Generation of functional multipotent adult stem cells from GPR125+ germline progenitors

Adult mammalian testis is a source of pluripotent stem cells. However, the lack of specific surface markers has hampered identification and tracking of the unrecognized subset of germ cells that gives rise to multipotent cells. Although embryonic-like cells can be derived from adult testis cultures after only several weeks in vitro, it is not known whether adult self-renewing spermatogonia in long-term culture can generate such stem cells as well. Here, we show that highly proliferative adult spermatogonial progenitor cells (SPCs) can be efficiently obtained by cultivation on mitotically inactivated testicular feeders containing CD34+ stromal cells. SPCs exhibit testicular repopulating activity in vivo and maintain the ability in long-term culture to give rise to multipotent adult spermatogonial-derived stem cells (MASCs). Furthermore, both SPCs and MASCs express GPR125, an orphan adhesion-type G-protein-coupled receptor. In knock-in mice bearing a GPR125-beta-galactosidase (LacZ) fusion protein under control of the native Gpr125 promoter (GPR125-LacZ), expression in the testis was detected exclusively in spermatogonia and not in differentiated germ cells. Primary GPR125-LacZ SPC lines retained GPR125 expression, underwent clonal expansion, maintained the phenotype of germline stem cells, and reconstituted spermatogenesis in busulphan-treated mice. Long-term cultures of GPR125+ SPCs (GSPCs) also converted into GPR125+ MASC colonies. GPR125+ MASCs generated derivatives of the three germ layers and contributed to chimaeric embryos, with concomitant downregulation of GPR125 during differentiation into GPR125- cells. MASCs also differentiated into contractile cardiac tissue in vitro and formed functional blood vessels in vivo. Molecular bookmarking by GPR125 in the adult mouse and, ultimately, in the human testis could enrich for a population of SPCs for derivation of GPR125+ MASCs, which may be employed for genetic manipulation, tissue regeneration and revascularization of ischaemic organs.     

Wnt-dependent de novo hair follicle regeneration in adult mouse skin after wounding

The mammalian hair follicle is a complex 'mini-organ' thought to form only during development; loss of an adult follicle is considered permanent. However, the possibility that hair follicles develop de novo following wounding was raised in studies on rabbits, mice and even humans fifty years ago. Subsequently, these observations were generally discounted because definitive evidence for follicular neogenesis was not presented. Here we show that, after wounding, hair follicles form de novo in genetically normal adult mice. The regenerated hair follicles establish a stem cell population, express known molecular markers of follicle differentiation, produce a hair shaft and progress through all stages of the hair follicle cycle. Lineage analysis demonstrated that the nascent follicles arise from epithelial cells outside of the hair follicle stem cell niche, suggesting that epidermal cells in the wound assume a hair follicle stem cell phenotype. Inhibition of Wnt signalling after re-epithelialization completely abrogates this wounding-induced folliculogenesis, whereas overexpression of Wnt ligand in the epidermis increases the number of regenerated hair follicles. These remarkable regenerative capabilities of the adult support the notion that wounding induces an embryonic phenotype in skin, and that this provides a window for manipulation of hair follicle neogenesis by Wnt proteins. These findings suggest treatments for wounds, hair loss and other degenerative skin disorders.     

Direct measurement of antiferromagnetic domain fluctuations

Measurements of magnetic noise emanating from ferromagnets owing to domain motion were first carried out nearly 100 years ago, and have underpinned much science and technology. Antiferromagnets, which carry no net external magnetic dipole moment, yet have a periodic arrangement of the electron spins extending over macroscopic distances, should also display magnetic noise. However, this must be sampled at spatial wavelengths of the order of several interatomic spacings, rather than the macroscopic scales characteristic of ferromagnets. Here we present a direct measurement of the fluctuations in the nanometre-scale superstructure of spin- and charge-density waves associated with antiferromagnetism in elemental chromium. The technique used is X-ray photon correlation spectroscopy, where coherent X-ray diffraction produces a speckle pattern that serves as a 'fingerprint' of a particular magnetic domain configuration. The temporal evolution of the patterns corresponds to domain walls advancing and retreating over micrometre distances. This work demonstrates a useful measurement tool for antiferromagnetic domain wall engineering, but also reveals a fundamental finding about spin dynamics in the simplest antiferromagnet: although the domain wall motion is thermally activated at temperatures above 100 K, it is not so at lower temperatures, and indeed has a rate that saturates at a finite value-consistent with quantum fluctuations-on cooling below 40 K.     

