Rapid mapping and identification of mutations in Caenorhabditis elegans by restriction site-associated DNA mapping and genomic interval pull-down sequencing

Forward genetic screens provide a powerful approach for inferring gene function on the basis of the phenotypes associated with mutated genes. However, determining the causal mutation by traditional mapping and candidate gene sequencing is often the rate-limiting step, especially when analyzing many mutants. We report two genomic approaches for more rapidly determining the identity of the affected genes in Caenorhabditis elegans mutants. First, we report our use of restriction site-associated DNA (RAD) polymorphism markers for rapidly mapping mutations after chemical mutagenesis and mutant isolation. Second, we describe our use of genomic interval pull-down sequencing (GIPS) to selectively capture and sequence megabase-sized portions of a mutant genome. Together, these two methods provide a rapid and cost-effective approach for positional cloning of C. elegans mutant loci, and are also applicable to other genetic model systems.     

NOX5 NAD(P)H oxidase regulates growth and apoptosis in DU 145 prostate cancer cells

Reactive oxygen species (ROS) appear to play an important role in regulating growth and survival of prostate cancer. However, the sources for ROS production in prostate cancer cells have not been determined. We report that ROS are generated by intact American Type Culture Collection DU 145 cells and by their membranes through a mechanism blocked by NAD(P)H oxidase inhibitors. ROS are critical for growth in these cells, because NAD(P)H oxidase inhibitors and antioxidants blocked proliferation. Components of the human phagocyte NAD(P)H oxidase, p22^phox and gp91^phox, as well as the Ca²⁺ concentration-responsive gp91^phox homolog NOX5 were demonstrated in DU 145 cells by RT-PCR and sequencing. Although the protein product for p22^phox was not detectable, both gp91^phox and NOX5 were identified throughout the cell by immunostaining and confocal microscopy and NOX5 immunostaining was enhanced in a perinuclear location, corresponding to enhanced ROS production adjacent to the nuclear membrane imaged by 2',7'-dichlorofluorescin diacetate oxidation. The calcium ionophore ionomycin dramatically stimulated ferricytochrome c reduction in cell media, further supporting the importance of NOX5 for ROS production. Antisense oligonucleotides for NOX5 inhibited ROS production and cell proliferation in DU 145 cells. In contrast, antisense oligonucleotides to p22^phox or gp91^phox did not impair cell growth. Inhibition of ROS generation with antioxidants or NAD(P)H oxidase inhibitors increased apoptosis in cells. These results indicate that ROS generated by the newly described NOX5 oxidase are essential for prostate cancer growth, possibly by providing trophic intracellular oxidant tone that retards programmed cell death. superoxide anion; diphenylene iodonium; p22^phox; gp91^phox; adenosine 3',5'-cyclic monophosphate response element; caspases     

Responses of frog skin Na(+) and Cl(-) transport to guanylin

A possible role for the peptide hormone guanylin was investigated in frog skin (Rana pipiens) epithelium. Sodium and chloride fluxes in response to this peptide were evaluated in Ussing-type chambers. Net and unidirectional Na(+) fluxes were measured by using (22)Na(+) and atomic absorption analysis of total [Na(+)], whereas net Cl(-) fluxes were measured by using electrometric titration for [Cl(-)]. Mucosal application of guanylin (0.5-2.0 micromol/l) caused marked increases in serosal to mucosal net flux and efflux of Na(+). Serosal application of guanylin over the same dose range caused similar large increases in net serosal to mucosal (S-->M) Na(+) and Cl(-) flux as well as Na(+) efflux. Responses of Na(+) influx were small and inconsistent. When frog skin was bathed on the serosal side with Cl(-)-free Ringer's solution mucosal application of guanylin stimulated large efflux and S-->M net fluxes of Na(+). Serosal treatment yielded large Na(+) effluxes and S-->M Na(+) and Cl(-) net fluxes. When frog skin serosal surfaces were bathed with Na(+)- free Ringer's solution mucosal guanylin treatment had no effect but serosal treatment produced large S-->M Cl(-) net fluxes.     

A Systems-Level Interrogation Identifies Regulators of Drosophila Blood Cell Number and Survival

In multicellular organisms, cell number is typically determined by a balance of intracellular signals that positively and negatively regulate cell survival and proliferation. Dissecting these signaling networks facilitates the understanding of normal development and tumorigenesis. Here, we study signaling by the Drosophila PDGF/VEGF Receptor (Pvr) in embryonic blood cells (hemocytes) and in the related cell line Kc as a model for the requirement of PDGF/VEGF receptors in vertebrate cell survival and proliferation. The system allows the investigation of downstream and parallel signaling networks, based on the ability of Pvr to activate Ras/Erk, Akt/TOR, and yet-uncharacterized signaling pathway/s, which redundantly mediate cell survival and contribute to proliferation. Using Kc cells, we performed a genome wide RNAi screen for regulators of cell number in a sensitized, Pvr deficient background. We identified the receptor tyrosine kinase (RTK) Insulin-like receptor (InR) as a major Pvr Enhancer, and the nuclear hormone receptors Ecdysone receptor (EcR) and ultraspiracle (usp), corresponding to mammalian Retinoid X Receptor (RXR), as Pvr Suppressors. In vivo analysis in the Drosophila embryo revealed a previously unrecognized role for EcR to promote apoptotic death of embryonic blood cells, which is balanced with pro-survival signaling by Pvr and InR. Phosphoproteomic analysis demonstrates distinct modes of cell number regulation by EcR and RTK signaling. We define common phosphorylation targets of Pvr and InR that include regulators of cell survival, and unique targets responsible for specialized receptor functions. Interestingly, our analysis reveals that the selection of phosphorylation targets by signaling receptors shows qualitative changes depending on the signaling status of the cell, which may have wide-reaching implications for other cell regulatory systems.     

