Search

Impaired DNA damage repair is a common pathological endophenotype of some types of neurodegenerative diseases, intellectual disabilities, and psychiatric diseases. Dysfunctional DNA repair and DNA damage, including DNA double-stranded breaks, are linked to transcriptional dysfunction and abnormal DNA methylation. Impaired DNA repair in neural stem cells leads to microcephaly or cerebellar ataxia. Furthermore, DNA repair defects and DNA damage in mature neurons lead to progressive cognitive impairment, which might be a common feature of Alzheimer&aposs disease, Huntington’s disease, and other polyglutamine diseases. Oxidative DNA damage and altered DNA repair gene expression are observed in GABAergic neurons in schizophrenia. These findings indicate that impaired DNA repair is a common pathological endophenotype of neurological diseases, and that DNA damage might lead to diverse disease symptoms dependent on timing and the affected cell type.

Understanding the expression of tumor specific receptors is important not only for tumor diagnosis but also for planning the strategy for patient treatment. Tumor receptor has been one of the most critical targets for treatment in cancer such as breast, prostate and thyroid cancers. Positron emission tomography (PET) is a part of molecular imaging techniques based on detecting the radiopharmaceuticals that can capture functional or phenotypic changes associated with pathology. The advantages of detecting tumor specific receptors by PET are its non-invasiveness, providing comprehensive information about receptor expression, avoiding the sampling errors, selecting strategy for the treatment of patients and monitoring tumor response to therapy. Hormonal therapy plays a major role in cancer treatment. Therefore, we review the PET radiopharmaceuticals for sex steroid hormone receptor imaging in this article.

11C -methyl-l-tryptophan (-MTrp) has been developed as a tracer for the study of the synthesis of serotonin in the brain with PET. However, it has been shown that in pathologic conditions the tracer may reflect the activation of kynurenine metabolism. Increased levels of serotonin and quinolinic acid have been described in resected epileptogenic cortex, raising the possibility that -MTrp can localize seizure foci in patients with intractable partial epilepsy. The authors assessed the uptake of -MTrp in 18 patients (11 men, mean ± SD age 27.1 ± 10.1 years, range 13 to 54) with intractable partial epilepsy to correlate the PET findings with the epileptogenic area defined by electroclinical and neuroimaging data.

PQBP-1 was identified as a binding protein to the polyglutamine tract present in various transcription-related factors and causative genes for neurodegenerative disorders. This novel gene contains at least two functional domains, WW domain and carboxyl-terminal domain (CTD), strictly conserved beyond species. Although human PQBP-1 additionally contains the polar amino acid-rich domain by which it binds to the polyglutamine tract, genuine physiological function(s) have not been clarified. In this study, we showed that U5-15kD, human homologue of fission yeast dim1p, is a partner molecule of PQBP-1 binding to CTD. This finding suggests physiological functions of PQBP-1 in splicing, cell cycle, and ubiquitination, through which we can speculate the pathological roles of PQBP-1 in triplet repeat diseases.

To investigate whether in selected patients with internal carotid artery (ICA) occlusion and initially normal oxygen extraction fraction (OEF) measured with PET, subsequent changes of cerebral hemodynamics and metabolism occur during long-term follow-up and, if so, whether the changes are associated with atrophy of the corpus callosum or subsequent ischemic strokes.

Both syntaxin4 and VAMP2 are implicated in insulin regulation of glucose transporter-4 (GLUT4) trafficking in adipocytes as target (t) soluble N-ethylmaleimide-sensitive factor attachment protein receptors (SNARE) and vesicle (v)-SNARE proteins, respectively, which mediate fusion of GLUT4-containing vesicles with the plasma membrane. Synaptosome-associated 23-kDa protein (SNAP23) is a widely expressed isoform of SNAP25, the principal t-SNARE of neuronal cells, and colocalizes with syntaxin4 in the plasma membrane of 3T3-L1 adipocytes. In the present study, two SNAP23 mutants, SNAP23-DeltaC8 (amino acids 1 to 202) and SNAP23-DeltaC49 (amino acids 1 to 161), were generated to determine whether SNAP23 is required for insulin-induced translocation of GLUT4 to the plasma membrane in 3T3-L1 adipocytes. Wild-type SNAP23 (SNAP23-WT) promoted the interaction between syntaxin4 and VAMP2 both in vitro and in vivo. Although SNAP23-DeltaC49 bound to neither syntaxin4 nor VAMP2, the SNAP23-DeltaC8 mutant bound to syntaxin4 but not to VAMP2. In addition, although SNAP23-DeltaC8 bound to syntaxin4, it did not mediate the interaction between syntaxin4 and VAMP2. Moreover, overexpression of SNAP23-DeltaC8 in 3T3-L1 adipocytes by adenovirus-mediated gene transfer inhibited insulin-induced translocation of GLUT4 but not that of GLUT1. In contrast, overexpression of neither SNAP23-WT nor SNAP23-DeltaC49 in 3T3-L1 adipocytes affected the translocation of GLUT4 or GLUT1. Together, these results demonstrate that SNAP23 contributes to insulin-dependent trafficking of GLUT4 to the plasma membrane in 3T3-L1 adipocytes by mediating the interaction between t-SNARE (syntaxin4) and v-SNARE (VAMP2).

