Discovery of Reactive Microbiota-Derived Metabolites that Inhibit Host Proteases.

The gut microbiota modulate host biology in numerous ways, but little is known about the molecular mediators of these interactions. Previously, we found a widely distributed family of nonribosomal peptide synthetase gene clusters in gut bacteria. Here, by expressing a subset of these clusters in Escherichia coli or Bacillus subtilis, we show that they encode pyrazinones and dihydropyrazinones. At least one of the 47 clusters is present in 88% of the National Institutes of Health Human Microbiome Project (NIH HMP) stool samples, and they are transcribed under conditions of host colonization. We present evidence that the active form of these molecules is the initially released peptide aldehyde, which bears potent protease inhibitory activity and selectively targets a subset of cathepsins in human cell proteomes. Our findings show that an approach combining bioinformatics, synthetic biology, and heterologous gene cluster expression can rapidly expand our knowledge of the metabolic potential of the microbiota while avoiding the challenges of cultivating fastidious commensals.

Identifying Human miRNA Target Sites via Learning the Interaction Patterns between miRNA and mRNA Segments.

miRNAs (microRNAs) target specific mRNA (messenger RNA) sites to regulate their translation expression. Although miRNA targeting can rely on seed region base pairing, animal miRNAs, including human miRNAs, typically cooperate with several cofactors, leading to various noncanonical pairing rules. Therefore, identifying the binding sites of animal miRNAs remains challenging. Because experiments for mapping miRNA targets are costly, computational methods are preferred for extracting potential miRNA-mRNA fragment binding pairs first. However, existing prediction tools can have significant false positives due to the prevalent noncanonical miRNA binding behaviors and the information-biased training negative sets that were used while constructing these tools. To overcome these obstacles, we first prepared an information-balanced miRNA binding pair ground-truth data set. A miRNA-mRNA interaction-aware model was then designed to help identify miRNA binding events. On the test set, our model (auROC = 94.4%) outperformed existing models by at least 2.8% in auROC. Furthermore, we showed that this model can suggest potential binding patterns for miRNA-mRNA sequence interacting pairs. Finally, we made the prepared data sets and the designed model available at http://cosbi2.ee.ncku.edu.tw/mirna_binding/download.

A Pressure Test to Make 10 Molecules in 90 Days: External Evaluation of Methods to Engineer Biology.

Centralized facilities for genetic engineering, or "biofoundries", offer the potential to design organisms to address emerging needs in medicine, agriculture, industry, and defense. The field has seen rapid advances in technology, but it is difficult to gauge current capabilities or identify gaps across projects. To this end, our foundry was assessed via a timed "pressure test", in which 3 months were given to build organisms to produce 10 molecules unknown to us in advance. By applying a diversity of new approaches, we produced the desired molecule or a closely related one for six out of 10 targets during the performance period and made advances toward production of the others as well. Specifically, we increased the titers of 1-hexadecanol, pyrrolnitrin, and pacidamycin D, found novel routes to the enediyne warhead underlying powerful antimicrobials, established a cell-free system for monoterpene production, produced an intermediate toward vincristine biosynthesis, and encoded 7802 individually retrievable pathways to 540 bisindoles in a DNA pool. Pathways to tetrahydrofuran and barbamide were designed and constructed, but toxicity or analytical tools inhibited further progress. In sum, we constructed 1.2 Mb DNA, built 215 strains spanning five species ( Saccharomyces cerevisiae, Escherichia coli, Streptomyces albidoflavus, Streptomyces coelicolor, and Streptomyces albovinaceus), established two cell-free systems, and performed 690 assays developed in-house for the molecules.

Yeast homologous recombination-based promoter engineering for the activation of silent natural product biosynthetic gene clusters.

