Cardiac abnormalities cause early lethality of jumonji mutant mice

jumonji (jmj) mutant mice, obtained by a gene trap strategy, showed several morphological abnormalities including neural tube and cardiac defects, and died in utero around embryonic day 11.5 (E11.5). It is unknown what causes the embryonic lethality. Here, we demonstrate that exogenous expression of jmj gene in the heart of jmj mutant mice rescued the morphological phenotypes in the heart, and these embryos survived until E13.5. These results suggest that there are at least two lethal periods in jmj mutant mice, and that cardiac abnormalities may cause the earlier lethality. In addition, the rescue of the cardiac abnormalities by the jmj transgene provided solid evidence that the cardiac abnormalities resulted from mutation of the jmj gene.     

Repression of tax expression is associated both with resistance of human T-cell leukemia virus type 1-infected T cells to killing by tax-specific cytotoxic T lymphocytes and with impaired tumorigenicity in a rat model

Human T-cell leukemia virus type 1 (HTLV-1) causes adult T-cell leukemia (ATL). Although the viral transactivation factor, Tax, has been known to have apparent transforming ability, the exact function of Tax in ATL development is still not clear. To understand the role of Tax in ATL development, we introduced short-interfering RNAs (siRNAs) against Tax in a rat HTLV-1-infected T-cell line. Our results demonstrated that expression of siRNA targeting Tax successfully downregulated Tax expression. Repression of Tax expression was associated with resistance of the HTLV-1-infected T cells to Tax-specific cytotoxic-T-lymphocyte killing. This may be due to the direct effect of decreased Tax expression, because the Tax siRNA did not alter the expression of MHC-I, CD80, or CD86. Furthermore, T cells with Tax downregulation appeared to lose the ability to develop tumors in T-cell-deficient nude rats, in which the parental HTLV-1-infected cells induce ATL-like lymphoproliferative disease. These results indicated the importance of Tax both for activating host immune response against the virus and for maintaining the growth ability of infected cells in vivo. Our results provide insights into the mechanisms how the host immune system can survey and inhibit the growth of HTLV-1-infected cells during the long latent period before the onset of ATL.     

Cytokine gene expression in Walker 256: a comparison of variants A (aggressive) and AR (regressive)

Two variants of this Walker 256 tumor have been previously reported as Walker 256 A and variant AR. The variant A has more aggressive property than variant AR and can induce systemic effects such as anorexia, sodium and water retention, followed by weight loss and death. The mechanisms involved in enhancing tumor regression and progression in this model are still incompletely understood. In the present study, serum and spleen mononuclear cells and tumor cells from animals inoculated with variants A and AR, were isolated to investigate the TGF-beta, IL-12, IFN-gamma and TNF-alpha and relationship with anemia, weight of animals, weight of spleen, volume of tumor and osmotic fragility compared with controls inoculated with Ringer Lactate. Results demonstrate that the group inoculated with variant A, compared to variant AR, shows high levels of TGF-beta gene expression in both tumor tissue and spleen cells, no expression of IFN-gamma and a progressive and higher levels of IL-12 in tumor tissue without inflammatory infiltrate visualized by optical microscopy. These results suggest that the aggressively of variant A is relate to cytokine modulation, facilitating the growth and escape of tumor cells. Furthermore, IL-12 seems to be constitutively expressed in both tumor lineage A and AR.     

Syntrophin-2 is required for eye development in Drosophila

Syntrophins are components of the dystrophin glycoprotein complex (DGC), which is encoded by causative genes of muscular dystrophies. The DGC is thought to play roles not only in linking the actin cytoskeleton to the extracellular matrix, providing stability to the cell membrane, but also in signal transduction. Because of their binding to a variety of different molecules, it has been suggested that syntrophins are adaptor proteins recruiting signaling proteins to membranes and the DGC. However, critical roles in vivo remain elusive. Drosophila Syntrophin-2 (Syn2) is an orthologue of human γ1/γ2-syntrophins. Western immunoblot analysis here showed Syn2 to be expressed throughout development, with especially high levels in the adult head. Morphological aberrations were observed in Syn2 knockdown adult flies, with lack of retinal elongation and malformation of rhabdomeres. Furthermore, Syn2 knockdown flies exhibited excessive apoptosis in third instar larvae and alterations in the actin localization in the pupal retinae. Genetic crosses with a collection of Drosophila deficiency stocks allowed us to identify seven genomic regions, deletions of which caused enhancement of the rough eye phenotype induced by Syn2 knockdown. This information should facilitate identification of Syn2 regulators in Drosophila and clarification of roles of Syn2 in eye development.     

