Progranulin loss induces mitochondrial dysfunction and ferroptosis in human cerebral organoids

Loss-of-function mutations in the granulin (GRN) gene cause frontotemporal dementia when the mutations are heterozygous and neuronal ceroid lipofuscinosis, a lysosomal storage disease, when homozygous. While it is well established that disease-causing GRN mutations decrease progranulin (PGRN) levels, leading to neurodegeneration, the cellular and molecular mechanisms underlying these conditions remain poorly understood. In this study, we utilized human induced pluripotent stem cell (iPSC) derived forebrain organoids to investigate the impact of PGRN homozygous deficiency on neuronal and glial cell populations. Through single-cell RNA sequencing, we identified robust downregulation of the mitochondrial oxidative phosphorylation pathway in PGRN KO organoids. In line with these results, PGRN KO organoids showed decreased mitochondrial respiration. Furthermore, our study demonstrated that PGRN loss induced increased levels of reactive oxygen species (ROS), lipid peroxidation and iron accumulation. Finally, we observed increased vulnerability to ferroptotic cell death in PGRN KO organoids. Our findings suggest that mitochondrial dysfunction and impaired responses to oxidative stress are early manifestations of PGRN loss, and offer insights into the molecular mechanisms driving neurodegeneration caused by PGRN deficiency. O_FIG O_LINKSMALLFIG WIDTH=200 HEIGHT=115 SRC="FIGDIR/small/691344v1_ufig1.gif" ALT="Figure 1"> View larger version (18K): org.highwire.dtl.DTLVardef@c477e5org.highwire.dtl.DTLVardef@9b61eforg.highwire.dtl.DTLVardef@13aadeborg.highwire.dtl.DTLVardef@1702929_HPS_FORMAT_FIGEXP M_FIG O_FLOATNOGraphical AbstractC_FLOATNO Proposed molecular mechanisms that lead to ferroptosis of PGRN KO cells. Created with BioRender.com. C_FIG