Energy-dependent regulation of cell structure by AMP-activated protein kinase

AMP-activated protein kinase (AMPK, also known as SNF1A) has been primarily studied as a metabolic regulator that is activated in response to energy deprivation. Although there is relatively ample information on the biochemical characteristics of AMPK, not enough data exist on the in vivo function of the kinase. Here, using the Drosophila model system, we generated the first animal model with no AMPK activity and discovered physiological functions of the kinase. Surprisingly, AMPK-null mutants were lethal with severe abnormalities in cell polarity and mitosis, similar to those of lkb1-null mutants. Constitutive activation of AMPK restored many of the phenotypes of lkb1-null mutants, suggesting that AMPK mediates the polarity- and mitosis-controlling functions of the LKB1 serine/threonine kinase. Interestingly, the regulatory site of non-muscle myosin regulatory light chain (MRLC; also known as MLC2) was directly phosphorylated by AMPK. Moreover, the phosphomimetic mutant of MRLC rescued the AMPK-null defects in cell polarity and mitosis, suggesting MRLC is a critical downstream target of AMPK. Furthermore, the activation of AMPK by energy deprivation was sufficient to cause dramatic changes in cell shape, inducing complete polarization and brush border formation in the human LS174T cell line, through the phosphorylation of MRLC. Taken together, our results demonstrate that AMPK has highly conserved roles across metazoan species not only in the control of metabolism, but also in the regulation of cellular structures.     

Combining forecasts using optimal combination weight and generalized autoregression

In this paper, we consider a combined forecast using an optimal combination weight in a generalized autoregression framework. The generalized autoregression provides not only a combined forecast but also an optimal combination weight for combining forecasts. By simulation, we find that short‐ and medium‐horizon (as well as partly long‐horizon) forecasts from the generalized autoregression using the optimal combination weight are more efficient than those from the usual autoregression in terms of the mean‐squared forecast error. An empirical application with US gross domestic product confirms the simulation result. Copyright © 2008 John Wiley & Sons, Ltd.     

Display of proteins on Bacillus subtilis endospores

The targeting and anchoring of heterologous proteins and peptides to the outer surface of bacteriophages and cells is becoming increasingly important, and has been employed as a tool for fundamental and applied research in microbiology, molecular biology, vaccinology, and biotechnology. Less known are endospores or spores produced by some Gram-positive species. Spores of Bacillus subtilis are surrounded by a spore coat on their outside, and a few proteins have been identified being located on the outside layer and have been successfully used to immobilize antigens and some other proteins and enzymes. The major advantage of spores over the other published systems is their synthesis within the cytoplasm of the bacterial cell. Therefore, any heterologous protein to be anchored on the outside does not have to cross any membrane. Furthermore, spores are extremely resistant against high temperature, irradiation and many chemicals, and can be stored for many years at room temperature.     

Spatial and temporal evolutions of groundwater arsenic approximately along the flow path in the Hetao basin, Inner Mongolia

Patchy distribution of high As groundwater has normally been observed in As-affected areas. Spatial and temporal evolutions help in better understanding mechanisms of As mobilization and in developing effective strategies for ensuring drinking water safety. Four multilevel samplers were installed approximately along the groundwater flow path to investigate spatial and temporal variations in groundwater As in the Hetao basin, Inner Mongolia. Both water chemistry and groundwater level were monitored for about two years. Groundwater As concentration generally showed increasing trends, and Eh values showed decreasing trends along the flow path, indicating that As was mobilized via reductive dissolution of Fe oxides. However, in evaporation discharge area, shallow groundwater As was generally lower than those upstream and downstream. In addition to evaporation, siderite and pyrite precipitations controlled groundwater As concentrations. The negative correlations between As concentration and SIpyrite (or SIsiderite) implied that siderite and pyrite precipitations wold scavenge groundwater As and lower As concentration. Temporal variation showed different trends in different locations. It may reflect replenishment of high/low As groundwater for the increase/decrease in As concentrations, resulting from water level fluctuation. The increase trends in groundwater As concentrations at depth around 15m in the discharge areas would result from the increase in the recharge of underlying groundwater (20m) with high As concentration due to enhanced evaporation in the seasons with high water levels. The investigation suggested that monitoring of groundwater As should be routinely carried out to ensure the drinking water safety in the As-affected areas.     

Prediction of Essential Proteins Using Topological Properties in GO-Pruned PPI Network Based on Machine Learning Methods

The prediction of essential proteins, the minimal set required for a living cell to support cellular life, is an important task to understand the cellular processes of an organism. Fast progress in high-throughput technologies and the production of large amounts of data enable the discovery of essential proteins at the system level by analyzing Protein-Protein Interaction (PPI) networks, and replacing biological or chemical experiments. Furthermore, additional gene-level annotation information, such as Gene Ontology (GO) terms, helps to detect essential proteins with higher accuracy. Various centrality algorithms have been used to determine essential proteins in a PPI network, and, recently motif centrality GO, which is based on network motifs and GO terms, works best in detecting essential proteins in a Baker’s yeast Saccharomyces cerevisiae PPI network, compared to other centrality algorithms. However, each centrality algorithm contributes to the detection of essential proteins with different properties, which makes the integration of them a logical next step. In this paper, we construct a new feature space, named CENT-ING-GO consisting of various centrality measures and GO terms, and provide a computational approach to predict essential proteins with various machine learning techniques. The experimental results show that CENT-ING-GO feature space improves performance over the INT-GO feature space in previous work by Acencio and Lemke in 2009. We also demonstrate that pruning a PPI with informative GO terms can improve the prediction performance further.