Alpha-synuclein (aSyn) is a cytosolic 140 amino acids protein and maintaining its cellular level is pivotal to preventing neuronal cell death. In health, aSyn is enriched in the presynaptic terminal and known to interact with the VAMP2 protein responsible for neurotransmission, although the outcomes in neurotransmission are elusive. On the other hand, in Parkinson’s disease patients, aSyn and its aggregate which is composed with organellar membranes and biomolecules are found in the soma and overall neurons. Indeed, emerging evidence suggests the secretion of aSyn aggregates depends on late endosomal/lysosomal VAMP7, which implies a possible aSyn-VAMP7 interaction. Several model systems have brought an invaluable understanding of aSyn and aggregates, yet none of them satisfy to be interpreted in cellulo context due to their extreme artificial condition. Altogether, with my recent publications and preliminary data, I establish hypotheses: i) organelle-specific lipid types and distribution define the aSyn aggregate, ii) VAMP7 interacts with aSyn, and iii) aSyn and aggregates distinctly impact neurotransmission and secretion. Accordingly, in this interdisciplinary project, I will 1) recreate each organellar membrane-dependent aSyn aggregate and systemically compare the physicochemical properties, 2) molecular dissect the aSyn-interacting domain of VAMP7, and 3) characterize the impact of aSyn and aggregates in neurotransmission and secretion by recapitulating the plasma membrane environment in great detail in my high-end 3D-printed membrane setup. Finally, I will 4) validate the outcomes in standard model membranes and bioengineered bacterial and eukaryotic cells.

Functional ultrasound imaging (fUS) reports changes of blood volume with a mesoscopic spatial resolution. It is used to image brain activity. However, the extent to which the fUS signal quantitatively reports local brain activation is unknown. We propose to characterize the cellular and vascular signals underlying fUS responses to odor, and to quantitatively model the link between these signals in control and CADASIL mice. First, we will use the olfactory bulb as a neurovascular model and compare the fUS signal from a single voxel to cellular and hemodynamic signals evoked by odor, and measured with 2-photon microscopy in the same co-registered brain volume. We will then establish the transfer functions (TFs) linking these signals and test the TF robustness to predict fUS signals from cellular responses. Finally, we will use CADASIL mice to validate TFs as quantitative tools to follow vascular dysfunction with aging, and assess the deficit correction with immunotherapy.

Psychosis is one of the mental disorders with the largest impact due to high personal and family costs. Building research at the very beginning of the psychotic process is crucial to give access to core pathophysiological features of the disease before all the pathological processes are fixed and before medication has side effects on brain function. Recent consensus work points to the need for further basic and therapeutic research in psychosis by applying a staging strategy that would differentiate the earliest stages such as Clinical High Risk for Psychosis (CHR-P) and the full blown First Episode of Psychosis (FEP) from later stages such as Schizophrenia. The direct application of this pathophysiological perspective is to identify the best markers predicting the progression of psychosis. However, while the pathophysiological aspects have been widely explored in schizophrenia, a major research effort is still needed to understand the underlying neural mechanisms and better predict the risk of psychosis progression in the earliest stages. Perceptual disturbances are key elements in the understanding of psychosis. In addition to clinically observed hallucinations and sensory distortions, there is now a large body of evidence for auditory and visual neurocognitive impairment in chronic psychosis. Concerning the early stages of psychosis, while sensory distortions are of high clinical value in assessing the risk of transition, there is still limited data on the underlying auditory or visual neurocognition. The aim of this project is to explore perceptual input and integrated processing in CHR-P patients, in comparison to first-episode psychosis patients and healthy volunteers. We hypothesize neurocognitive disturbances in the early stages, in relation to sensory distortions. We will explore visual processing, with tests measuring the processing of information as it enters the visual system, but also its transformation into a coherent whole, as in a face, as well as the way it is interpreted according to our expectations. We will also study auditory perception, with tests measuring the auditory perception of the input signal as well as the way certain sounds are interpreted in an emotional context. Finally, we will study the way time is perceived. A one-year follow-up in patients with CHR-P will measure whether specific sensory markers predict the risk of transition to psychosis. This project is based on the recruitment of a cohort of patients in four early intervention centres, all supported by research teams known for their works on perception. We will use proven markers of sensory functioning, which have been previously shown to be impaired in chronic psychosis. The research consortium is connected with the RHU Psycare network and will use its recruitment standards.

