Biology subjects

Nunez, G.

Publications and source records attributed to Nunez, G..

6 recordsLinked to original sources

bioRxiv2026

Butyrate extends health and lifespan in mice with mitochondrial deficiency

Mitochondrial diseases progressively lead to multisystemic failure with treatment options remaining extremely limited. To investigate novel strategies that alleviate mitochondrial dysfunction, we have generated an ubiquitous and tamoxifen-inducible knockout mouse model of mitochondrial transcription factor A (TFAM), a nuclear-encoded protein involved in mitochondrial DNA (mtDNA) maintenance -- Tfamfl/flUbCre-ERT2 (iTfamKO) mice. Systemic TFAM deficiency triggers mitochondrial decline in a myriad of tissues in adult mice. Consequently, iTfamKO mice manifest multiorgan dysfunction including lipodystrophy, sarcopenia, metabolic alterations, kidney failure, neurodegeneration, and locomotor dysregulation, which result in the premature death of these mice. Interestingly, iTfamKO mice display intestinal barrier disruption and gut dysbiosis, with diminished levels of microbiota-derived short-fatty acids (SCFAs), such as butyrate. Mice with a deficient proof-reading version of the mtDNA polymerase gamma (mtDNA-mutator mice) phenocopy the dysfunction of the intestinal barrier and bacterial dysbiosis with reduced levels of butyrate, suggesting that different mouse models of mitochondrial dysfunction share deficient generation of butyrate. Transfer of microbiota from healthy control mice or administration of tributyrin, a butyrate precursor, delay multiple signs of multimorbidity extending lifespan in iTfamKO mice. Mechanistically, butyrate supplementation recovers epigenetic histone acylation marks that are lost in the intestine of Tfam deficient mice. Overall, our findings highlight the relevance of preserving host-microbiota symbiosis in disorders related to mitochondrial dysfunction.

molecular biology↗

bioRxiv2024

Sup4h5-L19 activation tagging line partially restores root hair growth in p4h5 mutant by introducing small transcriptomic changes in Arabidopsis thaliana

An specific group of 2-oxoglutarate (2OG) dioxygenases named as Prolyl 4-Hydroxylases (P4H) produce trans-4-hydroxyproline (Hyp/O) from peptidyl-proline, catalyzing proline hydroxylation of cell wall glycoproteins EXT, AGPs, and HRGPs in plant cells, a crucial modification for O-glycosylation. Out of the Arabidopsis thaliana 13 P4Hs, P4H5 regulate root hair cell elongation and T-DNA insertional p4h5 mutant has arrested cell elongation and shortened root hairs. P4H5 selectively hydroxylates EXT proline units indicating that EXT proline hydroxylation as an essential modification for root hair growth. In this work, we isolate an activation-tagging line called Sup4h5-L19/p4h5 (p4h5-L19) that partially suppressed root hair phenotype in the p4h5 mutant background. The T-DNA insertion site was mapped by Thermal Asymmetric Interlaced PCR (TAIL-PCR) followed by PCR product sequencing and the T-DNA is inserted at the beginning of the sixth exon of the AT3G17750 gene, an uncharacterized cytosolic kinase. By analyzing expression changes and mutants analysis in this loci, no clear direct effect was detected. By RNA-seq analysis, it become clear that p4h5-L19 may largely reverse the genetic alterations caused by the p4h5 mutant in Wt Col-0, particularly at 10{degrees}C where there is an increase in root hair growth, with a total of 14 genes that have been activated and 83 genes that have been suppressed due to the enhancer of the activation tagging L19 in p4h5 L19 compared to p4h5. Among these genes, 3 of them, Tonoplast Intrinsic Proteins (TIPs), were identified to be root hair specific (TIP1;1, TIP2;2, and TIP2;3) and the corresponding mutants for two of them (TIP1;1 and TIP2;3) showed reduced root hair growth response at low temperature. This study unmasked new components of the root hair growth response at low temperature that works independently of the O-glycosyated EXTs in the cell walls.

plant biology↗

bioRxiv2022

Site-specific adaptation mechanisms of an oral pathobiont in the oral and gut mucosae

Periodontal inflammation leads to oral dysbiosis with the expansion of oral pathobionts. Besides the pathogenic role of oral pathobionts during periodontal inflammation, studies have revealed that oral pathobionts contribute to diseases in distant organs beyond the oral mucosa. For example, the oral pathobiont Klebsiella aerogenes, which accumulates in the oral mucosa during periodontitis in mice, can exacerbate colitis when it ectopically colonizes the gastrointestinal tract. However, the precise mechanisms by which oral pathobionts establish their colonization in extra-oral mucosal sites remains incompletely understood. We performed high-throughput in vivo genetic screening to identify fitness genes required for the adaptation of the oral pathobiont K. aerogenes to different mucosal sites - the oral and gut mucosae - at the steady state and during inflammation. In addition, the global transcriptome of K. aerogenes in different environments was analyzed. We determined that K. aerogenes employs genes related to iron acquisition and chaperone usher pili, which are encoded on a newly identified genomic locus named "locus of colonization in the inflamed gut" (LIG), for adaptation in the gut mucosa, particularly during inflammation. In contrast, the LIG virulence factors are not required for K. aerogenes to adapt to the oral mucosa. Thus, oral pathobionts likely exploit distinct adaptation mechanisms in their ectopically colonized intestinal niche compared to their original niche. Author SummaryThe symbiotic bacterial community evolves uniquely at each body site. However, under certain circumstances, symbionts may disseminate far from their original niche and colonize a site ectopically. It has been reported that oral resident bacteria associated with periodontal disease, namely oral pathobionts, contribute to gastrointestinal diseases, such as inflammatory bowel disease and colorectal cancer, through ectopic colonization of the gut. However, the molecular mechanisms by which oral pathobionts adapt to the gut environment remain largely unexplored. In this study, using a model oral pathobiont Klebsiella aerogenes, we screened genes essential for the colonization of the pathobiont at different mucosal sites. We discovered that the oral pathobiont uses distinct virulence mechanisms at two different mucosal sites - the oral and gut mucosae. Understanding the strategies of bacteria localized in ectopic organs may lead to the development of strategies to prevent disease caused by the dissemination of pathogenic oral bacteria.