Large-scale sequencing of prokaryotic (meta)genomic DNA suggests that most bacterial natural product gene clusters are not expressed under common laboratory culture conditions. Silent gene clusters represent a promising resource for natural product discovery and the development of a new generation of therapeutics. Unfortunately, the characterization of molecules encoded by these clusters is hampered owing to our inability to express these gene clusters in the laboratory. To address this bottleneck, we have developed a promoter-engineering platform to transcriptionally activate silent gene clusters in a model heterologous host. Our approach uses yeast homologous recombination, an auxotrophy complementation-based yeast selection system and sequence orthogonal promoter cassettes to exchange all native promoters in silent gene clusters with constitutively active promoters. As part of this platform, we constructed and validated a set of bidirectional promoter cassettes consisting of orthogonal promoter sequences, Streptomyces ribosome binding sites, and yeast selectable marker genes. Using these tools we demonstrate the ability to simultaneously insert multiple promoter cassettes into a gene cluster, thereby expediting the reengineering process. We apply this method to model active and silent gene clusters (rebeccamycin and tetarimycin) and to the silent, cryptic pseudogene-containing, environmental DNA-derived Lzr gene cluster. Complete promoter refactoring and targeted gene exchange in this "dead" cluster led to the discovery of potent indolotryptoline antiproliferative agents, lazarimides A and B. This potentially scalable and cost-effective promoter reengineering platform should streamline the discovery of natural products from silent natural product biosynthetic gene clusters.

Discovery of indolotryptoline antiproliferative agents by homology-guided metagenomic screening.

Natural product discovery by random screening of broth extracts derived from cultured bacteria often suffers from high rates of redundant isolation, making it ever more challenging to identify novel biologically interesting natural products. Here we show that homology-based screening of soil metagenomes can be used to specifically target the discovery of new members of traditionally rare, biomedically relevant natural product families. Phylogenetic analysis of oxy-tryptophan dimerization gene homologs found within a large soil DNA library enabled the identification and recovery of a unique tryptophan dimerization biosynthetic gene cluster, which we have termed the bor cluster. When heterologously expressed in Streptomyces albus, this cluster produced an indolotryptoline antiproliferative agent with CaMKIIδ kinase inhibitory activity (borregomycin A), along with several dihydroxyindolocarbazole anticancer/antibiotics (borregomycins B-D). Similar homology-based screening of large environmental DNA libraries is likely to permit the directed discovery of new members within other previously rare families of bioactive natural products.

Targeted metagenomics: finding rare tryptophan dimer natural products in the environment.

Natural product discovery from environmental genomes (metagenomics) has largely been limited to the screening of existing environmental DNA (eDNA) libraries. Here, we have coupled a chemical-biogeographic survey of chromopyrrolic acid synthase (CPAS) gene diversity with targeted eDNA library production to more efficiently access rare tryptophan dimer (TD) biosynthetic gene clusters. A combination of traditional and synthetic biology-based heterologous expression efforts using eDNA-derived gene clusters led to the production of hydroxysporine (1) and reductasporine (2), two bioactive TDs. As suggested by our phylogenetic analysis of CPAS genes, identified in our survey of crude eDNA extracts, reductasporine (2) contains an unprecedented TD core structure: a pyrrolinium indolocarbazole core that is likely key to its unusual bioactivity profile. This work demonstrates the potential for the discovery of structurally rare and biologically interesting natural products using targeted metagenomics, where environmental samples are prescreened to identify the most phylogenetically unique gene sequences and molecules associated with these genes are accessed through targeted metagenomic library construction and heterologous expression.

Mutations in the proteolipid subunits of the vacuolar H+-ATPase provide resistance to indolotryptoline natural products.

Indolotryptoline natural products represent a small family of structurally unique chromopyrrolic acid-derived antiproliferative agents. Like many prospective anticancer agents before them, the exploration of their potential clinical utility has been hindered by the limited information known about their mechanism of action. To study the mode of action of two closely related indolotryptolines (BE-54017, cladoniamide A), we selected for drug resistant mutants using a multidrug resistance-suppressed (MDR-sup) Schizosaccharomyces pombe strain. As fission yeast maintains many of the basic cancer-relevant cellular processes present in human cells, it represents an appealing model to use in determining the potential molecular target of antiproliferative natural products through resistant mutant screening. Full genome sequencing of resistant mutants identified mutations in the c and c' subunits of the proteolipid substructure of the vacuolar H(+)-ATPase complex (V-ATPase). This collection of resistance-conferring mutations maps to a site that is distant from the nucleotide-binding sites of V-ATPase and distinct from sites found to confer resistance to known V-ATPase inhibitors. Acid vacuole staining, cross-resistance studies, and direct c/c' subunit mutagenesis all suggest that indolotryptolines are likely a structurally novel class of V-ATPase inhibitors. This work demonstrates the general utility of resistant mutant selection using MDR-sup S. pombe as a rapid and potentially systematic approach for studying the modes of action of cytotoxic natural products.

