Biology subjects

Perlaza-Jimenez, L.

Publications and source records attributed to Perlaza-Jimenez, L..

10 recordsLinked to original sources

bioRxiv2026

Ancient origin of the dorso-ventral patterning system of vertebrate paired fins

The origin of paired fins was a major event in early vertebrate history that fuelled the adaptive radiation of the gnathostome clade. Evidence for the conservation of ancient regulatory systems between paired and median fins supports a model in which appendage-patterning mechanisms first evolved in the midline and were later redeployed to a new embryonic context, the flank. However, while paired fins and limbs are asymmetric along the dorso-ventral (DV) axis, the equivalent axis does not exist in median fins, which are symmetric across the midline, raising questions of how DV patterning evolved. Here, we combine genetic tools in zebrafish with comparative expression analyses in representative ray-finned and cartilaginous fishes to show that a subset of limb dorsoventral (DV) patterning genes are expressed during median fin development. Using genetic lineage tracing of the canonical limb dorsalizing factor lmx1bb, we further demonstrate that, although lmx1bb-derived cells occupy distinct spatial domains across fin types, a subset of this lineage is fated to differentiate into fin-ray osteoblasts in both paired and median fins. To test the potential conservation of regulatory modules across fin types, we generated a series of deletion mutants for two known lmx1b mouse limb enhancers, LARM1 and LARM2, that we show are partially conserved upstream of zebrafish lmx1bb. These experiments revealed that LARM function is essential for dorsoventral patterning in the paired pectoral and pelvic fins of zebrafish but is dispensable for formation of the unpaired dorsal and anal fins. To determine if the paired fin specificity of LARM-mediated lmx1b regulation is a feature of more basal gnathostomes, we used a single cell multiomics (RNAseq + ATACseq) approach in the epaulette shark Hemiscyllium ocellatum, a representative chondrichthyan and outgroup to osteichthyans. Strikingly, these analyses demonstrated linkages between the LARM1 enhancer and lmx1b in the unpaired dorsal fins of epaulette sharks, as well as the deployment of a Lmx1b-mediated regulatory network whose core downstream components are conserved between dorsal fins, paired fins, and limbs. Collectively, these data support the ancient origin of a "DV" regulatory module in median fins that was redeployed during the early evolution paired fins, facilitating the assembly of the DV patterning axis. Intriguingly, multiome-based inference of global fin network architecture in epaulette shark also revealed reduced regulatory complexity in pectoral relative to median fins, suggesting that co-option as a mechanism for anatomical innovation can proceed through selective streamlining of ancestral network components.

developmental biology↗

bioRxiv2025

Widespread horizontal transfer and strong selection enhance microbial adaptation in Antarctic soils

Terrestrial Antarctica harbors compositionally diverse and functionally distinct microbial life. Yet the ecological and evolutionary processes enabling these communities to adapt to the polyextreme conditions of the continent remain largely unknown. Here, we address how horizontal gene transfer (HGT) and de novo mutations influence adaptation of microbial communities in 16 proglacial and mountainous Antarctic soils, from a combination of short- and long-read datasets. Phylogenetic reconciliation and mobile genetic element analysis of 676 metagenome-assembled genomes show that HGT events occur frequently within these microbial communities. While the transferred genes are distributed across diverse functional categories, those involved in energy metabolism are exchanged at relatively higher frequency. The genes for aerotrophy, i.e. the consumption of atmospheric trace gases to provide energy, carbon, and hydration, are among the most frequently and widely disseminated. Approximately a quarter of all carbon monoxide (CO) dehydrogenases and [NiFe]-hydrogenases that catalyze atmospheric CO and hydrogen (H2) oxidation are predicted to be horizontally acquired and are often closely associated with mobile genetic elements. In parallel, analysis of polymorphisms in protein-encoding genes suggests widespread purifying selection, demonstrated by a predominance of synonymous mutations. This selection is particularly intense for aerotrophy genes, providing further evidence that this process is critical for microbial survival in Antarctica. The genetic variation of hydrogenases is tightly associated with their predicted protein structures, with intense selection acting on critical sites that preserve their stability and function in Antarctic environments. Together, these findings show that previously unrecognised eco-evolutionary dynamics shape the composition and function of Antarctic desert microbial communities, and confirm aerotrophy is a strongly selected and horizontally disseminated trait.

