Author: biota

Selvanantham T, Lin Q, Guo CX, Surendra A, Fieve S, Escalante NK, Guttman DS, Streutker CJ, Robertson SJ, Philpott DJ, Mallevaey T.

J Immunol. 2016 Dec 1;197(11):4464-4472.

PMID: 27799307

Abstract

NKT cells are unconventional T cells that respond to self and microbe-derived lipid and glycolipid Ags presented by the CD1d molecule. Invariant NKT (iNKT) cells influence immune responses in numerous diseases. Although only a few studies have examined their role during intestinal inflammation, it appears that iNKT cells protect from Th1-mediated inflammation but exacerbate Th2-mediated inflammation. Studies using iNKT cell-deficient mice and chemically induced dextran sodium sulfate (DSS) colitis have led to inconsistent results. In this study, we show that CD1d-deficient mice, which lack all NKT cells, harbor an altered intestinal microbiota that is associated with exacerbated intestinal inflammation at steady-state and following DSS treatment. This altered microbiota, characterized by increased abundance of the bacterial phyla Proteobacteria, Deferribacteres, and TM7, among which the mucin-eating Mucispirillum, as well as members of the genus Prevotella and segmented filamentous bacteria, was transmissible upon fecal transplant, along with the procolitogenic phenotype. Our results also demonstrate that this proinflammatory microbiota influences iNKT cell function upon activation during DSS colitis. Collectively, alterations of the microbiota have a major influence on colitis outcome and therefore have to be accounted for in such experimental settings and in studies focusing on iNKT cells.

Laflamme B, Middleton M, Lo T, Desveaux D, Guttman DS.

Mol Plant Microbe Interact. 2016 Dec;29(12):919-924.

PMID: 27996374

Abstract

Measuring the extent and severity of disease is a critical component of plant pathology research and crop breeding. Unfortunately, existing visual scoring systems are qualitative, subjective, and the results are difficult to transfer between research groups, while existing quantitative methods can be quite laborious. Here, we present plant immunity and disease image-based quantification (PIDIQ), a quantitative, semi-automated system to rapidly and objectively measure disease symptoms in a biologically relevant context. PIDIQ applies an ImageJ-based macro to plant photos in order to distinguish healthy tissue from tissue that has yellowed due to disease. It can process a directory of images in an automated manner and report the relative ratios of healthy to diseased leaf area, thereby providing a quantitative measure of plant health that can be statistically compared with appropriate controls. We used the Arabidopsis thaliana-Pseudomonas syringae model system to show that PIDIQ is able to identify both enhanced plant health associated with effector-triggered immunity as well as elevated disease symptoms associated with effector-triggered susceptibility. Finally, we show that the quantitative results provided by PIDIQ correspond to those obtained via traditional in planta pathogen growth assays. PIDIQ provides a simple and effective means to nondestructively quantify disease from whole plants and we believe it will be equally effective for monitoring disease on excised leaves and stems.

Hota SS, Sales V, Tomlinson G, Salpeter MJ, McGeer A, Coburn B, Guttman DS, Low DE, Poutanen SM.

Clin Infect Dis. 2017 Feb 1;64(3):265-271

PMID: 28011612

Abstract

BACKGROUND:Fecal transplantation (FT) is a promising treatment for recurrent Clostridium difficile infection (CDI), but its true effectiveness remains unknown. We compared 14 days of oral vancomycin followed by a single FT by enema with oral vancomycin taper (standard of care) in adult patients experiencing acute recurrence of CDI.

METHODS:In a phase 2/3, single-center, open-label trial, participants from Ontario, Canada, experiencing recurrence of CDI were randomly assigned in a 1:1 ratio to 14 days of oral vancomycin treatment followed by a single 500-mL FT by enema, or a 6-week taper of oral vancomycin. Patients with significant immunocompromise, history of fulminant CDI, or irreversible bleeding disorders were excluded. The primary endpoint was CDI recurrence within 120 days. Microbiota analysis was performed on fecal filtrate from donors and stool samples from FT recipients, as available.

RESULTS:The study was terminated at the interim analysis after randomizing 30 patients. Nine of 16 (56.2%) patients who received FT and 5 of 12 (41.7%) in the vancomycin taper group experienced recurrence of CDI, corresponding with symptom resolution in 43.8% and 58.3%, respectively. Fecal microbiota analysis of 3 successful FT recipients demonstrated increased diversity. A futility analysis did not support continuing the study. Adverse events were similar in both groups and uncommon.

