Hiroko Yanagisawa

Exon 9 mutations in the WT1 gene, without influencing KTS splice isoforms, are also responsible for Frasier syndrome

We report new mutations in exon 9 of the WT1 gene that did not alter the ratio of +/– KTS splice isoforms in two unrelated patients with Frasier syndrome (FS). The mutation of intron 9 inducing defective alternative splicing was reported to be responsible for this syndrome. The mutations found in our cases occurred in the same exon of the WT1 gene as detected in Denys‐Drash syndrome (DDS) and could not be explained by the previously proposed mechanism. The results suggest that the two syndromes originate from the same WT1 gene abnormality. From a molecular biological point of view, we concluded that the two diseases were not separable, and that FS should be included as an atypical form of DDS. Hum Mutat 14:466–470, 1999.

High glucose-induced activation of the polyol pathway and changes of gene expression profiles in immortalized adult mouse Schwann cells IMS32

We investigated the polyol pathway activity and the gene expression profiles in immortalized adult mouse Schwann cells (IMS32) under normal (5.6 mm) and high (30 and 56 mm) glucose conditions for 7–14 days in culture. Messenger RNA and the protein expression of aldose reductase (AR) and the intracellular sorbitol and fructose contents were up‐regulated in IMS32 under high glucose conditions compared with normal glucose conditions. By employing DNA microarray and subsequent RT–PCR/northern blot analyses, we observed significant up‐regulation of the mRNA expressions for serum amyloid A3 (SAA3), angiopoietin‐like 4 (ANGPTL4) and ecotropic viral integration site 3 (Evi3), and the down‐regulation of aldehyde reductase (AKR1A4) mRNA expression in the cells under high glucose (30 mm) conditions. The application of an AR inhibitor, SNK‐860, to the high glucose medium ameliorated the increased sorbitol and fructose contents and the reduced AKR1A4 mRNA expression, while it had no effect on mRNA expressions for SAA3, ANGPTL4 or Evi3. Considering that the exposure to the high glucose (≥ 30 mm) conditions mimicking hyperglycaemia in vivo accelerated the polyol pathway in IMS32, but not in other previously reported Schwann cells, the culture system of IMS32 under those conditions may provide novel findings about the polyol pathway‐related abnormalities in diabetic neuropathy.

Spontaneously immortalized Schwann cells from adult Fischer rat as a valuable tool for exploring neuron–Schwann cell interactions

We established spontaneously immortalized Schwann cell lines from long‐term cultures of adult Fischer 344 rat dorsal root ganglia (DRG) and peripheral nerves. One of these cell lines, designated immortalized Fischer rat Schwann cells 1 (IFRS1), showed spindle‐shaped morphology; immunoreactivity for S100, p75 neurotrophin receptor (p75NTR), glial fibrillary acidic protein (GFAP), laminin, and vimentin; and mRNA expression of neurotrophic factors (NGF, GDNF, and CNTF), neurotrophin receptors (p75NTR, truncated TrkB, and TrkC), cell adhesion molecules (L1, NCAM, and N‐cadherin), myelin proteins [P0, PMP22, and myelin‐associated glycoprotein (MAG)], transcription factors (Krox20, Sox10, and Oct6), neuregulin‐1 receptors (ErbB2 and ErbB3), and an orphan G protein‐coupled receptor (Gpr126). Conditioned medium (CM) obtained from IFRS1 cells exhibited potent biological activity for the promotion of neuronal survival and neurite outgrowth of cultured adult rat DRG neurons. Furthermore, light and electron microscopic analyses revealed that IFRS1 cells were capable of myelinating neurites while in coculture with adult rat DRG neurons. These findings indicate that IFRS1 cells possess some biological properties of mature Schwann cells and that the coculture system with adult DRG neurons and IFRS1 cells can be a useful tool for the study of peripheral nerve degeneration and regeneration.

