Abstract
In most eukaryotic cells, fatty acid synthesis (FAS) occurs in the cytoplasm and in mitochondria. However, the relative contribution of mitochondrial FAS (mtFAS) to the cellular lipidome is not well defined. Here we show that loss of function of Drosophila mitochondrial enoyl coenzyme A reductase (Mecr), which is the enzyme required for the last step of mtFAS, causes lethality, while neuronal loss of Mecr leads to progressive neurodegeneration. We observe a defect in Fe–S cluster biogenesis and increased iron levels in flies lacking mecr, leading to elevated ceramide levels. Reducing the levels of either iron or ceramide suppresses the neurodegenerative phenotypes, indicating an interplay between ceramide and iron metabolism. Mutations in human MECR cause pediatric-onset neurodegeneration, and we show that human-derived fibroblasts display similar elevated ceramide levels and impaired iron homeostasis. In summary, this study identifies a role of mecr/MECR in ceramide and iron metabolism, providing a mechanistic link between mtFAS and neurodegeneration.
This is a preview of subscription content, access via your institution
Access options
Access Nature and 54 other Nature Portfolio journals
Get Nature+, our best-value online-access subscription
$29.99 / 30 days
cancel any time
Subscribe to this journal
Receive 12 digital issues and online access to articles
$119.00 per year
only $9.92 per issue
Rent or buy this article
Prices vary by article type
from$1.95
to$39.95
Prices may be subject to local taxes which are calculated during checkout








Data availability
All relevant data generated or analysed in this study are included in this article. All other data supporting the findings of this study are available upon request. Source data are provided with this paper.
Code availability
No custom code was used for this study.
References
Maier, T., Jenni, S. & Ban, N. Architecture of mammalian fatty acid synthase at 4.5 A resolution. Science 311, 1258–1262 (2006).
Fhu, C. W. & Ali, A. Fatty acid synthase: an emerging target in cancer. Molecules 25, 3935 (2020).
Miinalainen, I. J. et al. Characterization of 2-enoyl thioester reductase from mammals. An ortholog of YBR026p/MRF1′p of the yeast mitochondrial fatty acid synthesis type II. J. Biol. Chem. 278, 20154–20161 (2003).
Nair, R. R. et al. Genetic modifications of Mecr reveal a role for mitochondrial 2-enoyl-CoA/ACP reductase in placental development in mice. Hum. Mol. Genet. 26, 2104–2117 (2017).
Venkatesan, R. et al. Insights into mitochondrial fatty acid synthesis from the structure of heterotetrameric 3-ketoacyl-ACP reductase/3R-hydroxyacyl-CoA dehydrogenase. Nat. Commun. 5, 4805 (2014).
Nowinski, S. M. et al. Mitochondrial fatty acid synthesis coordinates oxidative metabolism in mammalian mitochondria. eLife 9, e58041 (2020).
Kursu, V. A. S. et al. Defects in mitochondrial fatty acid synthesis result in failure of multiple aspects of mitochondrial biogenesis in Saccharomyces cerevisiae. Mol. Microbiol. 90, 824–840 (2013).
Torkko, J. M. et al. Candida tropicalis Etr1p and Saccharomyces cerevisiae Ybr026p (Mrf1′p), 2-enoyl thioester reductases essential for mitochondrial respiratory competence. Mol. Cell. Biol. 21, 6243–6253 (2001).
Nair, R. R. et al. Impaired mitochondrial fatty acid synthesis leads to neurodegeneration in mice. J. Neurosci. 38, 9781–9800 (2018).
Heimer, G. et al. MECR mutations cause childhood-onset dystonia and optic atrophy, a mitochondrial fatty acid synthesis disorder. Am. J. Hum. Genet. 99, 1229–1244 (2016).
Gorukmez, O., Gorukmez, O. & Havalı, C. Novel MECR mutation in childhood-onset dystonia, optic atrophy, and basal ganglia signal abnormalities. Neuropediatrics 50, 336–337 (2019).
Liu, Z. et al. Whole exome sequencing identifies a novel homozygous MECR mutation in a Chinese patient with childhood-onset dystonia and basal ganglia abnormalities, without optic atrophy. Mitochondrion 57, 222–229 (2021).
Grassi, D. et al. Identification of a highly neurotoxic α-synuclein species inducing mitochondrial damage and mitophagy in Parkinson’s disease. Proc. Natl Acad. Sci. USA 115, E2634–E2643 (2018).
Kastaniotis, A. J., Autio, K. J. & Nair, R. R. Mitochondrial fatty acids and neurodegenerative disorders. Neuroscientist 27, 143–158 (2021).
Majmudar, J. D. et al. 4′-Phosphopantetheine and long acyl chain-dependent interactions are integral to human mitochondrial acyl carrier protein function. Medchemcomm 10, 209–220 (2019).
Zhang, L., Joshi, A. K., Hofmann, J., Schweizer, E. & Smith, S. Cloning, expression, and characterization of the human mitochondrial β-ketoacyl synthase: complementation of the yeast cem1 knock-out strain. J. Biol. Chem. 280, 12422–12429 (2005).
