Δ3-tubulin impairs mitotic spindle morphology and increases nuclear size in pancreatic cancer cells

Cancer cell proliferation is affected by post-translational modifications of tubulin. Especially, overexpression or depletion of enzymes for modifications on the tubulin C-terminal region perturbs dynamic instability of the spindle body. Those modifications include processing of C-terminal amino acids of α-tubulin; detyrosination, and a removal of penultimate glutamic acid (Δ2). We previously found a further removal of the third last glutamic acid, which generates so-called Δ3-tubulin. The effects of Δ3-tubulin on spindle integrities and cell proliferation remain to be elucidated. In this study, we investigated the impacts of forced expression of Δ3-tubulin on the structure of spindle bodies and cell division in a pancreatic cancer cell line, PANC-1. Overexpression of HA-tagged Δ3-tubulin impaired the morphology and orientation of spindle bodies during cell division in PANC-1 cells. In particular, spindle bending was most significantly increased. Expression of EGFP-tagged Δ3-tubulin driven by the endogenous promoter of human TUBA1B also deformed and misoriented spindle bodies. Spindle bending and condensation defects were significantly observed by EGFP-Δ3-tubulin expression. Furthermore, EGFP-Δ3-tubulin expression increased the nuclear size in a dose-dependent manner of EGFP-Δ3-tubulin expression. The expression of EGFP-Δ3-tubulin tended to slow down cell proliferation. Taken together, our results demonstrate that Δ3-tubulin affects the spindle integrity and cell division.

Circadian oscillation in primary cilium length by clock genes regulates fibroblast cell migration

Various mammalian cells have autonomous cellular clocks that are produced by the transcriptional cycle of clock genes. Cellular clocks provide circadian rhythms for cellular functions via transcriptional and cytoskeletal regulation. The vast majority of mammalian cells possess a primary cilium, an organelle protruding from the cell surface. Here, we investigated the little-known relationship between circadian rhythm and primary cilia. The length and number of primary cilia showed circadian dynamics both in vitro and in vivo. The circadian rhythm of primary cilium length was abolished by SR9011 and Bmal1 knockout. A centrosomal protein, pericentrin, transiently accumulates in centriolar satellites, the base of primary cilia at the shortest cilia phase, and induces elongation of primary cilia at the longest cilia phase in the circadian rhythm of primary cilia. In addition, rhythmic cell migration during wound healing depends on the length of primary cilia and affects the rate of wound healing. Our findings demonstrate that the circadian dynamics of primary cilium length by clock genes control fibroblast migration and could provide new insights into chronobiology.

Time-lapse imaging of primary cilium behavior with physiological expression of fluorescent ciliary proteins

Almost all cell types of mammals have a small protrusion named a primary cilium on their surface. Primary cilia are enriched by cilia-specific ion channels and G-protein-coupled receptors. They are known to regulate various cellular functions that contribute to the development and homeostasis of living organisms by receiving extracellular signals and transfusing them to the cell body. All functions are performed when the structure of the primary cilia is maintained properly. Abnormalities in primary cilia or their signaling can lead to a collection of diseases in various organs called ciliopathies. The primary cilium is dynamic, static, or fixed. The length of primary cilia varies as the cell cycle progresses and is also altered by extracellular stimuli. Ligand binding to cilia-specific receptors is also known to alter the length. Thus, there is a need for a method to study the morphological changes of the primary cilium in a time-dependent manner, especially under stimuli or mechanical shocks. Time-lapse imaging of primary cilia is one of the most powerful methods to capture the time-dependent behavior of primary cilia. Overexpression of ciliary proteins fused to fluorescent proteins is commonly used for the time-lapse imaging of primary cilia. However, overexpression has drawbacks in terms of artifacts. In addition, the time-lapse imaging of the tiny primary cilia requires some technical tricks. Here, we present a detailed description of the methods for time-lapse imaging of primary cilium, from the generation of cell lines that stably express fluorescent protein-labeled cilia-localized proteins at the physiological level to image analysis, including quantification through image acquisition.

A pair of primers facing at the double-strand break site enables to detect NHEJ-mediated indel mutations at a 1-bp resolution

The introduction of small insertion/deletion (indel) mutations in the coding region of genes by the site-specific nucleases such as Cas9 allows researchers to obtain frameshift null mutants. Technically simple and costly reasonable genotyping methods are awaited to efficiently screen the frameshift null mutant candidates. Here, we developed a simple genotyping method called DST-PCR (Double-strand break Site-Targeted PCR) using “face-to-face” primers where the 3’ ends of forward and reverse primers face each other at the position between 3-bp and 4-bp upstream of the PAM sequence, which is generally the Cas9-mediated double-strand break site. Generated amplicons are directly subjected to TBE-High-Resolution PAGE, which contains a high concentration of bis-acrylamide, for mutant clones detection with 1-bp resolution. We present actual cases of screening of CRISPR/Cas9-engineered knockout (KO) cells for six genes, where we screen indels to obtain potential KO cell clones utilizing our approach. This method allowed us to detect 1-bp to 2-bp insertion and 1-bp to 4-bp deletion in one or both alleles of mutant cell clones. In addition, this technique also allowed the identification of heterozygous and homozygous biallelic functional KO candidates. Thus, DST-PCR is a simple and fast method to screen KO candidates generated by the CRISPR/Cas9 system before the final selection of clones with sequencing.

