Biology subjects

Dardalhon, V.

Publications and source records attributed to Dardalhon, V..

6 recordsLinked to original sources

bioRxiv2025

Intrathymic progenitor cell transplantation restores T cell development through ILC3-TEC crosstalk

T cell deficiencies are commonly treated by intravenous hematopoietic stem/progenitor cell (HSPC) transplantation. However, this approach often leads to delayed and incomplete T cell reconstitution, partly due to impaired thymic function. In contrast, intrathymic delivery of HSPCs enables rapid, thymus-autonomous T cell development. Using a ZAP-70-deficient mouse model of severe immunodeficiency, we show that intrathymic transplantation of wild-type HSPCs results in robust thymic engraftment, with mature T cells and FOXP3+ regulatory T cells (Treg) detectable within four weeks. This reconstitution parallels the regeneration of a functional thymic medulla and the emergence of mature medullary thymic epithelial cells (mTECs). Importantly, we identify an early wave of donor-derived ROR{gamma}T+ ILC3s that correlates with medullary regeneration. While dispensable for steady-state thymopoiesis, ILC3s accelerate medulla formation and support optimal T cell differentiation in this immunodeficient setting. These findings uncover a critical role for ILC3-TEC crosstalk in thymic repair and highlight intrathymic HSPC transplantation as a strategy to enhance immune reconstitution in immunodeficient hosts.

immunology↗

bioRxiv2023

Single molecule DNA methylation and hydroxymethylation reveal unique epigenetic identity profiles of T helper cells

Both identity and plasticity of CD4 T helper (Th) cells are regulated in part by epigenetic mechanisms. However, a method that reliably and readily profiles DNA base modifications is still needed to finely study Th cell differentiation. Cytosine methylation (5mC) and cytosine hydroxymethylation (5hmC) are DNA modifications that identify stable cell phenotypes but their potential to characterize intermediate cell transitions has not yet been evaluated. To assess transition states in Th cells, we developed a new method to profile Th cell identity using cas9-targeted single molecule nanopore sequencing and found that 5mC and 5hmC can be used as markers of cellular identity. Targeting as few as 10 selected genomic loci, we were able to distinguish major differentiated T cell subtypes as well as intermediate phenotypes by their native DNA 5mC/5hmC patterns. Moreover, by using off-target sequences we were able to infer transcription factor activities relevant to each cell subtype. Our analysis demonstrates the importance of epigenetic regulation by 5mC and 5hmC modifications in the establishment of Th cell identity. Furthermore, our data highlight the potential to exploit this immune profiling application to elucidate the pathogenic role of Th transition states in autoimmune diseases.

immunology↗

bioRxiv2022

Arginine-dependent hypusination of the eukaryotic translation initiation factor (eIF)5A drives erythroid lineage differentiation

Metabolic programs contribute to hematopoietic stem and progenitor cell (HSPC) fate but it is not known whether the metabolic regulation of protein synthesis controls HSPC differentiation. We discovered that SLC7A1/CAT1-dependent arginine uptake and its catabolism to spermidine control the erythroid specification of HSPCs via activation of eukaryotic translation initiation factor 5A (eIF5A). eIF5A activity is dependent on the metabolism of spermidine to hypusine and inhibiting hypusine synthesis abrogates erythropoiesis and diverts EPO-stimulated HSPCs to a myeloid fate. Proteomic profiling reveals mitochondrial translation to be a critical target of hypusinated eIF5A and induction of mitochondrial function partially rescues erythropoiesis in the absence of hypusine. Within the hypusine network, ribosomal proteins are highly enriched and we identify defective eIF5A hypusination in erythroid pathologies caused by abnormal ribosome biogenesis. Thus, eIF5A-dependent protein synthesis is critical in the branching of erythro-myeloid differentiation and attenuated eIF5A activity characterizes ribosomal protein-linked disorders of ineffective erythropoiesis.