Masud, A. J., Kastaniotis, A. J., Rahman, M. T., Autio, K. J. & Hiltunen, J. K. Mitochondrial acyl carrier protein (ACP) at the interface of metabolic state sensing and mitochondrial function. Biochim. Biophys. Acta Mol. Cell Res. 1866, 118540 (2019).
Kastaniotis, A. J. et al. Mitochondrial fatty acid synthesis, fatty acids and mitochondrial physiology. Biochim. Biophys. Acta Mol. Cell Biol. Lipids 1862, 39–48 (2017).
Solmonson, A. & DeBerardinis, R. J. Lipoic acid metabolism and mitochondrial redox regulation. J. Biol. Chem. 293, 7522–7530 (2018).
Hiltunen, J. K. et al. Mitochondrial fatty acid synthesis and respiration. Biochim. Biophys. Acta 1797, 1195–1202 (2010).
Schneider, R., Massow, M., Lisowsky, T. & Weiss, H. Different respiratory-defective phenotypes of Neurospora crassa and Saccharomyces cerevisiae after inactivation of the gene encoding the mitochondrial acyl carrier protein. Curr. Genet. 29, 10–17 (1995).
Guler, J. L., Kriegova, E., Smith, T. K., Lukeš, J. & Englund, P. T. Mitochondrial fatty acid synthesis is required for normal mitochondrial morphology and function in Trypanosoma brucei. Mol. Microbiol. 67, 1125–1142 (2008).
Clay, H. B. et al. Altering the mitochondrial fatty acid synthesis (mtFASII) pathway modulates cellular metabolic states and bioactive lipid profiles AS revealed by metabolomic profiling. PLoS ONE 11, e0151171 (2016).
Kanca, O. et al. An efficient CRISPR-based strategy to insert small and large fragments of DNA using short homology arms. eLife 8, e51539 (2019).
Lee, P. T. et al. A gene-specific T2A-GAL4 library for Drosophila. eLife 7, e35574 (2018).
Schuldiner, O. et al. piggyBac-based mosaic screen identifies a postmitotic function for cohesin in regulating developmental axon pruning. Dev. Cell 14, 227–238 (2008).
Venken, K. J. T. et al. Versatile P[acman] BAC libraries for transgenesis studies in Drosophila melanogaster. Nat. Methods 6, 431–434 (2009).
Hu, Y. et al. An integrative approach to ortholog prediction for disease-focused and other functional studies. BMC Bioinformatics 12, 357 (2011).
Wang, J. et al. MARRVEL: integration of human and model organism genetic resources to facilitate functional annotation of the human genome. Am. J. Hum. Genet. 100, 843–853 (2017).
Golic, K. G. & Lindquist, S. The FLP recombinase of yeast catalyzes site-specific recombination in the Drosophila genome. Cell 59, 499–509 (1989).
Xu, T. & Rubin, G. M. Analysis of genetic mosaics in developing and adult Drosophila tissues. Development 117, 1223–1237 (1993).
Yamazoe, M. et al. A protein which binds preferentially to single-stranded core sequence of autonomously replicating sequence is essential for respiratory function in mitochondria of Saccharomyces cerevisiae. J. Biol. Chem. 269, 15244–15252 (1994).
Kim, D. G. et al. A novel cytosolic isoform of mitochondrial trans-2-enoyl-CoA reductase enhances peroxisome proliferator-activated receptor a activity. Endocrinol. Metab. 29, 185–194 (2014).
Masuda, N. et al. Nuclear receptor binding factor-1 (NRBF-1), a protein interacting with a wide spectrum of nuclear hormone receptors. Gene 221, 225–233 (1998).
Parl, A. et al. The mitochondrial fatty acid synthesis (mtFASII) pathway is capable of mediating nuclear–mitochondrial cross talk through the PPAR system of transcriptional activation. Biochem. Biophys. Res. Commun. 441, 418–424 (2013).
Sarov, M. et al. A genome-wide resource for the analysis of protein localisation in Drosophila. eLife 5, e12068 (2016).
Yoon, W. H. et al. Loss of nardilysin, a mitochondrial co-chaperone for α-ketoglutarate dehydrogenase, promotes mTORC1 activation and neurodegeneration. Neuron 93, 115–131 (2017).
Baqri, R. M. et al. Disruption of mitochondrial DNA replication in Drosophila increases mitochondrial fast axonal transport in vivo. PLoS ONE 4, e7874 (2009).
Splinter, K. et al. Effect of genetic diagnosis on patients with previously undiagnosed disease. N. Engl. J. Med. 379, 2131–2139 (2018).
Ishibashi, Y., Kohyama-Koganeya, A. & Hirabayashi, Y. New insights on glucosylated lipids: metabolism and functions. Biochim. Biophys. Acta 1831, 1475–1485 (2013).
Checa, A. et al. Hexosylceramides as intrathecal markers of worsening disability in multiple sclerosis. Mult. Scler. 21, 1271–1279 (2015).
