Biology subjects

Andersson, O.

Publications and source records attributed to Andersson, O..

7 recordsLinked to original sources

bioRxiv2025

Cholangiocytes contribute to hepatocyte regeneration after partial liver injury during growth spurt in zebrafish

The livers regenerative ability depends on injury extent. Minor injuries are repaired by hepatocyte self-duplication, while severe damage triggers cholangiocyte involvement in hepatocyte recovery. This paradigm is well-documented for adult animals but is less explored during rapid growth. We design two new partial liver injury models in zebrafish, which were investigated during growth spurts: 1) partial ablation, killing half the hepatocytes; and 2) partial hepatectomy, removing half a liver lobe. In both injuries, de novo hepatocytes emerged alongside existing ones. Single-cell transcriptomics and lineage tracing with Cre-driver lines generated by genome editing identified cholangiocytes as the source of de novo hepatocytes. We further identify active mTORC1 signalling in the uninjured liver of growing animal to be a regulator of the enhanced plasticity of cholangiocytes. Our study suggests cholangiocyte-to-hepatocyte transdifferentiation as the primary mechanism of liver regeneration during periods of rapid growth.

developmental biology↗

bioRxiv2025

Deciphering the zebrafish hepatic duct heterogeneity and cell plasticity using lineage tracing and single-cell transcriptomics

Despite the livers recognized regenerative potential, the role of the hepatic ductal cells (a.k.a. biliary epithelial cells), its heterogeneity, and functionality remain incompletely understood in this process. This study provides a comprehensive examination of the molecular and cellular mechanisms underpinning liver ductal development and liver regeneration in zebrafish, with a spotlight on the functional roles of her family genes in these processes. Using state-of-the-art knock-in zebrafish models and single-cell transcriptomics we reveal the differential expression patterns of the different her genes, of which her2, her6, and her9, were identified as specific molecular signatures for distinguishing different ductal cell types with unique morphology and spatial distribution. Particularly, her9 serves as a pan-ductal marker and shows responsiveness to the synergistic effect of Notch and BMP signaling. By analyzing multiple single-cell RNA-seq datasets, we identify numerous ductal markers which are functional proteins for ductal integrity, and most notably CRISPR mutagenesis demonstrates that her9 is essential for hepatocyte recovery. Using multiple transgenic and knock-in zebrafish lines and genetic fate mapping, we provide a detailed characterization of the ductal remodeling process under development and extreme loss of intra-hepatic duct, highlighting the remarkable ductal cell plasticity. Single-cell transcriptomics of lineage-traced her9-expressing liver ducts in static and regenerative states uncover distinct cell clusters with unique molecular signatures and morphology, reflecting the livers regenerative dynamics and highlight relevant key biological processes that could be leveraged to expedite liver regeneration.

developmental biology↗

bioRxiv2024

Characterization of liver-pancreas crosstalk following beta-cell loss reveals a role for the molybdenum cofactor in beta-cell regeneration

Regeneration of insulin-producing {beta}-cells is an alternative avenue to manage diabetes, and it is crucial to unravel this process in vivo during physiological responses to the lack of {beta}-cells. Here, we aimed to characterize how hepatocytes can contribute to {beta}-cell regeneration in a zebrafish model of {beta}-cell ablation. Using lineage-tracing, we show that hepatocytes do not directly convert into {beta}-cells even under extreme {beta}-cell ablation conditions. A transcriptomics analysis of isolated hepatocytes following {beta}-cell ablation displayed altered lipid- and glucose-related processes. Based on the transcriptomics, we performed a genetic screen that uncovers a potential role for the molybdenum cofactor (Moco) biosynthetic pathway in {beta}-cell regeneration and glucose metabolism in zebrafish. Consistently, Mocs2 haploinsufficiency in mice indicated dysregulated glucose metabolism and liver function. Together, our study sheds light on the liver-pancreas crosstalk and suggests that the molybdenum cofactor biosynthesis pathway should be further studied in relation to glucose metabolism and diabetes.

developmental biology↗

bioRxiv2023

Biodistribution of DNA-origami nanostructures in live zebrafish embryos with single-cell resolution