Impulsivity and Concussion in Juvenile Rats: Examining Molecular and Structural Aspects of the Frontostriatal Pathway

Impulsivity and poor executive control have been implicated in the pathogenesis of many developmental and neuropsychiatric disorders. Similarly, concussions/mild traumatic brain injuries (mTBI) have been associated with increased risk for neuropsychiatric disorders and the development of impulsivity and inattention. Researchers and epidemiologists have therefore considered whether or not concussions induce symptoms of attention-deficit/hyperactivity disorder (ADHD), or merely unmask impulsive tendencies that were already present. The purpose of this study was to determine if a single concussion in adolescence could induce ADHD-like impulsivity and impaired response inhibition, and subsequently determine if inherent impulsivity prior to a pediatric mTBI would exacerbate post-concussion symptomology with a specific emphasis on impulsive and inattentive behaviours. As these behaviours are believed to be associated with the frontostriatal circuit involving the nucleus accumbens (NAc) and the prefrontal cortex (PFC), the expression patterns of 8 genes (Comt, Drd2, Drd3, Drd4, Maoa, Sert, Tph1, and Tph2) from these two regions were examined. In addition, Golgi-Cox staining of medium spiny neurons in the NAc provided a neuroanatomical examination of mTBI-induced structural changes. The study found that a single early brain injury could induce impulsivity and impairments in response inhibition that were more pronounced in males. Interestingly, when animals with inherent impulsivity experienced mTBI, injury-related deficits were exacerbated in female animals. The single concussion increased dendritic branching, but reduced synaptic density in the NAc, and these changes were likely associated with the increase in impulsivity. Finally, mTBI-induced impulsivity was associated with modifications to gene expression that differed dramatically from the gene expression pattern associated with inherent impulsivity, despite very similar behavioural phenotypes. Our findings suggest the need to tailor treatment strategies for mTBI in light of an individual’s premorbid characteristics, given significant differences in molecular profiles of the frontostriatal circuits that depend upon sex and the etiology of the behavioural phenotype.     

Species- and tissue-specific relationships between mitochondrial permeability transition and generation of ROS in brain and liver mitochondria of rats and mice

In animal models of neurodegenerative diseases pathological changes vary with the type of organ and species of the animals. We studied differences in the mitochondrial permeability transition (mPT) and reactive oxygen species (ROS) generation in the liver (LM) and brain (BM) of Sprague-Dawley rats and C57Bl mice. In the presence of ADP mouse LM and rat LM required three times less Ca²⁺ to initiate mPT than the corresponding BM. Mouse LM and BM sequestered 70% and 50% more Ca²⁺ phosphate than the rat LM and BM. MBM generated 50% more ROS with glutamate than the RBM, but not with succinate. With the NAD substrates, generation of ROS do not depend on the energy state of the BM. Organization of the respiratory complexes into the respirasome is a possible mechanism to prevent ROS generation in the BM. With BM oxidizing succinate, 80% of ROS generation was energy dependent. Induction of mPT does not affect ROS generation with NAD substrates and inhibit with succinate as a substrate. The relative insensitivity of the liver to systemic insults is associated with its high regenerative capacity. Neuronal cells with low regenerative capacity and a long life span protect themselves by minimizing ROS generation and by the ability to withstand very large Ca²⁺ insults. We suggest that additional factors, such as oxidative stress, are required to initiate neurodegeneration. Thus the observed differences in the Ca²⁺-induced mPT and ROS generation may underlie both the organ-specific and species-specific variability in the animal models of neurodegenerative diseases. permeability transition; reactive oxygen species generation; interspecies difference     

Absence of Circular Plasmid Deoxyribonucleic Acid Attributable to a Genetic Determinant for Methicillin Resistance in Staphylococcus aureus

Plasmid deoxyribonucleic acid was not detected by centrifugal analysis of lysates of penicillinase-negative strains of Staphylococcus aureus harboring a determinant of methicillin resistance derived from strain Villaluz. When these strains contained a penicillinase plasmid, the plasmid deoxyribonucleic acid of methicillin-resistant and methicillin-susceptible strains was indistinguishable by the methods employed. The results indicate that the genetic determinant for methicillin resistance in the strains examined was not associated with a circular plasmid comparable to those that have been shown to determine resistance to benzylpenicillin, tetracycline, and chloramphenicol in S. aureus.