Miyake, Y., Kozutsumi, Y., Nakamura, S., Fujita, T. & Kawasaki, T. Serine palmitoyltransferase is the primary target of a sphingosine-like immunosuppressant, ISP-1/myriocin. Biochem. Biophys. Res. Commun. 211, 396–403 (1995).
Lin, G. et al. Phospholipase PLA2G6, a Parkinsonism-associated gene, affects Vps26 and Vps35, retromer function, and ceramide levels, similar to α-synuclein gain. Cell Metab. 28, 605–618 (2018).
Vos, M. et al. Ceramide accumulation induces mitophagy and impairs β-oxidation in PINK1 deficiency. Proc. Natl Acad. Sci. USA 118, e2025347118 (2021).
Jaiswal, M. et al. Impaired mitochondrial energy production causes light-induced photoreceptor degeneration independent of oxidative stress. PLoS Biol. 13, e1002197 (2015).
Ozaki, M., Le, T. D. & Inoue, Y. H. Downregulating mitochondrial DNA polymerase γ in the muscle stimulated autophagy, apoptosis, and muscle aging-related phenotypes in Drosophila adults. Biomolecules 12, 1105 (2022).
Larsen, S. B., Hanss, Z. & Krüger, R. The genetic architecture of mitochondrial dysfunction in Parkinson’s disease. Cell Tissue Res. 373, 21–37 (2018).
Zorova, L. D. et al. Mitochondrial membrane potential. Anal. Biochem. 552, 50–59 (2018).
Scaduto, R. C. & Grotyohann, L. W. Measurement of mitochondrial membrane potential using fluorescent rhodamine derivatives. Biophys. J. 76, 469–477 (1999).
Donti, T. R. et al. Screen for abnormal mitochondrial phenotypes in mouse embryonic stem cells identifies a model for succinyl-CoA ligase deficiency and mtDNA depletion. Dis. Model. Mech. 7, 271–280 (2014).
Ji, R. et al. Increased de novo ceramide synthesis and accumulation in failing myocardium. JCI Insight 2, e82922 (2017).
Srivastava, S. et al. SPTSSA variants alter sphingolipid synthesis and cause a complex hereditary spastic paraplegia. Brain 146, 1420–1435 (2022).
Chen, K. et al. Loss of frataxin activates the iron/sphingolipid/PDK1/Mef2 pathway in mammals. eLife 5, e20732 (2016).
Chen, K. et al. Loss of frataxin induces iron toxicity, sphingolipid synthesis, and Pdk1/Mef2 activation, leading to neurodegeneration. eLife 5, e16043 (2016).
Lee, Y. J. et al. Sphingolipid signaling mediates iron toxicity. Cell Metab. 16, 90–96 (2012).
Maio, N. & Rouault, T. A. Outlining the complex pathway of mammalian Fe–S cluster biogenesis. Trends Biochem. Sci. 45, 411–426 (2020).
Meguro, R. et al. Nonheme-iron histochemistry for light and electron microscopy: a historical, theoretical and technical review. Arch. Histol. Cytol. 70, 1–19 (2007).
Galaris, D., Barbouti, A. & Pantopoulos, K. Iron homeostasis and oxidative stress: an intimate relationship. Biochim. Biophys. Acta Mol. Cell Res. 1866, 118535 (2019).
Dixon, S. J. & Stockwell, B. R. The role of iron and reactive oxygen species in cell death. Nat. Chem. Biol. 10, 9–17 (2014).
Houglum, K., Filip, M., Witztum, J. L. & Chojkier, M. Malondialdehyde and 4-hydroxynonenal protein adducts in plasma and liver of rats with iron overload. J. Clin. Invest. 86, 1991–1998 (1990).
Csala, M. et al. On the role of 4-hydroxynonenal in health and disease. Biochim. Biophys. Acta 1852, 826–838 (2015).
Kruman, I., Bruce-Keller, A. J., Bredesen, D., Waeg, G. & Mattson, M. P. Evidence that 4-hydroxynonenal mediates oxidative stress-induced neuronal apoptosis. J. Neurosci. 17, 5089–5100 (1997).
Chung, H. L. et al. Loss- or gain-of-function mutations in ACOX1 cause axonal loss via different mechanisms. Neuron 106, 589–606 (2020).
Knovich, M. A., Storey, J. A., Coffman, L. G., Torti, S. V. & Torti, F. M. Ferritin for the clinician. Blood Rev. 23, 95–104 (2009).
Missirlis, F. et al. Homeostatic mechanisms for iron storage revealed by genetic manipulations and live imaging of Drosophila ferritin. Genetics 177, 89–100 (2007).
Soriano, S. et al. Deferiprone and idebenone rescue frataxin depletion phenotypes in a Drosophila model of Friedreich’s ataxia. Gene 521, 274–281 (2013).
Elincx-Benizri, S. et al. Clinical experience with deferiprone treatment for Friedreich ataxia. J. Child Neurol. 31, 1036–1040 (2016).
Vanlander, A. V. & Van Coster, R. Clinical and genetic aspects of defects in the mitochondrial iron–sulfur cluster synthesis pathway. J. Biol. Inorg. Chem. 23, 495–506 (2018).