DNA origami-based nanotechnology is a versatile tool for exploring fundamental biological questions and holds significant promise for future biomedical applications. However, the development of DNA origami-based therapeutic agents is hindered by the challenge of translating in vitro performance into effective applications in vivo. Here, we exploit the optical transparency of the embryonic zebrafish to track intravenously injected, fluorescently labelled wireframe DNA origami nanostructures. Our approach integrated long-term, high-resolution imaging of transgenic live embryos with single-cell RNA sequencing, to elucidate the biodistribution of DNA nanostructures over time, up to 3 days post-injection (dpi). Notably, we observed rapid accumulation of nanostructures in the caudal hematopoietic tissue (CHT), akin to the fetal liver in mammals. We tested the effects of coating the nanostructures with an oligolysine PEG copolymer (K-PEG), a widely used strategy to enhance their stability. The K-PEG coating mitigated the accumulation rate in CHT, enabling higher percentages of the nanostructures to engage with other tissues. Additionally, our findings highlighted the pivotal role of scavenger endothelial cells in DNA origami clearance, with K-PEG offering sustained protection for the nanostructures at the CHT. Furthermore, by monitoring DNA origami in a transgenic zebrafish line designed for targeted macrophage ablation, we found that macrophages contribute to nanostructure clearance at later time points. This study introduces a framework for the analyses of the biodistribution and clearance of DNA origami nanostructures in vivo with single cell resolution and establishes a foundation for the investigation of DNA origami-based nanomedicines in animal models.

bioengineering↗

bioRxiv2023

Inhibition of mammalian mtDNA transcription paradoxically activates liver fatty acid oxidation to reverse diet-induced hepatosteatosis and obesity

The oxidative phosphorylation (OXPHOS) system in mammalian mitochondria plays a key role in harvesting energy from ingested nutrients1, 2. Mitochondrial metabolism is very dynamic and can be reprogrammed to support both catabolic and anabolic reactions, depending on physiological demands or disease states3, 4. Rewiring of mitochondrial metabolism is intricately linked to metabolic diseases5, 6 and is also necessary to promote tumour growth7-11. Here, we demonstrate that per oral treatment with an inhibitor of mitochondrial transcription (IMT)11 shifts whole animal metabolism towards fatty acid oxidation, which, in turn, leads to rapid normalization of body weight, reversal of hepatosteatosis and restoration of glucose tolerance in mice on high-fat diet. Paradoxically, the IMT treatment causes a severe reduction of OXPHOS capacity concomitant with a marked upregulation of fatty acid oxidation in the liver, as determined by proteomics and non-targeted metabolomics analyses. The IMT treatment leads to a marked reduction of complex I, the main dehydrogenase that feeds electrons into the ubiquinone (Q) pool, whereas the levels of electron transfer flavoprotein dehydrogenase (ETF-DH) and other dehydrogenases connected to the Q pool are increased. This rewiring of metabolism caused by reduced mtDNA expression in the liver provides a novel principle for drug treatment of obesity and obesity-related pathology.

physiology↗

bioRxiv2022

Efficient knock-in method enabling lineage tracing in zebrafish

The CRISPR-Cas9 system aids generation of knock-in zebrafish lines, but it has been hard to integrate large constructs and avoid disrupting the targeted genes. Here we devised a 3 knock-in strategy of PCR-amplified dsDNA, which coded for fluorescence proteins and Cre recombinase in frame with the endogenous gene but separated from each other by self-cleavable peptides. Primers with 5 AmC6 end-protections generated improved PCR amplicons harboring either short or long homologous arms, which were co-injected with pre-assembled Cas9/gRNA ribonucleoprotein complexes for early integration. We targeted four genetic loci (krt92, nkx6.1, krt4, and id2a) and generated ten knock-in lines, which function as reporters for the endogenous gene expression. The knocked-in iCre or CreERT2 were used for lineage tracing, which suggested nkx6.1+ cells are multipotent pancreatic progenitors that gradually restrict to bipotent duct; while id2a+ cells are multipotent in both liver and pancreas and gradually restrict to ductal cells. Additionally, hepatic id2a+ duct show progenitor properties upon extreme hepatocyte loss. Thus, we present an efficient knock-in technique with widespread use for both cellular labelling and lineage tracing.

genetics↗

bioRxiv2021

Regenerating insulin-producing β-cells ectopically from a mesodermal origin in the absence of endothelial specification

To investigate the role of the vasculature in pancreatic {beta}-cell regeneration, we crossed a zebrafish {beta}-cell ablation model into the avascular npas4l mutant (i.e. cloche). Surprisingly, {beta}-cell regeneration increased markedly in npas4l mutants owing to the ectopic differentiation of {beta}-cells in the mesenchyme, a phenotype not previously reported in any models. The ectopic {beta}-cells expressed endocrine markers of pancreatic {beta}-cells, and also reduced glucose levels in the {beta}-cell ablation model. Through lineage tracing, we determined that the vast majority of these ectopic {beta}-cells derived from the mesodermal lineage. Notably, ectopic {beta}-cells were found in npas4l mutants as well as following knockdown of the endothelial determinant Etv2. Together, these data indicate that in the absence of endothelial specification, mesodermal cells possess a remarkable plasticity enabling them to form {beta}-cells, which are normally endodermal in origin. Understanding the restriction of this differentiation plasticity will help exploit an alternative source for {beta}-cell regeneration.

developmental biology↗