Author: Sylva Donaldson

Gianni M Castiglione , Yan L I Chiu , Eduardo de A Gutierrez , Alexander Van Nynatten , Frances E Hauser , Matthew Preston , Nihar Bhattacharyya , Ryan K Schott , Belinda S W Chang

Curr Biol. 2023 Nov 6;33(21):4733-4740.e4. doi: 10.1016/j.cub.2023.09.015

Pubmed: 37776863

Abstract

Animals with enhanced dim-light sensitivity are at higher risk of light-induced retinal degeneration when exposed to bright light conditions.^1,2,3,4 This trade-off is mediated by the rod photoreceptor sensory protein, rhodopsin (RHO), and its toxic vitamin A chromophore by-product, all-trans retinal.^5,6,7,8 Rod arrestin (Arr-1) binds to RHO and promotes sequestration of excess all-trans retinal,^9,10 which has recently been suggested as a protective mechanism against photoreceptor cell death.^2,11 We investigated Arr-1 evolution in animals at high risk of retinal damage due to periodic bright-light exposure of rod-dominated retinas. Here, we find the convergent evolution of enhanced Arr-1/RHO all-trans-retinal sequestration in owls and deep-diving whales. Statistical analyses reveal a parallel acceleration of Arr-1 evolutionary rates in these lineages, which is associated with the introduction of a rare Arr-1 mutation (Q69R) into the RHO-Arr-1 binding interface. Using in vitro assays, we find that this single mutation significantly enhances RHO-all-trans-retinal sequestration by ∼30%. This functional convergence across 300 million years of evolutionary divergence suggests that Arr-1 and RHO may play an underappreciated role in the photoprotection of the eye, with potentially vast clinical significance.

Keywords: Stargardt; age-related macular degeneration; all trans retinal; arrestin; blindness; evolution; owl; rhodopsin; vision; whale.

Castiglione GM, Hauser FE, Van Nynatten A, Chang BSW.

Mol Biol Evol. 2023 Apr 4;40(4):msad030. doi: 10.1093/molbev/msad030.

Pubmed: 36763103

Abstract

Extreme environments, such as Antarctic habitats, present major challenges for many biological processes. Antarctic icefishes (Crynotothenioidea) represent a compelling system to investigate the molecular basis of adaptation to cold temperatures. Here, we explore how the sub-zero habitats of Antarctic icefishes have impacted rhodopsin (RH1) function, the temperature-sensitive dim-light visual pigment found in rod photoreceptors. Using likelihood models and ancestral reconstruction, we find that accelerated evolutionary rates in icefish RH1 underlie unique amino acid mutations absent from other deep-dwelling fishes, introduced before (S160A) and during (V259M) the onset of modern polar conditions. Functional assays reveal that these mutations red-shift rhodopsin spectral absorbance, consistent with spectral irradiance under sea ice. These mutations also lower the activation energy associated with retinal release of the light-activated RH1, and accelerate its return to the dark state, likely compensating for a cold-induced decrease in kinetic rates. These are adaptations in key properties of rhodopsin that mediate rod sensitivity and visual performance in the cold dark seas of the Antarctic.

Keywords: icefish; rhodopsin; vision.

Raygoza Garay JA, Turpin W, Lee SH, Smith MI, Goethel A, Griffiths AM, Moayyedi P, Espin-Garcia O, Abreu M, Aumais GL, Bernstein CN, Biron IA, Cino M, Deslandres C, Dotan I, El-Matary W, Feagan B, Guttman DS, Huynh H, Dieleman LA, Hyams JS, Jacobson K, Mack D, Marshall JK, Otley A, Panaccione R, Ropeleski M, Silverberg MS, Steinhart AH, Turner D, Yerushalmi B, Paterson AD, Xu W; CCC GEM Project Research Consortium; Croitoru K.

Gastroenterology. 2023 Sep;165(3):670-681. doi: 10.1053/j.gastro.2023.05.032

Pubmed: 37263307

Abstract

Background & aims: The cause of Crohn’s disease (CD) is unknown, but the current hypothesis is that microbial or environmental factors induce gut inflammation in genetically susceptible individuals, leading to chronic intestinal inflammation. Case-control studies of patients with CD have cataloged alterations in the gut microbiome composition; however, these studies fail to distinguish whether the altered gut microbiome composition is associated with initiation of CD or is the result of inflammation or drug treatment.

