Biology subjects

Bravo, J. I.

Publications and source records attributed to Bravo, J. I..

7 recordsLinked to original sources

bioRxiv2026

Acute LINE-1 overexpression rewires the transcriptome, proteome and secretome of primary human fibroblasts

A large portion of eukaryotic genomes is composed of transposable elements, which are usually kept repressed in young, healthy cells but can be derepressed in response to cell senescence and organismal aging. LINE-1 (L1) is the most abundant TE in the human genome by percent coverage, and its derepression has been implicated in inflammaging responses. However, whether L1 transcription itself is sufficient to drive aging-associated molecular phenotypes in healthy cells has not been extensively explored. Here, we leverage a multi-omic approach combining transcriptomics, proteomics, and secretomics of primary human IMR-90 fibroblasts transiently overexpressing a human L1Hs element in order to define the systems-level consequences of L1 transcription. Intriguingly, transient L1Hs overexpression induced widespread remodeling of the transcriptome, proteome and secretome, impacting pathways related to cell cycle regulation and interferon signaling. Interrogation of multiple independent L1 elements revealed both shared and distinct cellular responses to acute expression. Thus, our findings demonstrate that acute L1 expression induces coordinated molecular remodeling extending beyond canonical retrotransposition-associated pathways, rather than simply mimicking senescence or triggering antiviral signaling. This study establishes a comprehensive multi-omics resource for investigating the impact of L1 transcription in human cells and highlights the need to consider individual transposable element families as distinct regulators of cellular state during aging and disease.

genomics↗

bioRxiv2025

A multi-omics analysis of human fibroblasts overexpressing an Alu transposon reveals widespread disruptions in aging-associated pathways

During aging and cellular senescence, repetitive elements are frequently transcriptionally derepressed across species and cell types. Among these, the most abundant repeats by copy number in the human genome are Alu retrotransposons. Though Alu elements are often studied for their mutagenic potential, there is increasing appreciation for their contributions to other biological functions, including pro-inflammatory signaling and mitochondrial dysfunction. However, a comprehensive analysis of Alu-driven molecular changes remains to be conducted, and Alus potential contributions to aging features remain incompletely characterized. Here, we show that overexpression of an AluJb transposon in human primary IMR-90 fibroblasts leads to large-scale alterations across the transcriptome, cellular proteome, and secretome. Functional genomics analyses reveal alterations in aging pathways, broadly, and mitochondrial metabolism, proteostasis, cell cycle, and extracellular matrix pathways, more specifically. Our results demonstrate that Alu transcriptional upregulation is sufficient to drive widespread disruptions to cellular homeostasis that mirror aging-associated alterations.

genomics↗

bioRxiv2024

Multi-ancestry GWAS reveals loci linked to human variation in LINE-1- and Alu-copy numbers

LINE-1 (L1) and Alu are two families of transposable elements (TEs) occupying [~]17% and [~]11% of the human genome, respectively. Though only a small fraction of L1 copies is able to produce the machinery to mobilize autonomously, Alu and degenerate L1s can hijack their functional machinery and mobilize in trans. The expression and subsequent mobilization of L1 and Alu can exert pathological effects on their hosts. These features have made them promising focus subjects in studies of aging where they can become active. However, mechanisms regulating TE activity are incompletely characterized, especially in diverse human populations. To address these gaps, we leveraged genomic data from the 1000 Genomes Project to carry out a trans-ethnic GWAS of L1/Alu insertion singletons. These are rare, recently acquired insertions observed in only one person and which we used as proxies for variation in L1/Alu insertion numbers. Our approach identified SNVs in genomic regions containing genes with potential and known TE regulatory properties, and it enriched for SNVs in regions containing known regulators of L1 expression. Moreover, we identified reference TE copies and structural variants that associated with L1/Alu singletons, suggesting their potential contribution to TE insertion number variation. Finally, a transcriptional analysis of lymphoblastoid cells highlighted potential cell cycle alterations in a subset of samples harboring L1/Alu singletons. Collectively, our results suggest that known TE regulatory mechanisms may be active in diverse human populations, expand the list of loci implicated in TE insertion number variability, and reinforce links between TEs and disease.