Isaya, G. Mitochondrial iron–sulfur cluster dysfunction in neurodegenerative disease. Front. Pharmacol. 5, 29 (2014).
Van Vranken, J. G. et al. The mitochondrial acyl carrier protein (ACP) coordinates mitochondrial fatty acid synthesis with iron sulfur cluster biogenesis. eLife 5, e17828 (2016).
Cory, S. A. et al. Structure of human Fe–S assembly subcomplex reveals unexpected cysteine desulfurase architecture and acyl-ACP–ISD11 interactions. Proc. Natl Acad. Sci. USA 114, E5325–E5334 (2017).
Castro, L., Tórtora, V., Mansilla, S. & Radi, R. Aconitases: non-redox iron–sulfur proteins sensitive to reactive species. Acc. Chem. Res. 52, 2609–2619 (2019).
Cheng, Z., Tsuda, M., Kishita, Y., Sato, Y. & Aigaki, T. Impaired energy metabolism in a Drosophila model of mitochondrial aconitase deficiency. Biochem. Biophys. Res. Commun. 433, 145–150 (2013).
Crooks, D. R. et al. Acute loss of iron–sulfur clusters results in metabolic reprogramming and generation of lipid droplets in mammalian cells. J. Biol. Chem. 293, 8297–8311 (2018).
Cho, Y. H., Kim, G. H. & Park, J. J. Mitochondrial aconitase 1 regulates age-related memory impairment via autophagy/mitophagy-mediated neural plasticity in middle-aged flies. Aging Cell 20, e13520 (2021).
Olona, A. et al. Sphingolipid metabolism during Toll-like receptor 4 (TLR4)-mediated macrophage activation. Br. J. Pharmacol. 178, 4575–4587 (2021).
Reginato, A. et al. The role of fatty acids in ceramide pathways and their influence on hypothalamic regulation of energy balance: a systematic review. Int. J. Mol. Sci. 22, 5357 (2021).
Nowinski, S. M., Van Vranken, J. G., Dove, K. K. & Rutter, J. Impact of mitochondrial fatty acid synthesis on mitochondrial biogenesis. Curr. Biol. 28, R1212–R1219 (2018).
Brody, S. & Mikolajczyk, S. Neurospora mitochondria contain an acyl‐carrier protein. Eur. J. Biochem. 173, 353–359 (1988).
Stith, J. L., Velazquez, F. N. & Obeid, L. M. Advances in determining signaling mechanisms of ceramide and role in disease. J. Lipid Res. 60, 913–918 (2019).
Pinto, S. N., Silva, L. C., Futerman, A. H. & Prieto, M. Effect of ceramide structure on membrane biophysical properties: the role of acyl chain length and unsaturation. Biochim. Biophys. Acta 1808, 2753–2760 (2011).
Alonso, A. & Goñi, F. M. The physical properties of ceramides in membranes. Annu. Rev. Biophys. 47, 633–654 (2018).
Rao, R. P. & Acharya, J. K. Sphingolipids and membrane biology as determined from genetic models. Prostaglandins Other Lipid Mediat. 85, 1–16 (2008).
Hernández-Corbacho, M. J., Salama, M. F., Canals, D., Senkal, C. E. & Obeid, L. M. Sphingolipids in mitochondria. Biochim. Biophys. Acta Mol. Cell Biol. Lipids 1862, 56–68 (2017).
Kogot-Levin, A. & Saada, A. Ceramide and the mitochondrial respiratory chain. Biochimie 100, 88–94 (2014).
Alessenko, A. V. & Albi, E. Exploring sphingolipid implications in neurodegeneration. Front. Neurol. 11, 437 (2020).
van Kruining, D. et al. Sphingolipids as prognostic biomarkers of neurodegeneration, neuroinflammation, and psychiatric diseases and their emerging role in lipidomic investigation methods. Adv. Drug Deliv. Rev. 159, 232–244 (2020).
Wang, D. et al. Skin fibroblast metabolomic profiling reveals that lipid dysfunction predicts the severity of Friedreich’ s ataxia. J. Lipid Res. 63, 100255 (2022).
Anderson, P. R., Kirby, K., Hilliker, A. J. & Phillips, J. P. RNAi-mediated suppression of the mitochondrial iron chaperone, frataxin, in Drosophila. Hum. Mol. Genet. 14, 3397–3405 (2005).
Esposito, G. et al. Aconitase causes iron toxicity in Drosophila pink1 mutants. PLoS Genet. 9, e1003478 (2013).
Custodia, A. et al. Ceramide metabolism and Parkinson’s disease—therapeutic targets. Biomolecules 11, 945 (2021).
Thomas, G. E. C. et al. Regional brain iron and gene expression provide insights into neurodegeneration in Parkinson’s disease. Brain 144, 1787–1798 (2021).
Foley, P. B., Hare, D. J. & Double, K. L. A brief history of brain iron accumulation in Parkinson disease and related disorders. J. Neural Transm. 129, 505–520 (2022).
Oakley, A. E. et al. Individual dopaminergic neurons show raised iron levels in Parkinson disease. Neurology 68, 1820–1825 (2007).