Methods: In this prospective cohort study, 3483 healthy first-degree relatives (FDRs) of patients with CD were recruited to identify the gut microbiome composition that precedes the onset of CD and to what extent this composition predicts the risk of developing CD. We applied a machine learning approach to the analysis of the gut microbiome composition (based on 16S ribosomal RNA sequencing) to define a microbial signature that associates with future development of CD. The performance of the model was assessed in an independent validation cohort.

Results: In the validation cohort, the microbiome risk score (MRS) model yielded a hazard ratio of 2.24 (95% confidence interval, 1.03-4.84; P = .04), using the median of the MRS from the discovery cohort as the threshold. The MRS demonstrated a temporal validity by capturing individuals that developed CD up to 5 years before disease onset (area under the curve > 0.65). The 5 most important taxa contributing to the MRS included Ruminococcus torques, Blautia, Colidextribacter, an uncultured genus-level group from Oscillospiraceae, and Roseburia.

Conclusion: This study is the first to demonstrate that gut microbiome composition is associated with future onset of CD and suggests that gut microbiome is a contributor in the pathogenesis of CD.

Keywords: Faecalibacterium; Fecal Calprotectin; Microbiome; Preclinical Inflammatory Bowel Disease; Vitamins B.

Vincent Lau & Nicholas J. Provart

Methods Mol Biol. 2023:2698:351-360. doi: 10.1007/978-1-0716-3354-0_20

Pubmed: 37682484

Abstract

Gene regulatory networks (GRNs) are important for determining how an organism develops and how it responds to external stimuli. In the case of Arabidopsis thaliana, several GRNs have been identified covering many important biological processes. We present AGENT, the Arabidopsis GEne Network Tool, for exploring and analyzing published GRNs. Using tools in AGENT, regulatory motifs such as feed-forward loops can be easily identified. Nodes with high centrality-and hence importance-can likewise be identified. Gene expression data can also be overlaid onto GRNs to help discover subnetworks acting in specific tissues or under certain conditions.

Keywords: Bioinformatics; Feed-forward loops; Gene regulatory networks; Hypothesis generation; Motifs; Protein–DNA interactions; Protein–protein interactions.

Ashley M. Rooney , Kyla Cochrane, Stephanie Fedsin, Samantha Yao, Shaista Anwer, Satyender Dehmiwal, Susy Hota, Susan Poutanen, Emma Allen-Vercoe , Bryan Coburn , MTOP Investigators

mBio. 2023 Aug 31;14(4):e0348222. doi: 10.1128/mbio.03482-22

Pubmed: 37404011

Abstract

Intestinal colonization with pathogens and antimicrobial-resistant organisms (AROs) is associated with increased risk of infection. Fecal microbiota transplant (FMT) has successfully been used to cure recurrent Clostridioides difficile infection (rCDI) and to decolonize intestinal AROs. However, FMT has significant practical barriers to safe and broad implementation. Microbial consortia represent a novel strategy for ARO and pathogen decolonization, with practical and safety advantages over FMT. We undertook an investigator-initiated analysis of stool samples collected from previous interventional studies of a microbial consortium, microbial ecosystem therapeutic (MET-2), and FMT for rCDI before and after treatment. Our aim was to assess whether MET-2 was associated with decreased Pseudomonadota (Proteobacteria) and antimicrobial resistance gene (ARG) burden with similar effects to FMT. Participants were selected for inclusion if baseline stool had Pseudomonadota relative abundance ≥10%. Pre- and post-treatment Pseudomonadota relative abundance, total ARGs, and obligate anaerobe and butyrate-producer relative abundances were determined by shotgun metagenomic sequencing. MET-2 administration had similar effects to FMT on microbiome outcomes. The median Pseudomonadota relative abundance decreased by four logs after MET-2 treatment, a greater decrease than that observed after FMT. Total ARGs decreased, while beneficial obligate anaerobe and butyrate-producer relative abundances increased. The observed microbiome response remained stable over 4 months post-administration for all outcomes. IMPORTANCE Overgrowth of intestinal pathogens and AROs is associated with increased risk of infection. With the rise in antimicrobial resistance, new therapeutic strategies that decrease pathogen and ARO colonization in the gut are needed. We evaluated whether a microbial consortium had similar effects to FMT on Pseudomonadota abundances and ARGs as well as obligate anaerobes and beneficial butyrate producers in individuals with high Pseudomonadota relative abundance at baseline. This study provides support for a randomized, controlled clinical trial of microbial consortia (such as MET-2) for ARO decolonization and anaerobe repletion.

