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result(s) for
"Johnson, Timothy S."
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Genome-wide association of volatiles reveals candidate loci for blueberry flavor
by
Johnson, Timothy S.
,
Edger, Patrick P.
,
Benevenuto, Juliana
in
Allelochemicals
,
Association analysis
,
biosynthesis
2020
• Plants produce a range of volatile organic compounds (VOCs), some of which are perceived by the human olfactory system, contributing to a myriad flavors. Despite the importance of flavor for consumer preference, most plant breeding programs have neglected it, mainly because of the costs of phenotyping and the complexity of disentangling the role of VOCs in human perception.
• To develop molecular breeding tools aimed at improving fruit flavor, we carried out target genotyping of and VOC extraction from a blueberry population. Metabolite genome-wide association analysis was used to elucidate the genetic architecture, while predictive models were tested to prove that VOCs can be accurately predicted using genomic information. A historical sensory panel was considered to assess how the volatiles influenced consumers.
• By gathering genomics, metabolomics, and the sensory panel, we demonstrated that VOCs are controlled by a few major genomic regions, some of which harbor biosynthetic enzyme-coding genes; can be accurately predicted using molecular markers; and can enhance or decrease consumers’ overall liking.
• Here we emphasized how the understanding of the genetic basis and the role of VOCs in consumer preference can assist breeders in developing more flavorful cultivars at a more inexpensive and accelerated pace.
Journal Article
Urinary levels of pro-fibrotic transglutaminase 2 (TG2) may help predict progression of chronic kidney disease
2022
Renal clinical chemistry only detects kidney dysfunction after considerable damage has occurred and is imperfect in predicting long term outcomes. Consequently, more sensitive markers of early damage and better predictors of progression are being urgently sought, to better support clinical decisions and support shorter clinical trials. Transglutaminase 2 (TG2) is strongly implicated in the fibrotic remodeling that drives chronic kidney disease (CKD). We hypothesized that urinary TG2 and its ε-(γ-glutamyl)-lysine crosslink product could be useful biomarkers of kidney fibrosis and progression. Animal models: a rat 4-month 5/6 th subtotal nephrectomy model of CKD and a rat 8-month streptozotocin model of diabetic kidney disease had 24-hour collection of urine, made using a metabolic cage, at regular periods throughout disease development. Patients: Urine samples from patients with CKD ( n = 290) and healthy volunteers ( n = 33) were collected prospectively, and progression tracked for 3 years. An estimated glomerular filtration rate (eGFR) loss of 2–5 mL/min/year was considered progressive, with rapid progression defined as > 5 mL/min/year. Assays: TG2 was measured in human and rat urine samples by enzyme-linked immunosorbent assay (ELISA) and ε-(γ-glutamyl)-lysine by exhaustive proteolytic digestion and amino acid analysis. Urinary TG2 and ε-(γ-glutamyl)-lysine increased with the development of fibrosis in both animal model systems. Urinary TG2 was 41-fold higher in patients with CKD than HVs, with levels elevated 17-fold by CKD stage 2. The urinary TG2:creatinine ratio (UTCR) was 9 ng/mmol in HV compared with 114 ng/mmol in non-progressive CKD, 1244 ng/mmol in progressive CKD and 1898 ng/mmol in rapidly progressive CKD. Both urinary TG2 and ε-(γ-glutamyl)-lysine were significantly associated with speed of progression in univariate logistic regression models. In a multivariate model adjusted for urinary TG2, ε-(γ-glutamyl)-lysine, age, sex, urinary albumin:creatinine ratio (UACR), urinary protein:creatinine ratio (UPCR), and CKD stage, only TG2 remained statistically significant. Receiver operating characteristic (ROC) curve analysis determined an 86.4% accuracy of prediction of progression for UTCR compared with 73.5% for UACR. Urinary TG2 and ε-(γ-glutamyl)-lysine are increased in CKD. In this pilot investigation, UTCR was a better predictor of progression in patients with CKD than UACR. Larger studies are now warranted to fully evaluate UTCR value in predicting patient outcomes.
Journal Article
The Peroxidative Cleavage of Kaempferol Contributes to the Biosynthesis of the Benzenoid Moiety of Ubiquinone in Plants
by
Johnson, Timothy S.
