Bioremediation of MTBE: a review from a practical perspective

The addition of methyl tert-butyl ether (MTBE) to gasoline has resulted in public uncertainty regarding the continued reliance on biological processes for gasoline remediation. Despite this concern, researchers have shown that MTBE can be effectively degraded in the laboratory under aerobic conditions using pure and mixed cultures with half-lives ranging from 0.04 to 29 days. Ex-situ aerobic fixed-film and aerobic suspended growth bioreactor studies have demonstrated decreases in MTBE concentrations of 83% and 96% with hydraulic residence times of 0.3 hrs and 3 days, respectively. In microcosm and field studies, aerobic biodegradation half-lives range from 2 to 693 days. These half-lives have been shown to decrease with increasing dissolved oxygen concentrations and, in some cases, with the addition of exogenous MTBE-degraders. MTBE concentrations have also been observed to decrease under anaerobic conditions; however, these rates are not as well defined. Several detailed field case studies describing the use of ex-situ reactors, natural attenuation, and bioaugmentation are presented in this paper and demonstrate the potential for successful remediation of MTBE-contaminated aquifers. In conclusion, a substantial amount of literature is available which demonstratesthat the in-situ biodegradation of MTBE is contingent on achieving aerobic conditions in the contaminated aquifer.     

Structure and polymorphism of the human gene for the interferon-induced p78 protein (MX1): evidence of association with alopecia areata in the Down syndrome region

Alopecia areata (AA) is a chronic inflammatory disease characterised by patchy hair loss with T cell infiltration of hair follicles. AA occurs in approximately 0.1% of the general population, but this is increased to 9% in Down syndrome (DS). DS is associated with an additional copy (full or partial) of chromosome 21, and the DS region may potentially include genes involved in the pathogenesis of AA. MX1 is the gene encoding the interferon-induced p78 protein (MxA). MxA protein confers resistance to influenza viruses, and we have previously shown that MxA protein is strongly expressed in lesional anagen hair bulbs from patients with AA but not in normal follicles. We therefore studied the possible involvement of MX1 in the pathogenesis of AA. To establish markers in the MX1 region which could be screened by PCR-based methods, we defined the human MX1 exon/intron organisation and screened the exons and the introns by conformation-sensitive gel electrophoresis. We found that the MX1 gene contains 17 exons extending over 33 kb. The size and sequence of the region from exon 6 to exon 16 are highly conserved between human and mouse. Screening of 4747 bp within the MX1 gene revealed four single nucleotide polymorphisms in intron 6. These polymorphisms are concentrated within 147 bp and show strong linkage disequilibrium. In a case-control association study for the MX1 (+9959) polymorphism in 165 AA patients and 510 controls we found a significant association of this marker with AA (odds ratio 1.79, 95% CI 1.21-2.66, chi2 = 8.464, P = 0.0036). The risk of disease was greater for patchy AA (mild disease) and with early age at onset (odds ratio 2.34, 95% CI 1.24-4.43, P = 0.0072), providing new evidence of genetic heterogeneity in AA. Our demonstration of genetic association between the MX1 gene and disease supports the hypothesis that this is a new candidate gene in AA.     

CRISPRseek: A Bioconductor Package to Identify Target-Specific Guide RNAs for CRISPR-Cas9 Genome-Editing Systems

CRISPR-Cas systems are a diverse family of RNA-protein complexes in bacteria that target foreign DNA sequences for cleavage. Derivatives of these complexes have been engineered to cleave specific target sequences depending on the sequence of a CRISPR-derived guide RNA (gRNA) and the source of the Cas9 protein. Important considerations for the design of gRNAs are to maximize aimed activity at the desired target site while minimizing off-target cleavage. Because of the rapid advances in the understanding of existing CRISPR-Cas9-derived RNA-guided nucleases and the development of novel RNA-guided nuclease systems, it is critical to have computational tools that can accommodate a wide range of different parameters for the design of target-specific RNA-guided nuclease systems. We have developed CRISPRseek, a highly flexible, open source software package to identify gRNAs that target a given input sequence while minimizing off-target cleavage at other sites within any selected genome. CRISPRseek will identify potential gRNAs that target a sequence of interest for CRISPR-Cas9 systems from different bacterial species and generate a cleavage score for potential off-target sequences utilizing published or user-supplied weight matrices with position-specific mismatch penalty scores. Identified gRNAs may be further filtered to only include those that occur in paired orientations for increased specificity and/or those that overlap restriction enzyme sites. For applications where gRNAs are desired to discriminate between two related sequences, CRISPRseek can rank gRNAs based on the difference between predicted cleavage scores in each input sequence. CRISPRseek is implemented as a Bioconductor package within the R statistical programming environment, allowing it to be incorporated into computational pipelines to automate the design of gRNAs for target sequences identified in a wide variety of genome-wide analyses. CRISPRseek is available under the GNU General Public Licence v3.0 at http://www.bioconductor.org.     

