Regulation of mitochondrial morphology and cell survival by Mitogenin I and mitochondrial single-stranded DNA binding protein

We found that a mouse homolog of human DNA polymerase delta interacting protein 38, referred to as Mitogenin I in this paper, and mitochondrial single-stranded DNA-binding protein (mtSSB), identified as upregulated genes in the heart of mice with juvenile visceral steatosis, play a role in the regulation of mitochondrial morphology. We demonstrated that overexpression of Mitogenin I or mtSSB increased elongated or fragmented mitochondria in mouse C2C12 myoblast cells, respectively. On the other hand, the silencing of Mitogenin I or mtSSB by RNA interference led to an increase in fragmented or elongated mitochondria in the cells, respectively, suggesting that Mitogenin I and mtSSB are involved in the processes of mitochondrial fusion and fission, respectively. In addition, we showed that the silencing of Mitogenin I resulted in an increase in the number of trypan blue-positive cells and the silencing of mtSSB resulted in an enhancement of the sensitivity of the cells to apoptotic stimulation by etoposide. The present results demonstrated that these proteins play a role in cell survival.     

Crystal structure of the O intermediate of the Leu93→Ala mutant of bacteriorhodopsin

The lifetime of the O intermediate of bacteriorhodopsin (BR) is extended by a factor of ～250 in the Leu93‐to‐Ala mutant (BR_L93A). To clarify the structural changes occurring in the last stage of the proton pumping cycle of BR, we crystallized BR_L93A into a hexagonal P622 crystal. Diffraction data from the unphotolyzed state showed that the deletion of three carbon atoms from Leu93 is compensated by the insertion of four water molecules in the cytoplasmic vicinity of retinal. This insertion of water is suggested to be responsible for the blue‐shifted λ_max (540 nm) of the mutant. A long‐lived substate of O with a red‐shifted λ_max (～565 nm) was trapped when the crystal of BR_L93A was flash‐cooled after illumination with green light. This substate (O_slow) bears considerable similarity to the M intermediate of native BR; that is, it commonly shows deformation of helix C and the FG loop, downward orientation of the side chain of Arg82, and disruption of the Glu194/Glu204 pair. In O_slow, however, the main chain of Lys216 is less distorted and retinal takes on the 13‐cis/15‐syn configuration. Another significant difference is seen in the pH dependence of the structure of the proton release group, the pK_a value of which is suggested to be much lower in O_slow than in M. Proteins 2012;. © 2012 Wiley Periodicals, Inc.     

Triiodothyronine induces UCP-1 expression and mitochondrial biogenesis in human adipocytes

Uncoupling protein (UCP)-1 expressed in brown adipose tissue plays an important role in thermogenesis. Recent data suggest that brown-like adipocytes in white adipose tissue (WAT) and skeletal muscle play a crucial role in the regulation of body weight. Understanding of the mechanism underlying the increase in UCP-1 expression level in these organs should, therefore, provide an approach to managing obesity. The thyroid hormone (TH) has profound effects on mitochondrial biogenesis and promotes the mRNA expression of UCP in skeletal muscle and brown adipose tissue. However, the action of TH on the induction of brown-like adipocytes in WAT has not been elucidated. Thus we investigate whether TH could regulate UCP-1 expression in WAT using multipotent cells isolated from human adipose tissue. In this study, triiodothyronine (T(3)) treatment induced UCP-1 expression and mitochondrial biogenesis, accompanied by the induction of the CCAAT/enhancer binding protein, peroxisome proliferator-activated receptor-γ coactivator-1α, and nuclear respiratory factor-1 in differentiated human multipotent adipose-derived stem cells. The effects of T(3) on UCP-1 induction were dependent on TH receptor-β. Moreover, T(3) treatment increased oxygen consumption rate. These findings indicate that T(3) is an active modulator, which induces energy utilization in white adipocytes through the regulation of UCP-1 expression and mitochondrial biogenesis. Our findings provide evidence that T(3) serves as a bipotential mediator of mitochondrial biogenesis.     

