Biology subjects

Keller, I.

Publications and source records attributed to Keller, I..

11 recordsLinked to original sources

bioRxiv2026

Microbiota during early life windows orchestrates intestinal maturation and barrier formation in the offspring

There is a critical window in early life for immune development that prepares a young mammal for postnatal exposure to environmental, dietary and microbial antigens. Both the maternal microbiota and endogenous colonization have emerged as pivotal drivers in this process. Using gnotobiotic mouse models and reversible colonization to model the effects of the maternal microbiota during pregnancy compared with early life colonization on the small intestinal epithelium we show that both microbial metabolites originating from the maternal microbiota and the postnatal endogenous microbiota drive intestinal epithelial maturation by modulating epigenetic signatures. Microbiota-derived signals from both the pregnant mother and from endogenous postnatal colonisation drove the BLIMP1-guided epithelial neonatal-to-adult transition at weaning through epigenetic mechanisms and direct transcriptional effects. These microbial signals also shaped the developmental trajectory of barrier-forming tight junctional claudins in the neonatal intestine, increased aerobic respiration, and increased the gene expression of xenosensors. Thus, both maternal and endogenous microbiota derived drivers of the offspring's epigenetic and transcriptomic intestinal epithelial landscape fine-tuned the timing of epithelial maturation and augmented functional plasticity at weaning.

microbiology↗

bioRxiv2024

Ribonuclease Inhibitor and Angiogenin collaboratively regulate cell-type-specific global translation

Translation of mRNAs is a fundamental process that occurs in all cell-types of multicellular organisms. Conventionally, it has been considered a default step in gene expression, lacking specific regulation. However, recent studies have documented that certain mRNAs exhibit cell-type-specific translation1-3. Despite this, it remains unclear whether global translation is controlled in a cell-type-specific manner. Here we report that a ribosome-associated protein ribonuclease inhibitor-1 (RNH1) and its binding partner Angiogenin (ANG) collaboratively regulates cell-type-specific global translation. By employing human cell-lines and mouse models, we found that deletion of RNH1 decreases global translation selectively in hematopoietic origin cells but not in the non-hematopoietic origin cells. RNH1 mediated such cell-type-specific translation is mechanistically linked to ANG. We found that ANG, which is known to regulate ribosomal biogenesis4, is predominantly expressed in non-hematopoietic origin cells and absent in hematopoietic origin cells. ANG safeguards the non-hematopoietic origin cells from RNH1-knockout-mediated translation defects by upregulating ribosomal biogenesis. Further, we discovered that RNH1 controls the translation of ribosomal protein (RP) transcripts and influences mRNA circularization. Collectively, this study unravels the existence of cell-type-specific global translation regulators and highlights the complex translation regulation in vertebrates.

biochemistry↗

bioRxiv2024

Neuronal substance-P drives breast cancer growth and metastasis via an extracellular RNA/TLR7 axis

Increased tumour innervation is associated with adverse survival outcomes in multiple cancers1-4. To better understand the mechanisms underlying this, we studied the impact of innervation on breast cancer metastatic progression. Metastatic mammary tumours of mice were substantially more innervated than non-metastatic isogenic tumours. Three dimensional co-cultures and in vivo models revealed that sensory dorsal root ganglion (DRG) neurons enhanced the growth, invasion, and systemic dissemination of cancer cells--thereby driving breast cancer metastasis. By in vitro screening of neuropeptides known to be secreted by DRG neurons, we identified substance-P (SP) as a mediator of these pro-metastatic functions. Neuronal SP signaled through tumoural tachykinin receptors (TACR1) to drive single-stranded RNA (ssRNA) secretion from cancer cells. Extracellular RNA acted on tumoural TLR7 receptors to activate an autocrine pro-metastatic gene expression program. In support of these findings, patient tumours with increased SP expression exhibited higher rates of lymph node metastasis. Additionally, this SP/ssRNA induced Tlr7 gene expression signature associated with reduced breast cancer survival outcomes in two independent patient cohorts. Finally, therapeutic targeting of this neuro-cancer axis with the TACR1 antagonist aprepitant, an approved anti-nausea drug, suppressed breast cancer metastasis in multiple mouse models. Our findings reveal multiple aspects of metastatic progression to be regulated by neurons via a therapeutically targetable neuropeptide/extracellular RNA sensing axis.

