Polycistronic gene expression in Aspergillus niger.

BACKGROUND: Genome mining approaches predict dozens of biosynthetic gene clusters in each of the filamentous fungal genomes sequenced so far. However, the majority of these gene clusters still remain cryptic because they are not expressed in their natural host. Simultaneous expression of all genes belonging to a biosynthetic pathway in a heterologous host is one approach to activate biosynthetic gene clusters and to screen the metabolites produced for bioactivities. Polycistronic expression of all pathway genes under control of a single and tunable promoter would be the method of choice, as this does not only simplify cloning procedures, but also offers control on timing and strength of expression. However, polycistronic gene expression is a feature not commonly found in eukaryotic host systems, such as Aspergillus niger. RESULTS: In this study, we tested the suitability of the viral P2A peptide for co-expression of three genes in A. niger. Two genes descend from Fusarium oxysporum and are essential to produce the secondary metabolite enniatin (esyn1, ekivR). The third gene (luc) encodes the reporter luciferase which was included to study position effects. Expression of the polycistronic gene cassette was put under control of the Tet-On system to ensure tunable gene expression in A. niger. In total, three polycistronic expression cassettes which differed in the position of luc were constructed and targeted to the pyrG locus in A. niger. This allowed direct comparison of the luciferase activity based on the position of the luciferase gene. Doxycycline-mediated induction of the Tet-On expression cassettes resulted in the production of one long polycistronic mRNA as proven by Northern analyses, and ensured comparable production of enniatin in all three strains. Notably, gene position within the polycistronic expression cassette matters, as, luciferase activity was lowest at position one and had a comparable activity at positions two and three. CONCLUSIONS: The P2A peptide can be used to express at least three genes polycistronically in A. niger. This approach can now be applied to heterologously express entire secondary metabolite gene clusters polycistronically or to co-express any genes of interest in equimolar amounts.

Benefits of MR-proADM-guided decision-making in the emergency department: clinical and economic evaluation in Italy, Germany, Spain, and the UK.

AIM: In a randomized control trial mid-regional proadrenomedullin (MR-proADM)-guided decision-making has been proven to safely reduce hospital admissions based on an accurate assessment of disease severity in the Emergency Department (ED). This study aimed to assess the impact of a MR-proADM-Guided Triage (MR-GT) versus standard Hospital Triage (HT) on clinical and economic outcomes in ED patients with suspected infection in Spain, Italy, Germany, and the UK, using Patient-Level Data (PLD) from two observational studies. METHODS: PLD was collected from patients enrolled at a Spanish hospital during two observational studies. Logistic regression was used to identify predictors of hospitalization. A patient-level simulation model was subsequently developed to evaluate the clinical and economic impact of MR-GT versus HT using results from the statistical analysis and country-specific cost data from the published literature. Probabilistic and deterministic sensitivity analyses were carried out. RESULTS: Four hundred seventy-three patients were enrolled in this study. MR-proADM had the strongest association with hospital admission, followed by age and National Early Warning Score (NEWS). In the simulation model, MR-GT was associated with an overall reduction in hospitalization relative to HT, equal to 22.6 percentage points (40.9 vs. 63.5%). In addition, the use of MR-GT would reduce the total hospital cost per patient presenting to the ED with suspected infection by roughly 30%, with a mean cost saving per patient of €626, €1,484, €1,154, and £1,113 in Spain, Italy, Germany, and the UK, respectively. The robustness of these findings was confirmed by sensitivity analyses. LIMITATIONS: The statistical analyses were not performed on the same population simulated in the model. Clinical input parameters were assumed to be the same for all countries. CONCLUSIONS: MR-proADM showed to be the main predictor of hospitalization. An MR-proADM decision algorithm provides cost savings in Spain, Italy, Germany, and the UK.