,
Kim, Jeongim
,
Soubeyrand, Eric
in
Arabidopsis - metabolism
,
BREAKTHROUGH REPORT
,
Gene Expression Regulation, Plant
2018
Land plants possess the unique capacity to derive the benzenoid moiety of the vital respiratory cofactor, ubiquinone (coenzyme Q), from phenylpropanoid metabolism via β-oxidation of p-coumarate to form 4-hydroxybenzoate. Approximately half of the ubiquinone in plants comes from this pathway; the origin of the rest remains enigmatic. In this study, Phe-[Ring-13C₆] feeding assays and gene network reconstructions uncovered a connection between the biosynthesis of ubiquinone and that of flavonoids in Arabidopsis (Arabidopsis thaliana). Quantification of ubiquinone in Arabidopsis and tomato (Solanum lycopersicum) mutants in flavonoid biosynthesis pinpointed the corresponding metabolic branch-point as lying between flavanone-3-hydroxylase and flavonoid-3′-hydroxylase. Further isotopic labeling and chemical rescue experiments demonstrated that the B-ring of kaempferol is incorporated into ubiquinone. Moreover, heme-dependent peroxidase activities were shown to be responsible for the cleavage of B-ring of kaempferol to form 4-hydroxybenzoate. By contrast, kaempferol 3-β-D-glucopyranoside, dihydrokaempferol, and naringenin were refractory to peroxidative cleavage. Collectively, these data indicate that kaempferol contributes to the biosynthesis of a vital respiratory cofactor, resulting in an extraordinary metabolic arrangement where a specialized metabolite serves as a precursor for a primary metabolite. Evidence is also provided that the ubiquinone content of tomato fruits can be manipulated via deregulation of flavonoid biosynthesis.
Journal Article
The effect of TG2-inhibitory monoclonal antibody zampilimab on tissue fibrosis in human in vitro and primate in vivo models of chronic kidney disease
2024
Fibrotic remodeling is the primary driver of functional loss in chronic kidney disease, with no specific anti-fibrotic agent available for clinical use. Transglutaminase 2 (TG2), a wound response enzyme that irreversibly crosslinks extracellular matrix proteins causing dysregulation of extracellular matrix turnover, is a well-characterized anti-fibrotic target in the kidney. We describe the humanization and characterization of two anti-TG2 monoclonal antibodies (zampilimab [hDC1/UCB7858] and BB7) that inhibit crosslinking by TG2 in human in vitro and rabbit/cynomolgus monkey i n vivo models of chronic kidney disease. Determination of zampilimab half-maximal inhibitory concentration (IC 50 ) against recombinant human TG2 was undertaken using the KxD assay and determination of dissociation constant (K d ) by surface plasmon resonance. Efficacy in vitro was established using a primary human renal epithelial cell model of tubulointerstitial fibrosis, to assess mature deposited extracellular matrix proteins. Proof of concept in vivo used a cynomolgus monkey unilateral ureteral obstruction model of chronic kidney disease. Zampilimab inhibited TG2 crosslinking transamidation activity with an IC 50 of 0.25 nM and K d of <50 pM. In cell culture, zampilimab inhibited extracellular TG2 activity (IC 50 119 nM) and dramatically reduced transforming growth factor-β1-driven accumulation of multiple extracellular matrix proteins including collagens I, III, IV, V, and fibronectin. Intravenous administration of BB7 in rabbits resulted in a 68% reduction in fibrotic index at Day 25 post-unilateral ureteral obstruction. Weekly intravenous administration of zampilimab in cynomolgus monkeys with unilateral ureteral obstruction reduced fibrosis at 4 weeks by >50%, with no safety signals. Our data support the clinical investigation of zampilimab for the treatment of kidney fibrosis.
Journal Article
Using skin biopsies to measure target occupancy of anti-fibrotic molecules: assay development and application for zampilimab in a primate model of chronic kidney disease and in healthy human volunteers
2025
Background
Assessing target engagement (TE) and target occupancy (TO) of novel antifibrotic molecules is challenging, as the target organs are inaccessible. In clinical trials, this often requires biopsies of internal organs, which increases both risk and discomfort for participants. Zampilimab (UCB7858) is a humanized monoclonal antibody that specifically inhibits the extracellular activity of transglutaminase 2 (TG2). Blocking TG2 activity reduces fibrosis in experimental models of chronic kidney disease. Here, a low-risk skin ‘biopsy-on-biopsy’ approach has been developed as a surrogate to assess TO of zampilimab in the kidney, ahead of further investigation of zampilimab in clinical studies.
Methods
A dual-antibody competitive immunofluorescence assay was developed to assess TO of TG2 with zampilimab. A cynomolgus monkey unilateral ureteral obstruction model was used to assess zampilimab TO in the kidney and compare this with TE measured by an in situ TG activity assay. Data were compared with TO in dermal wounds in the same animals. A human skin ‘biopsy-on-biopsy’ dermal wound approach was developed to induce fibrosis-relevant pathways. Skin sections from healthy volunteers were incubated ex vivo with increasing doses of zampilimab to assess TO.