cancer biology↗

bioRxiv2023

CD4+ T cell-derived IL21 regulates stem cell fate in acute myeloid leukemia by activation of p38-MAPK signaling

Self-renewal programs in leukemia stem cells (LSCs) predict poor prognosis in acute myeloid leukemia (AML) patients. We identified CD4+ T cell-derived interleukin (IL) 21 as an important negative regulator of self-renewal of murine and human LSCs, but not hematopoietic stem cells. IL21/IL21R signaling favored asymmetric cell division and differentiation in LSCs through accumulation of reactive oxygen species (ROS) and activation of p38-MAPK signaling, resulting in reduced LSCs number and significantly prolonged survival in murine AML models. In human AML, serum IL21 at diagnosis was identified as an independent positive prognostic biomarker for outcome and correlated with better survival and higher complete remission rate in patients that underwent high-dose chemotherapy. IL21 inhibited primary AML LSCs function in vitro by activating ROS and p38-MAPK signaling and this effect was enhanced by cytarabine treatment. Consequently, promoting IL21/IL21R signaling on LSCs may be a novel approach to decrease stemness and increase differentiation in AML.

cancer biology↗

bioRxiv2023

Carbohydrate distribution via SWEET17 is critical for Arabidopsis inflorescence branching under drought

Sugars Will Eventually be Exported Transporters (SWEETs) are the most recently discovered family of plant sugar transporters. Functioning as uniporters and thus facilitating the diffusion of sugars across cell membranes, SWEETs play an important role in various physiological processes such as abiotic stress adaptation. AtSWEET17, a vacuolar fructose facilitator, was shown to be involved in the modulation of the root system during drought. Moreover, overexpression of a homolog from apple results in increased drought tolerance of tomato plants. Therefore, SWEET17 appears to be essential for the plants drought response. Nevertheless, the role and function of SWEET17 in aboveground tissues under drought stress to date remains enigmatic. By combining gene expression analysis with analysis of the sugar profile of various aboveground tissues, we uncovered a putative role of SWEET17 in the carbohydrate supply, and thus cauline branch emergence and growth, particularly during periods of carbon limitation as occurs under drought stress. SWEET17 thereby being of critical importance for maintaining efficient reproduction under drought stress. HighlightThe fructose transporter SWEET17 supports shoot branching by increasing mobilization of carbohydrates from vacuoles to supply the newly forming inflorescence branch, thereby maintaining efficient reproduction under drought stress.

plant biology↗

bioRxiv2022

The vacuolar sugar transporter EARLY RESPONSE TO DEHYDRATION 6-LIKE4 regulates fructose signaling and plant growth

Regulation of intracellular sugar homeostasis is maintained by regulation of activities of sugar import and export proteins residing at the tonoplast. We show here that the EARLY RESPONSE TO DEHYDRATION6-LIKE4 protein, being the closest homolog to the proton/glucose symporter ERDL6, resides in the vacuolar membrane. Gene expression and subcellular fractionation studies indicated that ERDL4 was involved in fructose allocation across the tonoplast. Overexpression of ERDL4 increased total sugar levels in leaves, due to a concomitantly induced stimulation of TST2 expression, coding for the major vacuolar sugar loader. This conclusion is supported by the finding that tst1-2 knockout lines overexpressing ERDL4 lack increased cellular sugar levels. ERDL4 activity contributing to the coordination of cellular sugar homeostasis is also indicated by two further observations. Firstly, ERDL4 and TST genes exhibit an opposite regulation during a diurnal rhythm, and secondly, the ERDL4 gene is markedly expressed during cold acclimation representing a situation in which TST activity needs to be upregulated. Moreover, ERDL4-overexpressing plants show larger size of rosettes and roots, a delayed flowering time and increased total seed yield. Consistently, erdl4 knock-out plants show impaired cold acclimation and freezing tolerance along with reduced plant biomass. In summary, we show that modification of cytosolic fructose levels influences plant organ development and stress tolerance. One sentence summaryThe activity of the vacuolar sugar porter ERDL4 is important for balanced cytosolic monosaccharide homeostasis and influences plant growth and cold response in Arabidopsis The author responsible for distribution of materials integral to the findings presented in this article in accordance with the policy described in the Instructions for Authors is: Benjamin Pommerrenig (pommerre@bio.uni-kl.de).