A pharmacokinetic-pharmacodynamic model based on multi-organ-on-a-chip for drug-drug interaction studies

In drug discovery, the emergence of unexpected toxicity is often a problem resulting from a poor understanding of the pharmacokinetics of drug-drug interactions (DDI). Organ-on-a-chip (OoC) has been proposed as an in vitro model to evaluate drug efficacy and toxicity in pharmacology, but it has not been applied to DDI studies yet. In this study, we aim to evaluate whether organ-on-a-chip technologies can be applied to DDI studies. To assess the usefulness of OoC for DDI studies, we proposed a multi-organ-on-a-chip (MOoC) with a liver part as the metabolic model and a cancer part as the drug target model, and a pharmacokinetic-pharmacodynamic (PK-PD) model describing the MOoC. An anticancer prodrug, CPT-11, was used to evaluate the drug efficacy of the metabolite in the liver part of the MOoC. To evaluate DDI using the MOoC, the inhibitory effect of simvastatin and ritonavir on the metabolism of CPT-11 was tested. The DDI estimation method was evaluated by comparing the results of the concomitant administration experiment using the MOoC and the results of simulation using the proposed PK-PD model with the estimated parameters. The results were similar, suggesting that the combination of the PK-PD model and the MOoC is a useful way to predict DDI. We conclude that OoC technologies could facilitate a better understanding of pharmacokinetic mechanisms with DDI.

A negative feedback loop between JNK-associated leucine zipper protein and TGF-β1 regulates kidney fibrosis

Renal fibrosis is controlled by profibrotic and antifibrotic forces. Exploring anti-fibrosis factors and mechanisms is an attractive strategy to prevent organ failure. Here we identified the JNK-associated leucine zipper protein (JLP) as a potential endogenous antifibrotic factor. JLP, predominantly expressed in renal tubular epithelial cells (TECs) in normal human or mouse kidneys, was downregulated in fibrotic kidneys. Jlp deficiency resulted in more severe renal fibrosis in unilateral ureteral obstruction (UUO) mice, while renal fibrosis resistance was observed in TECs-specific transgenic Jlp mice. JLP executes its protective role in renal fibrosis via negatively regulating TGF-β1 expression and autophagy, and the profibrotic effects of ECM production, epithelial-to-mesenchymal transition (EMT), apoptosis and cell cycle arrest in TECs. We further found that TGF-β1 and FGF-2 could negatively regulate the expression of JLP. Our study suggests that JLP plays a central role in renal fibrosis via its negative crosstalk with the profibrotic factor, TGF-β1.

Qi Yan et al. find that JNK-associated leucine zipper protein (Jlp) counteracts the profibrotic effects of TGF-β1 and autophagy on renal tubular epithelial cells and that TGF-β1 and FGF-2 can negatively regulate the expression of Jlp. These findings provide insights into the role of Jlp in kidney fibrosis.

Inhibition of the glutamine transporter SNAT1 confers neuroprotection in mice by modulating the mTOR-autophagy system

The pathophysiological role of mammalian target of rapamycin complex 1 (mTORC1) in neurodegenerative diseases is established, but possible therapeutic targets responsible for its activation in neurons must be explored. Here we identified solute carrier family 38a member 1 (SNAT1, Slc38a1) as a positive regulator of mTORC1 in neurons. Slc38a1flox/flox and Synapsin I-Cre mice were crossed to generate mutant mice in which Slc38a1 was selectively deleted in neurons. Measurement of 2,3,5-triphenyltetrazolium chloride (TTC) or the MAP2-negative area in a mouse model of middle cerebral artery occlusion (MCAO) revealed that Slc38a1 deficiency decreased infarct size. We found a transient increase in the phosphorylation of p70S6k1 (pp70S6k1) and a suppressive effect of rapamycin on infarct size in MCAO mice. Autophagy inhibitors completely mitigated the suppressive effect of SNAT1 deficiency on neuronal cell death under in vitro stroke culture conditions. These results demonstrate that SNAT1 promoted ischemic brain damage via mTOR-autophagy system.

JLP-JNK signaling protects cancer cells from reactive oxygen species-induced cell death

Oxidative stress, which can be caused by an overproduction of reactive oxygen species (ROS), often leads to cell death. In recent years, c-Jun NH₂-terminal kinase (JNK)-associated leucine zipper protein (JLP, also known as SPAG9 or JIP4), a scaffold protein for JNK mitogen-activated protein kinase (MAPK) signaling pathways, was found to serve as a novel biomarker for cancer. However, although JNK MAPK pathways are reported to be activated in response to various stimuli, including oxidative stress, whether JLP is involved in ROS signaling remains unknown. In this study, we examined the role of JLP in hydrogen peroxide (H₂O₂)-induced cancer cell death, and found that JLP knockdown (KD) cells exhibit a substantially enhanced cell death response, along with increased intracellular ROS levels. This is the first demonstration of a protective role for JLP in response to cell-death stimulation. We also found that the H₂O₂-induced JNK activation was attenuated in JLP KD cancer cells. The decreases in cell viability and JNK activation in the JLP KD cells were almost completely reversed by expressing wild-type JLP, but not a mutant JLP lacking the JNK-binding domain. These data collectively suggest that the JLP-JNK signaling pathway counteracts ROS-induced cancer cell death.

