Relief of hypoxia by angiogenesis promotes neural stem cell differentiation by targeting glycolysis

Blood vessels are part of the stem cell niche in the developing cerebral cortex, but their in vivo role in controlling the expansion and differentiation of neural stem cells (NSCs) in development has not been studied. Here, we report that relief of hypoxia in the developing cerebral cortex by ingrowth of blood vessels temporo‐spatially coincided with NSC differentiation. Selective perturbation of brain angiogenesis in vessel‐specific Gpr124 null embryos, which prevented the relief from hypoxia, increased NSC expansion at the expense of differentiation. Conversely, exposure to increased oxygen levels rescued NSC differentiation in Gpr124 null embryos and increased it further in WT embryos, suggesting that niche blood vessels regulate NSC differentiation at least in part by providing oxygen. Consistent herewith, hypoxia‐inducible factor (HIF)‐1α levels controlled the switch of NSC expansion to differentiation. Finally, we provide evidence that high glycolytic activity of NSCs is required to prevent their precocious differentiation in vivo. Thus, blood vessel function is required for efficient NSC differentiation in the developing cerebral cortex by providing oxygen and possibly regulating NSC metabolism.     

Spatially balanced sampling and ground‐level imagery for vegetation monitoring on reclaimed well pads

Land reclamation associated with natural gas development has become increasingly important to mitigate land surface disturbance in western North America. Since well pads occur on sites with multiple land use and ownership, the progress and outcomes of these efforts are of interest to multiple stakeholders including industry, practitioners and consultants, regulatory agents, private landowners, and the scientific community. Reclamation success criteria often vary within, and among, government agencies and across land ownership type. Typically, reclamation success of a well pad is judged by comparing vegetation cover from a single transect on the pad to a single transect in an adjacent reference site and data are collected by a large number of technicians with various field monitoring skills. We utilized “SamplePoint” image analysis software and a spatially balanced sampling design, called balanced acceptance sampling, to demonstrate how spatially explicit quantitative data can be used to determine if sites are meeting various reclamation success criteria and used chi‐square tests to show how sites in vegetation percent cover differ from a statistical standpoint. This method collects field data faster than traditional methods. We demonstrate how quantitative and spatially explicit data can be utilized by multiple stakeholders, how it can improve upon current reference site selection, how it can satisfy reclamation monitoring requirements for multiple regulatory agencies, how it may help improve future seed mix selection, and discuss how it may reduce costs for operations responsible for reclamation and how it may reduce observer bias.     

Endoglin is required for myogenic differentiation potential of neural crest stem cells

Genetic studies show that TGFbeta signaling is essential for vascular development, although the mechanism through which this pathway operates is incompletely understood. Here we demonstrate that the TGFbeta auxiliary coreceptor endoglin (eng, CD105) is expressed in a subset of neural crest stem cells (NCSCs) in vivo and is required for their myogenic differentiation. Overexpression of endoglin in the neural crest caused pericardial hemorrhaging, correlating with altered vascular smooth muscle cell investment in the walls of major vessels and upregulation of smooth muscle alpha-actin protein levels. Clonogenic differentiation assay of NCSCs derived from neural tube explants demonstrated that only NCSC expressing high levels of endoglin (NCSC(CD105+)) had myogenic differentiation potential. Furthermore, myogenic potential was deficient in NCSCs obtained from endoglin null embryos. Expression of endoglin in NCSCs declined with age, coinciding with a reduction in both smooth muscle differentiation potential and TGFbeta1 responsiveness. These findings demonstrate a cell autonomous role for endoglin in smooth muscle cell specification contributing to vascular integrity.     

Caenorhabditis elegans mutants resistant to attachment of Yersinia biofilms

The detailed composition and structure of the Caenorhabditis elegans surface are unknown. Previous genetic studies used antibody or lectin binding to identify srf genes that play roles in surface determination. Infection by Microbacterium nematophilum identified bus (bacterially unswollen) genes that also affect surface characteristics. We report that biofilms produced by Yersinia pestis and Y. pseudotuberculosis, which bind the C. elegans surface predominantly on the head, can be used to identify additional surface-determining genes. A screen for C. elegans mutants with a biofilm absent on the head (Bah) phenotype identified three novel genes: bah-1, bah-2, and bah-3. The bah-1 and bah-2 mutants have slightly fragile cuticles but are neither Srf nor Bus, suggesting that they are specific for surface components involved in biofilm attachment. A bah-3 mutant has normal cuticle integrity, but shows a stage-specific Srf phenotype. The screen produced alleles of five known surface genes: srf-2, srf-3, bus-4, bus-12, and bus-17. For the X-linked bus-17, a paternal effect was observed in biofilm assays.     