genomics↗

bioRxiv2023

A Computational Approach for the Identification of Novel L1 Transcriptional Regulators

Long interspersed element 1 (L1) are a family of autonomous, actively mobile transposons that occupy [~]17% of the human genome. A number of pleiotropic effects induced by L1 (promoting genome instability, inflammation, or cellular senescence) have been observed, and L1s contributions to aging and aging diseases is an area of active research. However, because of the cell type-specific nature of transposon control, the catalogue of L1 regulators remains incomplete. Here, we employ an eQTL approach leveraging transcriptomic and genomic data from the GEUVADIS and 1000Genomes projects to computationally identify new candidate regulators of L1 RNA levels in lymphoblastoid cell lines. To cement the role of candidate genes in L1 regulation, we experimentally modulate the levels of top candidates in vitro, including IL16, STARD5, HSDB17B12, and RNF5, and assess changes in TE family expression by Gene Set Enrichment Analysis (GSEA). Remarkably, we observe subtle but widespread upregulation of TE family expression following IL16 and STARD5 overexpression. Moreover, a short-term 24-hour exposure to recombinant human IL16 was sufficient to transiently induce subtle, but widespread, upregulation of L1 subfamilies. Finally, we find that many L1 expression-associated genetic variants are co-associated with aging traits across genome-wide association study databases. Our results expand the catalogue of genes implicated in L1 RNA control and further suggest that L1-derived RNA contributes to aging processes. Given the ever-increasing availability of paired genomic and transcriptomic data, we anticipate this new approach to be a starting point for more comprehensive computational scans for transposon transcriptional regulators.

bioinformatics↗

bioRxiv2019

Remodeling of the H3 nucleosomal landscape during mouse aging

In multi-cellular organisms, the control of gene expression is key not only for development, but also for adult cellular homeostasis, and deregulation of gene expression correlates with aging. A key layer in the study of gene regulation mechanisms lies at the level of chromatin: cellular chromatin states (i.e. the epigenome) can tune transcriptional profiles, and, in line with the prevalence of transcriptional alterations with aging, accumulating evidence suggests that the chromatin landscape is altered with aging across cell types and species. However, though alterations in the chromatin make-up of cells are considered to be a hallmark of aging, little is known of the genomic loci that are specifically affected by age-related chromatin state remodeling and of their biological significance. Here, we report the analysis of genome-wide profiles of core histone H3 occupancy in aging male mice tissues (i.e. heart, liver, cerebellum and olfactory bulb) and primary cultures of neural stem cells. We find that, although no drastic changes in H3 levels are observed, local changes in H3 occupancy occur with aging across tissues and cells with both regions of increased or decreased occupancy. These changes are compatible with a general increase in chromatin accessibility at pro-inflammatory genes and may thus mechanistically underlie known shift in gene expression programs with aging.

genomics↗

bioRxiv2018

Introducing THOR, a model microbiome for genetic dissection of community behavior