The Oct‐3 gene is expressed in highly undifferentiated cells and is implicated in mammalian early embryogenesis. We have generated a series of hybrid cells between pluripotent embryonal carcinoma cells (Oct‐3+) and fibroblasts (Oct‐3‐), and have studied the regulation and function of Oct‐3. Upon fusion, the hybrid cells differentiated to nestin+/Brn‐2+ cells resembling neuroepithelial stem cells. Expression of Oct‐3 was extinguished at the transcriptional level in all the hybrid cells examined. The Oct‐3 modulating activity required for the Oct‐3‐mediated enhancer activation was also extinguished. When the Oct‐3 transactivating function was introduced into the hybrid cells, they transformed into morphologically distinct nestin‐/Brn‐2‐ cells (‘revertants’). When the ‘revertant’ cells subsequently lost Oct‐3 expression, they differentiated back to nestin+/Brn‐2+ cells. The close correlation between the phenotypic changes and the gain/loss of Oct‐3 function indicates that Oct‐3 can induce dedifferentiation of the neural cells.

Oct3 is an embryonic octamer‐binding transcription factor, whose expression is rapidly repressed by retinoic acid (RA). In this report, we have determined the transcriptional control region of the oct3 gene and studied the mechanism of the RA‐mediated repression. The chromosomal oct3 gene consists of five exons. Three subdomains of the POU region and transactivating domain are located in separate exons. Transcription initiates at multiple sites in the GC‐rich region lacking a typical TATA box. The upstream 2 kb region can confer the cell type‐specific expression and RA‐mediated repression. Analysis of the upstream region by deletion mutagenesis locates a cis element (RARE1) which functions as a stem cell‐specific, yet RA‐repressible, enhancer. Footprint and gel‐retardation assays show that RARE1 is composed of two domains, each of which is recognized by distinct factors. Microinjection of oct3‐lacZ constructs into fertilized eggs indicates that RARE1 can function in early embryos. We suggest that RARE1 is a critical cis element for oct3 gene expression in embryonic stem cells and for the RA‐mediated repression.

Insulin induces the translocation of vesicles containing the glucose transporter GLUT4 from an intracellular compartment to the plasma membrane in adipocytes. SNARE proteins have been implicated in the docking and fusion of these vesicles with the cell membrane. The role of Munc18c, previously identified as an n-Sec1/Munc18 homolog in 3T3-L1 adipocytes, in insulin-regulated GLUT4 trafficking has now been investigated in 3T3-L1 adipocytes. In these cells, Munc18c was predominantly associated with syntaxin4, although it bound both syntaxin2 and syntaxin4 to similar extents in vitro. In addition, SNAP-23, an adipocyte homolog of SNAP-25, associated with both syntaxins 2 and 4 in 3T3-L1 adipocytes. Overexpression of Munc18c in 3T3-L1 adipocytes by adenovirus-mediated gene transfer resulted in inhibition of insulin-stimulated glucose transport in a virus dose-dependent manner (maximal effect, approximately 50%) as well as in inhibition of sorbitol-induced glucose transport (by approximately 35%), which is mediated by a pathway different from that used by insulin. In contrast, Munc18b, which is also expressed in adipocytes but which did not bind to syntaxin4, had no effect on glucose transport. Furthermore, overexpression of Munc18c resulted in inhibition of insulin-induced translocation of GLUT4, but not of that of GLUT1, to the plasma membrane. These results suggest that Munc18c is involved in the insulin-dependent trafficking of GLUT4 from the intracellular storage compartment to the plasma membrane in 3T3-L1 adipocytes by modulating the formation of a SNARE complex that includes syntaxin4.

Previous studies using transfected cells have indicated that the mammalian receptor tyrosine kinase trkB binds the neurotrophins brain-derived neurotrophic factor, neurotrophin-3 and neurotrophin-4. However, most studies demonstrating that these neurotrophins prevent the death of embryonic neurons and have specific neuronal receptors have been performed with chick neurons. In order to explore the possibility that trkB is the molecular entity representing the high-affinity receptor for brain-derived neurotrophic factor on embryonic chick neurons, we cloned and expressed a chick trkB cDNA. In situ hybridisation results indicate that the distribution of trkB mRNA in the peripheral nervous system of the developing chick embryo correlates well with the structures known to respond to brain-derived neurotrophic factor. Binding studies performed with a cell line stably transfected with the ctrkB cDNA indicate a dissociation constant for brain-derived neurotrophic factor of 9.9 x 10(-10) M, which is distinctly higher than that found on primary chick sensory neurons (1.5 x 10(-11) M). When binding of brain-derived neurotrophic factor was determined in the presence of other neurotrophins, neurotrophin-3 was found efficiently to prevent the binding of brain-derived neurotrophic factor to both the ctrkB cell line and embryonic sensory neurons. In vitro, neurotrophin-3 at high concentrations completely blocked the survival normally seen with brain-derived neurotrophic factor. Thus, unlike previous cases of receptor occupancy by heterologous neurotrophins (which resulted in agonistic effects), the interaction between the brain-derived neurotrophic factor receptor and neurotrophin-3 on sensory neurons is antagonistic.

