Biology subjects

Ollivier, J.

Publications and source records attributed to Ollivier, J..

4 recordsLinked to original sources

bioRxiv2026

Polarized neutrons for the study of individual and collective fast dynamics in proteins

Neutron scattering is a powerful technique to investigate atomic structures and molecular dynamics of proteins at the nano-scale. When it comes to dynamics, incoherent and coherent scattering respectively provide information on the single and collective dynamics of nuclei. In proteins, hydrogen has the highest incoherent cross-section, and it is common practice to overlook the contribution of coherent terms stemming from all nuclei. However, the fast collective dynamics of heavier nuclei could also be studied if coherent scattering and incoherent scattering were experimentally separated. The recent advent of polarized neutron spectroscopy with sufficient flux and energy resolution has made it possible, and opens new perspectives to investigate the relative importance of coherent scattering and the information it provides on biological samples. The present study reports on the use of polarized quasi-elastic neutron scattering (QENS) and the application of a minimalistic model adapted to both individual and collective dynamics. Using a perdeuterated green fluorescent protein as a model globular protein, the study provides an interpretation of the dynamical parameters obtained with QENS, and a comparative study of the Elastic Coherent and Incoherent Scattering Factor. Based on both experiments and calculations, we discuss the relative importance of distinct and self components of coherent scattering, which is often wrongly assumed to be representative of collective dynamics only. The results highlight the current impediments rendering complicated a straightforward analysis of fast collective dynamics in hydrated protein samples.

biophysics↗

bioRxiv2026

Early microglial activation in the TME enables FLASH-RT to eradicate medulloblastoma while promoting neuron-astrocyte crosstalk to minimize toxicity in the hippocampus

BackgroundFLASH-RT defines a promising treatment modality against medulloblastoma, as it minimizes treatment-related complications. To support its clinical translation, we dissected the cellular and molecular determinants of the FLASH response in the tumor-microenvironment (TME) and healthy hippocampus using an orthotopic human medulloblastoma mouse model treated with a hypo-fractionated FLASH regimen. MethodsFive cohorts of 4 weeks-old UW228-MB-bearing female nude mice (n=57) were irradiated, or sham-irradiated using 3x10 Gy (BED=60), delivered 48h apart at 0.1 Gy/s (CONV) or 5.5x106 Gy/s (FLASH) using an electron beam (eRT6). Digital spatial profiling (DSP) was performed 24h after radiotherapy in one cohort, while the four other cohorts were followed for long-term tumor response, cognition, and neuroinflammation. ResultsBoth CONV and FLASH-RT induced a complete and long-lasting anti-tumor response in 100% of animals associated with cognitive decline. However, more mice maintained a very good discrimination score after FLASH exposure (38%) than CONV (7%). DSP revealed a sustained microglial activation in the cerebellar tumor micro-environment, where FLASH enhanced expression of genes with phagocytic and proteolytic activity. In the tumor free hippocampus, FLASH exposure induced a preferential neuron/astrocyte transcriptional crosstalk, which manifested over protracted times to minimize neuroinflammation and cognitive complications. ConclusionThe study shows the tumor-ablative efficacy of hypo-fractionated FLASH-RT in a human medulloblastoma mouse model. It is associated with qualitatively distinct transcriptional signatures prone to tumor and debris clearance mediated by microglial cells of the TME. Moreover, in the hippocampus, FLASH mitigates radiation-induced neurotoxicity by enhancing genes involved in synaptic plasticity, attenuating neuroinflammation, and preserving metabolic function. Key PointsO_LIComplete response of medulloblastoma and reduction of neurotoxicity with hypo-fractionated FLASH regimen. C_LIO_LIClearance-prone phagocytic and proteolytic activity in the microglia of the TME. C_LIO_LINeuron/astrocyte transcriptional crosstalk in the hippocampus. C_LI Importance of the studyThis study constitutes a milestone for the future implementation of FLASH-RT in the treatment of children with brain cancer. It shows that FLASH does not protect medulloblastoma and on the contrary can be ablative when delivered in 3 fractions of 10 Gy. FLASH promotes a metabolically active, phagocytosis-prone phenotype in microglial cells consistent with immune activation and tumor surveillance, in contrast to the proliferative and immunosuppressive signaling programs induced by CONV. It also shows how FLASH may differentially shape long-term brain function in patients with brain tumors by modifying the transcriptional program of hippocampal subregions known to be critical for memory encoding, pattern separation, and consolidation. In summary, this study supports the idea that FLASH has the potential to shift treatment paradigms and change the dismal therapeutic outcome in patients with brain cancer.

