ischaemia. During ischaemia, adenosine is in a concentration range (muM) that stimulates all four adenosine receptor subtypes (A(1), A(2A), A(2B) and A(3)). In recent years, evidence has indicated that the A(2A) receptor subtype is of critical importance in stroke. We have previously shown that 24 h after medial cerebral artery occlusion (MCAo), A(2A) receptors up-regulate on neurons and microglia of ischaemic striatum and cortex and that subchronically administered adenosine A(2A) receptor antagonists protect against brain damage and neurological deficit and reduce activation of p38 mitogen-activated protein kinase (MAPK) in microglial cells. The mechanisms by which A(2A) receptors are noxious during ischaemia still remain elusive. The objective of the present study was to investigate whether the adenosine A(2A) antagonist SCH58261 affects JNK and MEK1/ERK MAPK activation. A further aim was to investigate cell types expressing activated JNK and MEK1/ERK MAPK after ischaemia. We hereby report that the selective adenosine A(2A) receptor antagonist, SCH58261, administered subchronically (0.01 mg/kg i.p) 5 min, 6 and 20 h after MCAo in male Wistar rats, reduced JNK MAPK activation (immunoblot analysis: phospho-JNK54 isoform by 81% and phospho-JNK46 isoform by 60%) in the ischaemic striatum. Twenty-four hours after MCAo, the Olig2 transcription factor of oligodendroglial progenitor cells and mature oligodendrocytes was highly expressed in cell bodies in the ischaemic striatum. Immunofluorescence staining showed that JNK MAPK is maximally expressed in Olig2-stained oligodendrocytes and in a few NeuN stained neurons. Striatal cell fractioning into nuclear and extra-nuclear fractions demonstrated the presence of Olig2 transcription factor and JNK MAPK in both fractions. The A(2A) antagonist reduced striatal Olig 2 transcription factor (immunoblot analysis: by 55%) and prevented myelin disorganization, assessed by myelin-associated glycoprotein staining. Twenty-four hours after MCAo, ERK1/2 MAPK was highly activated in the ischaemic striatum, mostly in microglia, while it was reduced in the ischaemic cortex. The A(2A) antagonist did not affect activation of the ERK1/2 pathway. The efficacy of A(2A) receptor antagonism in reducing activation of JNK MAPK in oligodendrocytes suggests a mechanism of protection consisting of scarring oligodendrocyte inhibitory molecules that can hinder myelin reconstitution and neuron functionality.

Clinicopathological and immunohistochemical features of three pilomyxoid astrocytomas: comparative study with 11 pilocytic astrocytomas

Pilomyxoid astrocytoma, first described by Tihan et al., was recently included as an established variant of pilocytic astrocytoma in the World Health Organization classification of CNS tumors. Histologically, it much resembles pilocytic astrocytoma, but monomorphic myxoid tumor of pilocytic cells with prominent angiocentric growth pattern without Rosenthal fibers or eosinophilic granular bodies is characteristic of pilomyxoid astrocytoma. Pilomyxoid astrocytoma is thought to be more aggressive with more frequent local recurrence as well as cerebrospinal spread. The authors recently encountered a case of pilomyxoid astrocytoma, therefore the purpose of the present study was undertake a retrospective review of pilocytic astrocytomas previously diagnosed during the past 10 years. Consequently, two of them were found to have histological features suggestive of pilomyxoid astrocytoma and both involved multiple recurrence, suggesting aggressive behavior in comparison to pilocytic astrocytoma. Therefore, knowledge of this entity is essential to surgical pathologists and clinicians for patient management.

Deficit of pericapillary oligodendrocytes in the prefrontal cortex in schizophrenia

OBJECTIVE

Our previous studies have shown a significant decrease of numerical density of oligodendrocytes in the prefrontal cortex in postmortem schizophrenic brains. Deficit of oligodendrocytes was associated with loss of oligodendroglial satellites of pyramidal neurons. In this study we tested the hypothesis that there might be a deficit and loss of pericapillary oligodendrocytes in the prefrontal cortex in schizophrenia.

METHOD

Autopsy samples from the prefrontal cortex (BA 10) were obtained from 12 normal controls and 12 chronic schizophrenic cases. Capillaries and oligodendrocytes were viewed in paraffin sections stained with a Luxol-fast blue and cresyl violet. Electron microscopy was applied to study the ultrastructure of oligodendrocytes. For morphometric analysis, an average of 100 rectilinear capillary segments from layer V was sampled for each individual. The number of oligodendrocytes visible along rectilinear segments was expressed as the number of oligodendrocytes per 0.01 mm of capillary length.