microbiology↗

bioRxiv2025

Integrated cross-sectoral surveillance of antimicrobial resistance genotypes and phenotypes across disparate reservoirs

Antimicrobial-resistant (AMR) bacteria and genes are continually exchanged among humans, animals, and environmental reservoirs. Disparate and siloed surveillance methods present a major challenge for tracing and disrupting AMR transmission, with clinical monitoring focusing on detecting specific pathogens or specific genes of interest, and environmental surveys often relying on inferences drawn from indicator organisms. Here, we demonstrate that, following sample-specific pre-processing, common surveillance approaches can be applied consistently to profile AMR abundance, distribution, and phenotypes across diverse reservoirs, including soil, sediment, water, wastewater, and faecal samples from both urban and agricultural settings. Across all sample types, three core methods provided complementary insights: (i) quantitative PCR (qPCR) arrays to measure multiple AMR genes, (ii) gene- and genome-centric metagenomics for comprehensive resistome profiling, and (iii) culture-based genomics with susceptibility testing to link genotypes to phenotypes. We applied this approach to profile 1,032 metagenome-assembled genomes, 66 bacterial isolate genomes, and 78 and 6,442 AMR genes/reference sequences via qPCR and metagenomics, respectively. This integrated framework revealed a moderate prevalence but high diversity of resistance mechanisms in both pathogens and non-pathogenic bacteria with potentially transmissible genes, with wastewater especially enriched in AMR genes. We detected mismatches between genotype and phenotype predictions and a prevalence of intermediate resistance phenotypes, highlighting how many mechanisms of environmental resistance remain poorly understood. Overall, this study demonstrates that unified field-leading surveillance methods can be extended beyond clinical contexts into diverse environmental and animal samples, while highlighting that multiple methods are needed to capture the diverse AMR genotypes and phenotypes in these settings to enable comprehensive monitoring and adaptive solutions to restrict transmission.

microbiology↗

bioRxiv2025

Single-Cell Pharmacogenomic Landscapes of Epigenetic Therapy in Gastric Cancer

Gene expression signatures ("molecular phenotypes") are extensively utilized in cancer research. To study how gastric cancer (GC) molecular phenotypes are shaped by cell-intrinsic genetic alterations interacting with cell-extrinsic therapeutic pressures, we performed direct capture Perturb-seq (dcPerturb-seq) to interrogate >200 GC-related genes across 4 distinct epigenetic drug classes in multiple gastric lines. We captured 17.7 million pharmocogenomic expression interactions in 625,866 cells representing baseline and post-therapeutic molecular phenotypes. This single-cell pharmacogenomic compendium confirmed previously known gene-driven molecular phenotypes, elucidated poorly characterized genes, and uncovered novel gene dosage-molecular phenotype relationships. Molecular phenotypes in post-therapeutic surviving cells revealed diverse gene perturbation-associated pathways causing convergent drug resistance (EMT plasticity, cell cycle alterations, metabolic reprogramming), highlighting combinatorial strategies for restoring sensitivity. Mapping of in vitro molecular phenotypes to primary human GCs imparted prognostic information and insights into spatial heterogeneity. Comparative analysis of gene perturbations across therapies and lines revealed both conserved and context-specific molecular alterations. Our results illustrate how Perturb-seq approaches can systematically map diverse cancer-associated molecular phenotypes across multiple gene/drug/cell line interactions, yielding translational insights.