Codelivery of Chemotherapeutics via Crosslinked Multilamellar Liposomal Vesicles to Overcome Multidrug Resistance in Tumor

Multidrug resistance (MDR) is a significant challenge to effective cancer chemotherapy treatment. However, the development of a drug delivery system that allows for the sustained release of combined drugs with improved vesicle stability could overcome MDR in cancer cells. To achieve this, we have demonstrated codelivery of doxorubicin (Dox) and paclitaxel (PTX) via a crosslinked multilamellar vesicle (cMLV). This combinatorial delivery system achieves enhanced drug accumulation and retention, in turn resulting in improved cytotoxicity against tumor cells, including drug-resistant cells. Moreover, this delivery approach significantly overcomes MDR by reducing the expression of P-glycoprotein (P-gp) in cancer cells, thus improving antitumor activity in vivo. Thus, by enhancing drug delivery to tumors and lowering the apoptotic threshold of individual drugs, this combinatorial delivery system represents a potentially promising multimodal therapeutic strategy to overcome MDR in cancer therapy.     

Moderated estimation of fold change and dispersion for RNA-seq data with DESeq2

In comparative high-throughput sequencing assays, a fundamental task is the analysis of count data, such as read counts per gene in RNA-seq, for evidence of systematic changes across experimental conditions. Small replicate numbers, discreteness, large dynamic range and the presence of outliers require a suitable statistical approach. We present DESeq2, a method for differential analysis of count data, using shrinkage estimation for dispersions and fold changes to improve stability and interpretability of estimates. This enables a more quantitative analysis focused on the strength rather than the mere presence of differential expression. The DESeq2 package is available at http://www.bioconductor.org/packages/release/bioc/html/DESeq2.html.

Electronic supplementary material

The online version of this article (doi:10.1186/s13059-014-0550-8) contains supplementary material, which is available to authorized users.     

Osteoclast Derivation from Mouse Bone Marrow

Osteoclasts are highly specialized cells that are derived from the monocyte/macrophage lineage of the bone marrow. Their unique ability to resorb both the organic and inorganic matrices of bone means that they play a key role in regulating skeletal remodeling. Together, osteoblasts and osteoclasts are responsible for the dynamic coupling process that involves both bone resorption and bone formation acting together to maintain the normal skeleton during health and disease.As the principal bone-resorbing cell in the body, changes in osteoclast differentiation or function can result in profound effects in the body. Diseases associated with altered osteoclast function can range in severity from lethal neonatal disease due to failure to form a marrow space for hematopoiesis, to more commonly observed pathologies such as osteoporosis, in which excessive osteoclastic bone resorption predisposes to fracture formation.An ability to isolate osteoclasts in high numbers in vitro has allowed for significant advances in the understanding of the bone remodeling cycle and has paved the way for the discovery of novel therapeutic strategies that combat these diseases. Here, we describe a protocol to isolate and cultivate osteoclasts from mouse bone marrow that will yield large numbers of osteoclasts.     

Correlated divergence of female and male genitalia in replicated lineages with ongoing ecological speciation

Divergence of genital traits among lineages has the potential to serve as a reproductive isolating barrier when copulation, insemination, and fertilization are inhibited by incompatibilities between female and male genitalia. Despite widespread evidence for genital trait diversity among closely related lineages and coevolution of female and male genitalia within lineages, few studies have investigated genital evolution during the early stages of speciation. We quantified genital variation in replicated population pairs of Poecilia mexicana with ongoing ecological speciation between sulfidic (H₂S containing) and nearby nonsulfidic habitats. These analyses revealed rapid and correlated divergence of female and male genitalia across evolutionarily independent population pairs exposed to divergent selection regimes. Both sexes exhibited convergent evolution of genital traits among populations inhabiting similar habitat types. Our results demonstrate that genital evolution can occur during the early stages of speciation‐with‐gene‐flow, potentially as a result of variation in the intensity of sexual conflict among populations. Our results suggest genitalia may contribute to early stages of divergence and challenge the generality of previously suggested mechanisms of genital evolution in poeciliids.     

