Establishment of an epidermal growth factor-dependent, multipotent neural precursor cell line

Summary We have established a multipotent clonal cell line, named MEB5, from embryonic mouse forebrains after the infection of a retrovirus carrying E7 oncogene of human papillomavirus type 16. MEB5 cells proliferated in serum-free, epidermal growth factor (EGF)-supplemented medium. They expressed markers for neural precursor cells (nestin, A2B5, and RC1) and did not express markers for neurons (class III β-tubulin), astrocytes (glial fibrillary acidic protein), and oligodendrocytes (galactocerebroside). MEB5 cells were stably maintained in an undifferentiated state with a diploid karyotype in the presence of EGF. When they were deprived of EGF, about 50% of the cells died due apoptosis within 24 h. The remaining cells differentiated into neurons, astrocytes, or oligodendrocytes within 2 wk. The newly developed cells with neuronal morphology were immunoreactive for γ-aminobutyric acid and exhibited neuronal electrophysiological properties. When MEB5 cells were treated with leukemia inhibitory for 7 d, they were induced to differentiate exclusively into astrocytes. These results inducate that MEB5 is a cell line with characteristics of EGF-dependent, multipotent neural precursor cells. This cell line should provide a good model system to study the mechanisms of survival, proliferation, and differentiation of the multipotent precursor cells in the central nervous system.     

Protein kinase C delta regulates the phosphorylation of heat shock protein 27 in human hepatocellular carcinoma

We have recently reported that attenuated phosphorylation of heat shock protein (HSP) 27 correlates with tumor progression in patients with hepatocellular carcinoma (HCC). In the present study, we investigated what kind of kinase regulates phosphorylation of HSP27 in human HCC-derived HuH7 cells. 12-O-tetradecanoylphorbol-13-acetate (TPA) and 1-oleoyl-2-acetylglycerol, direct activators of protein kinase C (PKC), markedly strengthened the phosphorylation of HSP27. Bisindorylmaleimide I, an inhibitor of PKC, suppressed the TPA-induced levels of HSP27 phosphorylation in addition to its basal levels. Knock down of PKCdelta suppressed HSP27 phosphorylation, as well as p38 mitogen-activated protein kinase (MAPK) phosphorylation. SB203580, an inhibitor of p38 MAPK, suppressed the TPA-induced HSP27 phosphorylation. Our results strongly suggest that activation of PKCdelta regulates the phosphorylation of HSP27 via p38 MAPK in human HCC.     

Executive Function Deficits and Social-Behavioral Abnormality in Mice Exposed to a Low Dose of Dioxin In Utero and via Lactation

An increasing prevalence of mental health problems has been partly ascribed to abnormal brain development that is induced upon exposure to environmental chemicals. However, it has been extremely difficult to detect and assess such causality particularly at low exposure levels. To address this question, we here investigated higher brain function in mice exposed to dioxin in utero and via lactation by using our recently developed automated behavioral flexibility test and immunohistochemistry of neuronal activation markers Arc, at the 14 brain areas. Pregnant C57BL/6 mice were given orally a low dose of 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) at a dose of either 0, 0.6 or 3.0 µg/kg on gestation day 12.5. When the pups reached adulthood, they were group-housed in IntelliCage to assess their behavior. As a result, the offspring born to dams exposed to 0.6 µg TCDD/kg were shown to have behavioral inflexibility, compulsive repetitive behavior, and dramatically lowered competitive dominance. In these mice, immunohistochemistry of Arc exhibited the signs of hypoactivation of the medial prefrontal cortex (mPFC) and hyperactivation of the amygdala. Intriguingly, mice exposed to 3.0 µg/kg were hardly affected in both the behavioral and neuronal activation indices, indicating that the robust, non-monotonic dose-response relationship. In conclusion, this study showed for the first time that perinatal exposure to a low dose of TCDD in mice develops executive function deficits and social behavioral abnormality accompanied with the signs of imbalanced mPFC-amygdala activation.     

