Altered actin dynamics is possibly implicated in the inhibition of mechanical stimulation-induced dermal fibroblast differentiation into myofibroblasts.

The formation of hypertrophic scars and keloids is strongly associated with mechanical stimulation, and myofibroblasts are known to play a major role in abnormal scar formation. Wounds in patients with neurofibromatosis type 1 (NF1) become inconspicuous and lack the tendency to form abnormal scars. We hypothesized that there would be a unique response to mechanical stimulation and subsequent scar formation in NF1. To test this hypothesis, we investigated the molecular mechanisms of differentiation into myofibroblasts in NF1-derived fibroblasts and neurofibromin-depleted fibroblasts and examined actin dynamics, which is involved in fibroblast differentiation, with a focus on the pathway linking LIMK2/cofilin to actin dynamics. In normal fibroblasts, expression of α-smooth muscle actin (α-SMA), a marker of myofibroblasts, significantly increased after mechanical stimulation, whereas in NF1-derived and neurofibromin-depleted fibroblasts, α-SMA expression did not change. Phosphorylation of cofilin and subsequent actin polymerization did not increase in NF1-derived and neurofibromin-depleted fibroblasts after mechanical stimulation. Finally, in normal fibroblasts treated with Jasplakinolide, an actin stabilizer, α-SMA expression did not change after mechanical stimulation. Therefore, when neurofibromin was dysfunctional or depleted, subsequent actin polymerization did not occur in response to mechanical stimulation, which may have led to the unchanged expression of α-SMA. We believe this molecular pathway can be a potential therapeutic target for the treatment of abnormal scars.

SUMO1 impact on Alzheimer disease pathology in an amyloid-depositing mouse model.

Small ubiquitin-related modifiers (SUMOs) conjugated or bound to target proteins can affect protein trafficking, processing and solubility. SUMOylation has been suggested to play a role in the amyloid plaque and neurofibrillary tangle pathology of Alzheimer disease (AD) and related neurodegenerative diseases. The current study examines the impact of SUMO1 on processing of the amyloid precursor protein (APP) leading to the production and deposition of the amyloid-ß (Aß) peptide. An in vivo model of these pathways was developed by the generation of double transgenic mice over-expressing human SUMO1 and a mutant APP. The SUMO1-APP transgenics displayed normal APP processing but, at later ages, exhibited increased insoluble Aß and plaque density accompanied by increased dendritic spine loss, more pronounced synaptic and cognitive deficits. These findings suggest a potential impairment in Aß clearance as opposed to increased amyloid production. Examination of microglia indicated a reduction in the SUMO1-APP transgenics which is a possible mechanism for the SUMO1-mediated increase in amyloid load. These findings suggest an indirect activity of SUMO1 possibly in the removal of Aß plaques rather than a direct impact on amyloid generation.

Transcriptome analysis of distinct mouse strains reveals kinesin light chain-1 splicing as an amyloid-ß accumulation modifier.

Alzheimer's disease (AD) is characterized by the accumulation of amyloid-ß (Aß). The genes that govern this process, however, have remained elusive. To this end, we combined distinct mouse strains with transcriptomics to directly identify disease-relevant genes. We show that AD model mice (APP-Tg) with DBA/2 genetic backgrounds have significantly lower levels of Aß accumulation compared with SJL and C57BL/6 mice. We then applied brain transcriptomics to reveal the genes in DBA/2 that suppress Aß accumulation. To avoid detecting secondarily affected genes by Aß, we used non-Tg mice in the absence of Aß pathology and selected candidate genes differently expressed in DBA/2 mice. Additional transcriptome analysis of APP-Tg mice with mixed genetic backgrounds revealed kinesin light chain-1 (Klc1) as an Aß modifier, indicating a role for intracellular trafficking in Aß accumulation. Aß levels correlated with the expression levels of Klc1 splice variant E and the genotype of Klc1 in these APP-Tg mice. In humans, the expression levels of KLC1 variant E in brain and lymphocyte were significantly higher in AD patients compared with unaffected individuals. Finally, functional analysis using neuroblastoma cells showed that overexpression or knockdown of KLC1 variant E increases or decreases the production of Aß, respectively. The identification of KLC1 variant E suggests that the dysfunction of intracellular trafficking is a causative factor of Aß pathology. This unique combination of distinct mouse strains and model mice with transcriptomics is expected to be useful for the study of genetic mechanisms of other complex diseases.