plant biology↗

bioRxiv2022

PPAR-γ regulates the effector function of human TH9 cells by promoting glycolysis

T helper 9 cells (TH9) are key drivers of allergic tissue inflammation. They are characterized by the expression of type 2 cytokines, such as IL-9 and IL-13, and the peroxisome proliferator-activated receptor gamma (PPAR-{gamma}) transcription factor. However, the functional role of PPAR-{gamma} in human TH9 cells remains unknown. Here, we demonstrate that PPAR-{gamma} drives activation-induced glycolysis, which, in turn, specifically promotes the expression of IL-9, but not IL-13, in an mTORC1-dependent manner. In vitro and ex vivo experiments on skin samples of allergic contact dermatitis showed that the PPAR-{gamma}-mTORC1-IL-9 pathway was active in TH9 cells in human skin inflammation. Additionally, we found that tissue glucose levels were dynamically regulated in acute allergic skin inflammation, suggesting that in situ glucose availability is linked to distinct immunological signals in vivo. Furthermore, paracrine IL-9 induced the lactate transporter MCT1 in IL-9R+ TH cells, where it increased aerobic glycolysis and proliferative capacity. Taken together, our findings delineate a hitherto unknown relationship between PPAR-{gamma}-dependent glucose metabolism and the pathogenic effector function of human TH9 cells. Graphical abstract O_FIG O_LINKSMALLFIG WIDTH=200 HEIGHT=84 SRC="FIGDIR/small/503972v1_ufig1.gif" ALT="Figure 1"> View larger version (38K): org.highwire.dtl.DTLVardef@ce684borg.highwire.dtl.DTLVardef@12121acorg.highwire.dtl.DTLVardef@29d712org.highwire.dtl.DTLVardef@e71117_HPS_FORMAT_FIGEXP M_FIG C_FIG

immunology↗

bioRxiv2021

Cold-triggered induction of ROS- and raffinose metabolism in freezing-sensitive taproot tissue of sugar beet

Sugar beet (Beta vulgaris subsp. vulgaris) is the exclusive source of sugar in the form of sucrose in temperate climate zones. There, sugar beet is grown as an annual crop from spring to autumn because of the damaging effect of freezing temperatures to taproot tissue. Natural and breeded varieties display variance in the degree of tolerance to freezing temperatures and genotypes with elevated tolerance to freezing have been isolated. Here we compare initial responses to frost between genotypes with either low and high winter survival rates. The selected genotypes differed in the severity of frost injury. We combined transcriptomic and metabolite analyses of leaf- and taproot tissues from such genotypes to elucidate mechanisms of the early freezing response and to dissect genotype- and tissue-dependent responses. Freezing temperatures induced drastic downregulation of photosynthesis-related genes in leaves but upregulation of genes related to minor carbohydrate metabolism, particularly of genes involved in raffinose metabolism in both, leaf and taproot tissue. In agreement with this, it has been revealed that raffinose and the corresponding intermediates, inositol and galactinol, increased markedly in these tissues. We found that genotypes with improved tolerance to freezing, showed higher accumulation of raffinose in a defined interior region within the upper part of the taproot, the pith, representing the tissue most susceptible to freeze damages. This accumulation was accompanied by specific upregulation of raffinose synthesizing enzymes in taproots, suggesting a protective role for raffinose and its precursors for freezing damage in sugar beet.

