COQ6 Mutation Causes Podocyte Injury In An FSGS Patient

Background:Focal segmental glomerular sclerosis（FSGS）is a kidney disease that is commonly associated with proteinuria and the progressive loss of renal function,which is characterized by podocyte injury and the depletion and collapse of glomerular capillary segments.The pathogenesis of FSGS has not been completely elucidated;however,recent advances in molecular genetics have provided increasing evidence that podocyte structural and functional disruption is central to FSGS pathogenesis.Here,we have identified a patient with FSGS and have aimed to characterize the pathogenic gene and verify its mechanism.Methods:Using next-generation sequencing（NGS）and Sanger sequencing,we screened the causative gene that was linked to FSGS in this study.The patient’s total blood RNA was extracted to validate the mRNA expression of COQ6,and validated it by immunohistochemistry（IHC）.COQ6 knockdown in podocytes was performed in vitro with siRNA,and then F-actin were determined using immunofluorescence staining.Cell apoptosis was evaluated by flow cytometry and the expression of active Capase-3 determined by western blotting,and mitochondrial function was detected by MitoSOX.Results:Using whole-exome sequencing and Sanger sequencing,we screened causative gene-COQ6,NM₁82480:exonl:c.G41 A:p.W14X.The mRNA expression of COQ6 and validated it by immunohistochemistry showed decreases in COQ6 in the proband.Finally,we focused on the COQ6 gene to clarify the mechanism of podocyte injury.Flow cytometry showed significantly increased in the number of apoptotic podocytes,and western blotting showed increases in active Capase-3 in si-COQ6 podocytes.Meanwhile,ROS levels were increased and F-actin immunofluorescence was irregularly distributed in the si-COQ6 group.Conclusions:This study reports a possible mechanism for FSGS and suggests that a mutation in COQ6,which can cause respiratory chain defect,increase the generation of ROS,destroy the podocyte cytoskeleton and induce apoptosis.It provides basic theoretical basis for the screening of FSGS in the future.