SUMO1 Modification of Tau in Progressive Supranuclear Palsy.

Small ubiquitin-like modifiers (SUMO) have been implicated in several neurodegenerative diseases. SUMO1 conjugation has been shown to promote aggregation and regulate phosphorylation of the tau protein linked to Alzheimer's disease and related tauopathies. The current study has demonstrated that SUMO1 co-localizes with intraneuronal tau inclusions in progressive supranuclear palsy (PSP). Immunoprecipitation of isolated and solubilized tau fibrils from PSP tissues revealed SUMO1 conjugation to a cleaved and N-terminally truncated tau. The effects of SUMOylation were examined using tau-SUMO fusion proteins which showed a higher propensity for tau oligomerization of PSP-truncated tau and accumulation on microtubules as compared to the full-length protein. This was found to be specific for SUMO1 as the corresponding SUMO2 fusion protein did not display a significantly altered cytoplasmic distribution or aggregation of tau. Blocking proteasome-mediated degradation promoted the aggregation of the tau fusion proteins with the greatest effect observed for truncated tau-SUMO1. The SUMO1 modification of the truncated tau in PSP may represent a detrimental event that promotes aggregation and impedes the ability of cells to remove the resulting protein deposits. This combination of tau truncation and SUMO1 modification may be a contributing factor in PSP pathogenesis.

SCYL1 arginine methylation by PRMT1 is essential for neurite outgrowth via Golgi morphogenesis.

Arginine methylation is a common posttranslational modification that modulates protein function. SCY1-like pseudokinase 1 (SCYL1) is crucial for neuronal functions and interacts with γ2-COP to form coat protein complex I (COPI) vesicles that regulate Golgi morphology. However, the molecular mechanism by which SCYL1 is regulated remains unclear. Here, we report that the γ2-COP-binding site of SCYL1 is arginine-methylated by protein arginine methyltransferase 1 (PRMT1) and that SCYL1 arginine methylation is important for the interaction of SCYL1 with γ2-COP. PRMT1 was colocalized with SCYL1 in the Golgi fraction. Inhibition of PRMT1 suppressed axon outgrowth and dendrite complexity via abnormal Golgi morphology. Knockdown of SCYL1 by small interfering RNA (siRNA) inhibited axon outgrowth, and the inhibitory effect was rescued by siRNA-resistant SCYL1, but not SCYL1 mutant, in which the arginine methylation site was replaced. Thus, PRMT1 regulates Golgi morphogenesis via SCYL1 arginine methylation. We propose that SCYL1 arginine methylation by PRMT1 contributes to axon and dendrite morphogenesis in neurons.

Dysbindin engages in c-Jun N-terminal kinase activity and cytoskeletal organization.

A number of reports have provided genetic evidence for an association between the DTNBP1 gene (coding dysbindin) and schizophrenia. In addition, sandy mice, which harbor a deletion in the DTNBP1 gene and lack dysbindin, display behavioral abnormalities suggestive of an association with schizophrenia. However, the mechanism by which the loss of dysbindin induces schizophrenia-like behaviors remains unclear. Here, we report that small interfering RNA-mediated knockdown of dysbindin resulted in the aberrant organization of actin cytoskeleton in SH-SY5Y cells. Furthermore, we show that morphological abnormalities of the actin cytoskeleton were similarly observed in growth cones of cultured hippocampal neurons derived from sandy mice. Moreover, we report a significant correlation between dysbindin expression level and the phosphorylation level of c-Jun N-terminal kinase (JNK), which is implicated in the regulation of cytoskeletal organization. These findings suggest that dysbindin plays a key role in coordinating JNK signaling and actin cytoskeleton required for neural development.

Association study of the G72 gene with schizophrenia in a Japanese population: a multicenter study.