RESULTS

Subjects with schizophrenia had a significantly lower (-23%; P < 0.005) number of pericapillary oligodendrocytes compared to controls. Prominent ultrastructural dystrophic and degenerative alterations of pericapillary oligodendrocytes have been revealed in schizophrenic brains.

CONCLUSION

The present study provides evidence that there is a prominent reduction, damage and loss of pericapillary oligodendrocytes in the prefrontal cortex in schizophrenia. These changes may contribute to the pathophysiological basis for altered blood-brain barrier and lowered metabolic rates in subjects with schizophrenia.

Immunohistochemical and ultrastructural characterization of brain tumors in S100beta-v-erbB transgenic rats

Transgenic rats expressing v-erbB (viral form of the EGF receptor) under transcriptional regulation by the S100beta promoter develop brain tumors (Ohgaki et al. J Neuropathol Experimental Neurol 65: 1111-1117, 2006). In the present study, we carried out detailed immunohistochemical and ultrastructural characterization of the brain tumors that developed in these rats. Of 49 homozygous transgenic rats between 16 and 94 weeks of age (mean, 59 weeks), 31 rats were autopsied because they showed severe neurological symptoms and/or became moribund. Among these, 30 rats had brain tumors, which were classified histologically as malignant glioma, anaplastic oligodendroglioma, and low-grade oligodendroglioma. Six transgenic rats developed two different histologic types of brain tumor, which were considered to be of multiclonal origin, because of the lack of histological transitions. All brain tumors contained neoplastic cells immunoreactive for S100 and GFAP. Diffuse immunoreactivity for Olig2 and Nkx2.2 was observed in neoplastic cells in all seven anaplastic oligodendrogliomas and in all three low-grade oligodendrogliomas analyzed, but in none of 26 malignant gliomas. Electron microscopy, carried out on four malignant gliomas and four anaplastic oligodendrogliomas, revealed the presence of intermediate filament bundles devoid of side arms, indicating glial differentiation. There was no evidence of cilia, microvilli, neurosecretory granules, synaptic structures or neurofilaments, excluding the possibility of ependymal or neuronal tumors. The present study thus provides additional evidence that the brain tumors developing in S100beta-v-erbB transgenic rats are of glial origin, with or without oligodendroglial differentiation. Reproducible development of three distinct histologic types of brain tumor in unique localizations may be explained by activation of the v-erbB transgene driven by the S100beta promoter in specific precursor cells during development of the brain. Thus, S100beta-v-erbB transgenic rats may be useful to study the histogenesis and molecular mechanisms of development of glial tumors due to disruption of the EGFR pathway.

Diversity of glial cell components in pilocytic astrocytoma

To characterize the cellular density and proliferative activity of GFAP-negative cells in pilocytic astrocytoma (PA), surgically excised tissues of PAs (n=37) and diffuse astrocytomas (DAs) (n=11) were examined morphologically and immunohistochemically using antibodies against GFAP, Olig2, Iba1 and Ki-67 (MIB-1). In PA, Olig2 immunoreactivity was significantly expressed in protoplasmic astrocytes in microcystic, loose areas and cells in oligodendroglioma-like areas. Iba1-positive, activated microglia/macrophages were also commonly observed in microcystic areas. In compact areas, a prominent reaction for GFAP was observed, but for Olig2 and Iba1 to a lesser degree. On semiquantitative analysis, the number of Olig2-positive cells was significantly higher in PAs (mean labeling index (LI) +/- standard deviation (SD): 46.8+/-15.4%) than in DAs (13.3+/-7.8%) (P<0.001). Many Iba1-positive, microglia/macrophages were observed in PAs (19.9+/-6.5%), similarly to DAs (20.9+/-9.9%). Re-immunostaining of PA demonstrated that most Ki-67-positive, proliferating cells expressed Olig2, whereas GFAP or Iba1 expression in Ki-67-positive cells was less frequent (14.7+/-13.7%, and 8.8+/-13.6%) in a double immunostaining study. Conversely, the percentage of Olig2-positive, proliferating cells in total Olig2-positive cells (7.2+/-3.9%) was higher than that of Iba1-positive, proliferating cells in total Iba1-positive cells (0.9+/-0.6%). In conclusion, the present study found that PA consisted of numerous GFAP-negative cells, including Olig2-positive cells with high proliferation. Semiquantitative analysis of Olig2 immunohistochemistry in microcystic areas might therefore be useful for the differential diagnosis of PA and DA.

