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Supervisor: Julien Baruteau, Manju Kurian
Project Description:
Background
Major depression and anxiety disorders (MDAD) are leading public health burden with limited therapies and reliable preclinical models. Arginine metabolites (nitric oxide, polyamines) play key-role in neurotransmission and brain energy homeostasis. Why dysregulated arginine metabolism is observed in mental health diseases is unclear. Here, we will use the inherited deficiency of argininosuccinate lyase, the only enzyme synthesising arginine, as a model to interrogate the effect of arginine deprivation on chronic stress and synaptic plasticity, using induced pluripotent stem cells derived cortico-subpallial assembloids and nuclear imaging with positron emission tomography. We will identify and validate novel therapeutic targets with mRNA therapy.
The pathophysiology of MDAD remains poorly understood, explaining limited therapeutic efficacy. Patients with mental health disease can present dysregulated arginine metabolites e.g. nitric oxide, polyamines, creatine. Argininosuccinate lyase is the only mammalian enzyme enabling arginine synthesis. Patients with inherited argininosuccinate lyase deficiency (ASLD) present with psychiatric symptoms (AD, apathy mimicking depression, schizophrenia). ASLD mouse models show deficient cerebral GABA, the main inhibitory neurotransmitter and MDAD feature. GABA is both neuro- and glio-transmitter.
Aims and Objectives
This project investigates the hypothesis that psychiatric symptoms in ASLD are caused by deficient astrocytic arginine-GABA pathway altering neuron-astrocyte coupling. Modelling a rare inherited disease will help unravel MDAD pathophysiology.
Objective 1: Determine astrocytic GABA metabolism in arginine deprivation
The student will study GABA metabolism in two-dimensional ASLD iPSC-derived astrocytes with metabolomic, targeted and bulk transcriptomic, stable isotopes, assess ALDH1A1 expression, key-enzyme of arginine-GABA pathway with highly-specific radiotracer 18F MILK-10 detected by positron emission tomography (PET).
Objective 2: Determine the impact of arginine deprivation on neuronal function and synaptic transmission
Modelling the impact of GABA metabolism on neuron-astrocyte coupling in arginine deprivation will be studied in ASLD human hiPSC-derived mini brains or cortico-subpallial assembloids, in which GABAergic inhibitory neurons and astrocytes are functional. The student will characterise neuronal alterations of both tonic (extrasynaptic) and phasic (synaptic) GABAergic inhibition, excitability, synaptic transmission and synapse number in assembloids after >200 days of differentiation with electrophysiology tools extracellular recording, whole-cell recording and amplitude with patch-clamping in assembloid slices.
Objective 3: Determine GABA metabolism’s response to restored arginine synthesis
The student will determine mRNA efficacy in human ASLD astrocytes and assembloids using qPCR, stable isotopes, PET and electrophysiology as endpoints.
Methods
Metabolomics, transcriptomics, PET, iPSC-derived neurons, electrophysiology, mRNA therapy.
Timelines
Objective 1: 6 months
Objective 2: 18 months
Objective 3: 6 months
Thesis writing: 6 months
References
1. Duff et al. Generation of induced pluripotent stem cells from a patient with argininosuccinate lyase deficiency. Stem Cell Res. 2024;76:103365.
2. Gurung et al. mRNA therapy corrects defective glutathione metabolism and restores ureagenesis in preclinical argininosuccinic aciduria. Sci Transl Med. 2024;16(729):eadh1334.
3. Qiu et al. On-demand cell-autonomous gene therapy for brain circuit disorders. Science. 2022;378(6619):523-532.
4. Gurung et al. The incidence of movement disorder increases with age and contrasts with subtle and limited neuroimaging abnormalities in argininosuccinic aciduria. J Inherit Metab Dis. 2023.
5. Baruteau et al. Argininosuccinic aciduria fosters neuronal nitrosative stress reversed by Asl gene transfer. Nat Commun. 2018:29;9(1):3505
Contact Information:
Julien Baruteau