Disruption of Bmal1 Impairs Blood-Brain Barrier Integrity via Pericyte Dysfunction

Circadian rhythm disturbances are well established in neurological diseases. However, how these disruptions cause homeostatic imbalances remains poorly understood. Brain and muscle aryl hydrocarbon receptor nuclear translocator-like protein 1 (Bmal1) is a major circadian clock transcriptional activator, and Bmal1 deficiency in male Bmal1nestin-/- mice induced marked astroglial activation without affecting the number of astrocytes in the brain and spinal cord. Bmal1 deletion caused blood-brain barrier (BBB) hyperpermeability with an age-dependent loss of pericyte coverage of blood vessels in the brain. Using Nestin-green fluorescent protein (GFP) transgenic mice, we determined that pericytes are Nestin-GFP+ in the adult brain. Bmal1 deletion caused Nestin-GFP+ pericyte dysfunction, including the downregulation of platelet-derived growth factor receptor β (PDGFRβ), a protein necessary for maintaining BBB integrity. Knockdown of Bmal1 downregulated PDGFRβ transcription in the brain pericyte cell line. Thus, the circadian clock component Bmal1 maintains BBB integrity via regulating pericytes.SIGNIFICANCE STATEMENT Circadian rhythm disturbances may play a role in neurodegenerative disorders, such as Alzheimer's disease. Our results revealed that one of the circadian clock components maintains the integrity of the blood-brain barrier (BBB) by regulating vascular-embedded pericytes. These cells were recently identified as a vital component for the control of BBB permeability and cerebral blood flow. Our present study demonstrates the involvement of circadian clock component Bmal1 in BBB homeostasis and highlights the role of Bmal1 dysfunction in multiple neurological diseases.

Critical role of glioma-associated oncogene homolog 1 in maintaining invasive and mesenchymal-like properties of melanoma cells

Cutaneous melanoma is the most aggressive form of skin cancer. This aggressiveness appears to be due to the cancer cells' ability to reversibly switch between phenotypes with non-invasive and invasive potential, and microphthalmia-associated transcription factor (MITF) is known to play a central role in this process. The transcription factor glioma-associated oncogene homolog 1 (GLI1) is a component of the canonical and noncanonical sonic hedgehog pathways. Although GLI1 has been suggested to be involved in melanoma progression, its precise role and the mechanism underlying invasion remain unclear. Here we investigated whether and how GLI1 is involved in the invasive ability of melanoma cells. Gli1 knockdown (KD) melanoma cell lines, established by using Gli1-targeting lentiviral short hairpin RNA, exhibited a markedly reduced invasion ability, but their MITF expression and activity were the same as controls. Gli1 KD melanoma cells also led to less lung metastasis in mice compared with control melanoma cells. Furthermore, the Gli1 KD melanoma cells underwent a mesenchymal-to-epithelial-like transition, accompanied by downregulation of the epithelial-to-mesenchymal transition (EMT)-inducing transcription factors (EMT-TF) Snail1, Zeb1 and Twist1, but not Snail2 or Zeb2. Collectively, these results indicate that GLI1 is important for maintaining the invasive and mesenchymal-like properties of melanoma cells independent of MITF, most likely by modulating a subset of EMT-TF. Our findings provide new insight into how heterogeneity and plasticity are achieved and regulated in melanoma.

Scaffold protein JLP mediates TCR-initiated CD4+T cell activation and CD154 expression

CD4⁺ T-cell activation and its subsequent induction of CD154 (CD40 ligand, CD40L) expression are pivotal in shaping both the humoral and cellular immune responses. Scaffold protein JLP regulates signal transduction pathways and molecular trafficking inside cells, thus represents a critical component in maintaining cellular functions. Its role in regulating CD4⁺ T-cell activation and CD154 expression, however, is unclear. Here, we demonstrated expression of JLP in mouse tissues of lymph nodes, thymus, spleen, and also CD4⁺ T cells. Using CD4+ T cells from jlp-deficient and jlp-wild-type mice, we demonstrated that JLP-deficiency impaired T-cell proliferation, IL-2 production, and CD154 induction upon TCR stimulations, but had no impacts on the expression of other surface molecules such as CD25, CD69, and TCR. These observed impaired T-cell functions in the jlp-/- CD4⁺ T cells were associated with defective NF-AT activation and Ca²⁺ influx, but not the MAPK, NF-κB, as well as AP-1 signaling pathways. Our findings indicated that, for the first time, JLP plays a critical role in regulating CD4⁺ T cells response to TCR stimulation partly by mediating the activation of TCR-initiated Ca²⁺/NF-AT.