Low grade diffuse gliomas: shared cellular composition and morphometric differences

Low grade diffuse gliomas arising in the brain are challenging to treat because of their ability to infiltrate adjacent tissue. We attempted to clarify the cellular composition and histopathological features of low grade gliomas by utilizing morphometric and immunohistochemical analyses. Seventy-eight cases of low grade gliomas were examined including 21 diffuse astrocytomas (DA), 36 oligodendrogliomas (OL), and 21 oligoastrocytomas (OA), based on the WHO classification system. Moreover, OL were subdivided into three types based on the morphological characteristics advocated by Daumas-Duport et al.: OL type I, OL type II, and OL type III. The cellularity, nuclear form factor, and conditional entropy corresponding to the nuclear pleomorphism were measured in each sample by the image analysis software "Gunmetry." Twenty-two cases were immunohistochemically analyzed for the expression of several antigens. Morphometric data indicated that the cellularity of OL type II was significantly higher than that of DA, and that the conditional entropy of OL type III was significantly lower than that of DA. Although the results of the immunohistochemical studies were almost consistent with previous reports, there were significant differences in the expression of GFAP, nestin and p53 between DA and OL. Double immunostaining revealed that expression of Olig2 and GFAP, and Olig2 and nestin was mutually exclusive in most glioma cells. Moreover, the coexpression of nestin and GFAP occurred in DA and OA, but not in OL. We conclude that each glioma include cells expressing GFAP, cells expressing nestin, and cells expressing Olig2 in a characteristic proportion for each tumor type. We suggest that diffuse gliomas share cellular compositions in different ratios and that they can be distinguished by morphometrical analysis.

Oligodendrocyte lineage transcription factor 2 inhibits the motility of a human glial tumor cell line by activating RhoA

The basic helix-loop-helix transcription factor, oligodendrocyte lineage transcription factor 2 (OLIG2), is specifically expressed in the developing and mature central nervous system and plays an important role in oligodendrogenesis from neural progenitors. It is also expressed in various types of glial tumors, but rarely in glioblastoma. Although we previously showed that OLIG2 expression inhibits glioma cell growth, its role in tumorigenesis remains incompletely understood. Here, we investigated the effect of OLIG2 expression on the migration of the human glioblastoma cell line U12-1. In these cells, OLIG2 expression is controlled by the Tet-off system. Induction of OLIG2 expression inhibited both the migration and invasiveness of U12-1 cells. OLIG2 expression also increased the activity of the GTPase RhoA as well as inducing the cells to form stress fibers and focal adhesions. Experiments using short interfering RNA against p27(Kip1) revealed that up-regulation of the p27(Kip1) protein was not essential for RhoA activation, rather it contributed independently to the decreased motility of OLIG2-expressing U12-1 cells. Alternatively, semiquantitative reverse transcription-PCR analysis revealed that mRNA expression of RhoGAP8, which regulates cell migration, was decreased by OLIG2 expression. Furthermore, expression of C3 transferase, which inhibits Rho via ADP ribosylation, attenuated the OLIG2-induced inhibition of cell motility. Imaging by fluorescence resonance energy transfer revealed that in U12-1 cells lacking OLIG2, the active form of RhoA was localized to protrusions of the cell membrane. In contrast, in OLIG2-expressing cells, it lined almost the entire plasma membrane. Thus, OLIG2 suppresses the motile phenotype of glioblastoma cells by activating RhoA.

The glial response to CNS HIV infection includes p53 activation and increased expression of p53 target genes

