Faynus, M. A. | bioRxiv Science

bioRxiv2025

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

neuroscience↗

bioRxiv2024

YAP dysregulation triggers hypertrophy by CCN2 secretion and TGFβ uptake in human pluripotent stem cell-derived cardiomyocytes

Hypertrophy Cardiomyopathy (HCM) is the most prevalent hereditary cardiovascular disease - affecting >1:500 individuals. Advanced forms of HCM clinically present with hypercontractility, hypertrophy and fibrosis. Several single-point mutations in b-myosin heavy chain (MYH7) have been associated with HCM and increased contractility at the organ level. Different MYH7 mutations have resulted in increased, decreased, or unchanged force production at the molecular level. Yet, how these molecular kinetics link to cell and tissue pathogenesis remains unclear. The Hippo Pathway, specifically its effector molecule YAP, has been demonstrated to be reactivated in pathological hypertrophic growth. We hypothesized that changes in force production (intrinsically or extrinsically) directly alter the homeostatic mechano-signaling of the Hippo pathway through changes in stresses on the nucleus. Using human induced pluripotent stem cell-derived cardiomyocytes (hiPSC-CMs), we asked whether homeostatic mechanical signaling through the canonical growth regulator, YAP, is altered 1) by changes in the biomechanics of HCM mutant cardiomyocytes and 2) by alterations in the mechanical environment. We use genetically edited hiPSC-CM with point mutations in MYH7 associated with HCM, and their matched controls, combined with micropatterned traction force microscopy substrates to confirm the hypercontractile phenotype in MYH7 mutants. We next modulate contractility in healthy and disease hiPSC-CMs by treatment with positive and negative inotropic drugs and demonstrate a correlative relationship between contractility and YAP activity. We further demonstrate the activation of YAP in both HCM mutants and healthy hiPSC-CMs treated with contractility modulators is through enhanced nuclear deformation. We conclude that the overactivation of YAP, possibly initiated and driven by hypercontractility, correlates with excessive CCN2 secretion (connective tissue growth factor), enhancing cardiac fibroblast/myofibroblast transition and production of known hypertrophic signaling molecule TGF{beta}. Our study suggests YAP being an indirect player in the initiation of hypertrophic growth and fibrosis in HCM. Our results provide new insights into HCM progression and bring forth a testbed for therapeutic options in treating HCM. Graphical Abstract O_FIG O_LINKSMALLFIG WIDTH=200 HEIGHT=174 SRC="FIGDIR/small/597045v2_ufig1.gif" ALT="Figure 1"> View larger version (33K): org.highwire.dtl.DTLVardef@3357aforg.highwire.dtl.DTLVardef@c1c210org.highwire.dtl.DTLVardef@abb72forg.highwire.dtl.DTLVardef@187aa80_HPS_FORMAT_FIGEXP M_FIG C_FIG

cell biology↗