Characterization of an environmental DNA-derived gene cluster that encodes the bisindolylmaleimide methylarcyriarubin.

Bisindolylmaleimides represent a naturally occurring class of metabolites that are of interest because of their protein kinase inhibition activity. From a metagenomic library constructed with soil DNA, we identified the four gene mar cluster, a bisindolylmaleimide gene cluster that encodes for methylarcyriarubin (1) production. Heterologous expression of the mar gene cluster in E. coli revealed that the Rieske dioxygenase MarC facilitates the oxidative decarboxylation of a chromopyrrolic acid (CPA) intermediate to yield the bisindolylmaleimide core. The characterization of the mar cluster defines a new role for CPA in the biosynthesis of structurally diverse bacterial tryptophan dimers.

DMLS: an automated pipeline to extract the Drosophila modular transcription regulators and targets from massive literature articles.

Transcription regulation in multicellular species is mediated by modular transcription factor (TF) binding site combinations termed cis-regulatory modules (CRMs). Such CRM-mediated transcription regulation determines the gene expression patterns during development. Biologists frequently investigate CRM transcription regulation on gene expressions. However, the knowledge of the target genes and regulatory TFs participating in the CRMs under study is mostly fragmentary throughout the literature. Researchers need to afford tremendous human resources to fully surf through the articles deposited in biomedical literature databases in order to obtain the information. Although several novel text-mining systems are now available for literature triaging, these tools do not specifically focus on CRM-related literature prescreening, failing to correctly extract the information of the CRM target genes and regulatory TFs from the literature. For this reason, we constructed a supportive auto-literature prescreener called Drosophila Modular transcription-regulation Literature Screener (DMLS) that achieves the following: (i) prescreens articles describing experiments on modular transcription regulation, (ii) identifies the described target genes and TFs of the CRMs under study for each modular transcription-regulation-describing article and (iii) features an automated and extendable pipeline to perform the task. We demonstrated that the final performance of DMLS in extracting the described target gene and regulatory TF lists of CRMs under study for given articles achieved test macro area under the ROC curve (auROC) = 89.7% and area under the precision-recall curve (auPRC) = 77.6%, outperforming the intuitive gene name-occurrence-counting method by at least 19.9% in auROC and 30.5% in auPRC. The web service and the command line versions of DMLS are available at https://cobis.bme.ncku.edu.tw/DMLS/  and  https://github.com/cobisLab/DMLS/, respectively. Database Tool URL: https://cobis.bme.ncku.edu.tw/DMLS/.

Discovery and synthetic refactoring of tryptophan dimer gene clusters from the environment.

Here we investigate bacterial tryptophan dimer (TD) biosynthesis by probing environmental DNA (eDNA) libraries for chromopyrrolic acid (CPA) synthase genes. Functional and bioinformatics analyses of TD clusters indicate that CPA synthase gene sequences diverge in concert with the functional output of their respective clusters, making this gene a powerful tool for guiding the discovery of novel TDs from the environment. Twelve unprecedented TD biosynthetic gene clusters that can be arranged into five groups (A-E) based on their ability to generate distinct TD core substructures were recovered from eDNA libraries. Four of these groups contain clusters from both cultured and culture independent studies, while the remaining group consists entirely of eDNA-derived clusters. The complete synthetic refactoring of a representative gene cluster from the latter eDNA specific group led to the characterization of the erdasporines, cytotoxins with a novel carboxy-indolocarbazole TD substructure. Analysis of CPA synthase genes in crude eDNA suggests the presence of additional TD gene clusters in soil environments.

Cloning and characterization of an environmental DNA-derived gene cluster that encodes the biosynthesis of the antitumor substance BE-54017.

Soil is predicted to contain thousands of unique bacterial species per gram. Soil DNA libraries represent large reservoirs of biosynthetic diversity from which diverse secondary metabolite gene clusters can be recovered and studied. The screening of an archived soil DNA library using primers designed to target oxytryptophan dimerization genes allowed us to identify and functionally characterize the first indolotryptoline biosynthetic gene cluster. The recovery and heterologous expression of an environmental DNA-derived gene cluster encoding the biosynthesis of the antitumor substance BE-54017 is reported here. Transposon mutagenesis identified two monooxygenases, AbeX1 and AbeX2, as being responsible for the transformation of an indolocarbazole precursor into the indolotryptoline core of BE-54017.