HIV-associated dementia (HAD) is a chronic neuroinflammatory disease that remains an important clinical problem without available rational treatment. As HIV does not infect neurons, the pathogenesis of HAD is thought to be secondary to the impact of infected leukocytes, including parenchymal microglia, which can secrete inflammatory mediators and viral products that alter the function of surrounding uninfected cells. We previously reported that the transcription factor p53 accumulates in neurons, microglia, and astrocytes of HAD patients. We have also shown that microglia from p53-deficient mice fail to induce neurotoxicity in response to the HIV coat protein gp120 in a coculture system, supporting the hypothesis that p53 plays a pathogenic role in the chronic neuroinflammatory component of HIV-associated neurodegeneration. We analyzed the extent and cell type specificity of p53 accumulation in subcortical white matter of ten AIDS patients that had previously been shown to demonstrate white matter p53 accumulation. To determine if p53 activation functioned to alter gene expression in HAD, cortical tissue sections were also immunolabeled for the p53 target genes Bax and p21(WAF1). These studies reveal that microglia, astrocytes, and oligodendrocytes all demonstrate p53 activation in response to HIV infection. We observed immunoreactivity for both Bax and p21(WAF1) in neurons and glia from patients demonstrating elevated p53 immunoreactivity. Our findings demonstrate that widespread increased p53 expression is present in HAD. Activation of p53 mediated pathways in the glia of HAD patients may contribute to the neuroinflammatory processes that promote neurodegeneration by inhibiting glial proliferation and/or promoting glial cell dysfunction.

The ectonucleotidases alkaline phosphatase and nucleoside triphosphate diphosphohydrolase 2 are associated with subsets of progenitor cell populations in the mouse embryonic, postnatal and adult neurogenic zones

Subventricular zone (SVZ)-derived adult neurospheres express two ectonucleotidases, nucleoside triphosphate diphosphohydrolase 2 (NTPDase2) and tissue non-specific alkaline phosphatase (TNAP). Agonists of the nucleotide receptors P2Y(1) and P2Y(2) as well as adenosine augment growth factor-mediated progenitor cell proliferation. NTPDase2 converts ATP and UTP to ADP and UDP, respectively, which are all P2Y receptor agonists. TNAP hydrolyzes nucleoside triphosphates and diphosphates and produces the P1 receptor agonist adenosine. In the SVZ, NTPDase2 is specifically expressed by type B cells. In order to further scrutinize the association of key molecules of the purinergic signaling pathway with neurogenic regions, we analyzed the expression of TNAP at the lateral ventricles of the adult and developing mouse brain. In the adult brain, TNAP was expressed by type B, type A and at least subsets of type C cells of the SVZ and throughout the rostral migratory stream. Almost 100% of the proliferating, Ki-67-positive cells of the adult SVZ stained for TNAP, supporting the notion of a ubiquitous association of TNAP with SVZ progenitors. In contrast, NTPDase2-positive progenitors of the dentate gyrus were TNAP-negative. Essentially all cells of the telencephalic vesicle at embryonic day (E) 14 revealed TNAP activity, including doublecortin-positive neuroblasts. During further embryonic development, enhanced TNAP activity became restricted to cells of the ventricular and SVZ. In contrast to TNAP, NTPDase2 was first expressed in the SVZ perinatally, in association with TNAP-positive SVZ border cells. During later development, NTPDase2-positive cells disappeared from the ventricular surface and began to form sheaths around clusters of subventricular doublecortin-positive cells, apparently transforming into type B cells. Our results identify TNAP and NTPDase2 as novel markers for subsets of progenitors in the adult and developing mouse brain. They further support the notion that signaling via extracellular nucleotides and nucleosides contributes to embryonic and adult neurogenesis.

OLIG2 is a useful immunohistochemical marker in differential diagnosis of clear cell primary CNS neoplasms

AIMS

To analyse OLIG2 expression in clear cell primary central nervous system (CNS) tumours to clarify the diagnostic usefulness of OLIG2 immunohistochemistry in this subset of brain tumours.

METHODS AND RESULTS

We analysed OLIG2 expression in 60 oligodendroglial neoplasms (57 with and three without chromosome 1p aberration), 10 central neurocytomas, 10 clear cell ependymomas, nine dysembryoplastic neuroepithelial tumours (DNTs) and two clear cell meningiomas using immunohistochemistry. Additionally, we analysed oligodendroglial neoplasms with numerous gliofibrillary and minigemistocytic oligodendrocytes for OLIG2/glial fibrillary acidic protein (GFAP) coexpression and central neurocytoma for coexpression of neurone-specific nuclear protein (NeuN) and OLIG2 using double immunofluorescent labelling and confocal laser scanning microscopy. All oligodendroglial neoplasms and DNTs showed widespread OLIG2 expression. Eight of 10 central neurocytomas, all clear cell meningiomas and 8/10 clear cell ependymomas were negative for OLIG2. Two of 10 central neurocytomas and 2/10 clear cell ependymomas showed focal OLIG2 expression. We found prominent coexpression of GFAP and OLIG2 in gliofibrillary and minigemistocytic oligodendrocytes. Further, we found coexpression of NeuN and OLIG2 in single cells in central neurocytoma.

