Biology subjects

Romero, H.

Publications and source records attributed to Romero, H..

10 recordsLinked to original sources

bioRxiv2026

Heterochromatin organization and liquid-liquid phase separation: it is not about if but about when

Heterochromatin is a membraneless compartment within the cell nucleus. In recent years, a controversy arose on whether heterochromatin organization is driven by liquid-liquid phase separation or not. While many heterochromatin proteins were shown to undergo liquid-liquid phase separation in vitro, other studies reported that this does not happen in cells. Here, we tested the ability of heterochromatin proteins to generate heterochromatin barrier compartments in cells. We found that, while several proteins (H1.0, H1.4, HP1alpha, HP1beta, Mbd1, Mbd2 and MeCP2) form barrier compartments in mouse and/or human cells this differs between cell types. In addition, not all compartments in the same cell form barriers. We established and experimentally validated a model that predicted the ability to form barrier compartments is dependent on the protein accumulation in heterochromatin followed by the competition between compartments for the nucleoplasm pool of the protein and resulted in larger size for the barrier compartments. These findings resolve the existing controversy and rationalize how in cells heterochromatin compartments form and compete to establish dynamic barriers to the entry and exit of its components. HighlightsHeterochromatin barrier formation differs between proteins, cell lines and heterochromatin compartments within the cell. Barrier formation depends on heterochromatin anchors, including ligands and other scaffolds. Barrier compartments are defined by their larger size and higher protein enrichment. Graphical Abstract O_FIG O_LINKSMALLFIG WIDTH=200 HEIGHT=83 SRC="FIGDIR/small/729812v1_ufig1.gif" ALT="Figure 1"> View larger version (28K): org.highwire.dtl.DTLVardef@a63021org.highwire.dtl.DTLVardef@a20362org.highwire.dtl.DTLVardef@8c2390org.highwire.dtl.DTLVardef@72dde3_HPS_FORMAT_FIGEXP M_FIG C_FIG

cell biology↗

bioRxiv2026

Spatial transcriptomics reveals brain-wide circadian disruption in an Alzheimer's disease model

Diurnal rhythms in brain transcription align neural, immune, and metabolic processes with the light-dark cycle and are profoundly disrupted in Alzheimers disease (AD). However, the regional organization of diurnal transcription in the healthy and diseased brain remains poorly defined. Using large-scale spatial transcriptomics, we mapped 24-hour rhythmic transcription across cortical and subcortical regions of the mouse brain. We identified marked regional differences in rhythmicity, including distinct oscillatory signatures across cortical areas and along the rostro-caudal axis. In the APP23 mouse model of AD, pathology-vulnerable brain regions exhibited early, region-specific disruption of diurnal transcription prior to substantial amyloid plaque deposition. These findings reveal a spatially organized architecture of brain diurnal rhythms and identify early rhythmic dysregulation as a feature of Alzheimers disease pathogenesis.

neuroscience↗

bioRxiv2025

Inhibition of IL2Rβ-dependent STAT5 activity supports T-cell stemness and augments antitumor efficacy of CD8+ T cells by preventing T-cell exhaustion

CD8+ T-cell exhaustion is a leading cause of adoptive cell therapy (ACT) failure. In contrast, maintaining a stem-like state correlates with better expansion, persistence, and anti-tumor activity of infused T-cell products. IL-2 is extensively used in ACT protocols given its ability to expand T-cell populations. Yet, IL-2 drives more differentiated and exhausted states, diminishing the quality of T-cell products. Understanding how cytokines of the IL2R family drive T-cell differentiation is essential to ultimately design optimal ACT protocols, safeguarding stem-like programs while ensuring sufficient T-cell expansion. Here, we show that cytokine signaling through IL2R{beta} supports more differentiated exhausted T cells in chronic lymphocytic choriomeningitis infection. Similarly, high levels of IL-2 and IL-15 in vitro foster heightened differentiation and exhaustion of cells for adoptive cell therapy. In contrast, absence of IL2R{beta} in vivo or transient inhibition of Janus kinase 3 (JAK3) or signal transducer and activator of transcription 5 (STAT5) in vitro favors features of T-cell stemness. Transcriptional analyses of in vitro expanded T cells further reveal that inhibition of STAT5 sustains a stemness program, which correlates with better antitumor activity in a mouse melanoma model. When applied to a human CAR T expansion model, inhibition of STAT5 supports memory progenitor differentiation and limit inhibitory receptor expression. These results demonstrate that continuous exposure to high levels of cytokines, such as IL-2 and IL-15, constrain CD8+ T cells towards more advanced states of exhaustion. In contrast, limiting cytokine signaling using specific kinase inhibitors preserves stem-like T-cell programs and enhance the quality of ACT products. One Sentence SummarySustained IL-2/IL-15 signaling drives CD8+ T-cell exhaustion while JAK3/STAT5 inhibition preserves stemness, boosting adoptive cell therapy efficacy.