G72 is one of the most widely tested genes for association with schizophrenia. As G72 activates the D-amino acid oxidase (DAO), G72 is termed D-amino acid oxidase activator (DAOA). The aim of this study is to investigate the association between G72 and schizophrenia in a Japanese population, using the largest sample size to date (1774 patients with schizophrenia and 2092 healthy controls). We examined eight single nucleotide polymorphisms (SNPs), which had been associated with schizophrenia in previous studies. We found nominal evidence for association of alleles, M22/rs778293, M23/rs3918342 and M24/rs1421292, and the genotype of M22/rs778293 with schizophrenia, although there was no association of allele or genotype in the other five SNPs. We also found nominal haplotypic association, including M15/rs2391191 and M19/rs778294 with schizophrenia. However, these associations were no longer positive after correction for multiple testing. We conclude that G72 might not play a major role in the risk for schizophrenia in the Japanese population.

Effects of anesthesia on immunohistochemical detection of phosphorylated extracellular signal-regulated kinase in cerebral cortex.

During attempts to examine the phosphorylation status of extracellular signal-regulated kinase (ERK) in cerebral cortex immunohistochemically, we determined whether deep anesthesia for euthanasia disturbs the phosphorylation status of ERK, because the anesthesia might influence activity-dependent phosphorylation of ERK. We compared effects of short (2 and 5 min) and long (>10 min) anesthesia by pentobarbital on the immunoreactivity for phosphorylated ERK in the visual and entorhinal cortices of rat. The long anesthesia drastically reduced the density of phosphorylated ERK immunopositive cells to about 15% of the short anesthesia condition. The reduction was observed in all cortical regions. We found no significant difference in pERK immunoreactivity between 2 and 5 min groups. A reduction of similar degree was induced by long anesthesia with isoflurane. Even if a similar duration of anesthesia is given, the immunohistochemical results possibly contain a variation due to the individual difference in the sensitivity to the anesthetics. We demonstrated that the variation of pERK immunopositive cell density in the visual cortex was significantly reduced by normalizing the values to the density in the nonvisual area in the entorhinal cortex, thus enabling us to detect differences between animals under different visual conditions with higher sensitivity. Therefore, the variation could be reduced by calculating the ratio of immunoreactivity in the area of interest to that in other cortical area as reference.

Platelets surrounding primary tumor cells are related to chemoresistance.

Platelets are crucial components of the tumor microenvironment that function to promote tumor progression and metastasis. In the circulation, the interaction between tumor cells and platelets increases invasiveness, protects tumor cells from shear stress and immune surveillance, and facilitates tumor cell extravasation to distant sites. However, the role and presence of platelets in the primary tumor have not been fully determined. Here, we investigated the presence of platelets around breast cancer primary tumor cells and the associations between these cells. We further investigated the associations among platelets, tumor cells, chemoresistance, and epithelial-mesenchymal transition (EMT). We retrospectively analyzed data from 74 patients with human epidermal growth factor receptor 2 (HER2)­negative breast cancer who underwent biopsies before treatment and subsequent neo-adjuvant chemotherapy. In biopsy specimens, we evaluated the expression of platelet-specific markers and EMT markers using immunohistochemistry. The associations among the expression of platelet­specific markers in biopsy specimens, EMT, response to neo­adjuvant chemotherapy, and survival were analyzed. The presence of platelets was observed in 44 out of 74 (59%) primary breast cancer biopsy specimens. Platelet­positive tumor cells showed EMT­like morphological changes and EMT marker expression. Primary tumor cells associated with platelets were less responsive to neo­adjuvant chemotherapy (pCR rate: 10 vs. 50%, respectively; p=0.0001). Platelets were an independent predictor of the response to chemotherapy upon multivariable analysis (p<0.0001). In conclusion, there was a significant association between platelets surrounding primary tumor cells in the biopsy specimens and the chemotherapeutic response in breast cancer. Platelets surrounding primary tumor cells may represent novel predictors of chemotherapeutic responses.

Physiological ER Stress Mediates the Differentiation of Fibroblasts.