The quest to manipulate microbiomes has intensified, but many microbial communities have proven recalcitrant to sustained change. Developing model communities amenable to genetic dissection will underpin successful strategies for shaping microbiomes by advancing understanding of community interactions. We developed a model community with representatives from three dominant rhizosphere taxa: the Firmicutes, Proteobacteria, and Bacteroidetes. We chose Bacillus cereus as a model rhizosphere Firmicute and characterized twenty other candidates, including \"hitchhikers\" that co-isolated with B. cereus from the rhizosphere. Pairwise analysis produced a hierarchical interstrain-competition network. We chose two hitchhikers -- Pseudomonas koreensis from the top tier of the competition network and Flavobacterium johnsoniae from the bottom of the network to represent the Proteobacteria and Bacteroidetes, respectively. The model community has several emergent properties--induction of dendritic expansion of B. cereus colonies by either of the other members and production of more robust biofilms by the three members together than individually. Moreover, P. koreensis produces a novel family of alkaloid antibiotics that inhibit growth of F. johnsoniae, and production is inhibited by B. cereus. We designate this community THOR, because the members are the hitchhikers of the rhizosphere. The genetic, genomic, and biochemical tools available for dissection of THOR provide the means to achieve a new level of understanding of microbial community behavior.\n\nIMPORTANCEThe manipulation and engineering of microbiomes could lead to improved human health, environmental sustainability, and agricultural productivity. However, microbiomes have proven difficult to alter in predictable ways and their emergent properties are poorly understood. The history of biology has demonstrated the power of model systems to understand complex problems such as gene expression or development. Therefore, a defined and genetically tractable model community would be useful to dissect microbiome assembly, maintenance, and processes. We have developed a tractable model rhizosphere microbiome, designated THOR, containing Pseudomonas koreensis, Flavobacterium johnsoniae, and Bacillus cereus, which represent three dominant phyla in the rhizosphere, as well as in soil and the mammalian gut. The model community demonstrates emergent properties and the members are amenable to genetic dissection. We propose that THOR will be a useful model for investigations of community-level interactions.

microbiology↗

bioRxiv2018

Bacterial analogs of plant piperidine alkaloids mediate microbial interactions in a rhizosphere model system

Plants expend significant resources to select and maintain rhizosphere communities that benefit their growth and protect them from pathogens. A better understanding of assembly and function of rhizosphere microbial communities will provide new avenues for improving crop production. Secretion of antibiotics is one means by which bacteria interact with neighboring microbes and sometimes change community composition. In our analysis of a taxonomically diverse consortium from the soybean rhizosphere, we found that Pseudomonas koreensis selectively inhibits growth of Flavobacterium johnsoniae and other members of the Bacteroidetes grown in soybean root exudate. A genetic screen in P. koreensis identified a previously uncharacterized biosynthetic gene cluster responsible for the inhibitory activity. The metabolites were isolated based on biological activity and were characterized using tandem-mass spectrometry, multidimensional NMR, and Mosher ester analysis, leading to the discovery of a new family of bacterial piperidine alkaloids, koreenceine A-D (1-4). Three of these metabolites are analogs of the plant alkaloid {gamma}-coniceine. Comparative analysis of the koreenceine cluster with the {gamma}-coniceine pathway revealed distinct polyketide synthase (PKS) routes to the defining piperidine scaffold, suggesting convergent evolution. Koreenceine-type pathways are widely distributed among Pseudomonas species, and koreenceine C was detected in another Pseudomonas sp. from a distantly related cluster. This work suggests that Pseudomonas and plants convergently evolved the ability to produce similar alkaloid metabolites that can mediate inter-bacterial competition in the rhizosphere.\n\nIMPORTANCEThe microbiomes of plants are critical to host physiology and development. Microbes are attracted to the rhizosphere due to massive secretion of plant photosynthates from roots. Microorganisms that successfully join the rhizosphere community from bulk soil have access to more abundant and diverse molecules, producing a highly competitive and selective environment. In the rhizosphere, as in other microbiomes, there is little known about the genetic basis for individual species behaviors within the community. In this study, we characterized competition between Pseudomonas koreensis and Flavobacterium johnsoniae, two common rhizosphere inhabitants. We identified a widespread gene cluster in several Pseudomonas spp., which is necessary for the production of a novel family of piperidine alkaloids that are structural analogs of plant alkaloids. We expand the known repertoire of antibiotics produced from Pseudomonas in the rhizosphere and demonstrate the role of the metabolites in interactions with other bacteria of the rhizosphere.

microbiology↗