Oberlin, E. | bioRxiv Science

bioRxiv2023

VRK3 depletion induces cell cycle arrest and metabolic reprogramming of Pontine Diffuse Midline Glioma (DMG)-K27 altered cells

We previously identified VRK3 as a specific vulnerability in DMG-H3K27M cells in a synthetic lethality screen targeting the whole kinome. The aim of the present study was to elucidate the mechanisms by which VRK3 depletion impact DMG-K27M cell fitness. Gene expression studies after VRK3 knockdown emphasized the inhibition of genes involved in G1/S transition of the cell cycle resulting in growth arrest in G1. Additionally, a massive modulation of genes involved in chromosome segregation was observed, concomitantly with a reduction in the level of phosphorylation of serine 10 and serine 28 of histone H3 supporting the regulation of chromatin condensation during cell division. This last effect could be partly due to a concomitant decrease of the chromatin kinase VRK1 in DMG following VRK3 knock-down. Furthermore, a metabolic switch specific to VRK3 function was observed towards increased oxidative phosphorylation without change in mitochondria content, that we hypothesized would represent a cell rescue mechanism. This study further explored the vulnerability of DMG-H3K27M cells to VRK3 depletion suggesting potential therapeutic combinations, e.g. with the mitochondrial ClpP protease activator ONC201.

cancer biology↗

bioRxiv2018

Hierarchical organization of developing HSPC in the human embryonic liver

Despite advances to engineer transplantable hematopoietic stem and progenitor cells (HSPCs) for research and therapy, an in depth characterization of the developing human hematopoietic system is still lacking. The human embryonic liver is at the crossroad of several hematopoietic sites and harbours a complex hematopoietic hierarchy including the first, actively dividing, HSPCs that will further seed the definitive hematopoietic organs. However few is known about the hierarchical phenotypic and functional hematopoietic organization operating at these stages of development.\n\nHere, by using a combination of four endothelial and hematopoietic surface markers i.e. the endothelial-specific marker VE-cadherin, the pan-leukocyte antigen CD45, the hemato-endothelial marker CD34 and the Angiotensin-Converting Enzyme (ACE, CD143), encompassing all early human HSPCs, we identified a hematopoietic hierarchy and, among it, a population co-expressing the four markers that uniquely harbored a proliferation and differentiation potential both ex vivo and in vivo. Moreover, we traced back this population to the yolk sac and AGM sites of hematopoietic emergence. Taken together, our data will help to identify human HSPC self-renewal and amplification mechanisms for future cell therapies.\n\nSUMMARY STATEMENTWe uncover the phenotypic and functional hematopoietic hierarchy operating in the early human embryo. It will bring insights into the mechanisms driving hematopoietic stem cell self-renewal for future cell therapies.

developmental biology↗