cancer biology↗

bioRxiv2024

Pooled genetic screens identify breast cancer risk genes involved in evasion from T cell-mediated killing

Genome-wide association studies have identified more than 220 loci associated with breast cancer susceptibility. A major challenge is now to identify the effector genes with plausible functions in the context of breast cancer risk. We have previously performed pooled CRISPR screens to identify target genes at risk loci that drive cancer hallmarks including proliferation or modulating DNA damage response. We now extend these screens to identify genes involved in response to cytotoxic T lymphocyte (CTL) killing. We performed knockout and inhibition screens to identify genes that affect the response of the MCF7 human breast cancer cell line to CTL killing in an in vitro co-culture system. We identified 33 candidate risk genes associated with resistance or sensitisation to T cell-mediated killing. Using single gene perturbation, we showed that deletion of candidate risk genes IRF1, ATF7IP, CCDC170 and CASP8 induced resistance, while ablation of CFLAR, CREBBP, and PRMT7 sensitized cells to CTL killing. We used reporter assays to show that the risk-associated alleles at rs736801 and rs3769821 reduced transactivation of the IRF1 and CASP8 promoters, respectively. We showed that pharmacological inhibition of PRMT7 rendered breast cells sensitive to CTL killing and PRMT7 levels were negatively correlated with CD8+ infiltration and patient survival in luminal A breast cancer patient cohorts. Our results demonstrate that phenotypic pooled CRISPR screens are a useful approach for high throughput functional follow-up of GWAS findings, identifying genes which alter immune responses to breast cancer which offer opportunities to enhance immunotherapy.

genetics↗

bioRxiv2024

SAM-DNMT3A, a strategy for induction of genome-wide DNA methylation, identifies DNA methylation as a vulnerability in ER-positive breast cancers

DNA methylation is an epigenetic mark that plays a critical role in regulation of gene expression. DNA methylase (DNMT) inhibitors, inhibit global DNA methylation, and have been a key tool in studies of DNA methylation in healthy or disease conditions. A major bottleneck is the lack of tools to induce global DNA methylation. Here, we engineered a CRISPR based approach, that was initially designed, to enable site specific DNA methylation. Using the synergistic activation mediator (SAM) system, we unexpectedly found that regardless of the targeted sequence any sgRNA induced global genome-wide DNA methylation. We termed this new method SAM-DNMT3A and show that induction of global DNA methylation is a unique vulnerability in ER-positive breast cancer suggesting a therapeutic approach. Our findings highlight the need of caution when using CRISPR based approaches for inducing DNA methylation and demonstrate a new method for global induction of DNA methylation.

genetics↗

bioRxiv2023

Hypoxic injury triggers maladaptive repair in human kidney organoids

Acute kidney injury (AKI) is a common clinical disorder linked to high rates of illness and death. Ischemia is a leading cause of AKI, which can result in chronic kidney disease (CKD) through maladaptive repair marked by impaired epithelial regeneration, inflammation, and metabolic dysregulation. There are no targeted therapies for AKI or to prevent progression to CKD and insight into human disease mechanisms remains limited. Here we show that human kidney organoids recapitulate key molecular and metabolic signatures of AKI and maladaptive repair in response to hypoxic injury. Transcriptional, proteomic, and metabolomic profiling revealed tubular injury, cell death, cell cycle arrest and metabolic reprogramming in organoids exposed to hypoxia. Following return to normoxic conditions, injured organoids had increased signatures of TNF and NF-{kappa}B signalling pathways and S100A8/9, associated with maladaptive repair. Single cell RNA sequencing localized AKI and maladaptive repair markers including GDF15, MMP7, ICAM1, IL32, SPP1, C3 and CCN1 to injured tubules. Metabolic phenotypes linked to CKD were also evident, including dysregulated gluconeogenesis, altered amino acid metabolism and lipid peroxidation. iPSC-derived macrophages incorporated into organoids displayed a robust activation and inflammatory response to hypoxia. Spatial transcriptomics revealed a shift from a tissue resident-like to inflammatory macrophage states and localized effects on tubular injury and inflammation. This multi-omic analysis defines conserved mechanisms of human ischemic AKI and maladaptive repair, highlighting new opportunities to test therapeutics and model immune-mediated interactions.