Cyclic vomiting syndrome in Taiwanese children.

BACKGROUND/PURPOSE: Cyclic vomiting syndrome (CVS) is a periodic and Stereotypic pattern of intractable nausea or vomiting episodes, which has been well-recognized in previous decades, although the actual pathogenesis is still unclear. Recurrent, discrete, but self-limited symptoms of nausea and vomiting bother children, and increase the cost of family and health care. This report described the clinical features of patients who fulfill the diagnostic criteria for CVS. METHODS: This was a retrospective study that reviewed the medical records of children with CVS in our department from 1992 to 2008. The clinical features and results of long-term follow-up of these children were analyzed. RESULTS: Twenty-four patients (16 boys and 8 girls) were enrolled in this study. The mean age of onset was 6.8 ± 3.3 years (2.2-15.4 years), and the mean interval from onset to proper diagnosis was 2.1 ± 2.2 years. Comparing initial presentation and latest condition, the duration of attack was 4.1 ± 2.2 days and 0.8 ± 1.4 days, respectively, and the admission/emergency department visit dropped from 2.3 ± 2.0 to 0.6 ± 1.1 times per year. Twenty-three of 24 patients had been treated with amitriptyline, cyproheptadine, or propranolol. Nine patients (38%) had no symptoms in the past 12 months. CONCLUSION: The diagnosis of CVS must be based on the detailed history of the clinical manifestations of vomiting pattern, complete symptom-free intervals between the attacks, and absence of neurological, gastrointestinal, or metabolic abnormalities. Most of our patients improve when they grow up, but prompt diagnosis and early intervention may improve quality of life.

Delirium due to scopolamine patch in a 4-year-old boy.

The scopolamine patch is usually used to reduce postoperative nausea and vomiting associated with anesthesia and/or surgery. It is also commonly used for the prevention of motion sickness. Transdermal scopolamine patches have been used for decades and there are few reports in the literature of toxic psychosis associated with the product. Most documented cases of acute psychosis following administration of scopolamine or other anticholinergic agents have been from the adult population. Here we present a 4-year-old boy with deteriorated cognitive function and changed mental status acutely. Besides flushing skin and psychotic behaviors including bizarre actions, hallucinations, aggressive behavior, hyperactivity, and incoherent speech were also noticed. Symptoms and signs were resolved after removal of scopolamine patch and conservative management. This case is possibly one of the youngest patients to exhibit such toxic effects. We hope to relay information about common agents with anticholinergic effects to clinical practitioners and remind that drug-induced psychosis should be considered in children with acute changes in behavior.

Gut-inhabiting Clostridia build human GPCR ligands by conjugating neurotransmitters with diet- and human-derived fatty acids.

Human physiology is regulated by endogenous signalling compounds, including fatty acid amides (FAAs), chemical mimics of which are made by bacteria. The molecules produced by human-associated microbes are difficult to identify because they may only be made in a local niche or they require a substrate sourced from the host, diet or other microbes. We identified a set of uncharacterized gene clusters in metagenomics data from the human gut microbiome. These clusters were discovered to make FAAs by fusing exogenous fatty acids with amines. Using an in vitro assay, we tested their ability to incorporate 25 fatty acids and 53 amines known to be present in the human gut, from which the production of six FAAs was deduced (oleoyl dopamine, oleoyl tyramine, lauroyl tryptamine, oleoyl aminovaleric acid, α-linolenoyl phenylethylamine and caproyl tryptamine). These molecules were screened against panels of human G-protein-coupled receptors to deduce their putative human targets. Lauroyl tryptamine is found to be an antagonist to the immunomodulatory receptor EBI2 against its native oxysterol ligand (0.98 µM half-maximal inhibitory concentration), is produced in culture by Eubacterium rectale and is present in human faecal samples. FAAs produced by Clostridia may serve as a mechanism to modulate their host by mimicking human signalling molecules.

Expanding small-molecule functional metagenomics through parallel screening of broad-host-range cosmid environmental DNA libraries in diverse proteobacteria.

