Phenogenetics of triploid intersexes in Drosophila melanogaster

Triploid intersexes homozygous for a mutant (msl-2) known to impede the hyperactivation of the X chromosome in diploid males differentiate into adults, sexually indistinguishable from their heterozygous sibs. A shift toward female sexual differentiation mediated by manipulating the rearing temperature is accompanied by an apparent increase in the level of an X-linked gene product. This unexpected result is rationalized in terms of differential lethality of individuals at the two extremities of the distribution of X-activity levels in intersexes raised at a particular temperature. No evidence of a mosaicism comparable to the sexual mosaicism exhibited could be found with respect to an X-linked gene product in triploid intersexes.     

COMPARISON OF ISOZYMES AMONG TYPHA SPECIES IN THE EASTERN UNITED STATES

Biochemical phenotsypes of four taxa of Typha from the eastern United States were determined by starch gel electrophoresis. The isozyme banding patterns of T. latifolia, T. angustifolia and T. domingensis are distinct and allow unambiguous species identification when morphological characters are inadequate or unsuitable. The fourth form, T. glauca, is not an F₁ hybrid, but it does appear to be intermediate between T. latifolia and T. angustifolia. The status of T. glauca and evolutionary relationships among the four forms may now be clarified by additional sampling because of the distinct and relatively invariant isozyme banding patterns which are described.     

Hepatitis C Virus Phylogenetic Clustering Is Associated with the Social-Injecting Network in a Cohort of People Who Inject Drugs

It is hypothesized that social networks facilitate transmission of the hepatitis C virus (HCV). We tested for association between HCV phylogeny and reported injecting relationships using longitudinal data from a social network design study. People who inject drugs were recruited from street drug markets in Melbourne, Australia. Interviews and blood tests took place three monthly (during 2005–2008), with participants asked to nominate up to five injecting partners at each interview. The HCV core region of individual isolates was then sequenced and phylogenetic trees were constructed. Genetic clusters were identified using bootstrapping (cut-off: 70%). An adjusted Jaccard similarity coefficient was used to measure the association between the reported injecting relationships and relationships defined by clustering in the phylogenetic analysis (statistical significance assessed using the quadratic assignment procedure). 402 participants consented to participate; 244 HCV infections were observed in 238 individuals. 26 genetic clusters were identified, with 2–7 infections per cluster. Newly acquired infection (AOR = 2.03, 95% CI: 1.04–3.96, p = 0.037, and HCV genotype 3 (vs. genotype 1, AOR = 2.72, 95% CI: 1.48–4.99) were independent predictors of being in a cluster. 54% of participants whose infections were part of a cluster in the phylogenetic analysis reported injecting with at least one other participant in that cluster during the study. Overall, 16% of participants who were infected at study entry and 40% of participants with newly acquired infections had molecular evidence of related infections with at least one injecting partner. Likely transmission clusters identified in phylogenetic analysis correlated with reported injecting relationships (adjusted Jaccard coefficient: 0.300; p<0.001). This is the first study to show that HCV phylogeny is associated with the injecting network, highlighting the importance of the injecting network in HCV transmission.     

Dietary specialization and climatic‐linked variations in extant populations of Ethiopian wolves

Understanding of the biology of rarity is central to the conservation of some endangered species. Rare taxa are often reported to be specialized, but they are usually poorly studied. The Ethiopian wolf (Canis simensis) is endemic to the Ethiopian highlands and in two major populations, Bale and Arsi in the southern range of the species, it preys almost exclusively upon diurnal rodents all year round, mainly molerats Tachyoryctes macrocephalus and common molerats T. splendens, respectively. Where these large rodents are absent or rare, wolves are expected to rely more heavily on nocturnal rats or livestock. Prey remains in 161 scats from five newly studied populations confirmed that wolves are indeed specialist rodent hunters elsewhere, and that their narrow diets are dominated by diurnal Murinae rats (60–83% of prey occurrences). Swamp rats Otomys typus were the main prey, followed by grass rats Arvicanthis abyssinicus. Common molerats, Lophuromys rats and nocturnal Stenocephalemys spp. constituted the variable portion of the diets, and their proportional contributions varied across populations in relation to elevation and latitude. Towards the north, where the climate is drier and human populations more dense, wolves predate more frequently on rat‐sized prey, including nocturnal species, with implications for the survival of small populations in the Northern Highlands.     