CONCLUSIONS

Widespread OLIG2 expression discriminates oligodendroglial neoplasms or DNTs from other clear cell primary brain tumour types. In clear cell primary brain tumours lacking OLIG2 expression, differential diagnosis may require additional immunohistochemical markers.

Predominant expression of OLIG2 over ID2 in oligodendroglial tumors

OLIG2 is a basic helix-loop-helix transcription factor regulating the generation of oligodendrocytes from neural progenitor cells, and the function of OLIG2 is inhibited posttranslationally through the interaction with ID2. This study aims to examine if the analysis of OLIG2 and ID2 expression in glioma tissues helps the differential diagnosis of chemosensitive oligodendroglial tumors from astrocytic tumors. Expression levels of OLIG2 and ID2 in 11 oligodendroglial and 27 astrocytic tumors were analyzed by reverse transcription-polymerase chain reaction (RT-PCR), real-time quantitative PCR, and immunohistochemistry. The mean expression level of OLIG2 was higher in oligodendroglial tumors than astrocytic tumors, but some astrocytic tumors showed high OLIG2 expression, indicating that OLIG2 cannot be an independent marker of oligodendroglial tumors. No significant difference was observed between ID2 expression in oligodendroglial tumors and astrocytic tumors. It was notable that OLIG2 expression was predominant over ID2 expression in oligodendroglial tumors, while ID2 expression was predominant over OLIG2 expression in astrocytic tumors. Comparative genomic hybridization revealed that gliomas with loss on chromosome 1p, which is closely associated with chemosensitivity, also showed the predominant expression of OLIG2 over ID2. These results indicate that the immunohistochemical study on the relative expression level of OLIG2 to ID2 can be a useful screening for oligodendroglial tumors.

Oligodendrocytes are a major target of the toxicity of spongiogenic murine retroviruses

The neurovirulent retroviruses FrCasE and Moloney MLV-ts1 cause noninflammatory spongiform neurodegeneration in mice, manifested clinically by progressive spasticity and paralysis. Neurons have been thought to be the primary target of toxicity of these viruses. However the neurons themselves appear not to be infected, and the possible indirect mechanisms driving the neuronal toxicity have remained enigmatic. Here we have re-examined the cells that are damaged by these viruses, using lineage-specific markers. Surprisingly, these cells expressed the basic helix-loop-helix transcription factor Olig2, placing them in the oligodendrocyte lineage. Olig2+ cells were found to be infected, and many of these cells exhibited focal cytoplasmic vacuolation, suggesting that infection by spongiogenic retroviruses is directly toxic to these cells. As cytoplasmic vacuolation progressed, however, signs of viral protein expression appeared to wane, although residual viral RNA was detectable by in situ hybridization. Cells with the most advanced cytoplasmic effacement expressed the C/EBP-homologous protein (CHOP). This protein is up-regulated as a late event in a cellular response termed the integrated stress response. This observation may link the cellular pathology observed in the brain with cellular stress responses known to be induced by these viruses. The relevance of these observations to oligodendropathy in humans is discussed.

Fc receptor-positive cells in remyelinating multiple sclerosis lesions

The capacity for spontaneous remyelination in cases of multiple sclerosis (MS) is limited and lesions are not fully repaired. Recent evidence has shown that oligodendrocyte precursor cells and immature oligodendrocytes (OPC/iOligs) are preserved in MS lesions. Induced differentiation of these cells into myelinating cells may ultimately lead to a novel remyelination therapy. A previous study showed that the gamma chain of immunoglobulin Fc receptors (FcRgamma), expressed in OPC/iOligs, is essential for their differentiation. Whether FcRgamma is expressed in preserved OPC/iOligs within MS lesions, however, remains uncertain. In the present study, we examined 10 autopsy cases of MS for the expression of FcRgamma both in remyelinating areas and demyelinated plaques. The expression of FcRgamma was confirmed in both OPC/iOligs and microglia in MS lesions. Statistical analysis showed that the density of FcRgamma-positive OPC/iOligs was approximately 3 times greater in remyelinating areas compared with demyelinated plaques; the opposite was true of FcRgamma-positive microglia. The distribution of FcRgamma-negative OPC/iOligs did not differ between the 2 types of lesions. Thus, an increase in FcRgamma-positive OPC/iOligs and a decrease in FcRgamma-positive microglia, but not in FcRgamma-negative OPC/iOligs, are associated with spontaneous remyelination in MS brains, suggesting a possible role for FcRgamma in the induction of remyelination.