Recently, accumulating reports have suggested the importance of endoplasmic reticulum (ER) stress signaling in the differentiation of several tissues and cells, including myoblasts and osteoblasts. Secretory cells are easily subjected to ER stress during maturation of their secreted proteins. Skin fibroblasts produce and release several proteins, such as collagens, matrix metalloproteinases (MMPs), the tissue inhibitors of metalloproteinases (TIMPs) and glycosaminoglycans (GAGs), and the production of these proteins is increased at wound sites. Differentiation of fibroblasts into myofibroblasts is one of the key factors for wound healing and that TGF-ß can induce fibroblast differentiation into myofibroblasts, which express α-smooth muscle actin. Well-differentiated myofibroblasts show increased production of collagen and TGF-ß, and bring about wound healing. In this study, we examined the effects of ER stress signaling on the differentiation of fibroblasts, which is required for wound healing, using constitutively ER stress-activated primary cultured fibroblasts. The cells expressed positive α-smooth muscle actin signals without TGF-ß stimulation compared with control fibroblasts. Gel-contraction assays suggested that ER stress-treated primary fibroblasts caused stronger shrinkage of collagen gels than control cells. These results suggest that ER stress signaling could accelerate the differentiation of fibroblasts to myofibroblasts at injured sites. The present findings may provide important insights for developing therapies to improve wound healing.

DISC1 (disrupted-in-schizophrenia-1) regulates differentiation of oligodendrocytes.

Disrupted-in-schizophrenia 1 (DISC1) is a gene disrupted by a translocation, t(1;11) (q42.1;q14.3), that segregates with major psychiatric disorders, including schizophrenia, recurrent major depression and bipolar affective disorder, in a Scottish family. Here we report that mammalian DISC1 endogenously expressed in oligodendroglial lineage cells negatively regulates differentiation of oligodendrocyte precursor cells into oligodendrocytes. DISC1 expression was detected in oligodendrocytes of the mouse corpus callosum at P14 and P70. DISC1 mRNA was expressed in primary cultured rat cortical oligodendrocyte precursor cells and decreased when oligodendrocyte precursor cells were induced to differentiate by PDGF deprivation. Immunocytochemical analysis showed that overexpressed DISC1 was localized in the cell bodies and processes of oligodendrocyte precursor cells and oligodendrocytes. We show that expression of the myelin related markers, CNPase and MBP, as well as the number of cells with a matured oligodendrocyte morphology, were decreased following full length DISC1 overexpression. Conversely, both expression of CNPase and the number of oligodendrocytes with a mature morphology were increased following knockdown of endogenous DISC1 by RNA interference. Overexpression of a truncated form of DISC1 also resulted in an increase in expression of myelin related proteins and the number of mature oligodendrocytes, potentially acting via a dominant negative mechanism. We also identified involvement of Sox10 and Nkx2.2 in the DISC1 regulatory pathway of oligodendrocyte differentiation, both well-known transcription factors involved in the regulation of myelin genes.

N-ethylmaleimide-sensitive factor interacts with the serotonin transporter and modulates its trafficking: implications for pathophysiology in autism.

BACKGROUND: Changes in serotonin transporter (SERT) function have been implicated in autism. SERT function is influenced by the number of transporter molecules present at the cell surface, which is regulated by various cellular mechanisms including interactions with other proteins. Thus, we searched for novel SERT-binding proteins and investigated whether the expression of one such protein was affected in subjects with autism. METHODS: Novel SERT-binding proteins were examined by a pull-down system. Alterations of SERT function and membrane expression upon knockdown of the novel SERT-binding protein were studied in HEK293-hSERT cells. Endogenous interaction of SERT with the protein was evaluated in mouse brains. Alterations in the mRNA expression of SERT (SLC6A4) and the SERT-binding protein in the post-mortem brains and the lymphocytes of autism patients were compared to nonclinical controls. RESULTS: N-ethylmaleimide-sensitive factor (NSF) was identified as a novel SERT-binding protein. NSF was co-localized with SERT at the plasma membrane, and NSF knockdown resulted in decreased SERT expression at the cell membranes and decreased SERT uptake function. NSF was endogenously co-localized with SERT and interacted with SERT. While SLC6A4 expression was not significantly changed, NSF expression tended to be reduced in post-mortem brains, and was significantly reduced in lymphocytes of autistic subjects, which correlated with the severity of the clinical symptoms. CONCLUSIONS: These data clearly show that NSF interacts with SERT under physiological conditions and is required for SERT membrane trafficking and uptake function. A possible role for NSF in the pathophysiology of autism through modulation of SERT trafficking, is suggested.