Hamster PIWI proteins bind to piRNAs with stage-specific size variations during oocyte maturation

In animal gonads, transposable elements are actively repressed to preserve genome integrity through the PIWI-interacting RNA (piRNA) pathway. In mice, piRNAs are abundantly expressed in male germ cells, and form effector complexes with three distinct PIWIs. The depletion of individual Piwi genes causes male-specific sterility with no discernible phenotype in female mice. Unlike mice, most other mammals have four PIWI genes, some of which are expressed in the ovary. Here, purification of PIWI complexes from oocytes of the golden hamster revealed that the size of the PIWIL1-associated piRNAs changed during oocyte maturation. In contrast, PIWIL3, an ovary-specific PIWI in most mammals, associates with short piRNAs only in metaphase II oocytes, which coincides with intense phosphorylation of the protein. An improved high-quality genome assembly and annotation revealed that PIWIL1- and PIWIL3-associated piRNAs appear to share the 5′-ends of common piRNA precursors and are mostly derived from unannotated sequences with a diminished contribution from TE-derived sequences, most of which correspond to endogenous retroviruses. Our findings show the complex and dynamic nature of biogenesis of piRNAs in hamster oocytes, and together with the new genome sequence generated, serve as the foundation for developing useful models to study the piRNA pathway in mammalian oocytes.     

Fine binding specificities to Ascaris suum and Ascaris lumbricoides antigens of the sera from patients of probable visceral larva migrans due to Ascaris suum

Fine binding specificities to Ascaris suum and A. lumbricoides antigens of the sera from patients with probable visceral larva migrans (VLM) due to A. suum infection were examined. Although multiple-dot enzyme-linked immunosorbent assay (ELISA) was found to be useful for the primary screening of patients, identification of the responsible species was sometimes difficult due to extensive cross reactions with other ascarid parasite antigens. Fine resolution to determine the causative pathogen was obtained by a rather classical Ouchterlony's double immunodiffusion test. The difference in the binding of the patients' sera to A. suum and A. lumbricoides antigens was also demonstrated by an inhibition ELISA. The patients' antibodies bound with higher avidity to the A. suum antigen than to the A. lumbricoides and Toxocara canis antigens. Combination of at least two different immunological assay methods is recommended for the diagnosis of VLM due to ascarid parasites.     

Development and function of invariant natural killer T cells producing T(h)2- and T(h)17-cytokines

There is heterogeneity in invariant natural killer T (iNKT) cells based on the expression of CD4 and the IL-17 receptor B (IL-17RB), a receptor for IL-25 which is a key factor in T_H2 immunity. However, the development pathway and precise function of these iNKT cell subtypes remain unknown. IL-17RB⁺ iNKT cells are present in the thymic CD44^+/− NK1.1⁻ population and develop normally even in the absence of IL-15, which is required for maturation and homeostasis of IL-17RB⁻ iNKT cells producing IFN-γ. These results suggest that iNKT cells contain at least two subtypes, IL-17RB⁺ and IL-17RB⁻ subsets. The IL-17RB⁺ iNKT subtypes can be further divided into two subtypes on the basis of CD4 expression both in the thymus and in the periphery. CD4⁺ IL-17RB⁺ iNKT cells produce T_H2 (IL-13), T_H9 (IL-9 and IL-10), and T_H17 (IL-17A and IL-22) cytokines in response to IL-25 in an E4BP4-dependent fashion, whereas CD4⁻ IL-17RB⁺ iNKT cells are a retinoic acid receptor-related orphan receptor (ROR)γt⁺ subset producing T_H17 cytokines upon stimulation with IL-23 in an E4BP4-independent fashion. These IL-17RB⁺ iNKT cell subtypes are abundantly present in the lung in the steady state and mediate the pathogenesis in virus-induced airway hyperreactivity (AHR). In this study we demonstrated that the IL-17RB⁺ iNKT cell subsets develop distinct from classical iNKT cell developmental stages in the thymus and play important roles in the pathogenesis of airway diseases.     

