Abstract
Purpose :
Our team identified a missense mutation in ITM2B underlying a novel autosomal dominant retinal dystrophy with ganglion cell loss, inner retinal dysfunction and progressive retinal degeneration1,2 but the function of ITM2B in the retina and physio-pathological mechanisms remains poorly understood. In a previous work, we obtained patient- and control-derived retinal organoids to model the disease recently showed that ITM2B may interact with mitochondrial proteins, implicated in oxidative stress in human retina. This project aims to investigate ITM2B in mitochondrial function and determined if it is altered in the disease.
Methods :
Two inducted pluripotent cell lines (iPSC) derived from an affected and unaffected sibling were used. ITM2B mitochondrial immunolocalization in 60 days aged organoids was studied using two mitochondrial markers COX5B and ATP-β. Three sections per conditions were used. Furthermore, IPSC metabolism was analyzed in control and mutant cell lines using a mitostress seahorse assay, using 3 replicates per condition.
Results :
ITM2B immuno-localizes with both COX5B and ATB-β mitochondrial markers in retinal organoids sections (figure 1). No difference was noticed between the mutant and the control organoids suggesting that mutant ITM2B does not modify the localization of the protein at this stage. Furthermore, a lower oxygen consumption rate was observed in mutant IPSC compared to control cells (figure 2), which highlight a mitochondrial defect in the mutant cell line, as well as a low capacity to respond to stress.
Conclusions :
Our findings suggest a central role of the mitochondria underlying ITM2B pathogenesis in the retina. Further studies on IPSC using biochemical assays, respiratory function using sea-horse and enzyme assays are currently under investigation using as a model fibroblast and iPSC-derived retinal ganglion cells from dissociated mutant organoids and an isogenic control are currently underway and will help determine the function of ITM2B in the retina and elucidate its implications in pathology.
This abstract was presented at the 2022 ARVO Annual Meeting, held in Denver, CO, May 1-4, 2022, and virtually.