The cAMP-dependent protein kinase (PKA) is the canonical effector of the β-adrenergic (β-AR)/cAMP cascade and a major physiological regulator of cardiac function. In the adult heart, PKA mediates the cardiotonic effects of acute β-AR stimulation, but persistent PKA activation has been linked to maladaptive remodeling, suggesting that PKA could be an interesting target in heart failure (HF). In the inactive state, PKA is a heterotetramer composed of two regulatory (R) subunits which bind and inhibit two catalytic (C) subunits. Upon β-AR stimulation, cAMP binds to the R subunits, causing the activation of the C subunits. Two types of PKA, type I and type II, vary according to their regulatory subunits, RIα and RIIα, respectively. While type II PKA has been involved in the regulation of cardiac contraction, the role of type I PKA in the heart is less well understood. Indeed, in mice global and cardiomyocyte-specific RIα knockout increase PKA activity and is embryonic lethal due to cardiac development failure. In humans, heterozygous inactivating mutations in the PRKAR1A gene resulting in RIα haploinsufficiency cause Carney Complex (CNC), a rare endocrine disease associated with cardiac myxomas that cause a high morbidity/mortality. Cardiac myxomas are benign, slowly proliferating lesions of sub-endocardial origin but the cells composing these tumours are not clearly identified. CNC-derived cardiac myxoma have been associated with congenital heart defects, suggesting their developmental origin. Based on this information, the two main objectives of this project are i) to determine the consequences of RIα inactivation in the adult mouse heart and in human engineered cardiac tissue and ii) to decipher the precise requirement of type I PKA in early cardiac morphogenesis and myxomagenesis. For this, the partners of this project developed new Cre/Lox mouse models with cardiac cell type specific and temporal knockout of RIα. They will use a unique collection of cardiac myxoma from CNC patients and single cell nuclei RNA sequencing to identify the cell population(s) constituting these tumours. In order to model CNC and explore the impact of RIα haploinsufficiency in human cardiogenesis and myxomagenesis, they will reprogram peripheral blood mononuclear cells from patients carrying an inactivating PRKAR1A mutation into human induced pluripotent stem cells (hiPSC) and differentiate them into different cardiac lineages including cardiomyocytes (hiPSC-CM), neural crest and vascular smooth muscle cells. In addtition, hiPSC-CM cells will be used to produce engineered human heart tissue (EHT) in collaboration with Prof. T. Eschenhagen in Hamburg (Germany). Preliminary results indicate that cardiomyocyte-specific RIα invalidation in adult mice induces chronic PKA activation and results in progressive HF, whereas deletion in cardiac neural crest cells causes partial lethality at embryonic day 15.5 associated with arterial trunk and septal defects reminiscent of congenital heart diseases. The planned work program will further characterize these phenotypes by a combination of state-of-the art techniques including unbiased transcriptomics to determine how RIα controls progenitor cell deployment during embryogenesis and identify new genes involved in maladaptive remodeling in the adult heart that will be validated by in vitro assays and in failing human hearts. The identification of cells composing human cardiac myxoma will pave the way to understand the mechanisms of myxomagenesis in humans and might help to envision therapeutic strategies to prevent the growth of these tumours. Using hiPSC-CM cells to generate EHT will overcome some limitations of hiPSC-CM and provide the first insights into the function of type I PKA in a human cardiac muscle context. Altogether, these findings will allow to better understand the mechanisms by which chronic PKA activation may precipitate congenital heart disease, cardiac myxoma and HF.