Molecular characterization of ENU mouse mutagenesis and archives

The large-scale mouse mutagenesis with ENU has provided forward-genetic resources for functional genomics. The frozen sperm archive of ENU-mutagenized generation-1 (G1) mice could also provide a "mutant mouse library" that allows us to conduct reverse genetics in any particular target genes. We have archived frozen sperm as well as genomic DNA from 9224 G1 mice. By genome-wide screening of 63 target loci covering a sum of 197 Mbp of the mouse genome, a total of 148 ENU-induced mutations have been directly identified. The sites of mutations were primarily identified by temperature gradient capillary electrophoresis method followed by direct sequencing. The molecular characterization revealed that all the identified mutations were point mutations and mostly independent events except a few cases of redundant mutations. The base-substitution spectra in this study were different from those of the phenotype-based mutagenesis. The ENU-based gene-driven mutagenesis in the mouse now becomes feasible and practical.     

Cthrc1 is a positive regulator of osteoblastic bone formation

Background

Bone mass is maintained by continuous remodeling through repeated cycles of bone resorption by osteoclasts and bone formation by osteoblasts. This remodeling process is regulated by many systemic and local factors.

Methodology/Principal Findings

We identified collagen triple helix repeat containing-1 (Cthrc1) as a downstream target of bone morphogenetic protein-2 (BMP2) in osteochondroprogenitor-like cells by PCR-based suppression subtractive hybridization followed by differential hybridization, and found that Cthrc1 was expressed in bone tissues in vivo. To investigate the role of Cthrc1 in bone, we generated Cthrc1-null mice and transgenic mice which overexpress Cthrc1 in osteoblasts (Cthrc1 transgenic mice). Microcomputed tomography (micro-CT) and bone histomorphometry analyses showed that Cthrc1-null mice displayed low bone mass as a result of decreased osteoblastic bone formation, whereas Cthrc1 transgenic mice displayed high bone mass by increase in osteoblastic bone formation. Osteoblast number was decreased in Cthrc1-null mice, and increased in Cthrc1 transgenic mice, respectively, while osteoclast number had no change in both mutant mice. In vitro, colony-forming unit (CFU) assays in bone marrow cells harvested from Cthrc1-null mice or Cthrc1 transgenic mice revealed that Cthrc1 stimulated differentiation and mineralization of osteoprogenitor cells. Expression levels of osteoblast specific genes, ALP, Col1a1, and Osteocalcin, in primary osteoblasts were decreased in Cthrc1-null mice and increased in Cthrc1 transgenic mice, respectively. Furthermore, BrdU incorporation assays showed that Cthrc1 accelerated osteoblast proliferation in vitro and in vivo. In addition, overexpression of Cthrc1 in the transgenic mice attenuated ovariectomy-induced bone loss.

Conclusions/Significance

Our results indicate that Cthrc1 increases bone mass as a positive regulator of osteoblastic bone formation and offers an anabolic approach for the treatment of osteoporosis.     

Design,synthesis, and conformation of a model peptide of endothelin with cystine-stabilized α-helix motif

A model 16-peptide of endothelin-1 (MET-1), which has the minimized sequence homology to the corresponding pan of endothelin-1 (ET-1), was designed to confirm the cystine-stabilized α-helix motif. The model structure consists of an extended structure, a β-turn part, and an α-helix structure that is stabilized by two disulfide bonds. The α-helix segment was designed to emphasize the amphiphilic nature. In order to combine the extended structure and the α-helix segment, a D -Ala-Pro sequence was selected to fix the β-turn. The model endothelin 16-peptide amide was synthesized by solid-phase synthesis on a 4-methylbenzhydrylamine resin. Its conformation was examined by CD and two-dimensional (2D) ¹H-nmr measurements. MET-1 showed similar CD patterns to ET-1 in both buffer and 50% aqueous trifluoroethanol solution. The 2D nmr experiments in 50% aqueous ethylene glycol revealed that MET-1 closely resembles the conformation of ET-1 with an extended structure, an α-helix, and a β-turn unit in the same position of the sequence. Furthermore, model peptides without disulfide bond(s) could not assume a stable structure in aqueous solution, while they did have similar α-helical content in 50% trifluoroethanol with MET-1. When the two disulfide bridges were simultaneously formed, the peptide with the correct disulfide bonds (MET-1) was obtained in threefold excess to the isomer (apamin type. MET-2). These findings obtained by the modeling of ET-1 showed an important role for the stabilization of peptide conformation with disulfide bonds. © 1994 John Wiley & Sons, Inc.