Results
Zampilimab TO in cynomolgus monkey kidney and skin were positively correlated using our immunofluorescence assay, with an inverse correlation between skin TO and kidney TE using our in situ TG activity assay. In the human dermal wound model, maximal TG2 staining was observed on days 4–6 post initial dermal wound (biopsy). TO measurements increased dose-dependently with zampilimab application.
Conclusions
Zampilimab inhibited TG2 in cynomolgus monkey kidney and skin. Skin is an accessible surrogate tissue to assess kidney TO and predict TE, and our ex vivo model of skin biopsy has potential for application in the development of other antifibrotic therapeutics. A phase I first-in-human study of zampilimab in healthy volunteers (NCT02879877; 26/08/2016) will provide further proof of concept.
Journal Article
Identification of mechanistic CKD biomarkers in a rat SNx kidney fibrosis model by transcriptomics and proteomics detectable in biofluids
2025
The rat sub-total nephrectomy (SNx) is a functional model of general chronic kidney disease (CKD) where the main pathological driver is glomerular hypertension representative of several subtypes of CKD. Comprehensive transcriptomics and proteomics analyses on the SNx rats were performed to identify biomarkers in plasma or urine that correlate with kidney disease and functional kidney loss. Kidneys were subjected to collagen I and III staining for fibrosis scoring, SWATH-MS proteomics and bulk RNA-sequencing transcriptomics, with SWATH-MS also performed on plasma and urine. Differential expression analysis demonstrated significant dysregulation of genes and proteins involved in fibrosis, metabolism, and immune response in the SNx rats compared to controls. Gene ontology analysis of the intersecting genes and proteins from both studies demonstrated common biology between animal cohorts that reached the predefined kidney disease thresholds (serum creatinine > two-fold or proteinuria > three-fold increase over sham-operated). Thirteen significantly differential molecules were detected with consistent directional changes in both omics datasets. These molecules were detected independently in kidney (both RNA and protein) and urine (protein only), but not in plasma. Bioinformatics analysis enabled the identification of mechanistic CKD biomarkers including lumican and collagen alpha-1(III) chain, whose co-expression has previously been both implicated in fibrosis and detected in urine in CKD patients.
Journal Article
Down regulation of p-coumarate 3-hydroxylase in petunia uniquely alters the profile of emitted floral volatiles
2019
Petunia
×
hybrida
cv ‘Mitchell Diploid’ floral volatile benzenoid/phenylpropanoid (FVBP) biosynthesis ultimately produces floral volatiles derived sequentially from phenylalanine, cinnamic acid, and
p
-coumaric acid. In an attempt to better understand biochemical steps after
p
-coumaric acid production, we cloned and characterized three petunia transcripts with high similarity to
p-coumarate 3-hydroxylase
(
C3H
),
hydroxycinnamoyl-CoA:shikimate/quinate hydroxycinnamoyl transferase
(
HCT
), and
caffeoyl shikimate esterase
(
CSE
). Transcript accumulation of
PhC3H
and
PhHCT
was highest in flower limb tissue during open flower stages.
PhCSE
transcript accumulation was also highest in flower limb tissue, but it was detected earlier at initial flower opening with a bell-shaped distribution pattern. Down regulation of endogenous
PhC3H
transcript resulted in altered transcript accumulation of many other FVBP network transcripts, a reduction in floral volatiles, and the emission of a novel floral volatile. Down regulation of
PhHCT
transcript did not have as large of an effect on floral volatiles as was observed for
PhC3H
down regulation, but eugenol and isoeugenol emissions were significantly reduced on the downstream floral volatiles. Together these results indicate that
PhC3H
is involved in FVBP biosynthesis and the reduction of
PhC3H
transcript influences FVBP metabolism at the network level. Additional research is required to illustrate
PhHCT
and
PhCSE
functions of petunia.
Journal Article
The PLUTO plastidial nucleobase transporter also transports the thiamin precursor hydroxymethylpyrimidine
by
Beaudoin, Guillaume A.W.
,
Johnson, Timothy S.