Bone Resorption Is Regulated by Circadian Clock in Osteoblasts

We have previously shown that endochondral ossification is finely regulated by the Clock system expressed in chondrocytes during postnatal skeletogenesis. Here we show a sophisticated modulation of bone resorption and bone mass by the Clock system through its expression in bone-forming osteoblasts. Brain and muscle aryl hydrocarbon receptor nuclear translocator-like protein 1 (Bmal1) and Period1 (Per1) were expressed with oscillatory rhythmicity in the bone in vivo, and circadian rhythm was also observed in cultured osteoblasts of Per1::luciferase transgenic mice. Global deletion of murine Bmal1, a core component of the Clock system, led to a low bone mass, associated with increased bone resorption. This phenotype was recapitulated by the deletion of Bmal1 in osteoblasts alone. Co-culture experiments revealed that Bmal1-deficient osteoblasts have a higher ability to support osteoclastogenesis. Moreover, 1α,25-dihydroxyvitamin D3 [1,25(OH)2 D3 ]-induced receptor activator of nuclear factor κB ligand (Rankl) expression was more strongly enhanced in both Bmal1-deficient bone and cultured osteoblasts, whereas overexpression of Bmal1/Clock conversely inhibited it in osteoblasts. These results suggest that bone resorption and bone mass are regulated at a sophisticated level by osteoblastic Clock system through a mechanism relevant to the modulation of 1,25(OH)2 D3 -induced Rankl expression in osteoblasts. © 2017 American Society for Bone and Mineral Research.

The intrinsic microglial clock system regulates interleukin-6 expression

Similar to neurons, microglia have an intrinsic molecular clock. The master clock oscillator Bmal1 modulates interleukin-6 upregulation in microglial cells exposed to lipopolysaccharide. Bmal1 can play a role in microglial inflammatory responses. We previously demonstrated that gliotransmitter ATP induces transient expression of the clock gene Period1 via P2X7 purinergic receptors in cultured microglia. In this study, we further investigated mechanisms underlying the regulation of pro-inflammatory cytokine production by clock molecules in microglial cells. Several clock gene transcripts exhibited oscillatory diurnal rhythmicity in microglial BV-2 cells. Real-time luciferase monitoring also showed diurnal oscillatory luciferase activity in cultured microglia from Per1::Luciferase transgenic mice. Lipopolysaccharide (LPS) strongly induced the expression of pro-inflammatory cytokines in BV-2 cells, whereas an siRNA targeting Brain and muscle aryl hydrocarbon receptor nuclear translocator-like protein 1 (Bmal1), a core positive component of the microglial molecular clock, selectively inhibited LPS-induced interleukin-6 (IL-6) expression. In addition, LPS-induced IL-6 expression was attenuated in microglia from Bmal1-deficient mice. This phenotype was recapitulated by pharmacological disruption of oscillatory diurnal rhythmicity using the synthetic Rev-Erb agonist SR9011. Promoter analysis of the Il6 gene revealed that Bmal1 is required for LPS-induced IL-6 expression in microglia. Mice conditionally Bmal1 deficient in cells expressing CD11b, including microglia, exhibited less potent upregulation of Il6 expression following middle cerebral artery occlusion compared with that in control mice, with a significant attenuation of neuronal damage. These results suggest that the intrinsic microglial clock modulates the inflammatory response, including the positive regulation of IL-6 expression in a particular pathological situation in the brain, GLIA 2016. GLIA 2017;65:198-208.

Genetic analysis of Runx2 function during intramembranous ossification

Runt-related transcription factor 2 (Runx2) is an essential transcriptional regulator of osteoblast differentiation and its haploinsufficiency leads to cleidocranial dysplasia because of a defect in osteoblast differentiation during bone formation through intramembranous ossification. The cellular origin and essential period for Runx2 function during osteoblast differentiation in intramembranous ossification remain poorly understood. Paired related homeobox 1 (Prx1) is expressed in craniofacial mesenchyme, and Runx2 deficiency in cells of the Prx1 lineage (in mice referred to here as Runx2prx1 (-/-)) resulted in defective intramembranous ossification. Runx2 was heterogeneously expressed in Prx1-GFP(+) cells located at the intrasutural mesenchyme in the calvaria of transgenic mice expressing GFP under the control of the Prx1 promoter. Double-positive cells for Prx1-GFP and stem cell antigen-1 (Sca1) (Prx1(+)Sca1(+) cells) in the calvaria expressed Runx2 at lower levels and were more homogeneous and primitive than Prx1(+)Sca1(-) cells. Osterix (Osx) is another transcriptional determinant of osteoblast lineages expressed by osteoblast precursors; Osx is highly expressed by Prx1(-)Runx2(+) cells at the osteogenic front and on the surface of mineralized bone in the calvaria. Runx2 deficiency in cells of the Osx lineage (in mice referred to here as Runx2osx (-/-)) resulted in severe defects in intramembranous ossification. These findings indicate that the essential period of Runx2 function in intramembranous ossification begins at the Prx1(+)Sca1(+) mesenchymal stem cell stage and ends at the Osx(+)Prx1(-)Sca1(-) osteoblast precursor stage.