Keywords: Proteobacteria; Pseudomonadota; anaerobes; antibiotic resistance; fecal microbiota transplant; gut microbiome; microbial consortium.

Katherine J. P. Schwenger, Divya Sharma, Yasaman Ghorbani, Wei Xu, Wendy Lou, Elena M. Comelli, Sandra E. Fischer, Timothy D. Jackson, Allan Okrainec, Johane P. Allard

Liver Int. 2024 Feb 14. doi: 10.1111/liv.15864 doi: 10.1111/liv.15864

Pubmed: 38353022

Abstract

Background and aims: Bacterial species and microbial pathways along with metabolites and clinical parameters may interact to contribute to non-alcoholic fatty liver disease (NAFLD) and disease severity. We used integrated machine learning models and a cross-validation approach to assess this interaction in bariatric patients.

Methods: 113 patients undergoing bariatric surgery had clinical and biochemical parameters, blood and stool metabolite measurements as well as faecal shotgun metagenome sequencing to profile the intestinal microbiome. Liver histology was classified as normal liver obese (NLO; n = 30), simple steatosis (SS; n = 41) or non-alcoholic steatohepatitis (NASH; n = 42); fibrosis was graded F0 to F4.

Results: We found that those with NASH versus NLO had an increase in potentially harmful E. coli, a reduction of potentially beneficial Alistipes putredinis and an increase in ALT and AST. There was higher serum glucose, faecal 3-(3-hydroxyphenyl)-3-hydroxypropionic acid and faecal cholic acid and lower serum glycerophospholipids. In NAFLD, those with severe fibrosis (F3-F4) versus F0 had lower abundance of anti-inflammatory species (Eubacterium ventriosum, Alistipes finegoldii and Bacteroides dorei) and higher AST, serum glucose, faecal acylcarnitines, serum isoleucine and homocysteine as well as lower serum glycerophospholipids. Pathways involved with amino acid biosynthesis and degradation were significantly more represented in those with NASH compared to NLO, with severe fibrosis having an overall stronger significant association with Superpathway of menaquinol-10 biosynthesis and Peptidoglycan biosynthesis IV.

Conclusions: In bariatric patients, NASH and severe fibrosis were associated with specific bacterial species, metabolic pathways and metabolites that may contribute to NAFLD pathogenesis and disease severity.

Keywords: fatty liver; hepatic fibrosis; metabolic pathways; metagenome; morbid obesity.

Jitender Yadav, Tao Liang, Tairan Qin, Nayanan Nathan, Katherine J.P. Schwenger, Lauren Pickel, Li Xie, Helena Lei, Daniel A. Winer, Heather Maughan, Susan J. Robertson, Minna Woo, Wendy Lou, Kate Banks, Timothy Jackson, Allan Okrainec, Susy S. Hota, Susan M. Poutanen, Hoon-Ki Sung, Johane P. Allard, Dana J. Philpott, and Herbert Y. Gaisano

Cell Rep Med 2023 May 16;4(5):101051. doi: 10.1016/j.xcrm.2023.101051

Pubmed: 37196633

Abstract

Alterations in the microbiome correlate with improved metabolism in patients following bariatric surgery. While fecal microbiota transplantation (FMT) from obese patients into germ-free (GF) mice has suggested a significant role of the gut microbiome in metabolic improvements following bariatric surgery, causality remains to be confirmed. Here, we perform paired FMT from the same obese patients (BMI > 40; four patients), pre- and 1 or 6 months post-Roux-en-Y gastric bypass (RYGB) surgery, into Western diet-fed GF mice. Mice colonized by FMT from patients’ post-surgery stool exhibit significant changes in microbiota composition and metabolomic profiles and, most importantly, improved insulin sensitivity compared with pre-RYGB FMT mice. Mechanistically, mice harboring the post-RYGB microbiome show increased brown fat mass and activity and exhibit increased energy expenditure. Moreover, improvements in immune homeostasis within the white adipose tissue are also observed. Altogether, these findings point to a direct role for the gut microbiome in mediating improved metabolic health post-RYGB surgery.