Behavioral characterization of mice overexpressing human dysbindin-1.

BACKGROUND: The dysbindin-1 gene (DTNBP1: dystrobrevin binding protein 1) is a promising schizophrenia susceptibility gene, known to localize almost exclusively to neurons in the brain, and participates in the regulation of neurotransmitter release, membrane-surface receptor expression, and synaptic plasticity. Sandy mice, with spontaneous Dtnbp1 deletion, display behavioral abnormalities relevant to symptoms of schizophrenia. However, it remains unknown if dysbindin-1 gain-of-function is beneficial or detrimental. RESULTS: To answer this question and gain further insight into the pathophysiology and therapeutic potential of dysbindin-1, we developed transgenic mice expressing human DTNBP1 (Dys1A-Tg) and analyzed their behavioral phenotypes. Dys1A-Tg mice were born viable in the expected Mendelian ratios, apparently normal and fertile. Primary screening of behavior and function showed a marginal change in limb grasping in Dys1A-Tg mice. In addition, Dys1A-Tg mice exhibited increased hyperlocomotion after methamphetamine injection. Transcriptomic analysis identified several up- and down-regulated genes, including the immediate-early genes Arc and Egr2, in the prefrontal cortex of Dys1A-Tg mice. CONCLUSIONS: The present findings in Dys1A-Tg mice support the role of dysbindin-1 in psychiatric disorders. The fact that either overexpression (Dys1A-Tg) or underexpression (Sandy) of dysbindin-1 leads to behavioral alterations in mice highlights the functional importance of dysbindin-1 in vivo.

XLMR protein related to neurite extension (Xpn/KIAA2022) regulates cell-cell and cell-matrix adhesion and migration.

X-linked mental retardation (XLMR) is a common cause of moderate to severe intellectual disability in males. XLMR protein related to neurite extension (Xpn, also known as KIAA2022) has been implicated as a gene responsible for XLMR in humans. Although Xpn is highly expressed in the developing brain and is involved in neurite outgrowth in PC12 cells and neurons, little is known about the functional role of Xpn. Here, we show that Xpn regulates cell-cell and cell-matrix adhesion and migration in PC12 cells. Xpn knockdown enhanced cell-cell and cell-matrix adhesion mediated by N-cadherin and ß1-integrin, respectively. N-Cadherin and ß1-integrin expression at the mRNA and protein levels was significantly increased in Xpn knockdown PC12 cells. Furthermore, overexpressed Xpn protein was strongly expressed in the nuclei of PC12 and 293T cells. Finally, depletion of Xpn perturbed cellular migration by enhancing N-cadherin and ß1-integrin expression in a PC12 cell wound healing assay. We conclude that Xpn regulates cell-cell and cell-matrix adhesion and cellular migration by regulating the expression of adhesion molecules.

DBZ (DISC1-binding zinc finger protein)-deficient mice display abnormalities in basket cells in the somatosensory cortices.

Disrupted-in-schizophrenia 1 (DISC1)-binding zinc finger protein (DBZ) is a DISC1-interacting molecule and the interaction between DBZ and DISC1 is involved in neurite outgrowth in vitro. DBZ is highly expressed in brain, especially in the cortex. However, the physiological roles of DBZ in vivo have not been clarified. Here, we show that development of basket cells, a morphologically defined class of parvalbumin (PV)-containing interneurons, is disturbed in DBZ knockout (KO) mice. DBZ mRNA was highly expressed in the ventral area of the subventricular zone of the medial ganglionic eminence, where PV-containing cortical interneurons were generated, at embryonic 14.5 days (E14.5). Although the expression level for PV and the number of PV-containing interneurons were not altered in the cortices of DBZ KO mice, basket cells were less branched and had shorter processes in the somatosensory cortices of DBZ KO mice compared with those in the cortices of WT mice. Furthermore, in the somatosensory cortices of DBZ KO mice, the level of mRNAs for the gamma-aminobutyric acid-synthesizing enzymes GAD67 was decreased. These findings show that DBZ is involved in the morphogenesis of basket cells.