physiology↗

bioRxiv2021

Ras/MAPK signalling intensity defines subclonal fitness in a mouse model of primary and metastatic hepatocellular carcinoma

Quantitative differences in signal transduction are to date an understudied feature of tumour heterogeneity. The MAPK Erk pathway, which is activated in a large proportion of human tumours, is a prototypic example of distinct cell fates being driven by signal intensity. We have used primary hepatocyte precursors transformed with different dosages of an oncogenic form of Ras to model subclonal variations in MAPK signalling. Orthotopic allografts of Ras-transformed cells in immunocompromised mice gave rise to fast-growing aggressive tumours, both at the primary location and in the peritoneal cavity. Fluorescent labelling of cells expressing different oncogene levels, and consequently varying levels of MAPK Erk activation, highlighted the selection processes operating at the two sites of tumour growth. Indeed, significantly higher Ras expression was observed in primary as compared to metastatic tumours, despite the evolutionary trade-off of increased apoptotic death in the liver that correlated with high Ras dosage. Analysis of the immune tumoral microenvironment at the two locations suggests that fast metastatic growth in the immunocompromised setting is abrogated in immunocompetent animals due to efficient antigen presentation by peritoneal dendritic cells. Furthermore, our data indicate that, in contrast to the metastatic outgrowth, strong MAPK signalling is required in the primary liver tumours to resist elimination by NK cells. Overall, this study describes a quantitative aspect of tumour heterogeneity and highlights potential vulnerability of a subtype of hepatocellular carcinoma as a function of MAPK Erk signalling intensity.

cancer biology↗

bioRxiv2020

Alpha-ketoglutarate inhibits Regulatory T cell differentiation by coupling lipidome remodelling to mitochondrial metabolism

The differentiation of CD4 T cells to a specific effector fate is metabolically regulated, integrating glycolysis and mitochondrial oxidative phosphorylation (OXPHOS) with transcriptional and epigenetic changes. OXPHOS is tightly coordinated with the tricarboxylic acid (TCA) cycle but the precise role of TCA intermediates in CD4 T cell differentiation remain unclear. Here we demonstrate that -ketoglutarate (KG) inhibited regulatory T cell (Treg) generation while conversely, increasing Th1 polarization. In accord with these data, KG promoted the effector profile of Treg-polarized chimeric antigen receptor-engineered T cells against the ErbB2 tumor antigen. Mechanistically, KG significantly altered transcripts of genes involved in lipid-related processes, inducing a robust lipidome-wide remodelling and decreased membrane fluidity. A massive increase in storage and mitochondria lipids was associated with expression of mitochondrial genes and a significantly augmented OXPHOS. Notably, inhibition of succinate dehydrogenase activity, the bridge between the TCA cycle and the electron transport chain, enforced Treg generation. Thus, our study identifies novel connections between KG, lipidome remodelling and OXPHOS in CD4 T cell fate decisions.

immunology↗

bioRxiv2019

Ki-67 supports global gene expression programmes driving tumourigenesis

Recent studies have shown that the cell proliferation antigen Ki-67 is not required for cell proliferation. Here, we demonstrate that Ki-67 enables implementation of transcriptional programmes conferring cellular plasticity, and is required for each step of tumour initiation, growth and metastasis. Ki-67 knockout causes global transcriptome remodelling, which, in mammary carcinoma cells, inhibits the epithelial-mesenchymal transition in a polycomb-repressive complex 2-dependent manner. This results in suppression of stem cell characteristics and sensitisation to various drug classes. Cancer cells lacking Ki-67 proliferate normally in vivo, but tumour growth is inhibited due to disrupted angiogenesis, and metastasis is abrogated. Finally, mice lacking Ki-67 are resistant to chemical or genetic induction of intestinal tumourigenesis. Thus, Ki-67, which is expressed in all proliferating cancer cells, confers the plasticity required for different steps of carcinogenesis.

cancer biology↗