Wang, J.-Y. et al. Meta-analysis of brain iron levels of Parkinson’s disease patients determined by postmortem and MRI measurements. Sci. Rep. 6, 36669 (2016).
Schweitzer, K. J. et al. Transcranial ultrasound in different monogenetic subtypes of Parkinson’s disease. J. Neurol. 254, 613–616 (2007).
Pan, X., Dutta, D., Lu, S. & Bellen, H. J. Sphingolipids in neurodegenerative diseases. Front. Neurosci. 17, 1137893 (2023).
Sawada, M. et al. p53 regulates ceramide formation by neutral sphingomyelinase through reactive oxygen species in human glioma cells. Oncogene 20, 1368–1378 (2001).
Li, X., Gulbins, E. & Zhang, Y. Oxidative stress triggers Ca2+-dependent lysosome trafficking and activation of acid sphingomyelinase. Cell. Physiol. Biochem. 30, 815–826 (2012).
Schalinske, K. L. et al. The iron–sulfur cluster of iron regulatory protein 1 modulates the accessibility of RNA binding and phosphorylation sites. Biochemistry 36, 3950–3958 (1997).
Levi, S. & Rovida, E. Neuroferritinopathy: from ferritin structure modification to pathogenetic mechanism. Neurobiol. Dis. 81, 134–143 (2015).
Kumar, N., Rizek, P. & Jog, M. Neuroferritinopathy: pathophysiology, presentation, differential diagnoses and management. Tremor Other Hyperkinet. Mov. 6, 355 (2016).
Muhoberac, B. B. & Vidal, R. Iron, ferritin, hereditary ferritinopathy, and neurodegeneration. Front. Neurosci. 13, 1195 (2019).
Port, F., Chen, H.-M., Lee, T. & Bullock, S. L. Optimized CRISPR/Cas tools for efficient germline and somatic genome engineering in Drosophila. Proc. Natl Acad. Sci. USA 111, E2967–E2976 (2014).
Kanca, O. et al. An expanded toolkit for Drosophila gene tagging using synthesized homology donor constructs for CRISPR-mediated homologous recombination. eLife 11, e76077 (2022).
Dutta, D. et al. De novo mutations in TOMM70, a receptor of the mitochondrial import translocase, cause neurological impairment. Hum. Mol. Genet. 29, 1568–1579 (2020).
Marcogliese, P. C. et al. IRF2BPL is associated with neurological phenotypes. Am. J. Hum. Genet. 103, 245–260 (2018).
Marcogliese, P. C. et al. Loss of IRF2BPL impairs neuronal maintenance through excess Wnt signaling. Sci. Adv. 8, eabl5613 (2022).
Lee, J. W. et al. UPLC–QqQ/MS-based lipidomics approach to characterize lipid alterations in inflammatory macrophages. J. Proteome Res. 16, 1460–1469 (2017).
Radenkovic, S. et al. Expanding the clinical and metabolic phenotype of DPM2 deficient congenital disorders of glycosylation. Mol. Genet. Metab. 132, 27–37 (2021).
Byeon, S. K., Madugundu, A. K. & Pandey, A. Automated data-driven mass spectrometry for improved analysis of lipids with dual dissociation techniques. J. Mass Spectrom. Adv. Clin. Lab 22, 43–49 (2021).
Mitchell, C. J., Kim, M. S., Na, C. H. & Pandey, A. PyQuant: a versatile framework for analysis of quantitative mass spectrometry data. Mol. Cell. Proteomics 15, 2829–2838 (2016).
Frazier, A. E. & Thorburn, D. R. Biochemical analyses of the electron transport chain complexes by spectrophotometry. Methods Mol. Biol. 837, 49–62 (2012).
Missirlis, F. et al. Characterization of mitochondrial ferritin in Drosophila. Proc. Natl Acad. Sci. USA 103, 5893–5898 (2006).
Schober, F. A. et al. The one-carbon pool controls mitochondrial energy metabolism via complex I and iron–sulfur clusters. Sci. Adv. 7, eabf0717 (2021).
Martelli, F. et al. Low doses of the neonicotinoid insecticide imidacloprid induce ROS triggering neurological and metabolic impairments in Drosophila. Proc. Natl Acad. Sci. USA 117, 25840–25850 (2020).
Dutta, D., Paul, M. S., Singh, A., Mutsuddi, M. & Mukherjee, A. Regulation of Notch signaling by the heterogeneous nuclear ribonucleoprotein Hrp48 and Deltex in Drosophila melanogaster. Genetics 206, 905–918 (2017).
