A HEME-DEPENDENT MITOCHONDRIAL FAILURE CONTRIBUTES TO THE PATHOGENESIS OF FLVCR1-RELATED DISEASES.

Francesca BERTINO¹, Francesca MAGNANI⁷, Raluca Elena ABALAI¹, Emily MCCOURT⁸, Heike KOBEL⁹, Austin LARSON¹⁰, Andreas ROOS¹¹, Timothy W. YU⁵, Dario FINAZZI³, Deborah CHIABRANDO¹, Eleonora GRASSO¹, Emanuela TOLOSANO¹, Joanna KOPECKA², Diletta Isabella ZANIN VENTURINI¹, Ram BASNET³, Stefania BELLINI ⁴, Luca MIGNANI³, Boxun ZHAO⁵, Andreas HENTSCHEL⁶

¹Department of Molecular Biotechnology and Health Sciences, Molecular Biotechnology Center, University of Turin, Turin, Italy
¹⁰Department of Pediatrics, Section of Clinical Genetics and Metabolism, University of Colorado School of Medicine, Aurora, CO, USA, Colorado, United States
¹¹Department of Pediatric Neurology, Developmental Neurology, and Social Pediatrics, Center for Neuromuscular Disorders in Children and Adolescents, University of Duisburg-Essen, Essen, Germany, Essen, Germany
²Department of Oncology, Molecular Biotechnology Center, University of Turin, Turin, Italy
³Section of Biotechnology, Department of Molecular and Translational Medicine, University of Brescia, Brescia, Italy
⁴Department of Medical Sciences, University of Torino, Turin, Italy
⁵Division of Genetics and Genomics, Boston Children’s Hospital, Boston, MA, USA, Boston, United States
⁶Leibniz-Institut für Analytische Wissenschaften-ISAS-e.V., 44227, Dortmund, Germany, Dortmund, Germany
⁷Department of Biology and Biotechnology "Lazzaro Spallanzani", University of Pavia, Italy., Pavia, Italy
⁸University of Colorado, Department of ophthalmology, Colorado, United States
⁹Department of Paediatric Neurology, Center for Neuromuscular Disorders in Children and Adolescents, Center for Translational Neuro- and Behavioral Sciences (C-TNBS), University Clinic Essen, Essen, Germany, Essen, Germany

FLVCR1-related diseases encompass a group of rare genetic disorders characterized by sensory neuropathy, sensory ataxia and retinitis pigmentosa, that are caused by mutations in the Feline Leukemia Virus Subgroup C Receptor 1 (FLVCR1) gene. Evidence suggest that mitochondrial failure represents a key pathogenetic mechanism underlying FLVCR1-related diseases and that patients may benefit from therapeutic strategies boosting mitochondrial energy metabolism. However, a comprehensive understanding of the cause responsible for mitochondrial dysfunction is mandatory to choose the best therapeutic approach in future. Considering that FLVCR1 mutations impact on both heme and choline metabolism, we sought to understand whether the mitochondrial failure in patients’ cells can be attributed to the alteration of one of these two processes and whether pharmacological treatments are effective in restoring mitochondrial function. Our findings reveal mitochondrial dysfunction and heightened lipid peroxidation in patient-derived fibroblasts and zebrafish morphants. Rescue experiments demonstrate that targeting heme metabolism fully reinstates TCA cycle flux, oxidative phosphorylation, and mitochondrial ATP content in patient fibroblasts, while choline supplementation only partially restores mitochondrial ATP content. Intriguingly, both interventions significantly mitigate lipid peroxidation in patient fibroblasts. Although the potential role of choline cannot be discounted, our results strongly suggest that a heme-dependent mitochondrial failure is a pivotal factor in the disease pathogenesis. This study defines FLVCR1-associated sensory neuropathy as a mitochondrial disorder specific to certain tissues, representing a significant stride towards identifying therapeutic approaches for this rare disease.