Neurotrophins homologous to the nerve growth factor (NGF) bind the neurotrophic receptors of the trk gene family. Since the target tissues release these neurotrophic factors to the neuron, it has been believed that their trophic effects are mediated by the retrograde axonal transport. However it remains an open question whether the neurotrophins act through the autocrine or the paracrine mechanisms, since the protein-level expression of trk has not been studied so far. We have made polyclonal antibodies against the recombinant proteins of chicken trkC and rat trkB. These antibodies showed immunoreactivity at the dendrite and the cell body of neuron. This subcellular localization strongly suggests the autocrine or the paracrine mechanism of the neurotrophic factors. At the same time, our data provide basic knowledge to decide where to deliver these neurotrophic factors in the therapy of neurodegenerative diseases.

The Oct‐3 gene is expressed in highly undifferentiated cells and is implicated in mammalian early embryogenesis. We have generated a series of hybrid cells between pluripotent embryonal carcinoma cells (Oct‐3+) and fibroblasts (Oct‐3‐), and have studied the regulation and function of Oct‐3. Upon fusion, the hybrid cells differentiated to nestin+/Brn‐2+ cells resembling neuroepithelial stem cells. Expression of Oct‐3 was extinguished at the transcriptional level in all the hybrid cells examined. The Oct‐3 modulating activity required for the Oct‐3‐mediated enhancer activation was also extinguished. When the Oct‐3 transactivating function was introduced into the hybrid cells, they transformed into morphologically distinct nestin‐/Brn‐2‐ cells (‘revertants’). When the ‘revertant’ cells subsequently lost Oct‐3 expression, they differentiated back to nestin+/Brn‐2+ cells. The close correlation between the phenotypic changes and the gain/loss of Oct‐3 function indicates that Oct‐3 can induce dedifferentiation of the neural cells.

Oct3 is an embryonic octamer‐binding transcription factor, whose expression is rapidly repressed by retinoic acid (RA). In this report, we have determined the transcriptional control region of the oct3 gene and studied the mechanism of the RA‐mediated repression. The chromosomal oct3 gene consists of five exons. Three subdomains of the POU region and transactivating domain are located in separate exons. Transcription initiates at multiple sites in the GC‐rich region lacking a typical TATA box. The upstream 2 kb region can confer the cell type‐specific expression and RA‐mediated repression. Analysis of the upstream region by deletion mutagenesis locates a cis element (RARE1) which functions as a stem cell‐specific, yet RA‐repressible, enhancer. Footprint and gel‐retardation assays show that RARE1 is composed of two domains, each of which is recognized by distinct factors. Microinjection of oct3‐lacZ constructs into fertilized eggs indicates that RARE1 can function in early embryos. We suggest that RARE1 is a critical cis element for oct3 gene expression in embryonic stem cells and for the RA‐mediated repression.

The rat aldolase C gene encodes a glycolytic enzyme strongly expressed in adult brain. We previously reported that a 115-base pair (bp) promoter fragment was able to ensure the brain-specific expression of the chloramphenicol acetyltransferase (CAT) reporter gene in transgenic mice, but only at a low level (Thomas, M., Makeh, I., Briand, P., Kahn, A., and Skala, H. (1993) Eur. J. Biochem. 218, 143-151). Here we show that in vivo activation of this promoter at a high level requires cooperation between an upstream 0.6-kilobase pair (kb) fragment and far upstream sequences. In the 0.6-kb region, a 28-bp DNA element is shown to include overlapping in vitro binding sites for POU domain regulatory proteins and for the Winged Helix hepatocyte nuclear factor-3beta factor. An hepatocyte nuclear factor-3beta-binding site previously described in the short proximal promoter fragment is also shown to interact in vitro with POU proteins, although with a lower affinity than the 28-bp motif. Additional binding sites for POU factors were detected in the upstream 0.6-kb sequences. Progressive deletion in this region resulted in decreased expression levels of the transgenes in mice, suggesting synergistic interactions between these multiple POU-binding sites. We propose that DNA elements characterized by a dual binding specificity for both POU domain and Winged Helix transcription factors could play an essential role in the brain-specific expression of the aldolase C gene and other neuronal genes.

The performance of the multilevel code based high data rate (HDR) codec (see reference 1) is evaluated with multiple-symbol differential detection over satellite channels. It is shown that multiple-symbol observation effectively fills the gap between conventional differentially coherent detection and ideal coherent detection with differential encoding. Being especially suitable for HDR application where carrier acquisition and tracking is extremely difficult, the codec reliably supports broadband ISDN transmission over a 72 MHz satellite transponder.

The performance of a high data rate (HDR) codec based on a multidimensional modulation code derived from multilevel codes is evaluated for a satellite channel. The codec reliably supports HDR transmission for broadband ISDN over a 72 MHz satellite transponder and is designed to be used with an 8PSK modem. Results show that significant coding gain with higher spectral efficiency can be achieved compared to uncoded QPSK.