systems biology↗

bioRxiv2022

Systematic loss of function screens identify pathway specific functional circular RNAs

Circular RNAs (circRNAs) are covalently closed single stranded RNAs that are produced by RNA back-splicing. A small number of circRNAs have been implicated as functional, however, we still lack systematic understanding of cellular processes and signalling pathways that are regulated by circRNAs. A major gap in understanding circRNA function is the ability to define pathways that are regulated by circRNAs. Here, we generated a pooled shRNA library targeting the back-splice junction of 3,354 human circRNAs that are expressed at low to high levels in humans. We used this library for loss of function proliferation screens in a panel of 18 cancer cell lines from four tissue types that harbour mutations leading to constitutive activity of defined pathways. Using this dataset, we identify context specific and non-specific circRNAs. We validated these observations with a secondary screen and uncovered a role for circRERE, a cell essential circRNA that regulates ferroptosis. Furthermore, we characterised the functional roles of pathway-specific circRNA, circSMAD2, a novel regulator of the WNT pathway and circMTO1, a regulator of MAPK signalling in a PTEN dependent manner. Our work sheds light on molecular pathways regulated by circRNAs and provides a catalogue of circRNAs with a measurable function in human cells.

genetics↗

bioRxiv2022

Treatment history shapes the evolution of complex carbapenem-resistant phenotypes in Klebsiella spp.

Antibiotic resistance is driven by selection, but how a bacterial strains evolutionary history shapes drug-resistance remains an open question. Here we reconstruct the genetic and evolutionary mechanisms of carbapenem resistance in a clinical isolate of Klebsiella. A combination of short and long read sequencing, machine learning, genetic and enzymatic analyses established that this carbapenem-resistant strain carries no carbapenemase-encoding genes. Genetic reconstruction of the resistance phenotype confirmed that two distinct genetic loci are necessary for the strain to acquire carbapenem resistance. Experimental evolution of the carbapenem-resistant strains in growth conditions without the antibiotic revealed that both loci confer a significant cost, and are readily lost by de novo mutation resulting in the rapid evolution of a carbapenem-sensitive phenotype. Thus, historical contingency - a patients treatment history - can shape the evolution of antibiotic resistance and suggests that the strategic combinations of antibiotics could direct the evolution of low-fitness, drug-resistant genotypes.

microbiology↗

bioRxiv2018

A genome-wide scan for correlated mutations detects macromolecular and chromatin loop interactions in Arabidopsis thaliana.

The concept of exploiting correlated mutations has been introduced and applied successfully to identify interactions within and between biological macromolecules. Its rationale lies in the preservation of physical interactions via compensatory mutations. With the massive increase of available sequence information, approaches based on correlated mutations have regained considerable attention.\n\nWe analyzed a set of 10,707,430 single nucleotide polymorphisms detected in 1,135 accessions of the plant Arabidopsis thaliana. To measure their covariance and to reveal the global genome-wide sequence correlation structure of the Arabidopsis genome, the adjusted mutual information has been estimated for each possible pair of polymorphic sites. We developed a series of filtering steps to account for genetic linkage and lineage relations between Arabidopsis accessions, as well as transitive covariance as possible confounding factors. We show that upon appropriate filtering, correlated mutations prove indeed informative with regard to molecular interactions, and furthermore, appear to reflect on chromosomal interactions.\n\nOur study demonstrates that the concept of correlated mutations can also be applied successfully to within-species sequence variation and establishes a promising approach to help unravel the complex molecular interactions in A. thaliana and other species with broad sequence information.

genomics↗