Biology subjects

Rojas, A. M.

Publications and source records attributed to Rojas, A. M..

6 recordsLinked to original sources

bioRxiv2026

Evolution of CTCF underlies the establishment of loop extrusion as a predominant chromatin folding mechanism in vertebrates

CTCF is a DNA-binding protein that emerged in the last bilaterian ancestor and that plays a central role in 3D genome organization. Yet, despite its relevance, genomic studies have revealed notable differences in CTCF function across animal clades. In vertebrates, CTCF is essential for TAD organization through cohesin-mediated loop extrusion, whereas its contribution to chromatin organization outside this clade appears to be more limited. Here we investigate the evolution of CTCF as an architectural factor through a cross-species functional replacement approach, in which orthologs from divergent bilaterian lineages are expressed in either mouse embryonic stem cells or Drosophila embryos. Chromosome conformation analyses demonstrated that the ability of CTCF to mediate loop extrusion-dependent TAD formation is encoded within the vertebrate protein. Yet, this property alone is insufficient to establish vertebrate-like genome architecture in an invertebrate background, suggesting the existence of additional lineage-specific factors. ChIP-seq analyses further revealed that CTCF DNA-binding specificity has been progressively refined during bilaterian evolution, with the vertebrate lineage exhibiting a preferential shift towards distal genomic regions that is consistent with an expansion of regulatory domains. Notably, despite failing to form TADs, the ortholog from a non-vertebrate chordate partially rescued the lethality associated with the loss of the vertebrate CTCF protein, indicating that its architectural and regulatory functions are evolutionary independent. Further Hi-C analyses in tunicate and cyclostome species suggest that the ability of CTCF to act as a loop extrusion barrier was already present in the last common ancestor of all vertebrates. Altogether, our findings establish the diversification of CTCF regulation and function as key drivers for the specialization of bilaterian 3D genome organization.

genomics↗

bioRxiv2025

Nuclear Argonaute HRDE-1 Sustains Chromatin-Independent Transcriptional Silencing and Epigenetic Inheritance

Epigenetic inheritance of transcriptional silencing is traditionally attributed to chromatin-based mechanisms in which Argonaute-small RNA complexes recruit histone-modifying enzymes. Here we show that, in Caenorhabditis elegans, the nuclear Argonaute HRDE-1 maintains germline transcriptional repression independently of canonical heterochromatin marks. Using inducible, germline-specific HRDE-1 depletion combined with nuclear sorting, CUT&Tag, and nascent transcription profiling, we identified endogenous genes that become transcriptionally activated upon loss of HRDE-1 despite retaining H3K9me3 and H3K23me3. HRDE-1 directly restrains RNA polymerase II (Pol II) while simultaneously promoting polyUG-dependent amplification of antisense 22G-RNAs in perinuclear condensates, thereby coupling nuclear transcriptional repression to small RNA biogenesis. HRDE-1 loss causes progressive erosion of 22G-RNAs and delays silencing re-establishment, revealing a transgenerational feedback loop in which small RNAs, and not chromatin modifications, constitute the primary heritable signal. These findings redefine nuclear Argonautes as active drivers of RNA-based epigenetic inheritance and broaden our understanding of how small RNA pathways maintain transcriptional silencing across generations.

molecular biology↗

bioRxiv2024

Illuminating the functional landscape of the dark proteome across the Animal Tree of Life through natural language processing models

Functional annotation is crucial in biology, but many protein-coding genes remain uncharacterized, especially in non-model organisms. FANTASIA (Functional ANnoTAtion based on embedding space SImilArity) integrates protein language models for large-scale functional annotation. Applied to [~]1,000 animal proteomes, it predicts functions to virtually all proteins, revealing previously uncharacterized functions that enhance our understanding of molecular evolution. FANTASIA is available on GitHub at https://github.com/CBBIO/FANTASIA.

evolutionary biology↗

bioRxiv2024

Decoding proteome functional information in model organisms using protein language models.

Protein language models have been tested and proved to be reliable when used on curated datasets but have not yet been applied to full proteomes. Accordingly, we tested how two different machine learning based methods performed when decoding functional information from the proteomes of selected model organisms. We found that protein Language Models are more precise and informative than Deep Learning methods for all the species tested and across the three gene ontologies studied, and that they better recover functional information from transcriptomics experiments. The results obtained indicate that these Language Models are likely to be suitable for large scale annotation and downstream analyses, and we recommend a guide for their use.

bioinformatics↗

bioRxiv2021

Peripheral NOD-like receptor deficient inflammatory macrophages trigger neutrophil infiltration disrupting daytime locomotion

Inflammation is known to disrupt normal behavior, yet the underlying neuroimmune interactions remain elusive. Here, we investigated whether inappropriate macrophage-evoked inflammation alters CNS control of daily-life animal locomotion using a set of zebrafish mutants selected for specific macrophage dysfunction and microglia deficiency. Large-scale genetic and computational analyses revealed that NOD-like receptor nlrc3l mutants are capable of normal motility and visuomotor response, but preferentially swim less in the daytime, suggesting low motivation rather than physical impairment. Examining their brain activities and structures implicate impaired dopaminergic descending circuits, where neutrophils abnormally infiltrate. Furthermore, neutrophil depletion recovered daytime locomotion. Restoring wild-type macrophages reversed behavioral and neutrophil aberrations, while three other microglia-lacking mutants failed to phenocopy nlrc3l mutants. Overall, we reveal how peripheral inflammatory macrophages with elevated pro-inflammatory cues (including il1b, tnfa, cxcl8a) in the absence of microglia co-opt neutrophils to infiltrate the brain, thereby enabling local modulation of neural circuits affecting spontaneous locomotion.

immunology↗

bioRxiv2021

The multivalency of the glucocorticoid receptor ligand-binding domain explains its manifold physiological activities

The glucocorticoid receptor (GR) is a ubiquitously expressed transcription factor that controls metabolic and homeostatic processes essential for life. Although numerous crystal structures of the GR ligand-binding domain (GR-LBD) have been reported, the functional oligomeric state of the full-length receptor, which is essential for its transcriptional activity, remains disputed. Here we present five new crystal structures of agonist-bound GR-LBD, along with a thorough analysis of previous structural work. Biologically relevant homodimers were identified by studying a battery of GR point mutants including crosslinking assays in solution and quantitative fluorescence microscopy in living cells. Our results highlight the relevance of non-canonical dimerization modes for GR, especially of contacts made by loop L1-3 residues such as Tyr545. Our work unveils likely pathophysiologically relevant quaternary assemblies of the nuclear receptor with important implications for glucocorticoid action and drug design.

biochemistry↗