Characteristic morphology of intracellular microcolonies of Legionella oakridgensis OR-10

Legionella oakridgensis occasionally causes pneumonia in humans. We report here the characteristic morphology of intracellular microcolonies of L. oakridgensis OR-10 in infected epithelial cells. By light microscopy after Gimenez staining, the bacteria showed serpentine-like chain, disk-like conglomerate, and granular forms when they grew intracellularly in Vero cells, HeLa cells, and A549 cells. In a time-lapse study, we observed the progressive change from a serpentine-like chain form to a conglomerate form in Vero cells. Transmission electron microscopy showed that L. oakridgensis OR-10 proliferated both inside membrane structures and in the cytoplasm. Such highly serpentine chain growth has not been reported in any intracellular bacteria. Furthermore, these results imply that L. oakridgensis OR-10 may be proliferating inside the endoplasmic reticulum.     

The Dr-nanos gene is essential for germ cell specification in the planarian Dugesia ryukyuensis

Homologs of nanos are required for the formation and maintenance of germline stem cell (GSC) systems and for gametogenesis in many metazoans. Planarians can change their reproductive mode seasonally, alternating between asexual and sexual reproduction; they develop and maintain their somatic stem cells (SSCs) and GCSs from pluripotent stem cells known as neoblasts. We isolated a nanos homolog, Dr-nanos, from the expressed sequence tags (ESTs) of the sexualized form of Dugesia ryukyuensis. We examined the expression of Dr-nanos in asexual and sexualized planarians by in situ hybridization and analyzed its function using RNA interference (RNAi) together with a planarian sexualization assay. A nanos homolog, Dr-nanos, was identified in the planarian D. ryukyuensis. Dr-nanos expression was observed in the ovarian primordial cells of the asexual worms. This expression increased in proportion to sexualization and was localized in the early germline cells of the ovaries and testes. In X-ray-irradiated worms, the expression of Dr-nanos decreased to a large extent, indicating that Dr-nanos is expressed in some subpopulations of stem cells, especially in GSCs. During the sexualization process, worms in which Dr-nanos was knocked down by RNAi exhibited decreased numbers of oogonia in the ovaries and failed to develop testes, whereas the somatic sexual organs were not affected. We conclude that Dr-nanos is essential for the development of germ cells in the ovaries and testes and may have a function in the early stages of germ cell specification, but not in the development of somatic sexual organs.     

Reproductive mode and ovarian morphology regulation in chimeric planarians composed of asexual and sexual neoblasts

Planarians are comprised of populations with different reproductive strategies: exclusively innately asexual (AS), exclusively innately sexual (InS), and seasonally switching. AS worms can be sexualized experimentally by feeding them with minced InS worms, and the resultant worms are characterized as acquired sexual (AqS). Differences between InS and AqS worms are expected to provide important clues to the poorly understood mechanism underlying the regulation of their reproductive mode. Morphological differences were found between InS and AqS worm ovaries, and we showed that the pluripotent stem cells (neoblasts) from InS worms, but not those of AqS worms, have the capacity to initiate the sexual state autonomously via neoblast fraction transplantation. To compare their reproductive mode and ovarian morphology regulation, InS donor neoblast fractions were transplanted into non-lethally X-ray-irradiated AS recipients. All transplants showed stable chimerism and reproduced sexually, suggesting that InS worm neoblasts can initiate sexual state autonomously, even when coexisting with AS worm neoblasts. The chimeras formed extraordinarily large and supernumerary ovaries equivalent to AqS worms, which were not seen in InS worms, suggesting that regulation of ovarian morphology in AS worm-derived cells in response to endogenous sexualizing stimulation distinctly differs from that of InS worms.     