plant biology↗

bioRxiv2021

Pyrimidine nucleotide availability is essential for efficient photosynthesis, ROS scavenging, and organelle development

Nucleotide limitation and imbalance is a well described phenomenon in animal research but understudied in the plant field. A peculiarity of pyrimidine de novo synthesis in plants is the complex subcellular organization. Here, we studied two organellar localized enzymes in the pathway, with chloroplast aspartate transcarbamoylase (ATC), and mitochondrial dihydroorotate dehydrogenase (DHODH). ATC knockdowns were most severely affected, exhibiting low levels of pyrimidine nucleotides, a low energy state, reduced photosynthetic capacity and accumulation of reactive oxygen species (ROS). Furthermore, altered leaf morphology and chloroplast ultrastructure were observed in ATC mutants. Although less affected, DHODH knockdown mutants showed impaired seed germination and altered mitochondrial ultrastructure. Transcriptome analysis of an ATC-amiRNA line revealed massive alterations in gene expression with central metabolic pathways being downregulated and stress response and RNA related pathways being upregulated. In addition, genes involved in central carbon metabolism, intracellular transport and respiration were mainly downregulated in ATC mutants, being putatively responsible for the observed impaired growth. ONE-SENTENCE SUMMARYImpaired pyrimidine nucleotide synthesis results in nucleotide limitation and imbalance, resulting in impaired photosynthesis, reduced growth, reproduction, and seed yield together with massively altered gene expression

plant biology↗

bioRxiv2020

Vernalization alters sugar beet (Beta vulgaris) sink and source identities and reverses phloem translocation from taproots to shoots

During vegetative growth, biennial sugar beets maintain a steep gradient between the shoot (source) and the sucrose-storing taproot (sink). To shift from vegetative to generative growth, they require a chilling phase, called vernalization. Here, we studied sugar beet sink-source dynamics upon cold temperature-induced vernalization and revealed a pre-flowering taproot sink to source reversal. This transition is induced by transcriptomic and functional reprogramming of sugar beet tissue, resulting in a reversal of flux direction in long distance transport system, the phloem. As a key process for this transition, vacuolar sucrose importers and exporters, BvTST2;1 and BvSUT4, are oppositely regulated, leading to re-mobilization of sugars from taproot storage vacuoles. Concomitant changes in the expression of floral regulator genes suggest that the now deciphered processes are a prerequisite for bolting. Our data may thus serve dissecting metabolic and developmental triggers for bolting, which are potential targets for genome editing or breeding approaches.

plant biology↗

bioRxiv2019

Identification of chloroplast envelope proteins with critical importance for cold acclimation

The ability of plants to cope with cold temperatures relies on their photosynthetic activity. This already demonstrates that the chloroplast is of utmost importance for cold acclimation and acquisition of freezing tolerance. During cold acclimation, the properties of the chloroplast change markedly. To provide the most comprehensive view of the protein repertoire of chloroplast envelope, we analysed this membrane system in Arabidopsis thaliana using MS-based proteomics. Profiling chloroplast envelope membranes was achieved by a cross comparison of protein intensities across plastid and the enriched membrane fraction both under normal and cold conditions. Multivariable logistic regression models the probabilities for the classification problem to address envelop localization. In total, we identified 38 envelope membrane intrinsic or associated proteins exhibiting altered abundance after cold acclimation. These proteins comprise several solute carries, such as the ATP/ADP antiporter NTT2 (substantially increased abundance) or the maltose exporter MEX1 (substantially decreased abundance). Remarkably, analysis of the frost recovery of ntt loss-of-function and mex1 overexpressor mutants confirmed that the comparative proteome is well suited to identify novel key factors involved in cold acclimation and acquisition of freezing tolerance. Moreover, for proteins with known physiological function we propose scenarios explaining their possible role in cold acclimation. Furthermore, spatial proteomics introduces a novel layer of complexity and enabled the identification of proteins differentially localized at the envelope membrane under the changing environmental regime.

plant biology↗