Papillary glioneuronal tumor: A clinicopathological and immunohistochemical study of two cases

Papillary glioneuronal tumor (PGNT) has recently been identified as a new variant of mixed neuronal-glial tumors. We report the clinical and pathological features of PGNT in two Chinese patients. One patient was a 35-year-old man who suffered from intractable seizures for 16 years. Another was a 26-year-old woman who presented with headache for 2 years. In both patients, magnetic resonance imaging showed well demarcated, mixed cystic and solid tumor in the temporal lobe. Histology of the excised tumors revealed a pseudopapillary architecture surrounded by a glial component and intervening areas were occupied by neuronally differentiated cells. No cortical dysplasia was found in the neighboring cortex in one of them. The glial component showed immunoreactivity with glial fibrillary acidic protein and S-100 protein. Neuronally differentiated cells were immunolabeled by antisynaptophysin, NF, NeuN and MAP2 antibodies. Some small cells surrounding the surface of the pseudopapillae and in the compact area were immunopositive for Olig2. The MIB-1 labeling index was < 3%. The tumor did not recur within the follow-up periods of 50 months and 13 months, and the patient with temporal lobe epilepsy became seizure-free after surgery.

Systematic immunohistochemical profiling of 378 brain tumors with 37 antibodies using tissue microarray technology

We performed a systematic immunohistochemical study on 378 brain tumors using 37 antibodies and tissue microarray (TMA) technology. The aim of this study was to find new diagnostic biomarkers using antibodies established in our laboratory. Our TMA consisted of a grid of 1.5-mm cores that were extracted from individual donor blocks. Staining for each antibody was scored using a three-point system. We used hierarchical clustering analysis to interpret these data, which resulted in separation of all the brain tumors into seven groups. Although there were some exceptions, cases with the same histological diagnosis were generally grouped together. We then carried out statistical analyses to find the most useful antibodies for grouping of brain tumors. Ten antibodies [glial fibrillary acidic protein (GFAP), Olig2, vimentin, epithelial membrane antigen (EMA), cytokeratin (AE1/AE3), alpha-internexin, nestin, pinealocytes PP5, aquaporin-4 (AQP4) M13d and AQP4M13e] discriminated between astrocytomas and oligodendroglial tumors. Six antibodies [EMA, AE1/AE3, TUJ1, nestin, neurofilament protein-MH (NF-MH) and perivascular cells GP-1] showed significant differences between high-grade and low-grade gliomas. Our data have revealed new antibodies with potential diagnostic utility (Olig2, PP5, GP-1) and demonstrate that TMA technology is highly useful for evaluating newly established antibodies in brain-tumor research.

Papillary glioneuronal tumor with minigemistocytic components and increased proliferative activity

Papillary glioneuronal tumor (PGNT) is a rare and new type of glioneuronal neoplasm of the central nervous system. It is characterized by pseudopapillary structures composed of hyalinized vessels rimmed by cuboidal glial cells and the proliferation of neuronal cells. We report a peculiar PGNT arising in the parietal lobe of a 67-year-old man, which was characterized by proliferation of minigemistocytic cells as well as typical components. The minigemistocytic cells had eccentric nuclei and plump eosinophilic cytoplasm that was filled with glial filaments. The Ki-67 labeling index was as high as 10% in the minigemistocytic areas. Recently, the presence of oligodendroglial-like component was suggested in PGNT. Considering that oligodendroglioma sometimes accompanies minigemistocytic components, the minigemistocytic cells in PGNT were suggested to be a part of oligodendroglial differentiation. Although PGNT is defined as an indolent glioneuronal tumor, the presence of minigemistocytic components with the high Ki-67 labeling index may indicate more aggressive nature.

Oligodendrocytes within astrocytes ("emperipolesis") in the cerebral white matter in hepatic and hypoglycemic encephalopathy

We report the occurrence of oligodendrocytes within astrocytes ("emperipolesis") in two autopsy cases of metabolic encephalopathy: one patient with hepatic encephalopathy due to citrullinemia who suffered recurrent unconsciousness (clinical duration, 32 months) and another with hypoglycemic encephalopathy who lapsed into a persistent vegetative state (clinical duration, 22 months). In both cases, hypertrophic astrocytes were found to have engulfed one to several oligodendrocytes in the devastated cerebral white matter. Previous studies have reported that emperipolesis occurs in various CNS diseases showing destruction of myelin or inflammation of the white matter, including multiple sclerosis, cerebral infarct and CJD. The present findings suggest that emperipolesis can occur even in chronic metabolic disorders that extensively involve the cerebral white matter.