Effects of ionic strength on the thermal unfolding process of granulocyte-colony stimulating factor

This paper reports the effect of ionic strength on the process of thermal unfolding of recombinant methionyl human granulocyte-colony stimulating factor (rmethuG-CSF) at acid pH. We previously reported that the protein aggregates were formed at the highest temperature at pD 2.1 in the pD range of 5.5-2.1 and that the aggregation proceeded a little at pD 2.1 because of the strong repulsive interaction between the unordered structures that play the role of a precursor for the aggregation. In the present study temperature-dependent IR spectra and far-UV CD spectra were measured for rmethuG-CSF in aqueous solutions containing various concentrations of NaCl at acid pH. Second derivative and curve-fitting analysis were performed to examine the obtained IR spectra. The results revealed that the structure of rmethuG-CSF becomes less stable with increasing ionic strength at all pDs investigated (pD 2.1, 2.5, and 4.0). We have also demonstrated that, at pD 2.1, the temperature at which the protein aggregation starts becomes lower and that the amount of the aggregates becomes larger with the addition of NaCl. This is probably because the addition of NaCl masks the repulsive electrostatic interaction between the unordered structures.     

Taking care of Dad's DNA

Inheritance of paternal genetic information requires proper sperm development and DNA packaging. A proteomic analysis of sperm chromatin in Caenorhabditis elegans has identified conserved proteins that are important for the transmission of sperm DNA and for male fertility.     

Phosphatidylinositol 4-phosphate 5-kinase is indispensable for mouse spermatogenesis

The lipid kinase phosphatidylinositol 4-phosphate 5-kinase (PIP5K) produces a versatile signaling phospholipid, phosphatidylinositol 4,5-bisphosphate. Three PIP5K isozymes, PIP5K1A, PIP5K1B, and PIP5K1C, have been identified in mammals so far. Although the functions of these three PIP5K isozymes have been extensively studied in vitro, the in vivo physiological roles of these PIP5K isozymes remain largely unknown. In this study, we examined the functions of PIP5K1A and PIP5K1B in spermatogenesis, using Pip5k1a-knockout (KO), Pip5k1b-KO, and Pip5k1a/Pip5k1b double (D)-KO mice. Pip5k1a-KO and D-KO males were subfertile and completely sterile, respectively. F-actin in the seminiferous epithelium was disorganized in the D-KO mice, although F-actin bundles at the apical ectoplasmic specialization was not affected. D-KO seminiferous tubules contained a greatly decreased number of elongated spermatids. Flagella of sperm from Pip5k1a-KO and D-KO mice remarkably underwent morphological change, whereas Pip5k1b-KO sperm were morphologically normal. Notably, the flagellar shape of D-KO sperm was more severely impaired than that of Pip5k1a-KO sperm. These results suggest that PIP5K1A and PIP5K1B may coordinately and/or redundantly function in the maintenance of sperm number and morphology during spermatogenesis.     

Brain insulin resistance accelerates Aβ fibrillogenesis by inducing GM1 ganglioside clustering in the presynaptic membranes

Type 2 diabetes mellitus is thought to be a significant risk factor for Alzheimer's disease. Insulin resistance also affects the central nervous system by regulating key processes, such as neuronal survival and longevity, learning and memory. However, the mechanisms underlying these effects remain uncertain. To investigate whether insulin resistance is associated with the assembly of amyloid β-protein (Aβ) at the cell surface of neurons, we inhibited insulin-signalling pathways of primary neurons. The treatments of insulin receptor (IR)-knockdown and a phosphatidylinositol 3-kinase inhibitor (LY294002), but not an extracellular signal-regulated kinase inhibitor, induced an increase in GM1 ganglioside (GM1) levels in detergent-resistant membrane microdomains of the neurons. The aged db/db mouse brain exhibited reduction in IR expression and phosphorylation of Akt, which later induced an increase in the high-density GM1-clusters on synaptosomes. Neurons treated with IR knockdown or LY294002, and synaptosomes of the aged db/db mouse brains markedly accelerated an assembly of Aβs. These results suggest that ageing and peripheral insulin resistance induce brain insulin resistance, which accelerates the assembly of Aβs by increasing and clustering of GM1 in detergent-resistant membrane microdomains of neuronal membranes.     

The effect of genetically enriched (E)-β-ocimene and the role of floral scent in the attraction of the predatory mite Phytoseiulus persimilis to spider mite-induced volatile blends of torenia

Plants under herbivore attack emit mixtures of volatiles (herbivore-induced plant volatiles, HIPVs) that can attract predators of the herbivores. Although the composition of HIPVs should be critical for the attraction, most studies of transgenic plant-emitted volatiles have simply addressed the effect of trans-volatiles without embedding in other endogenous plant volatiles. We investigated the abilities of transgenic wishbone flower plants (Torenia hybrida and Torenia fournieri) infested with spider mites, emitting a trans-volatile ((E)-β-ocimene) in the presence or absence of endogenous volatiles (natural HIPVs and/or floral volatiles), to attract predatory mites (Phytoseiulus persimilis). In both olfactory- and glasshouse-based assays, P. persimilis females were attracted to natural HIPVs from infested wildtype (wt) plants of T. hybrida but not to those of T. fournieri. The trans-volatile enhanced the ability to attract P. persimilis only when added to an active HIPV blend from the infested transgenic T. hybrida plants, in comparison with the attraction by infested wt plants. Intriguingly, floral volatiles abolished the enhanced attractive ability of T. hybrida transformants, although floral volatiles themselves did not elicit any attraction or avoidance behavior. Predator responses to trans-volatiles were found to depend on various background volatiles (e.g. natural HIPVs and floral volatiles) endogenously emitted by the transgenic plants.