Insulin acts as a myogenic differentiation signal for neural stem cells with multilineage differentiation potential

Reports of non-neural differentiation of neural stem cells (NSCs) have been challenged by alternative explanations for expanded differentiation potentials. In an attempt to demonstrate the plasticity of NSC, neurospheres were generated from single retrovirally labeled embryonic cortical precursors. In a defined serum-free insulin-containing media, 40% of the neurospheres contained both myogenic and neurogenic differentiated progeny. The number of NSCs displaying multilineage differentiation potential declines through gestation but does exist in the adult animal. In this system, insulin appears to function as a survival and dose-dependent myogenic differentiation signal for multilineage NSCs (MLNSC). MLNSC-derived cardiomyocytes contract synchronously, respond to sympathetic and parasympathetic stimulation, and regenerate injured heart tissues. These studies provide support for the hypothesis that MLNSCs exist throughout the lifetime of the animal, and potentially provide a population of stem cells for cell-based regenerative medicine strategies inside and outside of the nervous system.     

Ketopyrrolidines and ketoazetidines as potent dipeptidyl peptidase IV (DPP IV) inhibitors

In this paper, the synthesis and structure-activity relationships (SAR) of two classes of electrophile-based dipeptidyl peptidase IV (DPP IV) inhibitors, the ketopyrrolidines and ketoazetidines, is discussed. The SAR of these series demonstrate that the 2-thiazole, 2-benzothiazole, and 2-pyridylketones are optimal S1' binding groups for potency against DPP IV. In addition, both cyclohexyl glycine (CHG) and octahydroindole carboxylate (OIC) serve as the most potent S2 binding groups within each series. Stereochemistry at the alpha-position of the central ring is relevant to potency within the ketopyrrolidines series, but not in the ketoazetidine series. Finally, the ketoazetidines display enhanced stability over the corresponding ketopyrrolidines, while maintaining their potency. In fact, certain stabilized ketoazetidines can maintain their in vitro potency and inhibit DPP IV in the plasma for up to 6h.     

Challenges in constructing statistically based structure-activity relationship models for developmental toxicity

Regulatory agencies are increasingly called upon to review large numbers of environmental contaminants that have not been characterized for their potential to pose a health risk. Additionally, there is special interest in protecting potentially sensitive subpopulations and identifying developmental toxicants that may be present in the environment. Thus, there is an urgent need for efficient methods to screen large numbers of chemicals for their potential to pose a developmental hazard. One potential screening method involves the use of statistically based structure-activity relationship (SAR) tools to predict activity of untested chemicals. Such systems rely on statistical analyses to discern relationships between structure and activity for a training set of substances. Predictions can then be made for an untested substance as long as its structural features are encompassed by chemicals of the training set. In theory, such systems could assist regulatory agencies in their screening efforts; however, to date, there has been little independent evaluation of these tools for this use. To contribute to such an evaluation, the International Life Sciences Institute Risk Science Institute (ILSI RSI) convened a Working Group to examine methodology used to construct statistically based SAR systems for developmental toxicity. This document reports on the deliberations of the Working Group, which concluded that an improved process is needed for utilizing developmental toxicity data in the construction of statistically based SAR models. The process must be objective, reproducible, rational and transparent. Moreover, it must be informed by the expertise of developmental toxicologists and biologists and must be subject to peer review.     

Wnts as essential growth factors for the adult small intestine and colon

The study of physiologic functions of Wnt proteins has been complicated by the redundant nature of the families encoding the Wnt factors and their Frizzled receptors. Adenoviral expression of the secreted Wnt antagonist Dickkopf-1 (Dkk1) was used to achieve fully conditional inhibition of canonical Wnt signaling in adult mice. Systemic expression of Dkk1 resulted in rapid inhibition of Wnt target gene expression and of proliferation of the small intestine and colon, loss of proliferative crypts, and eventual inflammation and architectural degeneration. These studies indicate an essential requirement for extracellular Wnt signaling in the maintenance of adult small intestine and colon proliferation. The essential role of Wnt signaling in ongoing proliferation in the colon suggests potential clinical applications in mucosal repair for inflammatory bowel diseases and underscores the utility of adenoviral strategies for conditional ablation of gene function in adult organisms.     

Cancer cell dynamics in presence of telomerase inhibitors: analysis of in vitro data

The inhibition of telomerase activity in actively dividing cells leads to suppression of cell growth after a time delay (inhibitory delay) required to reach a threshold telomeric DNA size. We developed a mathematical model of the dynamics of telomere size distribution and cell growth in the presence of telomere inhibitors that allowed quantification of the inhibitory delay. The model based on the solution of a system of differential equations described quantitatively recent experimental data on dynamics of cultured cells in presence of telomerase inhibitors. The analysis of the data by this model suggested the existence of at least two distinct subpopulations of cells with different proliferative activity. Size distribution of telomeres, fraction of proliferating cells, and tumor doubling times are of critical importance for the dynamics of cancer cells growth in presence of telomerase inhibitors. Rapidly growing cells with large telomeric DNA heterogeneity and small proliferating fractions as well as those with very short homogeneous telomeres would be the most sensitive to telomerase inhibitors.