Restoration of Dioxin-Induced Damage to Fetal Steroidogenesis and Gonadotropin Formation by Maternal Co-Treatment with α-Lipoic Acid

2,3,7,8-Tetrachlorodibenzo-p-dioxin (TCDD), an endocrine disruptor, causes reproductive and developmental toxic effects in pups following maternal exposure in a number of animal models. Our previous studies have demonstrated that TCDD imprints sexual immaturity by suppressing the expression of fetal pituitary gonadotropins, the regulators of gonadal steroidogenesis. In the present study, we discovered that all TCDD-produced damage to fetal production of pituitary gonadotropins as well as testicular steroidogenesis can be repaired by co-treating pregnant rats with α-lipoic acid (LA), an obligate co-factor for intermediary metabolism including energy production. While LA also acts as an anti-oxidant, other anti-oxidants; i.e., ascorbic acid, butylated hydroxyanisole and edaravone, failed to exhibit any beneficial effects. Neither wasting syndrome nor CYP1A1 induction in the fetal brain caused through the activation of aryl hydrocarbon receptor (AhR) could be attenuated by LA. These lines of evidence suggest that oxidative stress makes only a minor contribution to the TCDD-induced disorder of fetal steroidogenesis, and LA has a restorative effect by targeting on mechanism(s) other than AhR activation. Following a metabolomic analysis, it was found that TCDD caused a more marked change in the hypothalamus, a pituitary regulator, than in the pituitary itself. Although the components of the tricarboxylic acid cycle and the ATP content of the fetal hypothalamus were significantly changed by TCDD, all these changes were again rectified by exogenous LA. We also provided evidence that the fetal hypothalamic content of endogenous LA is significantly reduced following maternal exposure to TCDD. Thus, the data obtained strongly suggest that TCDD reduces the expression of fetal pituitary gonadotropins to imprint sexual immaturity or disturb development by suppressing the level of LA, one of the key players serving energy production.     

Coordinated expression of functionally diverse fructosyltransferase genes is associated with fructan accumulation in response to low temperature in perennial ryegrass

* Fructan is the major nonstructural carbohydrate reserve in temperate grasses. To understand regulatory mechanisms in fructan synthesis and adaptation to cold environments, the isolation, functional characterization and genetic mapping of fructosyltransferase (FT) genes in perennial ryegrass (Lolium perenne) are described. * Six cDNAs (prft1-prft6) encoding FTs were isolated from cold-treated ryegrass plants, and three were positioned on a perennial ryegrass linkage map. Recombinant proteins were produced in Pichia pastoris and enzymatic activity was characterized. Changes in carbohydrate levels and mRNA levels of FT genes during cold treatment were also analysed. * One gene encodes sucrose-sucrose 1-fructosyltransferase (1-SST), and two gene encode fructan-fructan 6G-fructosyltransferase (6G-FFT). Protein sequences for the other genes (prfts 1, 2 and 6) were similar to sucrose-fructan 6-fructosyltransferase (6-SFT). The 1-SST and prft1 genes were colocalized with an invertase gene on the ryegrass linkage map. The mRNA levels of prft1 and prft2 increased gradually during cold treatment, while those of the 1-SST and 6G-FFT genes first increased, but then decreased before increasing again during a longer period of cold treatment. * Thus at least two different patterns of gene expression have developed during the evolution of functionally diverse FT genes, which are associated in a coordinated way with fructan synthesis in a cold environment.     

A new species of Bruchidius (Coleoptera: Chrysomelidae: Bruchinae) from Albizia in Northern Thailand and a review of Bruchidius group 5

A new species, Bruchidius paicus (Insecta, Coleoptera) reared from the seeds of a leguminous tree, Albizia lebbeck (Fabaceae: Mimosoideae: Ingeae), is described from Northern Thailand. Inspection of genital and external morphological traits of B. paicus revealed that the new species belongs to Bruchidius Group 5 (sensu ). The definition of Group 5 is reviewed based on both external and genital morphology. Further comparison of the group to molecular Clade I of Bruchidius (sensu ) indicates the two groups correspond to each other.