,
Hanson, Andrew D.
in
Arabidopsis - genetics
,
Arabidopsis - metabolism
,
Arabidopsis Proteins - genetics
2018
In plants, the hydroxymethylpyrimidine (HMP) and thiazole precursors of thiamin are synthesized and coupled together to form thiamin in plastids. Mutants unable to form HMP can be rescued by exogenous HMP, implying the presence of HMP transporters in the plasma membrane and plastids. Analysis of bacterial genomes revealed a transporter gene that is chromosomally clustered with thiamin biosynthesis and salvage genes. Its closest Arabidopsis homolog, the plastidic nucleobase transporter (PLUTO), is co-expressed with several thiamin biosynthetic enzymes. Heterologous expression of PLUTO in Escherichia coli or Saccharomyces cerevisiae increased sensitivity to a toxic HMP analog, and disrupting PLUTO in an HMP-requiring Arabidopsis line reduced root growth at low HMP concentrations. These data implicate PLUTO in plastidial transport and salvage of HMP.
Journal Article
Development of a unilateral ureteral obstruction model in cynomolgus monkeys
2021
Background Chronic kidney disease (CKD) has a high global prevalence and large unmet need. Central to developing new CKD therapies are in vivo models in CKD. However, next‐generation antibody, protein, and gene therapies are highly specific, meaning some do not cross‐react with rodent targets. This complicates preclinical development, as established in vivo rodent models cannot be utilized unless tool therapeutics are also developed. Tool compounds can be difficult to develop and, if available, typically have different epitopes, sequences, and/or altered affinity, making it unclear how efficacious the lead therapeutic may be, or what dosing regimen to investigate. To address this, we aimed to develop a nonhuman primate model of CKD. Methods In vivo rodent unilateral ureteral obstruction (UUO) models kidney fibrosis and is commonly used due to its rapidity, consistency, and ease. We describe translation of this model to the cynomolgus monkey, specifically optimizing the model duration to allow adequate time for assessment of novel therapeutics prior to the fibrotic plateau. Results We demonstrated that disease developed more slowly in cynomolgus monkeys than in rodents post‐UUO, with advanced fibrosis developing by 6 weeks. The tubulointerstitial fibrosis in cynomolgus monkeys was more consistent with human obstructive disease than in rodents, having a more aggressive tubular basement expansion and a higher fibroblast infiltration. The fibrosis was also associated with increased transglutaminase activity, consistent with that seen in patients with CKD. Conclusion This cynomolgus monkey UUO model can be used to test potential human‐specific therapeutics in kidney fibrosis. Next‐generation antibody, protein, and gene therapies are highly specific, meaning some do not cross‐react with rodent targets. We developed a nonhuman primate model of chronic kidney disease by translating rodent unilateral ureteral obstruction models to cynomolgus monkeys. This nonhuman primate model developed advanced fibrosis by 6 weeks that was more consistent with human pathology than rodent models and can be applied to evaluate the potential of human‐specific therapeutics in kidney fibrosis.
Journal Article
Transglutaminase 2 knockout mice are protected from bleomycin‐induced lung fibrosis with preserved lung function and reduced metabolic derangements
by
Huang, Linghong
,
Atkinson, John
,
Freeberg, Margaret A. T.
in
Aerobic capacity
,
Animals
,
Bleomycin
2024
Pulmonary fibrosis is an interstitial scarring disease of the lung characterized by poor prognosis and limited treatment options. Tissue transglutaminase 2 (TG2) is believed to promote lung fibrosis by crosslinking extracellular matrix components and activating latent TGFβ. This study assessed physiologic pulmonary function and metabolic alterations in the mouse bleomycin model with TG2 genetic deletion. TG2‐deficient mice demonstrated attenuated the fibrosis and preservation of lung function, with significant reduction in elastance and increases in compliance and inspiratory capacity compared to control mice treated with bleomycin. Bleomycin induced metabolic changes in the mouse lung that were consistent with increased aerobic glycolysis, including increased expression of lactate dehydrogenase A and increased production of lactate, as well as increased glutamine, glutamate, and aspartate. TG2‐deficient mice treated with bleomycin exhibited similar metabolic changes but with reduced magnitude. Our results demonstrate that TG2 is required for a typical fibrosis response to injury. In the absence of TG2, the fibrotic response is biochemically similar to wild‐type, but lesions are smaller and lung function is preserved. We also show for the first time that profibrotic pathways of tissue stiffening and metabolic reprogramming are interconnected, and that metabolic disruptions in fibrosis go beyond glycolysis. Tissue transglutaminase 2 (TG2) knockout mice demonstrated preserved lung function and reduced lesion area following bleomycin injury. Bleomycin fibrotic injury is associated with energy and amino acid metabolic changes. These metabolic changes are similar but overall reduced in magnitude in the TG2 KO mice. We also show for the first time that profibrotic pathways of tissue stiffening and metabolic reprogramming are interconnected, and that metabolic disruptions in fibrosis go beyond glycolysis.
Journal Article