Multipotent Cancer Stem Cells Derived from Human Malignant Peritoneal Mesothelioma Promote Tumorigenesis

During the progression of malignant peritoneal mesothelioma (MPeM), tumor nodules propagate diffusely within the abdomen and tumors are characterized by distinct phenotypic sub-types. Recent studies in solid organ cancers have shown that cancer stem cells (CSCs) play a pivotal role in the initiation and progression of tumors. However, it is not known whether tumorigenic stem cells exist and whether they promote tumor growth in MPeM. In this study, we developed and characterized a CSC model for MPeM using stably expandable tumorigenic stem cells derived from patient tumors. We found morphologically distinct populations of CSCs that divide asymmetrically or symmetrically in MPeM in vitro cell culture. The MPeM stem cells (MPeMSCs) express stem cell markers c-MYC, NES and VEGFR2 and in the presence of matrix components cells form colony spheres. MPeMSCs are multipotent, differentiate into neuronal, vascular and adipose progeny upon defined induction and the differentiating cells express lineage-specific markers such as TUBB3, an early neuronal marker; vWF, VEGFA, VEGFC and IL-8, endothelial markers; and PPARγ and FABP4, adipose markers. Xenotransplantation experiments using MPeMSCs demonstrated early tumor growth compared with parental cells. Limiting dilution experiments using MPeMSCs and endothelial lineage-induced cells derived from a single MPeMSC resulted in early tumor growth in the latter group indicating that endothelial differentiation of MPeMSCs is important for MPeM tumor initiation. Our observation that the MPeM tumors contain stem cells with tumorigenic potential has important implications for understanding the cells of origin and tumor progression in MPeM and hence targeting CSCs may be a useful strategy to inhibit malignant progression.     

Cloning and enzymatic characterization of four thermostable fungal endo-1,4-β-xylanases

Endo-1,4-β-xylanases (EC 3.2.1.8) hydrolyze the 1,4-β-D-xylosidic linkages in xylans, the most abundant hemicellulose in plant cell walls. Xylanase enzymes have numerous industrial applications, including the manufacturing of animal feed, bread, juice and wine, pulp and paper, and biofuels. In this study, two glycosyl hydrolase family 10 members designated GtXyn10A and GtXyn10B and two glycosyl hydrolase family 11 members, OpXyn11A and CcXyn11C, were functionally expressed and subjected to biochemical characterization. The K _M , V _max, and k _cat values of the four xylanases, determined using birchwood xylan, ranged from 0.27 to 1.1 mg/mL, 130 to 980 μmol/min/mg, and 109 to 344 s^?1, respectively, where OpXyn11A gave the highest and GtXyn10B the lowest values for all three parameters. Substrate specificity studies and analysis of the products released during the degradation of xylo-oligosaccharides and three types of xylan revealed significant differences in catalytic properties, particularly between OpXyn11A and the other xylanases and between the family 10 and the family 11 xylanases. Molecular modeling suggests that the unique substrate specificity of OpXyn11A can be attributed to the presence of a serine rather that an asparagine or aspartate residue at the +1 substrate binding site. Additionally, all four xylanases exhibited biochemical characteristics of interest for various commercial applications.     

Priming in the Type I-F CRISPR-Cas system triggers strand-independent spacer acquisition,bi-directionally from the primed protospacer

Clustered regularly interspaced short palindromic repeats (CRISPR), in combination with CRISPR associated (cas) genes, constitute CRISPR-Cas bacterial adaptive immune systems. To generate immunity, these systems acquire short sequences of nucleic acids from foreign invaders and incorporate these into their CRISPR arrays as spacers. This adaptation process is the least characterized step in CRISPR-Cas immunity. Here, we used Pectobacterium atrosepticum to investigate adaptation in Type I-F CRISPR-Cas systems. Pre-existing spacers that matched plasmids stimulated hyperactive primed acquisition and resulted in the incorporation of up to nine new spacers across all three native CRISPR arrays. Endogenous expression of the cas genes was sufficient, yet required, for priming. The new spacers inhibited conjugation and transformation, and interference was enhanced with increasing numbers of new spacers. We analyzed ∼350 new spacers acquired in priming events and identified a 5′-protospacer-GG-3′ protospacer adjacent motif. In contrast to priming in Type I-E systems, new spacers matched either plasmid strand and a biased distribution, including clustering near the primed protospacer, suggested a bi-directional translocation model for the Cas1:Cas2–3 adaptation machinery. Taken together these results indicate priming adaptation occurs in different CRISPR-Cas systems, that it can be highly active in wild-type strains and that the underlying mechanisms vary.     

Multifunctional roles of the autoimmune disease-associated tyrosine phosphatase PTPN22 in regulating T cell homeostasis

The non-receptor tyrosine phosphatase PTPN22 has a vital function in inhibiting antigen-receptor signaling in T cells, while polymorphisms in the PTPN22 gene are important risk alleles in human autoimmune diseases. We recently reported that a key physiological function of PTPN22 was to prevent naïve T cell activation and effector cell responses in response to low affinity antigens. PTPN22 also has a more general role in limiting T cell receptor-induced proliferation. Here we present new data emphasizing this dual function for PTPN22 in T cells. Furthermore, we show that T cell activation modulates the expression of PTPN22 and additional inhibitory phosphatases. We discuss the implication of these findings for our understanding of the roles of PTPN22 in regulating T cell responses and in autoimmunity.