Pleiotrophin induces neurite outgrowth and up-regulates growth-associated protein (GAP)-43 mRNA through the ALK/GSK3β/β-catenin signaling in developing mouse neurons

Pleiotrophin (PTN) is highly expressed in the nervous system during embryogenesis; however, little is known about its functional role in neural development. By using whole mount in situ hybridization, we observed that the expression pattern of PTN was similar to that of Wnt3a; PTN mRNA was abundant in the nervous tissue along the dorsal midline and in the forelimb and hindlimb buds of embryonic mice (E8.5-E12.5). Treatment with recombinant PTN (100ng/ml) induced phosphorylation of glycogen synthase kinase 3beta (GSK3beta), nuclear localization of beta-catenin and up-regulation of growth-associated protein (GAP)-43 mRNA in cultured embryonic mouse (E14.5) neurons. Furthermore, recombinant PTN enhanced neurite outgrowth from cortical explants embedded in Matrigel. These PTN-induced biochemical changes and neurite outgrowth were attenuated by the co-treatment with anti-anaplastic lymphoma kinase (ALK) antibodies, but not with anti-protein tyrosine phosphatase (PTP)zeta antibodies. These findings imply that ALK is involved in the PTN signaling on neural development.

Immortalized Adult Rodent Schwann Cells as In Vitro Models to Study Diabetic Neuropathy

We have established spontaneously immortalized Schwann cell lines from normal adult mice and rats and murine disease models. One of the normal mouse cell lines, IMS32, possesses some biological properties of mature Schwann cells and high proliferative activities. The IMS32 cells under hyperglycemic and/or hyperlipidemic conditions have been utilized to investigate the pathogenesis of diabetic neuropathy, especially the polyol pathway hyperactivity, glycation, increased oxidative stress, and reduced synthesis of neurotrophic factors. In addition to the mouse cell lines, our current study focuses on the characterization of a normal rat cell line, IFRS1, under normal and high glucose conditions. These Schwann cell lines can be valuable tools for exploring the detailed mechanisms leading to diabetic neuropathy and novel therapeutic approaches against that condition.

Differential Effects of High Glucose and Methylglyoxal on Viability and Polyol Metabolism in Immortalized Adult Mouse Schwann Cells

Cultured Schwann cells under exposure to high glucose and methylglyoxal (MG) have been individually em- ployed for studying diabetic neuropathy; however, similarities and differences between these two culture models have not been studied. We investigated the effects of high glucose and MG on viability, polyol pathway activity, and expression of oxidative stress markers (4-hydroxy-2-nonenal (4HNE), acrolein (ACR), and hexanoyl lysine (HEL)) in immortalized adult mouse Schwann cells (IMS32 cell line) in culture. Western blot and immunocytochemical analyses revealed that ex- pression of aldose reductase (AR), 4HNE, ACR, and HEL in IMS32 was induced by exposure to both high glucose (30 mM) and MG (0.5 mM) for 48 h. Treatment with MG (0.1, 0.2, and 0.5 mM) induced cell death in a concentration- dependent manner, whereas high glucose environments (30 mM and 56 mM) did not impair cell viability. In contrast, in- tracellular sorbitol and fructose levels were significantly increased by high glucose, but not by MG. Taking these findings together, IMS32 cell line under high glucose conditions appears to be useful for studying oxidative stress in relation to the polyol pathway hyperactivity in diabetes. MG is capable of causing more detrimental damage to IMS32 than high glucose, but MG-induced upregulation of AR is unlikely to accelerate the polyol pathway activity.

Adenoviral expression of TDP‐43 and FUS genes and shRNAs for protein degradation pathways in rodent motoneurons in vitro and in vivo

Formation of cytoplasmic aggregates in neuronal and glial cells is one of the pathological hallmarks of amyotrophic lateral sclerosis (ALS). Mutations in two genes encoding transactivation response (TAR) DNA‐binding protein 43 (TDP‐43) and fused in sarcoma (FUS), both of which are main constituents of cytoplasmic aggregates, have been identified in patients with familial and sporadic ALS. Impairment of protein degradation machineries has also been recognized to participate in motoneuron degeneration in ALS. In the present study, we produced recombinant adenovirus vectors encoding wild type and mutant TDP‐43 and FUS, and those encoding short hairpin RNAs (shRNAs) for proteasome (PSMC1), autophagy (ATG5), and endosome (VPS24) systems to investigate whether the coupled gene transductions in motoneurons by these adenoviruses elicit ALS pathology. Cultured neurons, astrocytes and oligodendrocytes differentiated from adult rat neural stem cells and motoneurons derived from mouse embryonic stem cells were successfully infected with these adenoviruses showing cytoplasmic aggregate formation. When these adenoviruses were injected into the facial nerves of adult rats, exogenous TDP‐43 and FUS proteins were strongly expressed in facial motoneurons by a retrograde axonal transport of the adenoviruses. Co‐infections of adenovirus encoding shRNA for PSMC1, ATG5 or VPS24 with TDP‐43 or FUS adenovirus enhanced cytoplasmic aggregate formation in facial motoneurons, suggesting that impairment of protein degradation pathways accelerates formation of TDP‐43 and FUS‐positive aggregates in ALS.

