Le rôle du peptide BRI23 dans une dystrophie rétinienne : études protéomiques et modélisation de la maladie à l'aide d'organoïdes rétiniens. pathologies par cellules souches pluripotentes

Inherited retinal dystrophies (IRDs) is a genetically heterogeneous group of disorders impacting retinal structure and function. This thesis focuses on understanding the ITM2B-related retinal dystrophy (IRRD) caused by a novel missense mutation in this gene, leading to a modification on the BRI23 associated secreted peptide. This variant is responsible of an atypical phenotype of early retinal ganglion cell (RGC) and photoreceptor (PhR) dysfunction. Through a comprehensive analysis of the BRI23 interactome in the human retina using a synthetic peptide-bead coupling system, we identified over 2302 interacting proteins, with prominent roles in mitochondrial processes, synaptic transmission, and photoreceptor function. Comparative studies between native BRI23 and the BRI23-RD variant linked to the IRRD, revealed altered protein interactions, including elevated affinity of the BRI23-RD with mitochondrial and synaptic proteins, suggesting that the IRRD mutation disrupts retinal protein interactions. Further investigation into the mutation’s effects was conducted using retinal organoids (ROs) derived from a patient (RD), an unaffected family member (WT), and a newly generated CRISPR/Cas9-edited iPSCs (CRISPR). Three CRISPR-edited isogenic iPSC lines were characterized for pluripotency, differentiation capacity and genetic integrity. Structural analysis of RD organoids showed retinal layer disorganization, predominantly in the outer plexiform layer (OPL), alongside with downregulation of key synaptic and photoreceptor genes. Transcriptomic and functional assessments indicated mitochondrial dysfunction and reactive gliosis, marked by GFAP upregulation and increased metabolic stress markers. Interestingly, RD organoids displayed an enhanced mitochondrial activity despite a reduction in mitochondrial marker staining, suggesting a compensatory response to cellular stress. CRISPR-edited organoids showed a rescue of these structural and functional alterations. These findings underscore the essential role of ITM2B and BRI23 in retinal health.