immunology↗

bioRxiv2025

Chromatin organization controls nuclear stiffness

Cellular differentiation is driven by epigenetic modifiers and readers, including the methyl CpG binding protein 2 (MeCP2), whose level and mutations cause the neurological disorder Rett syndrome. During differentiation, most of the genome gets densely packed into heterochromatin, whose function has been simplistically viewed as gene silencing. However, gene expression changes reported in mutations leading to Rett syndrome have failed to be a predictor of disease severity. Here, we show that MeCP2 increases nuclear stiffness in a concentration dependent manner and dependent on its ability to cluster heterochromatin during differentiation. MeCP2-dependent stiffness increase could not be explained by changes in the expression of mechanobiology-related genes, but we found it is disrupted by Rett syndrome mutations and correlated with disease severity. Our results highlight the impact of chromatin organization in the mechanical properties of the cell as an alternative or complementary mechanism to changes in cytoskeleton components. Graphical abstract O_FIG O_LINKSMALLFIG WIDTH=200 HEIGHT=103 SRC="FIGDIR/small/643219v2_ufig1.gif" ALT="Figure 1"> View larger version (19K): org.highwire.dtl.DTLVardef@cb077dorg.highwire.dtl.DTLVardef@158c0c6org.highwire.dtl.DTLVardef@1d830e3org.highwire.dtl.DTLVardef@719456_HPS_FORMAT_FIGEXP M_FIG C_FIG

cell biology↗

bioRxiv2024

Control of innate olfactory valence by segregated cortical amygdala circuits

Animals exhibit innate behaviors that are stereotyped responses to specific evolutionarily relevant stimuli in the absence of prior learning or experience. These behaviors can be reduced to an axis of valence, whereby specific odors evoke approach or avoidance responses. The posterolateral cortical amygdala (plCoA) mediates innate attraction and aversion to odor. However, little is known about how this brain area gives rise to behaviors of opposing motivational valence. Here, we sought to define the circuit features of plCoA that give rise to innate attraction and aversion to odor. We characterized the physiology, gene expression, and projections of this structure, identifying a divergent, topographic organization that selectively controls innate attraction and avoidance to odor. First, we examined odor-evoked responses in these areas and found sparse encoding of odor identity, but not valence. We next considered a topographic organization and found that optogenetic stimulation of the anterior and posterior domains of plCoA elicits attraction and avoidance, respectively, suggesting a functional axis for valence. Using single cell and spatial RNA sequencing, we identified the molecular cell types in plCoA, revealing an anteroposterior gradient in cell types, whereby anterior glutamatergic neurons preferentially express VGluT2 and posterior neurons express VGluT1. Activation of these respective cell types recapitulates appetitive and aversive behaviors, and chemogenetic inhibition reveals partial necessity for responses to innate appetitive or aversive odors. Finally, we identified topographically organized circuits defined by projections, whereby anterior neurons preferentially project to medial amygdala, and posterior neurons preferentially project to nucleus accumbens, which are respectively sufficient and necessary for innate attraction and aversion. Together, these data advance our understanding of how the olfactory system generates stereotypic, hardwired attraction and avoidance, and supports a model whereby distinct, topographically distributed plCoA populations direct innate olfactory responses by signaling to divergent valence-specific targets, linking upstream olfactory identity to downstream valence behaviors, through a population code. This suggests a novel amygdala circuit motif in which valence encoding is represented not by the firing properties of individual neurons, but by population level identity encoding that is routed through divergent targets to mediate distinct behaviors of opposing appetitive and aversive responses.

neuroscience↗

bioRxiv2022

Circadian modulation by time-restricted feeding restores brain transcription and slows amyloid deposition in a mouse model of Alzheimer's disease.

Alzheimers disease (AD) is a tragic neurodegenerative disease affecting more than 5 million Americans. Circadian disruptions impact nearly all AD patients, with reversal of sleep/wake cycles and agitation in the evening being common disturbances that manifest early in disease. These alterations support a role for circadian dysfunction as a driver of AD, emphasizing a critical need to investigate the therapeutic potential of circadian-modulating interventions. One of the most powerful regulators of the circadian system is the daily feed/fast cycle. Here we show that time-restricted feeding (TRF) without caloric restriction, improved key disease components including behavior, disease pathology and transcription in the APP23 mouse model of Alzheimers disease. We found that TRF had the remarkable capability of simultaneously reducing amyloid deposition, increasing A{beta}42 clearance, improving sleep and hyperactivity, and normalizing transcription of circadian, AD and neuroinflammation-associated genes in APP23 mice. Thus, our study unveils for the first time that circadian modulation through timed feeding has far-reaching effects beyond metabolism and affects the brain as the substrate for neurodegeneration. Since the pleiotropic effects of TRF can substantially modify disease trajectory, this intervention has immediate translational value, addressing the crucial need for accessible approaches to reduce or halt AD progression.

neuroscience↗

bioRxiv2022

Molecular basis for antiviral activity of pediatric neutralizing antibodies targeting SARS-CoV-2 Spike receptor binding domain