CONCLUSIONS:In patients experiencing an acute episode of recurrent CDI, a single FT by enema was not significantly different from oral vancomycin taper in reducing recurrent CDI. Further research is needed to explore optimal donor selection, FT preparation, route, timing, and number of administrations.

Chuong KH, Hwang DM, Tullis DE, Waters VJ, Yau YC, Guttman DS, O’Doherty KC.

BMC Med Ethics. 2017 Jan 11;18(1):1

PMID: 28077127

Abstract

BACKGROUND:Biobanks are considered to be key infrastructures for research development and have generated a lot of debate about their ethical, legal and social implications (ELSI). While the focus has been on human genomic research, rapid advances in human microbiome research further complicate the debate.

DISCUSSION:We draw on two cystic fibrosis biobanks in Toronto, Canada, to illustrate our points. The biobanks have been established to facilitate sample and data sharing for research into the link between disease progression and microbial dynamics in the lungs of pediatric and adult patients. We begin by providing an overview of some of the ELSI associated with human microbiome research, particularly on the implications for the broader society. We then discuss ethical considerations regarding the identifiability of samples biobanked for human microbiome research, and examine the issue of return of results and incidental findings. We argue that, for the purposes of research ethics oversight, human microbiome research samples should be treated with the same privacy considerations as human tissues samples. We also suggest that returning individual microbiome-related findings could provide a powerful clinical tool for care management, but highlight the need for a more grounded understanding of contextual factors that may be unique to human microbiome research.

CONCLUSIONS:We revisit the ELSI of biobanking and consider the impact that human microbiome research might have. Our discussion focuses on identifiability of human microbiome research samples, and return of research results and incidental findings for clinical management.

Seto D, Koulena N, Lo T, Menna A, Guttman DS, Desveaux D.

Nat Plants. 2017 Mar 13;3:17027

PMID: 28288096

Abstract

Nucleotide-binding domain and leucine-rich repeat domain-containing (NLR) proteins are sentinels of plant immunity that monitor host proteins for perturbations induced by pathogenic effector proteins. Here we show that the Arabidopsis ZAR1 NLR protein requires the ZRK3 kinase to recognize the Pseudomonas syringae type III effector (T3E) HopF2a. These results support the hypothesis that ZAR1 associates with an expanded ZRK protein family to broaden its effector recognition spectrum.

Tun HM, Konya T, Takaro TK, Brook JR, Chari R, Field CJ, Guttman DS, Becker AB, Mandhane PJ, Turvey SE, Subbarao P, Sears MR, Scott JA, Kozyrskyj AL; CHILD Study Investigators.

Microbiome. 2017 Apr 6;5(1):40

PMID: 28381231

Abstract

BACKGROUND:Early-life exposure to household pets has the capacity to reduce risk for overweight and allergic disease, especially following caesarean delivery. Since there is some evidence that pets also alter the gut microbial composition of infants, changes to the gut microbiome are putative pathways by which pet exposure can reduce these risks to health. To investigate the impact of pre- and postnatal pet exposure on infant gut microbiota following various birth scenarios, this study employed a large subsample of 746 infants from the Canadian Healthy Infant Longitudinal Development Study (CHILD) cohort, whose mothers were enrolled during pregnancy between 2009 and 2012. Participating mothers were asked to report on household pet ownership at recruitment during the second or third trimester and 3 months postpartum. Infant gut microbiota were profiled with 16S rRNA sequencing from faecal samples collected at the mean age of 3.3 months. Two categories of pet exposure (i) only during pregnancy and (ii) pre- and postnatally were compared to no pet exposure under different birth scenarios.

RESULTS:Over half of studied infants were exposed to at least one furry pet in the prenatal and/or postnatal periods, of which 8% were exposed in pregnancy alone and 46.8% had exposure during both time periods. As a common effect in all birth scenarios, pre- and postnatal pet exposure enriched the abundance of Oscillospira and/or Ruminococcus (P < 0.05) with more than a twofold greater likelihood of high abundance. Among vaginally born infants with maternal intrapartum antibiotic prophylaxis exposure, Streptococcaceae were substantially and significantly reduced by pet exposure (P < 0.001, FDRp = 0.03), reflecting an 80% decreased likelihood of high abundance (OR 0.20, 95%CI, 0.06-0.70) for pet exposure during pregnancy alone and a 69% reduced likelihood (OR 0.31, 95%CI, 0.16-0.58) for exposure in the pre- and postnatal time periods. All of these associations were independent of maternal asthma/allergy status, siblingship, breastfeeding exclusivity and other home characteristics.