Upregulation of Runt-Related Transcription Factor-2 Through CCAAT Enhancer Binding Protein-β Signaling Pathway in Microglial BV-2 Cells Exposed to ATP

We have shown constitutive expression of the master regulator of osteoblastogenesis, runt-related transcription factor-2 (Runx2), by microglia cells outside bone. Here, we attempted to evaluate the pathological significance of Runx2 in microglial BV-2 cells exposed to ATP at a high concentration. Marked upregulation of Runx2 transcript and protein expression was seen in cells exposed to 1 mM ATP for a period longer than 30 min without inducing cytotoxicity. The Runx2 upregulation by ATP was prevented by extracellular and intracellular Ca(2+) chelators, while thapsigargin upregulated Runx2 expression alone without affecting the upregulation by ATP. A calmodulin antagonist prevented the upregulation by ATP, with calcineurin inhibitors being ineffective. Although ATP markedly increased nuclear levels of nuclear factor of activated T cell-2 (NFAT2), Runx2 promoter activity was not simulated by the introduction of either NFAT1 or NFAT2, but facilitated by that of CCAAT enhancer binding protein-α (C/EBPα), C/EBPβ and nuclear factor (erythroid-derived 2)-like-2 (Nrf2). Exposure to ATP up-regulated C/EBPβ and Nrf2, but not C/EBPα, expression, in addition to increasing nuclear levels of respective corresponding proteins. Runx2 upregulation by ATP was deteriorated by knockdown of C/EBPβ but not by that of Nrf2, however, while exposure to ATP up-regulated matrix metalloproteinase-13 (Mmp13) expression in a Runx2-dependent manner. Overexpression of Runx2 up-regulated Mmp13 expression with promoted incorporation of fluorescent beads into BV-2 cells without ATP. These results suggest that extracellular ATP up-regulates Runx2 expression through activation of the C/EBPβ signaling in a calmodulin-dependent manner to play a pivotal role in phagocytosis in microglial BV-2 cells.

Critical role of JSAP1 and JLP in axonal transport in the cerebellar Purkinje cells of mice

JNK/stress-activated protein kinase-associated protein 1 (JSAP1) and JNK-associated leucine zipper protein (JLP) are structurally related scaffolding proteins that are highly expressed in the brain. Here, we found that JSAP1 and JLP play functionally redundant and essential roles in mouse cerebellar Purkinje cell (PC) survival. Mice containing PCs with deletions in both JSAP1 and JLP exhibited PC axonal dystrophy, followed by gradual, progressive neuronal loss. Kinesin-1 cargoes accumulated selectively in the swollen axons of Jsap1/Jlp-deficient PCs. In addition, autophagy inactivation in these mice markedly accelerated PC degeneration. These findings suggest that JSAP1 and JLP play critical roles in kinesin-1-dependent axonal transport, which prevents brain neuronal degeneration.

Constitutive and functional expression of runt-related transcription factor-2 by microglial cells

Runt-related transcription factor-2 (Runx2) is the master regulator of osteoblastogenesis with an ability to promote differentiation of mesenchymal stem cells into the osteoblastic lineage. We have previously shown constitutive and functional expression of Runx2 by astroglial cells. In this study, we investigated the possible expression of Runx2 by both murine microglia and microglial cell line BV-2 cells. Runx2 expression was seen in cultured microglia and BV-2 cells, while sustained exposure to 1mM ATP led to a significant but transient increase in mRNA and corresponding protein expression of Runx2 within 24 h. The increase in Runx2 expression was invariably prevented by several chemicals with antagonistic properties for P2X7 purinergic receptor, calmodulin and calcineurin in BV-2 cells, with a P2X7 receptor agonist more than quadrupling Runx2 expression. A significant increase in Runx2 expression was seen in osteoclastic cells, but not in osteoblastic or chondrocytic cells, when exposed to a high concentration of ATP. In BV2-cells with control siRNA, a significant decrease was found in the number of cells with at least one process within 3 h after the exposure to 1mM ATP, followed by an increase up to 24 h. However, Runx2 siRNA significantly deteriorated the property to induce delayed process extension during 6-24 h after exposure to ATP along with drastically decreased Runx2 protein levels. These results suggest that Runx2 is constitutively and functionally expressed by microglial cells with responsiveness to ATP for upregulation in the murine brain.