Acknowledgements
We extend our thanks to the affected individuals and families who participated in this study. We thank the reviewers for their time and insightful comments. We thank T. M. Dunn, D. Miller, S. J. Hayflick, A. J. Kastaniotis, M. S. Paul and H. Chung for helpful discussion, H. Pan and W.-W. Lin for injections to create transgenic flies and J. Kim for MS analyses. We also thank A. J. Kastaniotis at the University of Oulu for sharing human fibroblasts and N. Perrimon at Harvard Medical School for sharing S2 cells. We thank F. Missirlis at the Center for Research and Advanced Studies of the National Polytechnic Institute for the UAS-Fer1HCH, UAS-Fer2LCH stock. We also thank the Bloomington Drosophila Stock Center, the Vienna Drosophila Resource Center and the Kyoto Drosophila Genetic Resource Center and the Developmental Studies Hybridoma Bank from the University of Iowa for providing fly stocks and reagents. We acknowledge support from the Shan and Lee-Jun Wong fellowship of Baylor College of Medicine to D.D. We thank the Baylor College of Medicine Intellectual and Developmental Disabilities Research Center confocal microscopy core, supported by the National Institute of Child Health & Human Development (U54 HD083092). H.J.B. is supported by the NIH Common Fund through the Office of Strategic Coordination/Office of the NIH Director and the NINDS (U54NS093793), NIH/ORIP (24OD022005 and R24OD031447), is a recipient of the Chair of the Neurological Research Institute of Texas Children’s Hospital and is supported by the Huffington foundation. The content is solely the responsibility of the authors and does not necessarily represent the official views of the NIH.
Author information
Authors and Affiliations
Consortia
Contributions
Conceptualization: D.D. and H.J.B. Investigation: D.D., O.K., P.C.M., S.K.B., Z.Z., J.H.P, R.V.S., G.L., J.N.K., M.T.W., G.H. and M.G. Resources: H.J.B., A.P. and B.A.K. Writing, original draft: D.D. and H.J.B. Writing, review and editing: D.D., O.K., P.C.M., G.L., S.K.B., J.N.K., M.T.W., J.H.P, R.V.S., A.P., B.A.K., G.H. and H.J.B. Funding acquisition: H.J.B. Supervision: H.J.B.
Corresponding author
Ethics declarations
Competing interests
The authors declare no competing interests.
Peer review
Peer review information
Nature Metabolism thanks Alexander Whitworth, Juan A Navarro and the other, anonymous, reviewer(s) for their contribution to the peer review of this work. Primary Handling Editor: Yanina-Yasmin Pesch, in collaboration with the Nature Metabolism team.
Additional information
Publisher’s note Springer Nature remains neutral with regard to jurisdictional claims in published maps and institutional affiliations.
Extended data
Extended Data Fig. 1 The mitochondrial fatty acid synthesis pathway and generation of mecr mutants.
(a) Mitochondrial fatty acid synthesis pathway and its products. Briefly, an acetyl and malonyl moiety are condensed to make a four carbon long keto-acyl species, which remains attached to the mitochondrial Acyl Carrier Protein (mtACP), a protein that holds the growing acyl chain during the fatty acid synthesis within the mitochondria. Subsequently, this four-carbon long keto-acyl ACP undergoes a reduction-dehydration-reduction cycle to produce a butyryl-ACP (C4). C4 enters into the cycle, and two carbons from the malonyl moiety are attached to the butyryl species to make an acyl chain of six carbon length. This cycle continues until the carbon length of the growing acyl chain reaches up to 16–18 carbon. (b) Schema showing the mecr mutants used in this study. (c) Schema showing the Primers used for quantitative real-time PCR and the graphs showing the relative levels of mecr transcripts in mecrTG4 mutants. Each dot represents data from three technical replicates. (d) Western blot showing lipoic acid (LA) levels linked to Muc (ortholog of yeast Lat1 and a component of PDH complex in fruit fly) and CG5214 (ortholog of yeast Kgd2 and a component of OGDH complex in fruit fly) in mecr mutants. (e) Effects of a transgene containing mecr-GFP (Fosmid clone, CBGtg9060C0290D)36 or of ubiquitous expression of HA-tagged fly mecr on mecrTG4 homozygous mutants. One-way ANOVA followed by a Tukey’s post-hoc test was performed for the statistical analyses. Error bars represent SEM (****p < 0.0001).
Extended Data Fig. 2 The variants observed in patients are conserved in the fly Mecr protein and homozygous mecr mutants are not fully rescued by expressing these MECR variants.
(a) Protein alignments of Mecr proteins. Red boxes indicate the amino acid that are variant in MEPAN patients. Schema shows the relative position of the patient variants in MECR protein. (b) Effects of ubiquitous expression of human MECR variants when driven by da-GAL4 in mecr mutants. (c) Percentage of 15-day-old flies that are able to climb 8 cm within 30 seconds. Each dot represents the percentage of flies from three independent experiments. (d) Average time taken by 15-day-old flies to climb 8 cm. Each dot represents the time taken by one fly in each of the three experiments. n = 93 (MECRRef), n = 86 (MECRArg258Trp), n = 84 (MECRGly232Glu) flies. One-way ANOVA followed by a Tukey’s post-hoc test was performed for the statistical analyses. Error bars represent SEM (****p < 0.0001).
Extended Data Fig. 3 Loss of mecr causes a reduction in lifespan as well as in climbing ability.