The small-molecule biosynthetic diversity encoded within the genomes of uncultured bacteria is an attractive target for the discovery of natural products using functional metagenomics. Phenotypes commonly associated with the production of small molecules, such as antibiosis, altered pigmentation, or altered colony morphology, are easily identified from screens of arrayed metagenomic library clones. However, functional metagenomic screening methods are limited by their intrinsic dependence on a heterologous expression host. Toward the goal of increasing the small-molecule biosynthetic diversity found in functional metagenomic studies, we report the phenotypic screening of broad-host-range environmental DNA libraries in six different proteobacteria: Agrobacterium tumefaciens, Burkholderia graminis, Caulobacter vibrioides, Escherichia coli, Pseudomonas putida, and Ralstonia metallidurans. Clone-specific small molecules found in culture broth extracts from pigmented and antibacterially active clones, as well as the genetic elements responsible for the biosynthesis of these metabolites, are described. The host strains used in this investigation provided access to unique sets of clones showing minimal overlap, thus demonstrating the potential advantage conferred on functional metagenomics through the use of multiple diverse host species.

An uncommon cause of abdominal pain and diarrhea-gastrinoma in an adolescent.

Gastrinoma is a hormone-secreting tumor associated with the Zollinger-Ellison syndrome. It is quite rare among children, and it is also uncommon in locations other than the pancreas and the duodenum in the pediatric group. Here, we describe an adolescent male, presenting with recurrent secretory diarrhea and abdominal cramping pain, who had a solitary gastrinoma in the lesser sac, close to the stomach. The prognosis was good after complete resection.

The Effect of Processing Donor Milk on Its Nutrient and Energy Content.

Background: The pasteurization is a mandatory step to inactivate pathogenic microorganisms of bank milk. For storage, freezing and thawing are necessary. The concentration of macronutrients and energy of bank milk could be influenced by these procedures which are routinely used in human milk bank. Research Aim: The aim of this study is to analyze the effect of bank milk processing (pasteurization and freezing/thawing) on the macronutrients (fat, protein, and carbohydrate) concentration and energy content. Materials and Methods: The samples of donor milk were collected and studied before/after pasteurization and after frozen for 3 months. Total 100 samples of bank milk were tested using an infrared analyzer. The measurements of fat, protein, carbohydrate, and energy were statistically analyzed by SPSS. Results: There was a prominent reduction of fat mean concentration following pasteurization and frozen (20.5% and 6.5%, respectively). The processing did not cause significant changes in protein content, but there were significant increase after pasteurization and decrease after frozen in carbohydrate (p < 0.05). Overall (postpasteurization and frozen storage), a 9.6% decrease was observed for energy content. Conclusion: This study revealed that the processing of bank milk (including Holder Pasteurization and frozen storage) decreased fat and energy content of human milk significantly, and this could not meet the specific needs of preterm infants.

The prognostic value of C-X-C motif chemokine receptor 4 in patients with sporadic malignant peripheral nerve sheath tumors.

BACKGROUND: Recent studies indicate that C-X-C motif chemokine receptor 4 (CXCR4) and its ligand, C-X-C motif chemokine ligand 12 (CXCL12), stimulate expression of the cell cycle regulatory protein Cyclin D1 in neurofibromatosis 1-associated malignant peripheral nerve sheath tumor (MPNST) cells and promote their proliferation. In this study, we measured the expression of CXCR4, CXCL12, and Cyclin D1 proteins in sporadic MPNST tissues from Chinese patients and investigated their prognostic values. METHODS: CXCR4, CXCL12, and Cyclin D1 protein expression in samples from 58 Chinese patients with sporadic MPNST was assessed with immunohistochemical staining. Their prognostic values were evaluated with Kaplan-Meier analysis and a log-rank test. Multivariate Cox regression analysis was used to identify independent prognostic factors. RESULTS: High expression of CXCR4, CXCL12, and Cyclin D1 was observed in 19 (32.8%), 32 (55.2%), and 16 (27.6%) samples, respectively. CXCR4 expression was positively correlated with CXCL12 expression (r = 0.334, P = 0.010) and Cyclin D1 expression (r = 0.309, P = 0.018). Patients with high CXCR4 expression showed longer overall survival than those with low CXCR4 expression (χ2 = 4.642, P = 0.031). CONCLUSION: High CXCR4 expression may define a specific subtype of sporadic MPNST with favorable prognosis.