Biology subjects

Guallar, D.

Publications and source records attributed to Guallar, D..

4 recordsLinked to original sources

bioRxiv2026

The Holliday junction resolvase GEN1 preserves genome integrity and self-renewal in mouse embryonic stem cells

The maintenance of pluripotent stem cells (PSCs) under rapid proliferation requires mechanisms that both suppress replication-driven genome instability and preserve self-renewal capacity. Here, we show that, in contrast to somatic cells where it mainly acts as a backup, the Holliday junction resolvase GEN1 is required in mouse embryonic stem cells (ESCs), where its depletion severely compromises self-renewal and long-term maintenance. Loss of GEN1 induces the accumulation of cells with DNA content greater than 4C and chromosome fusions. Notably, a catalytically inactive GEN1 mutant rescues ESC colony formation, indicating that GEN1 supports ESC maintenance through non-enzymatic functions. In addition, GEN1 depletion increases ESC tolerance to topoisomerase I-mediated replication stress and renders this phenotype dependent on DNA-PK activity, suggesting that GEN1 loss alters how pluripotent cells cope with replication-associated DNA lesions. Together, these findings identify GEN1 as a non-redundant guardian of genome integrity in pluripotent cells, revealing both a catalysis-independent role in self-renewal and a contribution to the replication stress response, with implications for PSC genomic quality control. HighlightsO_LIIn contrast to somatic cells, GEN1 is specifically required for mouse pluripotent cell self-renewal and expansion in vitro. C_LIO_LIGEN1 loss induces accumulation of DNA content greater than 4C and chromosome fusions without loss of core pluripotency markers expression. C_LIO_LICatalytically inactive GEN1 mutant rescues ESC colony-forming capacity. C_LIO_LIGEN1 depletion increases ESC tolerance to topoisomerase I-mediated replication stress in a DNA-PK-dependent manner C_LI eTOCRamos-Lage et al. demonstrate that the resolvase GEN1 is essential for mouse embryonic stem cell self-renewal and genome stability. Strikingly, a catalytically dead mutant rescues colony formation, revealing an unexpected non-enzymatic role for GEN1 in pluripotency maintenance.

cell biology↗

bioRxiv2026

Inhibition of p107 alleviates liver steatosis by reducing de novo fatty acid synthesis.

Metabolic dysfunction-associated steatotic liver disease (MASLD) is characterized by excessive hepatic lipid accumulation driven by increased de novo lipogenesis (DNL) and impaired lipid oxidation. p107, a member of the retinoblastoma (Rb) family, extensively studied in the context of cell cycle regulation and adipocyte differentiation recently has been identified as a metabolic regulator controlling thermogenic activity. However, its role in hepatic lipid homeostasis remains poorly understood. Here, we identify the cell cycle regulator p107 as a key modulator of hepatic lipid metabolism. p107 expression is increased in patients with MASLD and correlates with disease severity. In mouse models, global and liver-specific p107 deficiency protect against high-fat diet-induced steatosis without affecting body weight. This is associated with reduced expression of lipogenic enzymes including fatty acid synthase (FASN), and enhanced mitochondrial oxidative pathways. Conversely, hepatic restoration of p107 reversed these effects and promoted lipid accumulation and endoplasmic reticulum stress. Consistent with this in human hepatocytes, p107 silencing reduces lipid accumulation, decreases DNL and enhances mitochondrial respiration, whereas p107 overexpression induces the opposite phenotype. Notably, FASN knockdown attenuates the pro-steatotic effects of p107, indicating that it is a critical downstream mediator of p107. Together, these findings establish p107 as a physiological regulator of hepatic lipid metabolism, with its dysregulation contributing to the development of MASLD.

physiology↗

bioRxiv2025

An astrocytic AMPK clock drives circadian behaviour

Circadian clocks coordinate behaviour and physiology with daily cycles of light and nutrient availability, but how metabolic signals influence brain timing remains incompletely understood. Astrocytes integrate metabolic and hormonal cues and exhibit time-of-day-dependent responses, suggesting that they may convey temporal information to hypothalamic circuits. Here, we show that hypothalamic AMP-activated protein kinase (AMPK) exhibits circadian regulation independently of light and feeding cues, is modulated by nutrient availability and astrocytic Ca{superscript 2} signalling, and regulates the temporal organisation of the hypothalamic phosphoproteome. Genetic manipulation of astrocytic AMPK signalling alters PER2 abundance and phosphorylation, including at a conserved residue implicated in circadian period regulation. At the behavioural level, AMPK and PER2 in ventromedial hypothalamic astrocytes contribute to food-anticipatory activity, whereas disruption of astrocytic AMPK signalling alters SCN-dependent circadian locomotor rhythms and energy homeostasis in a sex-dependent manner. Together, these findings identify astrocytic AMPK signalling as a temporally regulated pathway that couples metabolic signals to hypothalamic circadian timing and systemic homeostasis.

neuroscience↗

bioRxiv2021

A TET1-PSPC1-Neat1 molecular axis modulates PRC2 functions in controlling stem cell bivalency

TET1 maintains hypomethylation at bivalent promoters through its catalytic activity in embryonic stem cells (ESCs). However, whether and how TET1 exerts catalytic activity-independent functions in regulating bivalent genes is not well understood. Using a proteomics approach, we mapped the TET1 interactome in mouse ESCs and identified PSPC1 as a novel TET1 partner. Genome-wide location analysis reveals that PSPC1 functionally associates with TET1 and Polycomb repressive complex-2 (PRC2) complex. We establish that PSPC1 and TET1 repress, and Neat1, the PSPC1 cognate lncRNA, activates the bivalent gene expression. In ESCs, Neat1 tethers the TET1-PSPC1 pair with PRC2 at bivalent promoters. During the ESC-to-formative epiblast-like stem cell (EpiLC) transition, PSPC1 and TET1 promote PRC2 chromatin occupancy at bivalent gene promoters while restricting Neat1 functions in facilitating PRC2 binding to bivalent gene transcripts. Our study uncovers a novel TET1-PSPC1-Neat1 molecular axis that modulates PRC2 binding affinity to chromatin and bivalent gene transcripts in controlling stem cell bivalency. In BriefTET1 is a transcriptional repressor for bivalent genes in pluripotent stem cells, but its mechanistic action on stem cell bivalency is unclear. Huang et al. use proteomics and genetic approaches to reveal that catalytic activity-independent functions of TET1, coordinated with the paraspeckle components PSPC1 and its cognate lncRNA Neat1, dynamically regulates stem cell bivalency by modulating PRC2 binding affinity to chromatin and bivalent gene transcripts in pluripotent state transition. HighlightsO_LIThe TET1 interactome identifies PSPC1 as a novel partner in ESCs C_LIO_LITET1 and PSPC1 repress bivalent genes by promoting PRC2 chromatin occupancy C_LIO_LINeat1 facilitates bivalent gene activation by promoting PRC2 binding to their mRNAs C_LIO_LINeat1 bridges the TET1-PSPC1 and PRC2 complexes in regulating bivalent gene transcription C_LI

developmental biology↗