cancer biology↗

bioRxiv2024

Modification of the microstructure of the CERN- CLEAR-VHEE beam at the picosecond scale modifies ZFE morphogenesis but has no impact on hydrogen peroxide production.

FLASH has emerged as a significant breakthrough for the future of radiation oncology, as it reduces complications while preserving the tumor killing efficacy. To define the beam parameters for future clinical translation, Very High Energy Electrons (VHEE) delivered at CLEAR and able to reach deep seated tumors were used in conjunction with a FLASH-validated Intermediate Energy Electron (IIE) beam and a 160-225 keV X-ray beam, collectively able to deliver dose rates spanning from 1 Gy/min to 1011 Gy/s. High-throughput chemical assays were used to investigate radiochemical effects of FLASH, while zebrafish embryos served as a model to evaluate its impact on biological outcomes and morphogenesis. This study is the first comprehensive exploration investigating the impact of a large range of dose rates and various temporal parameters from early physico-chemical events to a complex biological system. Data derived at CLEAR revealed that the intensity of the bunch is a critical factor for observing the sparing effect of FLASH and uncovered an unforeseen biological response when electrons are delivered over the picosecond timescale. Present data also suggests that scanning with high intensity beamlets will be optimal for the future clinical translation of FLASH. HighlightsTo investigate the physics parameters required to trigger the FLASH sparing effect, CLEAR/VHEE/CERN beam macro/microstructure was varied. We show that delivery at the picosecond scale: - reduces alteration in the morphogenesis of zebrafish embryos, but - has no impact on secondary hydrogen peroxide production, Graphical abstract O_FIG O_LINKSMALLFIG WIDTH=175 HEIGHT=200 SRC="FIGDIR/small/629203v1_ufig1.gif" ALT="Figure 1"> View larger version (22K): org.highwire.dtl.DTLVardef@1df896aorg.highwire.dtl.DTLVardef@b6b824org.highwire.dtl.DTLVardef@1f35964org.highwire.dtl.DTLVardef@171d60f_HPS_FORMAT_FIGEXP M_FIG C_FIG

cancer biology↗

bioRxiv2023

FLASH-RT does not affect chromosome translocations and junction structures beyond that of CONV-RT dose-rates

The molecular and cellular mechanisms driving the enhanced therapeutic ratio of ultra-high dose-rate radiotherapy (FLASH-RT) over slower conventional (CONV-RT) radiotherapy dose-rate remain to be elucidated. However, attenuated DNA damage and transient oxygen depletion are among several proposed models. Here, we tested whether FLASH-RT under physioxic (4% O2) and hypoxic conditions ([≤]2% O2) reduces genome-wide translocations relative to CONV-RT and whether any differences identified revert under normoxic (21% O2) conditions. We employed high-throughput rejoin and genome-wide translocation sequencing (HTGTS-JoinT-seq), using S. aureus and S. pyogenes Cas9 "bait" DNA double strand breaks (DSBs), to measure differences in bait-proximal repair and their genome-wide translocations to "prey" DSBs generated by electron beam CONV-RT (0.08-0.13Gy/s) and FLASH-RT (1x102-5x106 Gy/s), under varying ionizing radiation (IR) doses and oxygen tensions. Normoxic and physioxic irradiation of HEK293T cells increased translocations at the cost of decreasing bait-proximal repair but were indistinguishable between CONV-RT and FLASH-RT. Although no apparent increase in chromosome translocations was observed with hypoxia-induced apoptosis, the combined decrease in oxygen tension with IR dose-rate modulation did not reveal significant differences in the level of translocations nor in their junction structures. Thus, Irrespective of oxygen tension, FLASH-RT produces translocations and junction structures at levels and proportions that are indistinguishable from CONV-RT.

molecular biology↗