microbiology↗

bioRxiv2021

Natural IgA and TNFRSF13B polymorphism: a double edged sword fueling balancing selection

TNFRSF13B encodes the "transmembrane-activator and CAML-interactor" (TACI) receptor, which drives plasma cell differentiation. Although TNFRSF13B supports host defense, dominant-negative TNFRSF13B alleles are common in humans and other species and only rarely associate with disease. We reasoned the high frequency of disruptive TNFRSF13B alleles reflects balancing selection, the loss of function conferring advantage in some settings. Testing that concept, we asked whether and how a common human dominant negative variant, TNFRSF13B A181E, imparts resistance to enteric pathogens. Mice engineered to express mono-allelic or bi-allelic A144E variants of tnrsf13B, corresponding to A181E exhibited striking resistance to pathogenicity and transmission of C. rodentium, a murine pathogen that models enterohemorrhagic E. coli, and resistance was principally owed to deficiency of natural IgA in the intestine. In wild type mice with gut IgA and in mutant mice fed IgA, binding of Ig induces expression of LEE encoded virulence genes, which confer pathogenicity and transmission. C. rodentium and probably some other enteric organisms thus appropriated binding of otherwise protective antibodies to signal induction of the virulence program and the high prevalence of TNFRSF13B dominant negative variants thus reflects balancing selection.

immunology↗

bioRxiv2020

G-CSF SECRETED BY EPIGENETICALLY REPROGRAMMED MUTANT IDH1 GLIOMA STEM CELLS REVERSES THE MYELOID CELLS'-MEDIATED IMMUNOSUPPRESSIVE TUMOR MICROENVIRONMENT

Mutation in isocitrate dehydrogenase (mIDH) is a gain of function mutation resulting in the production of the oncometabolite, R-2-hydroxyglutarate, that inhibits DNA and histone demethylases. The resultant hypermethylation phenotype reprograms the glioma cells transcriptome and elicits profound effects on glioma immunity. We report that in mouse models and human gliomas, mIDH1 in the context of ATRX and TP53 inactivation results in global expansion of the granulocytic myeloid cells compartment. Single-cell RNA-sequencing coupled with mass cytometry analysis revealed that these granulocytes are mainly non-immunosuppressive neutrophils and pre-neutrophils; with a small fraction of polymorphonuclear myeloid-derived suppressor cells. The mechanism of mIDH1 mediated pre-neutrophils expansion involves epigenetic reprogramming which leads to enhanced expression of the granulocyte colony-stimulating factor (G-CSF). Blocking G-CSF restored the inhibitory potential of PMN-MDSCs and enhanced tumor progression. Thus, G-CSF induces remodeling of the inhibitory PMN-MDSCs in mIDH1 glioma rendering them non-immunosuppressive; and having significant therapeutic implications. SIGNIFICANCEmIDH1 is the most common mutation in gliomas associated with improved prognosis. Gliomas harboring mIDH1, together with ATRX and TP53 inactivation, exhibit higher circulating levels of G-CSF, ensuing the recruitment and expansion of non-suppressive neutrophils, pre-neutrophils and small fraction of PMN-MDSCs to the TME leading to an immune permissive phenotype.

cancer biology↗

bioRxiv2019

Oral administration of an anti-CfaE secretory IgA antibody protects against Enterotoxigenic Escherichia coli diarrheal disease in a non-human primate model

ABSTACTEnterotoxigenic Escherichia coli (ETEC) is a leading cause of diarrhea-associated illness in developing countries. There is currently no vaccine licensed to prevent ETEC and the development of an efficacious prophylaxis would provide an intervention with significant impact. Recent studies suggested that effective protection could be achieved by inducing immunity to block colonization of ETEC. Here, we evaluated the efficacy of secretory (s) IgA2 and dimeric (d) IgA2 of an anti-colonization factor antigen antibody, 68-61, in the Aotus nancymaae non-human primate (NHP) ETEC challenge model via oral and parental delivery. Thirty-nine animals were distributed across 3 groups of 13, and challenged with 5.0x1011 cfu of H10407 on Day 0. Group 1 received a dIgA2 68-61 subcutaneously on day 0. Group 2 received a SIgA2 68-61 orally on days -1, 0, and +1, and Group 3 received an irrelevant SIgA2 antibody orally on days -1, 0, and +1. All animals were observed for symptoms of diarrhea, and stools were collected for ETEC colony counts. SIgA2 treatment significantly lowered the attack rate, resulting in a protective efficacy of 71.4% (p=0.025) in Group 2 as compared to Group 3. Anti-CfaE dIgA2 treatment group reduced the diarrheal attack rate, although the reduction did not reach significance (57.1%; P=0.072) as compared to the irrelevant SIgA2 Group 3. Our results demonstrated the feasibility of oral administration of SIgA as a potential immunoprophylaxis against enteric infections. To our knowledge, this is the first study to demonstrate the efficacy of administrated SIgA in a non-human primate model.

immunology↗