An analysis of skeletal development in osteoblast-specific and chondrocyte-specific runt-related transcription factor-2 (Runx2) knockout mice

Global gene deletion studies in mice and humans have established the pivotal role of runt related transcription factor-2 (Runx2) in both intramembranous and endochondral ossification processes during skeletogenesis. In this study, we for the first time generated mice carrying a conditional Runx2 allele with exon 4, which encodes the Runt domain, flanked by loxP sites. These mice were crossed with α1(I)-collagen-Cre or α1(II)-collagen-Cre transgenic mice to obtain osteoblast-specific or chondrocyte-specific Runx2 deficient mice, respectively. As seen in Runx2(-/-) mice, perinatal lethality was observed in α1(II)-Cre;Runx2(flox/flox) mice, but this was not the case in animals in which α1(I)-collagen-Cre was used to delete Runx2. When using double-staining with Alizarin red for mineralized matrix and Alcian blue for cartilaginous matrix, we observed previously that mineralization was totally absent at embryonic day 15.5 (E15.5) throughout the body in Runx2(-/-) mice, but was found in areas undergoing intramembranous ossification such as skull and clavicles in α1(II)-Cre;Runx2(flox/flox) mice. In newborn α1(II)-Cre;Runx2(flox/flox) mice, mineralization impairment was restricted to skeletal areas undergoing endochondral ossification including long bones and vertebrae. In contrast, no apparent skeletal abnormalities were seen in mutant embryo, newborn, and 3-week-old to 6-week old-mice in which Runx2 had been deleted with the α1(I)-collagen-Cre driver. These results suggest that Runx2 is absolutely required for endochondral ossification during embryonic and postnatal skeletogenesis, but that disrupting its expression in already committed osteoblasts as achieved here with the α1(I)-collagen-Cre driver does not affect overtly intramembranous and endochondral ossification. The Runx2 floxed allele established here is undoubtedly useful for investigating the role of Runx2 in particular cells.

Selective inhibition by ethanol of mitochondrial calcium influx mediated by uncoupling protein-2 in relation to N-methyl-D-aspartate cytotoxicity in cultured neurons

BACKGROUND

We have shown the involvement of mitochondrial uncoupling protein-2 (UCP2) in the cytotoxicity by N-methyl-D-aspartate receptor (NMDAR) through a mechanism relevant to the increased mitochondrial Ca(2+) levels in HEK293 cells with acquired NMDAR channels. Here, we evaluated pharmacological profiles of ethanol on the NMDA-induced increase in mitochondrial Ca(2+) levels in cultured murine neocortical neurons.

METHODOLOGY/PRINCIPAL FINDINGS

In neurons exposed to glutamate or NMDA, a significant increase was seen in mitochondrial Ca(2+) levels determined by Rhod-2 at concentrations of 0.1 to 100 µM. Further addition of 250 mM ethanol significantly inhibited the increase by glutamate and NMDA in Rhod-2 fluorescence, while similarly potent inhibition of the NMDA-induced increase was seen after exposure to ethanol at 50 to 250 mM in cultured neurons. Lentiviral overexpression of UCP2 significantly accelerated the increase by NMDA in Rhod-2 fluorescence in neurons, without affecting Fluo-3 fluorescence for intracellular Ca(2+) levels. In neurons overexpressing UCP2, exposure to ethanol resulted in significantly more effective inhibition of the NMDA-induced increase in mitochondrial free Ca(2+) levels than in those without UCP2 overexpression, despite a similarly efficient increase in intracellular Ca(2+) levels irrespective of UCP2 overexpression. Overexpression of UCP2 significantly increased the number of dead cells in a manner prevented by ethanol in neurons exposed to glutamate. In HEK293 cells with NMDAR containing GluN2B subunit, more efficient inhibition was similarly induced by ethanol at 50 and 250 mM on the NMDA-induced increase in mitochondrial Ca(2+) levels than in those with GluN2A subunit. Decreased protein levels of GluN2B, but not GluN2A, subunit were seen in immunoprecipitates with UCP2 from neurons with brief exposure to ethanol at concentrations over 50 mM.

CONCLUSIONS/SIGNIFICANCE

Ethanol could inhibit the interaction between UCP2 and NMDAR channels to prevent the mitochondrial Ca(2+) incorporation and cell death after NMDAR activation in neurons.

Promoted neuronal differentiation after activation of alpha4/beta2 nicotinic acetylcholine receptors in undifferentiated neural progenitors

BACKGROUND

Neural progenitor is a generic term used for undifferentiated cell populations of neural stem, neuronal progenitor and glial progenitor cells with abilities for proliferation and differentiation. We have shown functional expression of ionotropic N-methyl-D-aspartate (NMDA) and gamma-aminobutyrate type-A receptors endowed to positively and negatively regulate subsequent neuronal differentiation in undifferentiated neural progenitors, respectively. In this study, we attempted to evaluate the possible functional expression of nicotinic acetylcholine receptor (nAChR) by undifferentiated neural progenitors prepared from neocortex of embryonic rodent brains.

METHODOLOGY/PRINCIPAL FINDINGS

Reverse transcription polymerase chain reaction analysis revealed mRNA expression of particular nAChR subunits in undifferentiated rat and mouse progenitors prepared before and after the culture with epidermal growth factor under floating conditions. Sustained exposure to nicotine significantly inhibited the formation of neurospheres composed of clustered proliferating cells and 3-[4,5-dimethylthiazol-2-yl]-2,5-diphenyltetrazolium bromide reduction activity at a concentration range of 1 µM to 1 mM without affecting cell survival. In these rodent progenitors previously exposed to nicotine, marked promotion was invariably seen for subsequent differentiation into cells immunoreactive for a neuronal marker protein following the culture of dispersed cells under adherent conditions. Both effects of nicotine were significantly prevented by the heteromeric α4β2 nAChR subtype antagonists dihydro-β-erythroidine and 4-(5-ethoxy-3-pyridinyl)-N-methyl-(3E)-3-buten-1-amine, but not by the homomeric α7 nAChR subtype antagonist methyllycaconitine, in murine progenitors. Sustained exposure to nicotine preferentially increased the expression of Math1 among different basic helix-loop-helix proneural genes examined. In undifferentiated progenitors from embryonic mice defective of NMDA receptor subunit-1, nicotine was still effective in significantly inhibiting the proliferation.

