ED Sciences de la Vie et de la Santé
Neuronal and microglial function of P2X4 receptor in Amyotrophic lateral sclerosis and its potential use as a biomarker
by Sara CARRACEDO VICENTE (Institut des Maladies Neurodégénératives)
The defense will take place at h00 - Amphithéâtre Broca nouvelle aquitaine 3 Bâtiment Neurocampus Université de Bordeaux, 146 Rue Léo Saignat, 33000 Bordeaux, France
in front of the jury composed of
- Eric BOUE-GRABOT - Directeur de recherche - Université de Bordeaux - Directeur de these
- Séverine BOILLEE - Directrice de recherche - Institut du Cerveau - Rapporteur
- Philippe SEGUELA - Professeur - McGill University - Rapporteur
- Agnès NADJAR - Professeure - Neurocentre Magendie - Examinateur
- Bart EGGEN - Professeur - University Medical Center Groningen - Examinateur
Amyotrophic lateral sclerosis (ALS) is a neurodegenerative disease characterized by the progressive degeneration of motor neurons (MNs), driven by misfolded protein aggregation and neuroimmune dysregulation. P2X4 receptor, an ATP-gated ion channel expressed in neurons and glial cells, has emerged as a key player in ALS pathogenesis. Under normal conditions, P2X4 is primarily internalized, maintaining low surface expression. However, in pathological states such as ALS, P2X4 is increasingly localized to the cell surface. Using double-transgenic SOD1 G93A (SOD1) mice expressing either an internalization-defective P2X4-mCherryIN knock-in or invalidated for the P2X4 gene, it was reported that both the increase in surface P2X4 and its absence improved disease outcomes. These findings suggest complex cell-specific roles of P2X4 receptor, which remains unexplored. This study aims to investigate the distinct neuronal and microglial roles of the P2X4 receptor in ALS using triple-transgenic mice designed to selectively manipulate P2X4 expression in microglia/macrophages or neurons in the SOD1 mice model. Our results demonstrate that an increase in neuronal surface P2X4 accelerates ALS progression, while its upregulation in microglia/macrophages slows disease progression. In microglia, surface P2X4 mitigates immune overactivation in the spinal cord and reduces immune cell infiltration along MN axons in SOD1 mice. Consistent with this data, cell-specific deletion of P2X4 had opposing effects on ALS progression: the absence of P2X4 in neurons was protective, whereas its deletion in microglia/macrophages worsened disease outcomes. Altogether, we found that neuronal and microglial P2X4 play dual and opposing roles in ALS pathophysiology. In SOD1 mice, elevated surface P2X4 expression was previously observed in peritoneal macrophages even before symptom onset. Translating this finding to humans, we developed a flow cytometry-based method to measure the surface-to-total ratio of P2X4 in monocytes from peripheral blood samples. ALS patients, particularly women, exhibited significantly higher surface P2X4 levels in monocytes compared to patients with other neuromuscular diseases. This aberrant surface P2X4 expression was detected regardless of the disease onset and etiology, underscoring the broad utility of the receptor as a blood-based biomarker for ALS. In conclusion, our data reveal dual and opposing roles of neuronal and microglial P2X4 receptors in ALS progression and highlight its potential as a therapeutic target and biomarker for ALS.
ED Sciences Physiques et de l'Ingénieur
Study of the proton and neutron contributions to the excitation of the 2+ states of Silicon isotopes between N=20 and N=28
by Quentin DELIGNAC (Laboratoire de Physique des 2 Infinis de Bordeaux)
The defense will take place at 14h00 - Amphithéâtre 1 - Bâtiment A9 Amphithéâtre 1 - Bâtiment A9 351 Cours de la Libération, 33400 Talence
in front of the jury composed of
- Stéphane GREVY - Directeur de recherche - LP2I Bordeaux - CNRS - Directeur de these
- Magdalena ZIELINSKA - Cadre scientifique des EPIC - DPhN - CEA - Rapporteur
- Hervé SAVAJOLS - Directeur de recherche - GANIL - CNRS - Rapporteur
- Marlène ASSIE - Chargée de recherche - IJCLAB - CNRS - Examinateur
- Thomas ROGER - Chargé de recherche - GANIL - CNRS - Examinateur
- Nadezda SMIRNOVA - Professeure des universités - LP2I Bordeaux - Université de Bordeaux - Examinateur
This thesis focuses on the experimental study of the structure of exotic neutron-rich nuclei in the vicinity of the N=20 and N=28 shell closures in order to constrain the nucleon-nucleon interaction. Previous studies have shown a sudden emergence of deformation at N=20 between the 34Si and 32Mg isotones, while a region of deformation develops along the entire N=28 isotonic chain between the doubly magical and spherical 48Ca nucleus (20 protons/28 neutrons) and the 42Si nucleus, which is extremely deformed despite its semi-magical character (14 protons/28 neutrons). Furthermore, while the deformation of 32Mg is due to the reduction of the N=20 shell closure, it has been shown that the deformation at N=28 results from neutron excitations above the N=28 shell closure and also from proton excitations above the Z=14 subshell. These reductions in shell closures are interpreted as resulting from the monopole tensor component of the nucleon-nucleon interaction, but could also, at N=28, be favoured by a reduction in the spin-orbit force. The aim of this work was to follow the evolution of the deformation along the Si isotopic chain, between the spherical nucleus 34Si (N=20) and the deformed nucleus 42Si (N=28) with particular attention to the development of the proton-induced collectivity, absent at N=20 and which appears to be essential for describing the N=28 region. To achieve this purpose, an experiment was performed to measure the cross-section of inelastic proton scattering and the cross-section of Coulomb excitation, allowing the determination of B(E2, 0+ -> 2) values for the 36Si and 38Si nuclei. The experiment was set up during the 2022 campaign of the LISE (Ligne d'Ions Super Epluchés) spectrometer at GANIL (Grand Accélérateur National d'Ions Lourds). The spectrometer was used to produce and select the nuclei of interest, 36Si and 38Si, as well as reference nuclei such as 40S and 42S. In order to measure the cross-sections, the experiment was composed of two independent setups placed in series on the physics line to use the same radioactive beam, maximising the use of the beam and ensuring the same experimental conditions for both measurements (‘'Brochette‘' mode experiment). The first setup was ACTAR TPC detector (Active Target Time Projection Chamber) to measure the cross-section of inelastic proton scattering. The second setup was dedicated to the study of Coulomb excitation by measuring the values of B(E2, 0+ -> 2+) and required the deployment of different types of detectors to measure the kinematics of heavy ions (energy, positions) and to measure gamma radiation from the de-excitation of nuclei. In this manuscript, we will present the Coulomb excitation results and give new experimental B(E2) values for the 36Si and 38Si nuclei. On the theoretical side, these results will provide an opportunity to revisit the SDPF interaction developed to describe the evolution of the nuclear structure in the N=20 and N=28 regions.