Upregulation of galectin-3 in immortalized Schwann cells IFRS1 under diabetic conditions

A spontaneously immortalized adult Fischer rat Schwann cell line IFRS1 retains the characteristic features of normal Schwann cells, and can be a useful tool for the study of diabetic neuropathy. In the present study, we examined the effects of high glucose and 3-deoxyglucosone (3-DG) on the viability and the protein expression of advanced glycation endproducts (AGE)-binding proteins, such as galectin-3 (GAL-3) and receptor for AGE (RAGE) in IFRS1 cells. Exposure to 30mM of glucose or 0.2mM of 3-DG for 7 days failed to impair the IFRS1 cell viability, but significantly upregulated the expression of GAL-3. The same exposure tended to increase the expression of RAGE, but the changes were not significant. The high glucose-induced upregulation of GAL-3 was attenuated by cotreatment with 0.2mM of an anti-glycated agent aminoguanidine or 20nM of an anti-oxidant trans-resveratrol. In addition, treatment of IFRS1 cells with 1μg/ml of recombinant GAL-3 for 48h resulted in the upregulation of B-cell lymphoma 2 (Bcl-2) and the downregulation of 4-hydroxynonenal (4HNE). These findings suggest the involvement of GAL-3 in the glycation and oxidative stress under diabetic conditions and its cytoprotective role in Schwann cells.

Neonicotinoid Insecticides Alter the Gene Expression Profile of Neuron-Enriched Cultures from Neonatal Rat Cerebellum.

Neonicotinoids are considered safe because of their low affinities to mammalian nicotinic acetylcholine receptors (nAChRs) relative to insect nAChRs. However, because of importance of nAChRs in mammalian brain development, there remains a need to establish the safety of chronic neonicotinoid exposures with regards to children’s health. Here we examined the effects of long-term (14 days) and low dose (1 μM) exposure of neuron-enriched cultures from neonatal rat cerebellum to nicotine and two neonicotinoids: acetamiprid and imidacloprid. Immunocytochemistry revealed no differences in the number or morphology of immature neurons or glial cells in any group versus untreated control cultures. However, a slight disturbance in Purkinje cell dendritic arborization was observed in the exposed cultures. Next we performed transcriptome analysis on total RNAs using microarrays, and identified significant differential expression (p < 0.05, q < 0.05, ≥1.5 fold) between control cultures versus nicotine-, acetamiprid-, or imidacloprid-exposed cultures in 34, 48, and 67 genes, respectively. Common to all exposed groups were nine genes essential for neurodevelopment, suggesting that chronic neonicotinoid exposure alters the transcriptome of the developing mammalian brain in a similar way to nicotine exposure. Our results highlight the need for further careful investigations into the effects of neonicotinoids in the developing mammalian brain.

Involvement of oxidative stress and impaired lysosomal degradation in amiodarone‐induced schwannopathy

Amiodarone hydrochloride (AMD), an anti‐arrhythmic agent, has been shown to cause peripheral neuropathy; however, its pathogenesis remains unknown. We examined the toxic effects of AMD on an immortalized adult rat Schwann cell line, IFRS1, and cocultures of IFRS1 cells and adult rat dorsal root ganglion neurons or nerve growth factor‐primed PC12 cells. Treatment with AMD (1, 5, and 10 μm) induced time‐ and dose‐dependent cell death, accumulation of phospholipids and neutral lipids, upregulation of the expression of gangliosides, and oxidative stress (increased nuclear factor E2‐related factor in nuclear extracts and reduced GSH/GSSG ratios) in IFRS1 cells. It also induced the upregulation of LC3‐II and p62 expression, with phosphorylation of p62, suggesting that deficient autolysosomal degradation is involved in AMD‐induced IFRS1 cell death. Furthermore, treatment of the cocultures with AMD induced detachment of IFRS1 cells from neurite networks in a time‐ and dose‐dependent manner. These findings suggest that AMD‐induced lysosomal storage accompanied by enhanced oxidative stress and impaired lysosomal degradation in Schwann cells might be a cause of demyelination in the peripheral nervous system.