(a, b) Western blot (a) and quantification (b) showing relative levels of Mecr protein upon neuronal knockdown (elav-GAL4) with two different RNAi lines at 25 °C. Each dot represents the data from three independent experiments. For statistical analyses, one-way ANOVA followed by a Dunnett’s multiple comparison test is carried out. Error bars represent SEM (**p < 0.01). (c) Lifespan of flies with neuronal knockdown of mecr. (d) Percentage of 25-day-old flies that can climb 8 cm within 30 seconds. Each dot represents the percentage of flies from three independent experiments. (e) Average time taken by 25-day-old flies to climb 8 cm. n = 128 (luci-RNAi) and n = 55 (mecr-RNAi) flies. For statistical analyses, two-tailed Student’s t-test is carried out. Error bars represent SEM (*p<0.05; ****p < 0.0001). (f–h) Quantification of ERG traces from 3–5 day-old flies. Each dot represents the data from one fly. n = 8 (Control and mecrA; GR), n = 10 (mecrA) flies. For statistical analyses, one-way ANOVA followed by a Tukey’s post-hoc test is carried out. Error bars represent SEM.
Extended Data Fig. 4 mecr is expressed in neurons and glia, and Fly Mecr and Human MECR proteins are localized to mitochondria.
(a) Expression of mCherry driven by mecrKG4 (mecrKozak-GAL4, where we replaced the coding region of the gene with a Kozak sequence followed by a GAL4 gene) in larval brains. Elav-positive cells are neurons and Repo-positive cells are glia. (b) Expression of mCherry driven by mecrKozak-GAL4 in the adult brain. Note that mecr expression is sparse in the adult brains. However, a few cells including the prospective medial neurons, which typically produce insulin-like peptides express it abundantly. Scale bar 50 µm. (c) Colocalization of Mecr-GFP and ATP5α in 3rd instar larval fatbody tissue. Scale bar 10 µm. (d) Colocalization of human MECR and ATP5α in S2 cells. Scale bar 3.5 µm. Immunostaining was performed using an antibody against human MECR protein and an antibody against ATP5α. All experiments were carried out at least twice.
Extended Data Fig. 5 RNA levels of MECR are reduced in MEPAN patients and relative levels of phospholipids are differentially altered in patient-derived fibroblasts and mecr mutants.
(a) Pedigree of the two patients with MEPAN syndrome identified through Undiagnosed Diseases Network. (b) RNA-seq from blood showing reduced levels of MECR transcripts in both patients. (c–g) Relative phospholipids levels in MEPAN patient-derived fibroblasts compared to the parent-derived control fibroblasts: phosphatidylcholine (PC), phosphatidylethanolamine (PE), phosphatidylinositol (PI), phosphatidylserine (PS) and phosphatidylglycerol (PG). The dots represent values of technical replicates from one set of biological replicates. For statistical analyses one-way ANOVA followed by a Tukey’s post-hoc test are carried out. Error bars represent SEM (*p < 0.05) (h–l) Relative levels of different phospholipids in the mecrTG4 larvae compared to control. The dots represent values of technical replicates from one set of biological replicates (n = 350 2nd instar larva). For statistical analyses, two-tailed Student’s t-test are carried out. Error bars represent SEM (*p < 0.05; ***p < 0.001).
Extended Data Fig. 6 Altered ceramide levels in mecr mutants and human fibroblasts.
(a) Graph showing the ceramide species in the mecrTG4 larvae. Data are presented as mean values +/− SEM (b) Graph showing the relative levels of ceramidephosphoethanolamine (CPE) in the mecrTG4 larvae. For statistical analyses, two-tailed Student’s t-test are carried out. Error bars represent SEM (***p < 0.001). For a and b, the dots represent values of technical replicates from one set of biological replicates (n = 350 2nd instar larva). (c) Graph showing the ceramide species in both patient fibroblasts. The dots represent values of technical replicates from one set of biological replicates. Data are presented as mean values +/− SEM.
Extended Data Fig. 7 Desipramine and Deferiprone treatment lowers glucosylceramide levels in the fly heads in which mecr is reduced in neurons.
(a, b) Graphs showing the fold changes in different glucosylceramide species upon treatment with Desipramine and Deferiprone at 15- and 25-day timepoints. Each square indicates the average value of three technical replicates.
Extended Data Fig. 8 Loss of mecr/MECR leads to a respiratory deficit.
(a) Relative activity of ETC complexes (CI-IV) in mecrTG4 mutants and controls. mecrTG4 mutant larvae display reduced activity of Complex-I, I+III, and IV and increased activity of Complex-II. Each dot represents data from three technical replicates (n = 150 2nd instar larva). For statistical analyses, two-tailed Student’s t test are carried out. Error bars represent SEM (**p < 0.01; ***p < 0.001****p < 0.0001). (b) Relative levels of ATP in fibroblasts from patients and parental control. Each dot represents the values from four experiments. For statistical analyses, one-way ANOVA followed by a Tukey’s post-hoc test are carried out. Error bars represent SEM (***p < 0.001). (c–e) Relative oxygen consumption rates in control and patient derived fibroblasts as measured by Seahorse analyses. (c) Basal respiration, (d) maximal respiration, and (e) spare respiratory capacity are reduced in the patient-derived fibroblasts compared to fibroblasts derived from parent control. Each dot represents the values of replicates in each well from one set of biological replicates. For statistical analyses one-way ANOVA followed by a Dunnett’s multiple comparisons test are carried out. Error bars represent SEM (*p < 0.05; **p < 0.01; ***p < 0.001). (f) Co-IP from one set of biological replicates shows the interaction between NFS1 and ISCU in the fibroblasts. After performing immunoprecipitation using Mouse Anti-ISCU antibody, the blot was probed for NFS1, stripped, and reblotted for ISCU.