Kathryn J. McTavish, Renan N. D. Almeida, Jonathan Tersigni, Melina K. Raimundi, Yunchen Gong, Pauline W. Wang, Guilherme F. Gontijo, Ricardo M. de Souza, Mario L. V. de Resende, Darrell Desveaux, David S. Guttman

New Phytol 2024 Jan;241(1):409-429. doi: 10.1111/nph.19364

Pubmed: 37953378

Abstract

The emergence of new pathogens is an ongoing threat to human health and agriculture. While zoonotic spillovers received considerable attention, the emergence of crop diseases is less well studied. Here, we identify genomic factors associated with the emergence of Pseudomonas syringae bacterial blight of coffee. Fifty-three P. syringae strains from diseased Brazilian coffee plants were sequenced. Comparative and evolutionary analyses were used to identify loci associated with coffee blight. Growth and symptomology assays were performed to validate the findings. Coffee isolates clustered in three lineages, including primary phylogroups PG3 and PG4, and secondary phylogroup PG11. Genome-wide association study of the primary PG strains identified 37 loci, including five effectors, most of which were encoded on a plasmid unique to the PG3 and PG4 coffee strains. Evolutionary analyses support the emergence of coffee blight in PG4 when the coffee-associated plasmid and associated effectors derived from a divergent plasmid carried by strains associated with other hosts. This plasmid was only recently transferred into PG3. Natural diversity and CRISPR-Cas9 plasmid curing were used to show that strains with the coffee-associated plasmid grow to higher densities and cause more severe disease symptoms in coffee. This work identifies possible evolutionary mechanisms underlying the emergence of a new lineage of coffee pathogens.

Lucía Graña-Miraglia, Nadia Morales-Lizcano, Pauline W. Wang, David M. Hwang, Yvonne C. W. Yau, Valerie J. Waters, David S. Guttman

PLoS Comput Biol. 2023 Sep 6;19(9):e1011424. doi: 10.1371/journal.pcbi.1011424

Pubmed: 37672526

Abstract

Chronic Pseudomonas aeruginosa (Pa) lung infections are the leading cause of mortality among cystic fibrosis (CF) patients; therefore, the eradication of new-onset Pa lung infections is an important therapeutic goal that can have long-term health benefits. The use of early antibiotic eradication therapy (AET) has been shown to clear the majority of new-onset Pa infections, and it is hoped that identifying the underlying basis for AET failure will further improve treatment outcomes. Here we generated machine learning models to predict AET outcomes based on pathogen genomic data. We used a nested cross validation design, population structure control, and recursive feature selection to improve model performance and showed that incorporating population structure control was crucial for improving model interpretation and generalizability. Our best model, controlling for population structure and using only 30 recursively selected features, had an area under the curve of 0.87 for a holdout test dataset. The top-ranked features were generally associated with motility, adhesion, and biofilm formation.

Thaïs A. Bernos, Sunčica Avlijaš, Jaclyn Hill, Olivier Morissette, Anthony Ricciardi, Nicholas E. Mandrak, Kenneth M. Jeffries

Evolutionary Applications. 2023. 16 (1) 173-188. doi: 10.1111/eva.13520

Abstract

Introduced and geographically expanding populations experience similar eco-evolutionary challenges, including founder events, genetic bottlenecks, and novel environments. Theory predicts that reduced genetic diversity resulting from such phenomena limits the success of introduced populations. Using 1900 SNPs obtained from restriction-site-associated DNA sequencing, we evaluated hypotheses related to the invasion history and connectivity of an invasive population of Tench (Tinca tinca), a Eurasian freshwater fish that has been expanding geographically in eastern North America for three decades. Consistent with the reported history of a single introduction event, our findings suggest that multiple introductions from distinct genetic sources are unlikely as Tench had a small effective population size (~114 [95% CI = 106–123] individuals), no strong population subdivision across time and space, and evidence of a recent genetic bottleneck. The large genetic neighbourhood size (220 km) and weak within-population genetic substructure suggested high connectivity across the invaded range, despite the relatively large area occupied. There was some evidence for a small decay in genetic diversity as the species expanded northward, but not southward, into new habitats. As eradicating the species within a ~112 km radius would be necessary to prevent recolonization, eradicating Tench is likely not feasible at watershed—and possibly local—scales. Management should instead focus on reducing abundance in priority conservation areas to mitigate adverse impacts. Our study indicates that introduced populations can thrive and exhibit relatively high levels of genetic diversity despite severe bottlenecks (<1.5% of the ancestral effective population size) and suggests that landscape heterogeneity and population demographics can generate variability in spatial patterns of genetic diversity within a single range expansion.