High‐throughput screening identifies suppressors of mitochondrial fragmentation in OPA1 fibroblasts

Abstract

Mutations in OPA1 cause autosomal dominant optic atrophy (DOA) as well as DOA+, a phenotype characterized by more severe neurological deficits. OPA1 deficiency causes mitochondrial fragmentation and also disrupts cristae, respiration, mitochondrial DNA (mtDNA) maintenance, and cell viability. It has not yet been established whether phenotypic severity can be modulated by genetic modifiers of OPA1. We screened the entire known mitochondrial proteome (1,531 genes) to identify genes that control mitochondrial morphology using a first-in-kind imaging pipeline. We identified 145 known and novel candidate genes whose depletion promoted elongation or fragmentation of the mitochondrial network in control fibroblasts and 91 in DOA+ patient fibroblasts that prevented mitochondrial fragmentation, including phosphatidyl glycerophosphate synthase (PGS1). PGS1 depletion reduces CL content in mitochondria and rebalances mitochondrial dynamics in OPA1-deficient fibroblasts by inhibiting mitochondrial fission, which improves defective respiration, but does not rescue mtDNA depletion, cristae dysmorphology, or apoptotic sensitivity. Our data reveal that the multifaceted roles of OPA1 in mitochondria can be functionally uncoupled by modulating mitochondrial lipid metabolism, providing novel insights into the cellular relevance of mitochondrial fragmentation.

Mitochondrial Retinopathies

“…The therapeutic options for OPA1-related DOA are still in a very preliminary phase [ 189 ], with some encouraging results obtained by off-label idebenone administration in DOA patients [ 190 ]. At the preclinical stage numerous research pipelines are active, from screening molecules for repurposing [ 191 ], mechanistic studies to define therapeutic targets [ 192 , 193 ], and gene therapy strategies [ 194 ], including the recent gene editing of a frequent OPA1 missense mutation [ 195 ]. Clinically DOA does not have the confounder of spontaneous recovery of visual function as for LHON, but it is also a slowly progressing or substantially stable disease that questions are posed on which primary endpoint most reliably may reflects therapeutic efficacy.…”

“…For a more detailed description of therapeutic approaches for mitochondrial optic neuropathies, we refer the reader to a comprehensive review that has been recently published [ 195 ].…”

Deep learning in human neurons predicts mechanistic subtypes of Parkinson’s

“…Organelle features extracted included cell areas, expression intensity, the number of spots, roundness, length and width. We also included SER textural features which measure local patterns of pixel intensity providing the structural information of the organelle loading (reviewed here (Di Cataldo and Ficarra, 2017) (Cretin et al, 2021). We designed, trained and evaluated a Dense Neural Network by splitting the entire dataset (n = 1,560,315 identified cells) into training (40%), validation (30%) and test datasets (30%).…”

“…Morphologically defined features are included such as cell areas, expression intensity, the number of spot, roundness, length and width. SER texture features are also included defined as Spot, Hole, Edge, Ridge, Valley, Saddle, Bright and Dark which measure local patterns of pixel intensity providing the structural information of the organelle loading (reviewed here (Di Cataldo and Ficarra, 2017) (Cretin et al, 2021). b .…”

Players in Mitochondrial Dynamics and Female Reproduction

“…Functional mitochondrial fusion mediated by L-OPA1 preserves cardiac function, and mitochondrial fragmentation may trigger dilated cardiomyopathy and heart failure ( Wai et al, 2015 ). Fresh new research found that knockout of the phosphatidyl glycerophosphate synthase PSG1 causes cardiolipin reduction, thus rescuing mitochondrial fragmentation caused by OPA1 dysfunction ( Cretin et al, 2021 ). OPA1 is another major player in maintaining the mitochondrial architecture, regulating apoptosis, and sustaining the homeostasis of mitochondrial fusion and fission.…”