Climate change reduces resilience to fire in subalpine rainforests

Climate change is affecting the distribution of species and the functioning of ecosystems. For species that are slow growing and poorly dispersed, climate change can force a lag between the distributions of species and the geographic distributions of their climatic envelopes, exposing species to the risk of extinction. Climate also governs the resilience of species and ecosystems to disturbance, such as wildfire. Here we use species distribution modelling and palaeoecology to assess and test the impact of vegetation–climate disequilibrium on the resilience of an endangered fire‐sensitive rainforest community to fires. First, we modelled the probability of occurrence of Athrotaxis spp. and Nothofagus gunnii rainforest in Tasmania (hereon “montane rainforest”) as a function of climate. We then analysed three pollen and charcoal records spanning the last 7,500 cal year BP from within both high (n = 1) and low (n = 2) probability of occurrence areas. Our study indicates that climatic change between 3,000 and 4,000 cal year bp induced a disequilibrium between montane rainforests and climate that drove a loss of resilience of these communities. Current and future climate change are likely to shift the geographic distribution of the climatic envelopes of this plant community further, suggesting that current high‐resilience locations will face a reduction in resilience. Coupled with the forecast of increasing fire activity in southern temperate regions, this heralds a significant threat to this and other slow growing, poorly dispersed and fire sensitive forest systems that are common in the southern mid to high latitudes.     

Mouse genetics identifies unique and overlapping functions of fibroblast growth factor receptors in keratinocytes

Fibroblast growth factors (FGFs) are key regulators of tissue development, homeostasis and repair, and abnormal FGF signalling is associated with various human diseases. In human and murine epidermis, FGF receptor 3 (FGFR3) activation causes benign skin tumours, but the consequences of FGFR3 deficiency in this tissue have not been determined. Here, we show that FGFR3 in keratinocytes is dispensable for mouse skin development, homeostasis and wound repair. However, the defect in the epidermal barrier and the resulting inflammatory skin disease that develops in mice lacking FGFR1 and FGFR2 in keratinocytes were further aggravated upon additional loss of FGFR3. This caused fibroblast activation and fibrosis in the FGFR1/FGFR2 double‐knockout mice and even more in mice lacking all three FGFRs, revealing functional redundancy of FGFR3 with FGFR1 and FGFR2 for maintaining the epidermal barrier. Taken together, our study demonstrates that FGFR1, FGFR2 and FGFR3 act together to maintain epidermal integrity and cutaneous homeostasis, with FGFR2 being the dominant receptor.     

Combined ipilimumab and nivolumab first‐line and after BRAF‐targeted therapy in advanced melanoma

The combination of ipilimumab and nivolumab is a highly active systemic therapy for metastatic melanoma but can cause significant toxicity. We explore the safety and efficacy of this treatment in routine clinical practice, particularly in the setting of serine/threonine‐protein kinase B‐Raf (BRAF)‐targeted therapy. Consecutive patients with unresectable stage IIIC/IV melanoma commenced on ipilimumab and nivolumab across 10 tertiary melanoma institutions in Australia were identified retrospectively. Data collected included demographics, response and survival outcomes. A total of 152 patients were included for analysis, 39% were treatment‐naïve and 22% failed first‐line BRAF/MEK inhibitors. Treatment‐related adverse events occurred in 67% of patients, grade 3–5 in 38%. The overall objective response rate was 41%, 57% in treatment‐naïve and 21% in BRAF/MEK failure patients. Median progression‐free survival was 4.0 months (95% CI, 3.0–6.0) in the whole cohort, 11.0 months (95% CI, 6.0‐NR) in treatment‐naïve and 2.0 months (95% CI, 1.4–4.6) in BRAF/MEK failure patients. The combination of ipilimumab and nivolumab can be used safely and effectively in a real‐world population. While first‐line efficacy appears comparable to trial populations, BRAF‐mutant patients failing prior BRAF/MEK inhibitors show less response.