Extended Data Fig. 9 Ferritin levels are low in the additional MEPAN patients and the ATP levels, iron levels and aconitase activity are affected in the fibroblasts of Patient III.
(a) Table showing MEPAN patients including mutations, symptoms, and ferritin levels in blood. Out of these six patients described in the table, one patient (Patient III) was described earlier by Heimer et al.10. The other five patients are newly identified individuals who have not been reported elsewhere. (b) Graph showing relative ATP levels in fibroblasts from patient III compared to the fibroblasts from unrelated controls. Each dot represents the values of replicates from three experiments. (c) Graph showing the relative iron levels in the fibroblasts from patient III. Each dot represents the values of replicates from three experiments. (d) Graph showing the relative aconitase activity in the fibroblasts from patient III. Each dot represents the values of replicates from three experiments. For statistical analyses, one-way ANOVA followed by a Tukey’s post-hoc test are carried out. Error bars represent SEM (**p < 0.01).
Extended Data Fig. 10 Reducing iron levels alleviates age-dependent locomotor defects in flies with neuronal knockdown of mecr.
(a, b) Average percentage (a) and climbing time (b) to reach 8 cm of 25-day-old flies with neuronal knockdown of mecr (elav-GAL4>mecr-RNAi) and expressing ferritins. n = 81 (luci-RNAi), n = 76 (mecr-RNAi), n = 74 (mecr-RNAi and Fer1HCH-Fer2LCH) flies. (c, d) Average percentage (c) and climbing time (d) of 25-day-old flies upon neuronal (by elav-GAL4) knockdown of mecr treated with and without low iron food as well as deferiprone. n = 62 (luci-RNAi), n = 155 (mecr-RNAi), n = 105 (mecr-RNAi with low iron food), n = 55 (mecr-RNAi with deferiprone) flies. For a and c, each dot represents the percentage of flies from at least three independent experiments. For b and d, each dot represents the time taken by one fly in at least three independent experiments. (e) Relative amount of iron in the untreated, desipramine and deferiprone-treated fly heads with neuronal knockdown of mecr. Each dot represents the values of replicates from three experiments each using 25 fly heads. (f) Co-IP shows the interaction between Nfs1 and Iscu in the fly heads with neuronal knockdown of mecr. One-way ANOVA followed by a Tukey’s post-hoc test is carried out for statistical analyses. Error bars represent SEM (***p < 0.001; ****p < 0.0001).
Supplementary information
Supplementary Information
Undiagnosed Disease Network Consortia member list and Supplementary Fig. 1 and Table 1.
Supplementary Data Fig. 1
Statistical source data.
Source data
Source Data Fig. 1
Statistical source data.
Source Data Fig. 3
Statistical source data.
Source Data Fig. 4
Statistical source data.
Source Data Fig. 5
Statistical source data.
Source Data Fig. 6
Statistical source data.
Source Data Fig. 7
Statistical source data.
Source Data Fig. 7
Unprocessed western blots.
Source Data Fig. 8
Statistical source data.
Source Data Fig. 8
Unprocessed western blots.
Source Data Extended Data Fig. 1
Statistical source data.
Source Data Extended Data Fig. 1
Unprocessed western blots.
Source Data Extended Data Fig. 2
Statistical source data.
Source Data Extended Data Fig. 3
Statistical source data.
Source Data Extended Data Fig. 3
Unprocessed western blots.
Source Data Extended Data Fig. 5
Statistical source data.
Source Data Extended Data Fig. 6
Statistical source data.
Source Data Extended Data Fig. 7
Statistical source data.
Source Data Extended Data Fig. 8
Statistical source data.
Source Data Extended Data Fig. 8
Unprocessed western blots.
Source Data Extended Data Fig. 9
Statistical source data.
Source Data Extended Data Fig. 10
Statistical source data.
Source Data Extended Data Fig. 10
Unprocessed western blots.
Rights and permissions
Springer Nature or its licensor (e.g. a society or other partner) holds exclusive rights to this article under a publishing agreement with the author(s) or other rightsholder(s); author self-archiving of the accepted manuscript version of this article is solely governed by the terms of such publishing agreement and applicable law.
About this article
Cite this article
Dutta, D., Kanca, O., Byeon, S.K. et al. A defect in mitochondrial fatty acid synthesis impairs iron metabolism and causes elevated ceramide levels. Nat Metab 5, 1595–1614 (2023). https://doi.org/10.1038/s42255-023-00873-0
Received:
Accepted:
Published:
Issue Date:
DOI: https://doi.org/10.1038/s42255-023-00873-0