Oligodendroglial-specific transcriptional factor SOX10 is ubiquitously expressed in human gliomas

The two most common types of gliomas: astrocytoma and oligodendroglioma are distinguished based on their morphologic similarities to mature astrocytes and oligodendroglia. Whereas prototypical examples of the tumors have distinct pathogenetic and prognostic differences, the majority of the gliomas falls in the intermediate category and their distinction is problematic. The transcriptional factor SOX10 is one of the key determinants of oligodendroglial differentiation. We applied immunohistochemistry to analyze whether the expression of SOX10 can differentiate astrocytoma and oligodendroglioma. The majority of oligodendrogliomas, but also a large fraction of astrocytomas, including the least differentiated glioblastomas, expressed SOX10, albeit at lower levels. Comparison with 1p and 19q deletion status by FISH analysis also revealed no obvious associations. High levels of expression were also found in pilocytic astrocytoma, consistent with recent studies suggesting that pilocytic astrocytomas have greater overlap with oligodendroglial than astrocytic tumors. Our data raise a possibility that histogenesis of gliomas have more common features than previously anticipated.

A novel function of OLIG2 to suppress human glial tumor cell growth via p27Kip1 transactivation

The basic helix-loop-helix transcription factor OLIG2 is specifically expressed in cells of the oligodendrocyte lineage. It is also expressed in various tumors originating from glial cells; however, the expression of OLIG2 is rare or weak in glioblastomas, the most malignant gliomas. The role of OLIG2 in glioma remains unclear. To investigate the function of OLIG2 in glial tumor cells, we have established a glioblastoma cell line, U12-1, in which the expression of OLIG2 is induced by the Tet-off system. Induction of OLIG2 resulted in suppression of both the proliferation and anchorage-independent growth of U12-1. It also resulted in an increase in the expression of p27Kip1. A luciferase assay revealed that the CTF site of the p27Kip1 gene promoter was essential for OLIG2-dependent activation of p27Kip1 gene transcription. Electrophoretic mobility shift assays confirmed that a nuclear extract of OLIG2-expressing U12-1 cells contained a protein complex that binds to the CTF site of the p27Kip1 gene promoter. Furthermore, siRNA against p27Kip1 rescued the OLIG2-mediated growth and DNA synthesis inhibition of U12-1 cells. These results indicate that OLIG2 suppresses the proliferation of U12-1 and that this effect is mediated by transactivation of the p27Kip1 gene, and low expression of OLIG2 may be related to the malignant behavior of human glioblastoma.

Characterization of Ubiquitinated Intraneuronal Inclusions in a Novel Belgian Frontotemporal Lobar Degeneration Family

The most common histologic feature in patients with frontotemporal lobar degeneration (FTLD) is intracellular brain inclusions of yet uncharacterized proteins that react with antiubiquitin (Ub) antibodies, but not with tau or synuclein (FTLD-U). We identified a four-generation Belgian FTLD family in which 8 patients had dominantly inherited FTLD. In one patient, we showed frontotemporal atrophy with filamentous Ub-positive intracellular inclusions in absence of tau pathology or any alterations in the levels of soluble tau. We characterized the cellular and subcellular localization and morphology of the inclusions. Ub-positive inclusions predominantly occurred within neurons (>97%), but were also observed within oligodendroglia (approximately 2%) and microglia (<1%), but not within astroglia. Regarding the subcellular localization, the intranuclear inclusions (INI) were up to approximately four-fold more frequent than the cytoplasmic inclusions, although the latter were more specific to neurons. The INIs frequently appeared spindle-shaped and 3-dimensional confocal reconstructions identified flattened, leaf-like structures. Ultrastructurally, straight 10- to 18-nm-diameter filaments constituted the spindle-shaped inclusions that occurred in close proximity to the nuclear membrane. Staining for HSP40, p62, and valosin/p97 was observed in only a minority of the inclusions. Whereas the precise nature of the protein remains elusive, characterization of such familial FTLD-U patients would be helpful in identifying a common denominator in the pathogenesis of familial and the more prevalent sporadic FTLD-U.