CONCLUSIONS/SIGNIFICANCE

Functional α4β2 nAChR subtype would be constitutively expressed to play a role in the mechanism underlying the determination of proliferation and subsequent differentiation fate into a neuronal lineage in association with preferential promotion of Math1 expression in undifferentiated neural progenitors of developing rodent neocortex independently of NMDA receptor activation.

Selective downregulation of N-methyl-D-aspartate receptor (NMDAR) rather than non-NMDAR subunits in ipsilateral cerebral hemispheres in rats with middle cerebral artery occlusion

Ischemic brain damage is believed to involve the drastic increase in extracellular glutamate levels after reperfusion and subsequent overactivation of both N-methyl-D-aspartate (NMDA) receptor (NMDAR) and non-NMDAR channels for delayed neuronal cell death mediated by Ca2+ overload. In this study, we evaluated expression profiles of mRNA and corresponding proteins for different subunits of NMDAR and non-NMDAR in brains of rats with transient middle cerebral artery occlusion (MCAO). Cellular vitality was markedly reduced in proportion to increasing durations of MCAO for 1 to 8 h when determined 1 day after reperfusion. Within 7 days after reperfusion, MCAO for 2 h led to a gradual decrease in the neuronal marker microtubules-associated protein-2 (MAP2) level in the ipsilateral cerebral hemisphere, in addition to inducing a transient increase in the microglial marker CD11b expression without affecting the astroglial marker protein levels. MCAO for 2 h significantly decreased the expression of both mRNA and corresponding proteins for NR1, NR2A and NR2B subunits of NMDAR, but not for non-NMDAR subunits, in the ipsilateral hemisphere. These results suggest that NMDAR may be preferentially down-regulated in response to ischemic signal inputs amongst three different subtypes of ionotropic glutamate receptors in rats with MCAO.

Selective upregulation of Per1 mRNA expression by ATP through activation of P2X7 purinergic receptors expressed in microglial cells

Clock genes are believed to play a pivotal role in the generation and oscillation of circadian rhythm as a central clock in the hypothalamic suprachiasmatic nucleus in the mammalian brain. In this study, mRNA expression was for the first time demonstrated with clock genes in both cultured murine microglia and microglial cell line BV-2 cells. Exposure to ATP transiently increased Period-1 (Per1) mRNA expression without affecting that of other clock genes in BV-2 cells, while a similarly transient increase was shown in Per1 mRNA expression in a manner sensitive to P2X7 purinergic receptor antagonists in cultured microglia exposed to ATP. In BV-2 cells transfected with a Per1 promoter luciferase reporter plasmid, ATP significantly increased luciferase activity in a manner sensitive to a P2X7-receptor antagonist. In both microglia and BV-2 cells, a significant increase by ATP was seen in the immunocytochemical fluorescence intensity of cells expressing Per1 protein, with mRNA expression of different P2 receptors including P2X7. Per1 siRNA significantly decreased the number of cells with processes in BV-2 cells exposed to ATP. These results suggest that ATP selectively promotes Per1 expression through gene transactivation after stimulation of P2X7 purinergic receptors in microglial cells.

A possible pivotal role of mitochondrial free calcium in neurotoxicity mediated by N-methyl-d-aspartate receptors in cultured rat hippocampal neurons

We have previously shown that mitochondrial membrane potential disruption is involved in mechanisms underlying differential vulnerabilities to the excitotoxicity mediated by N-methyl-d-aspartate (NMDA) receptors between primary cultured neurons prepared from rat cortex and hippocampus. To further elucidate the role of mitochondria in the excitotoxicity after activation of NMDA receptors, neurons were loaded with the fluorescent dye calcein diffusible in the cytoplasm and organelles for determination of the activity of mitochondrial permeability transition pore (mPTP) responsible for the leakage of different mitochondrial molecules. The addition of CoCl(2) similarly quenched the intracellular fluorescence except mitochondria in both cultured neurons, while further addition of NMDA led to a leakage of the dye into the cytoplasm in hippocampal neurons only. An mPTP inhibitor prevented the NMDA-induced loss of viability in hippocampal neurons, while an activator of mPTP induced a similarly potent loss of viability in cortical and hippocampal neurons. Although NMDA was more effective in increasing rhodamine-2 fluorescence as a mitochondrial calcium indicator in hippocampal than cortical neurons, a mitochondrial calcium uniporter inhibitor significantly prevented the NMDA-induced loss of viability in hippocampal neurons. Expression of mRNA was significantly higher for the putative uniporter uncoupling protein-2 in hippocampal than cortical neurons. These results suggest that mitochondrial calcium uniporter would be at least in part responsible for the NMDA neurotoxicity through a mechanism relevant to promotion of mPTP orchestration in hippocampal neurons.