Neutralizing antibodies (NAbs) hold great promise for clinical interventions against SARS-CoV- 2 variants of concern (VOCs). Understanding NAb epitope-dependent antiviral mechanisms is crucial for developing vaccines and therapeutics against VOCs. Here we characterized two potent NAbs, EH3 and EH8, isolated from an unvaccinated pediatric patient with exceptional plasma neutralization activity. EH3 and EH8 cross-neutralize the early VOCs and mediate strong Fc-dependent effector activity in vitro. Structural analyses of EH3 and EH8 in complex with the receptor-binding domain (RBD) revealed the molecular determinants of the epitope-driven protection and VOC-evasion. While EH3 represents the prevalent IGHV3-53 NAb whose epitope substantially overlaps with the ACE2 binding site, EH8 recognizes a narrow epitope exposed in both RBD-up and RBD-down conformations. When tested in vivo, a single-dose prophylactic administration of EH3 fully protected stringent K18-hACE2 mice from lethal challenge with Delta VOC. Our study demonstrates that protective NAbs responses converge in pediatric and adult SARS-CoV-2 patients.

microbiology↗

bioRxiv2021

Archaeal origins of gamete fusion

Sexual reproduction consists of genome reduction by meiosis and subsequent gamete fusion. Presence of meiotic genes in prokaryotes suggests that DNA repair mechanisms evolved toward meiotic recombination; however, fusogenic proteins resembling those found in eukaryotes were not identified in prokaryotes. Here, we identify archaeal proteins that are homologs of fusexins, a superfamily of fusogens that mediate eukaryotic gamete and somatic cell fusion, as well as virus entry. The crystal structure of a trimeric archaeal Fusexin1 reveals novel features such as a six-helix bundle and an additional globular domain. Ectopically expressed Fusexin1 can fuse mammalian cells, and this process involves the additional domain and a conserved fusion loop. Archaeal fusexin genes exist within integrated mobile elements, potentially linking ancient archaeal gene exchanges and eukaryotic sex. One-Sentence SummaryCell membrane fusion proteins of viruses and eukaryotes are also present in archaea.

evolutionary biology↗

bioRxiv2019

Efficient and robust NK-Cell transduction with Baboon Envelope pseudotyped lentivector: a major tool for immunotherapy

NK-cell resistance to transduction is a major technical hurdle for developing NK-cell immunotherapy. By using Baboon envelope pseudotyped lentiviral vectors (BaEV-LVs) encoding eGFP, we obtained a transduction rate of 23.0{+/-}6.6% in freshly-isolated NK-cells (FI-NK) and 83.4{+/-}10.1% in NK-cells obtained from the NK-cell Activation and Expansion System (NKAES), even at low MOI, with a sustained transgene expression for at least 21 days. BaEV-LVs outperformed Vesicular Stomatitis Virus type-G (VSV-G)-, RD114-and Measles Virus (MV)-pseudotyped LVs (p<0.001). mRNA expression of both BaEV receptors, ASCT1 and ASCT2, was detected in FI-NK and NKAES, with much higher expression in NKAES. Transduction with BaEV-LVs encoding for CAR-CD22 resulted in robust CAR-expression on 44.2%{+/-}14.2% of NKAES cells, which allowed the specific killing of the NK-resistant pre-B-ALL-RS4;11 cell line. Using a larger vector, encoding a dual CD19/CD22-CAR separated by T2A, we were able to transduce and re-expand dual-CAR-expressing NKAES, even with low viral titer. These dual-CAR-NK efficiently and specifically killed both CD19KO-and CD22KO-RS4;11 cells, which may overcome antigen-loss escape in the clinical setting. Our results suggest that BaEV-LVs may efficiently enable NK-cell biological studies and translation of NK-cell-based immunotherapy to the clinic.

immunology↗

bioRxiv2016

Arabidopsis HAP2/GCS1 is a gamete fusion protein homologous to somatic and viral fusogens

Cell-cell fusion is inherent to any form of sexual reproduction. Loss of HAPLESS 2/GENERATIVE CELL SPECIFIC 1 (HAP2/GCS1) proteins results in gamete fusion failure in different organisms but their exact role is unclear. Here we show that Arabidopsis HAP2/GCS1 expression in mammalian cells is sufficient to promote cell-cell fusion. Hemifusion and complete fusion depend on HAP2/GCS1 presence in both fusing cells. Furthermore, expression of HAP2 on the surface of pseudotyped vesicular stomatitis virus and on the target cells results in HAP2-dependent virus-cell fusion. This bilateral requirement can be bypassed by replacing the plant gene with C. elegans EFF-1 somatic cell fusogen in one of the fusing cells or the virus, indicating that HAP2/GCS1 and EFF-1 share a similar fusion mechanism. Structural modeling of the HAP2/GCS1 protein family predicts that they are homologous to EFF-1 and class II fusion proteins from enveloped viruses (e.g. dengue and Zika viruses). We name this superfamily FUSEXINS: FUSion proteins essential for sexual reproduction and EXoplasmic merger of plasma membranes. Thus, Fusexins unify the origin and evolution of sexual reproduction, enveloped virus entry into cells and somatic cell fusion.

cell biology↗