TRAP1 controls mitochondrial fusion/fission balance through Drp1 and Mff expression.

Mitochondria are dynamic organelles that change in response to extracellular stimuli. These changes are essential for normal mitochondrial/cellular function and are controlled by a tight balance between two antagonistic pathways that promote fusion and fission. Although some molecules have been identified to mediate the mitochondrial fusion and fission process, the underlying mechanisms remain unclear. Tumor necrosis factor receptor-associated protein 1 (TRAP1) is a mitochondrial molecule that regulates a variety of mitochondrial functions. Here, we examined the role of TRAP1 in the regulation of morphology. Stable TRAP1 knockdown cells showed abnormal mitochondrial morphology, and we observed significant decreases in dynamin-related protein 1 (Drp1) and mitochondrial fission factor (Mff), mitochondrial fission proteins. Similar results were obtained by transient knockdown of TRAP1 in two different cell lines, SH-SY5Y neuroblastoma cells and KNS-42 glioma cells. However, TRAP1 knockdown did not affect expression levels of fusion proteins. The reduction in Drp1 and Mff protein levels was rescued following treatment with the proteasome inhibitor MG132. These results suggest that TRAP1 regulates the expression of fission proteins and controls mitochondrial fusion/fission, which affects mitochondrial/cellular function.

Mitochondrial TRAP1 regulates the unfolded protein response in the endoplasmic reticulum.

Stress in mitochondria or the endoplasmic reticulum (ER) independently causes cell death. Recently, it was reported that ER stress causes mitochondrial dysfunction via p53-upregulated modulator of apoptosis (PUMA). However, little is known regarding the mitochondria molecules that mediate ER dysfunction. The present study revealed that tumor necrosis factor receptor-associated protein 1 (TRAP1), which localizes in the mitochondria, is associated with the unfolded protein response (UPR) in the ER. TRAP1 knockdown activated the ER-resident caspase-4, which is activated by ER stress, to induce cell death in humans. However, TRAP1 knockdown cells did not show a significant increase in the level of cell death at least within 24 h after early phase of ER stress in comparison with that of the control cells. This finding could be attributed to a number of reasons. TRAP1 knockdown failed to activate caspase-9, which is activated by activated caspase-4. In addition, TRAP1 knockdown increased the basal level of GRP78/BiP expression, which protects cells, and decreased the basal level of C/EBP homologous protein (CHOP) expression, which induces cell death, even under ER stress. Thus, the present study revealed that mitochondria could be a potential regulator of the UPR in the ER through mitochondrial TRAP1.

Association study of KIBRA gene with memory performance in a Japanese population.

OBJECTIVES: Papassotiropoulos et al. (Science 314: p 475) discovered that a single nucleotide polymorphism (SNP) of the KIBRA gene (rs17070145) was associated with delayed recall performance in Caucasians. KIBRA is highly expressed in the brain and kidneys, and is reported to be involved in synaptic plasticity. Therefore, we first tried to replicate the association between the SNP and memory performance in a Japanese subjects. METHODS: We examined the association between the SNP and memory performance measured by the Wechsler Memory Scale-Revised (WMS-R) in 187 healthy Japanese people. RESULTS: The T allele carriers had significantly better verbal memory, attention/concentration and delayed recall performance than the C/C carriers (corrected P = 0.044, 0.047 and 0.0084, respectively). Furthermore, the C/T carriers and the T/T carriers had better delayed recall performance than the C/C carriers (post hoc P = 0.0017 and 0.0096). CONCLUSIONS: This data suggest that the C/C genotype might have an impact on memory performance in Asian populations as well as in Caucasian populations. Further investigation to clarify the association of the KIBRA gene with memory in other ethnic groups is warranted.