Biology subjects

Alencastro, F.

Publications and source records attributed to Alencastro, F..

4 recordsLinked to original sources

bioRxiv2025

Diploid Hepatocytes Resist Acetaminophen-Induced Liver Injury Through Suppressed JNK Signaling

Background & AimsThe liver contains both diploid and polyploid hepatocytes, but their functional differences remain poorly understood. Emerging evidence suggests that each ploidy state contributes to regeneration in an injury-specific manner. We hypothesized that diploid hepatocytes promote healing after acetaminophen (APAP)-induced liver injury. Approach & ResultsTo study ploidy populations in vivo, we utilized mice with a lifelong liver-specific knockout of E2f7/E2f8 (LKO), which are enriched in diploid hepatocytes (>70%) but otherwise normal. Control and LKO mice were treated with APAP (300 or 600 mg/kg), and injury was assessed over 0-96 hours. Although both groups sustained injury, LKO mice showed improved survival, lower serum liver enzyme levels, and reduced necrosis and DNA fragmentation, indicating resistance to APAP-induced injury. To determine if resistance was due to E2f7/E2f8 loss or increased diploidy, we deleted E2f7/E2f8 in adult hepatocytes (HKO), a model that does not alter ploidy. Injury was similar between controls and HKO, ruling out gene deletion as the protective factor. Transcriptomic and protein analyses revealed minimal baseline differences; however, following APAP treatment, LKO livers exhibited reduced JNK activation and less mitochondrial injury. Finally, APAP-treated wild-type hepatocytes exhibited a shift toward lower ploidy, supporting the idea that diploid cells are more resistant to injury. ConclusionsDiploid hepatocytes resist APAP-induced liver injury through reduced JNK activation and mitochondrial damage. These findings highlight hepatocyte ploidy as a key determinant of injury response and suggest a protective role for diploid hepatocytes in promoting liver resilience and regeneration.

genetics↗

bioRxiv2025

Constitutive Androstane Receptor induces Ribonucleotide Reductase-M2 expression and maintains hepatocyte ploidy in mice

The nuclear receptor Constitutive Androstane Receptor (CAR/NR1i3) is known for regulating various liver functions, including detoxification, nutrient metabolism, and hepatocyte proliferation. While CAR activation has been previously linked to higher ploidy, the underlying mechanisms are not fully known. Here, we uncover a basal role for CAR in maintaining hepatocyte ploidy, such that CAR deletion increases the number of diploid (2c) hepatocytes with a concomitant reduction in tetraploid (4c) hepatocytes. We demonstrate that CAR controls the de novo dNTP synthesis by directly transactivating the Ribonucleotide Reductase-M2 (RRM2) gene, which encodes the rate-limiting catalytic subunit of the enzyme, ribonucleotide reductase. Further, we find that the ligand-dependent CAR activation is sufficient to induce several genes involved in the de novo dNTP synthesis pathways, resulting in higher hepatic dATP and dTTP levels within the liver. Importantly, overexpressing RRM2 levels in CAR knockouts led to increased DNA synthesis and tetraploid (4c) hepatocytes compared to the control mice. Importantly, we demonstrate that CAR-mediated DNA synthesis in liver cells is dependent on catalytically active RRM2 function. Taken together, these findings reveal that the CAR-mediated RRM2 regulation contributes towards DNA synthesis and thereby maintains hepatocyte ploidy. O_FIG O_LINKSMALLFIG WIDTH=200 HEIGHT=68 SRC="FIGDIR/small/651109v2_ufig1.gif" ALT="Figure 1"> View larger version (29K): org.highwire.dtl.DTLVardef@1750110org.highwire.dtl.DTLVardef@98f579org.highwire.dtl.DTLVardef@1c0e87org.highwire.dtl.DTLVardef@1fdfda5_HPS_FORMAT_FIGEXP M_FIG C_FIG

cell biology↗

bioRxiv2024

ESRP2-microRNA-122 axis directs the postnatal onset of liver polyploidization and maturation

Hepatocyte polyploidy and maturity are critical to acquiring specialized liver functions. Multiple intra- and extracellular factors influence ploidy, but how they cooperate temporally to steer liver polyploidization and maturation or how post-transcriptional mechanisms integrate into these paradigms is unknown. Here, we identified an important regulatory hierarchy in which postnatal activation of Epithelial-Splicing-Regulatory-Protein-2 (ESRP2) stimulates biogenesis of liver-specific microRNA (miR-122), thereby facilitating polyploidization, maturation, and functional competence of hepatocytes. By determining transcriptome-wide protein-RNA interactions in vivo and integrating them with single-cell and bulk hepatocyte RNA-seq datasets, we delineate an ESRP2-driven RNA processing program that drives sequential replacement of fetal-to-adult transcript isoforms. Specifically, ESRP2 binds the primary miR-122 host gene transcript to promote its processing/biogenesis. Combining constitutive and inducible ESRP2 gain- and loss-of-function mice models with miR-122 rescue experiments, we demonstrate that timed activation of ESRP2 augments miR-122-driven program of cytokinesis failure, ensuring proper onset and extent of hepatocyte polyploidization.

developmental biology↗

bioRxiv2021

Coordinated Cross-Talk Between the Myc and Mlx Networks in Liver Regeneration and Neoplasia

Background & AimsThe c-Myc (Myc) bHLH-ZIP transcription factor is deregulated in most cancers. In association with Max, Myc controls target genes that supervise metabolism, ribosome biogenesis, translation and proliferation. This "Myc Network" cross-talks with the "Mlx Network", which consists of the Myc-like proteins MondoA and ChREBP and Max-like Mlx. Together, this "Extended Myc Network" regulates both common and distinct genes targets. Here we studied the consequence of Myc and/or Mlx ablation in the liver, particularly those pertaining to hepatocyte proliferation, metabolism and spontaneous tumorigenesis. MethodsWe examined the ability of hepatocytes lacking Mlx (MlxKO) or Myc+Mlx (double KO or DKO) to repopulate the liver over an extended period of time in a murine model of Type I tyrosinemia. We also compared this and other relevant behaviors, phenotypes and transcriptomes of the livers to those from previously characterized MycKO, ChrebpKO and MycKO x ChrebpKO mice. ResultsHepatocyte regenerative potential deteriorated as the Extended Myc Network was progressively dismantled. Genes and pathways dysregulated in MlxKO and DKO hepatocytes included those pertaining to translation, mitochondrial function and non-alcoholic fatty liver disease (NAFLD). The Myc and Mlx Networks were shown to cross-talk, with the latter playing a disproportionate role in target gene regulation. All cohorts also developed NAFLD and molecular evidence of early steatohepatitis. Finally, MlxKO and DKO mice displayed extensive hepatic adenomatosis. ConclusionsIn addition to demonstrating cooperation between the Myc and Mlx Networks, this study revealed the latter to be more important in maintaining proliferative, metabolic and translational homeostasis, while concurrently serving as a suppressor of benign tumorigenesis. SynopsisThe Myc and Mlx Networks exhibit extensive cross-talk and regulate distinct but overlapping sets of transcriptional targets. The current work demonstrates the cooperation between these two Networks in supporting the regenerative capabilities of normal hepatocytes while also revealing that the Mlx Network serves as a suppressor of spontaneous hepatic adenomatosis

cancer biology↗