Exacerbated vulnerability to oxidative stress in astrocytic C6 glioma cells with stable overexpression of the glutamine transporter slc38a1

We have previously demonstrated the functional expression of glutamine (Gln) transporter (GlnT) believed to predominate in neurons for the neurotransmitter glutamate pool by rat neocortical astrocytes devoid of neuronal marker expression, with exacerbated vulnerability to oxidative stress after transient overexpression. To evaluate molecular mechanisms underlying the exacerbation, we established stable GlnT transfectants in rat astrocytic C6 glioma cells. In two different clones of stable transfectants with increased intracellular Gln levels, exposure to hydrogen peroxide (H(2)O(2)) and A23187, but not to tunicamycin or 2,4-dinitrophenol, led to significant exacerbation of the cytotoxicity compared to cells with empty vector (EV). Stable GlnT overexpression led to a significant increase in heme oxygenase-1 protein levels in a manner sensitive to H(2)O(2), whereas H(2)O(2) was significantly more effective in increasing NO(2) accumulation and reactive oxygen species (ROS) generation in stable GlnT transfectants than in EV cells. Moreover, exposure to A23187 led to a more effective increase in the generation of ROS in stable GlnT transfectants than in stable EV transfectants. These results suggest that GlnT may play a role in the mechanisms underlying the determination of cellular viability in astrocytes through modulation of intracellular ROS generation.

Gradual downregulation of protein expression of the partner GABA(B)R2 subunit during postnatal brain development in mice defective of GABA(B)R1 subunit

We have previously shown the functional expression of GABA(B) receptors (GABA(B)R) composed of GABA(B)R1 and GABA(B)R2 subunits with ability to promote proliferation and neuronal differentiation in cultured neural progenitor cells (NPC) isolated from embryonic mouse brains. In this study, we evaluated postnatal changes in the expression profiles of different markers for progenitor, neuronal, astroglial, and microglial cells in brains of GABA(B)R1-null mice. Consistent with undifferentiated murine NPC cultured with epidermal growth factor, a significant and selective decrease was seen in mRNA expression of the proneural gene Mash1 in brains of GABA(B)R1-null mice at 1 day after birth. The expression of several NPC marker proteins was similarly decreased in brains of both wild-type and GABA(B)R1-null mice from 1 to 7 days after birth, while slight changes were induced in both mRNA and proteins for neuronal, astroglial, and microglial markers between wild-type and GABA(B)R1-null mouse brains within this developmental stage. In particular discrete brain structures of adult GABA(B)R1-null mice at 56 days after birth, a significant decrease was seen in neuronal marker protein levels along with a significant increase in both astroglial and microglial marker protein expression. Although no significant difference was found in mRNA expression of the partner GABA(B)R2 subunit between wild-type and GABA(B)R1-null mouse brains, GABA(B)R2 subunit protein levels were gradually declined during postnatal development within 56 days after birth in GABA(B)R1-null mouse brains. These results suggest that GABA(B)R2 protein levels are closely correlated with the partner subunit GABA(B)R1 protein levels in mouse brains during postnatal development in vivo.

Dietary balance chart for an on-line computerized graphical support system in MHTS

Dietary habits are believed to play an important role in the etiology of adult disease. For this reason, it is necessary to include effective dietary guidance in multiphasic health testing and services (MHTS) programmes for primary disease prevention. We have developed such a programme of simple dietary advice, using a computer system for the MHTS. Examinees' dietary habits are checked using optical character record (OCR) questionnaire forms, and the results are displayed on the screen of a colour display terminal. They are required to prepare a menu of their usual daily dietary intake in terms of quantity and type of food. Thus the data collected relate to the nutritional composition of the examinee's usual diet. Nutritional requirements of the Japanese according to sex, height, and level of physical activity, in accordance with criteria set by the Japanese Ministry of Health and Welfare, are fed into the computer in advance. For each examinee, these criteria and the results of the assessment of the diet are displayed together on the screen in the form of colour graphs for comparison.

Dietary Balance Chart for an On-line Computerized Graphical Support System inMHTS

Dietary habits are believed to play an important role in the etiology of adult disease. For this reason, it is necessary to include effective dietary guidance in multiphasic health testing and services (MHTS) programmes for primary disease prevention. We have developed such a programme of simple dietary advice, using a computer system for the MHTS. Examinees' dietary habits are checked using optical character record (OCR) questionnaire forms, and the results are displayed on the screen of a colour display terminal. They are required to prepare a menu of their usual daily dietary intake in terms of quantity and type of food. Thus the data collected relate to the nutritional composition of the examinee's usual diet. Nutritional requirements of the Japanese according to sex, height, and level of physical activity, in accordance with criteria set by the Japanese Ministry of Health and Welfare, are fed into the computer in advance. For each examinee, these criteria and the results of the assessment of the diet are displayed together on the screen in the form of colour graphs for comparison.