CONCLUSIONS:The impact of pet ownership varies under different birth scenarios; however, in common, exposure to pets increased the abundance of two bacteria, Ruminococcus and Oscillospira, which have been negatively associated with childhood atopy and obesity.

Holbrook-Smith D, Toh S, Tsuchiya Y, McCourt P.

Nat Chem Biol. 2016 Sep;12(9):724-9.

PMID: 27428512

Abstract

Striga spp. (witchweed) is an obligate parasitic plant that attaches to host roots to deplete them of nutrients. In Sub-Saharan Africa, the most destructive Striga species, Striga hermonthica, parasitizes major food crops affecting two-thirds of the arable land and over 100 million people. One potential weakness in the Striga infection process is the way it senses the presence of a host crop. Striga only germinates in the presence of the plant hormone strigolactone, which exudes from a host root. Hence small molecules that perturb strigolactone signaling may be useful tools for disrupting the Striga lifecycle. Here we developed a chemical screen to suppress strigolactone signaling in the model plant Arabidopsis. One compound, soporidine, specifically inhibited a S. hermonthica strigolactone receptor and inhibited the parasite’s germination. This indicates that strigolactone-based screens using Arabidopsis are useful in identifying lead compounds to combat Striga infestations.

Moorthy SD, Davidson S, Shchuka VM, Singh G, Malek-Gilani N, Langroudi L, Martchenko A, So V, Macpherson NN, Mitchell JA.

Genome Res. 2017 Feb;27(2):246-258.

PMID: 27895109

Abstract

Transcriptional enhancers are critical for maintaining cell-type-specific gene expression and driving cell fate changes during development. Highly transcribed genes are often associated with a cluster of individual enhancers such as those found in locus control regions. Recently, these have been termed stretch enhancers or super-enhancers, which have been predicted to regulate critical cell identity genes. We employed a CRISPR/Cas9-mediated deletion approach to study the function of several enhancer clusters (ECs) and isolated enhancers in mouse embryonic stem (ES) cells. Our results reveal that the effect of deleting ECs, also classified as ES cell super-enhancers, is highly variable, resulting in target gene expression reductions ranging from 12% to as much as 92%. Partial deletions of these ECs which removed only one enhancer or a subcluster of enhancers revealed partially redundant control of the regulated gene by multiple enhancers within the larger cluster. Many highly transcribed genes in ES cells are not associated with a super-enhancer; furthermore, super-enhancer predictions ignore 81% of the potentially active regulatory elements predicted by cobinding of five or more pluripotency-associated transcription factors. Deletion of these additional enhancer regions revealed their robust regulatory role in gene transcription. In addition, select super-enhancers and enhancers were identified that regulated clusters of paralogous genes. We conclude that, whereas robust transcriptional output can be achieved by an isolated enhancer, clusters of enhancers acting on a common target gene act in a partially redundant manner to fine tune transcriptional output of their target genes.

Waese J, Provart NJ

Methods Mol Biol. 2017;1533:119-148

PMID: 27987167

Abstract

Bioinformatic tools have become part of the way plant researchers undertake investigations. Large data sets encompassing genomes, transcriptomes, proteomes, epigenomes, and other “-omes” that have been generated in the past decade may be easily accessed with such tools, such that hypotheses may be generated at the click of a mouse. In this chapter, we’ll cover the use of bioinformatic tools available at the Bio-Analytic Resource for Plant Biology at http://bar.utoronto.ca for exploring gene expression and coexpression patterns, undertaking promoter analyses, performing functional classification enrichment analyses for sets of genes, and examining protein-protein interactions. We also touch on some newer bioinformatic tools that allow integration of data from several sources for improved hypothesis generation, both for Arabidopsis and translationally. Most of the data sets come from Arabidopsis, but useful BAR tools for other species will be mentioned where appropriate.