Altered mitochondrial function in cells carrying a premutation or unmethylated full mutation of the FMR1 gene


Fragile X-related disorders are due to a dynamic mutation of the CGG repeat at the 5′ UTR of the FMR1 gene, coding for the RNA-binding protein FMRP. As the CGG sequence expands from premutation (PM, 56-200 CGGs) to full mutation (> 200 CGGs), FMRP synthesis decreases until it is practically abolished in fragile X syndrome (FXS) patients, mainly due to FMR1 methylation. Cells from rare individuals with no intellectual disability and carriers of an unmethylated full mutation (UFM) produce slightly elevated levels of FMR1-mRNA and relatively low levels of FMRP, like in PM carriers. With the aim of clarifying how UFM cells differ from CTRL and FXS cells, a comparative proteomic approach was undertaken, from which emerged an overexpression of SOD2 in UFM cells, also confirmed in PM but not in FXS. The SOD2-mRNA bound to FMRP in UFM more than in the other cell types. The high SOD2 levels in UFM and PM cells correlated with lower levels of superoxide and reactive oxygen species (ROS), and with morphological anomalies and depolarization of the mitochondrial membrane detected through confocal microscopy. The same effect was observed in CTRL and FXS after treatment with MC2791, causing SOD2 overexpression. These mitochondrial phenotypes reverted after knock-down with siRNA against SOD2-mRNA and FMR1-mRNA in UFM and PM. Overall, these data suggest that in PM and UFM carriers, which have high levels of FMR1 transcription and may develop FXTAS, SOD2 overexpression helps to maintain low levels of both superoxide and ROS with signs of mitochondrial degradation.

This is a preview of subscription content, log in to check access.

Access options

Buy single article

Instant unlimited access to the full article PDF.

US$ 39.95

Price includes VAT for USA

Subscribe to journal

Immediate online access to all issues from 2019. Subscription will auto renew annually.

US$ 199

This is the net price. Taxes to be calculated in checkout.

Fig. 1
Fig. 2
Fig. 3
Fig. 4
Fig. 5
Fig. 6


  1. Alvarez-Mora MI, Rodriguez-Revenga L, Madrigal I, Guitart-Mampel M, Garrabou G, Milà M (2017) Impaired mitochondrial function and dynamics in the pathogenesis of FXTAS. Mol Neurobiol 54:6896–6902

  2. Ariza J, Steward C, Rueckert F, Widdison M, Coffman R, Afjei A, Noctor SC, Hagerman R, Hagerman P, Martínez-Cerdeño V (2015) Dysregulated iron metabolism in the choroid plexus in fragile X-associated tremor/ataxia syndrome. Brain Res 1598:88–96

  3. Ariza J, Rogers H, Hartvigsen A, Snell M, Dill M, Judd D, Hagerman P, Martínez-Cerdeño V (2017) Iron accumulation and dysregulation in the putamen in fragile X-associated tremor/ataxia syndrome. Mov Disord 32:585–591

  4. Bagni C, Greenough WT (2005) From mRNP trafficking to spine dysmorphogenesis: the roots of fragile X syndrome. Nat Rev Neurosci 6:376–387

  5. Borgstahl GE, Parge HE, Hickey MJ, Beyer WF Jr, Hallewell RA, Tainer JA (1992) The structure of human mitochondrial manganese superoxide dismutase reveals a novel tetrameric interface of two 4-helix bundles. Cell 71:107–118

  6. Brykczynska U, Pecho-Vrieseling E, Thiemeyer A, Klein J, Fruh I, Doll T, Manneville C, Fuchs S, Iazeolla M, Beibel M et al (2016) CGG repeat-Induced FMR1 silencing depends on the expansion size in human iPSCs and neurons carrying unmethylated full mutations. Stem Cell Rep 7:1059–1071

  7. Culotta VC, Yang M, O'Halloran TV (2006) Activation of superoxide dismutases: putting the metal to the pedal. Biochim Biophys Acta 1763:747–758

  8. Darnell JC, Van Driesche SJ, Zhang C, Hung KY, Mele A, Fraser CE, Stone EF, Chen C, Fak JJ, Chi SW et al (2011) FMRP stalls ribosomal translocation on mRNAs linked to synaptic function and autism. Cell 146:247–261

  9. Davidovic L, Navratil V, Bonaccorso CM, Catania MV, Bardoni B, Dumas ME (2011) A metabolomic and systems biology perspective on the brain of the fragile X syndrome mouse model. Genome Res 21:2190–2202

  10. Fernández E, Rajan N, Bagni C (2013) The FMRP regulon: from targets to disease convergence. Front Neurosci 7:191

  11. Ferrari F, Mercaldo V, Piccoli G, Sala C, Cannata S, Achsel T, Bagni C (2007) The fragile X mental retardation protein-RNP granules show an mGluR-dependent localization in the post-synaptic spines. Mol Cell Neurosci 34:343–354

  12. Fivenson EM, Lautrup S, Sun N, Scheibye-Knudsen M, Stevnsner T, Nilsen H, Bohr VA, Fang EF (2017) Mitophagy in neurodegeneration and aging. Neurochem Int 109:202–209

  13. Glineburg MR, Todd PK, Charlet-Berguerand N, Sellier C (2018) Repeat-associated non-AUG (RAN) translation and other molecular mechanisms in Fragile X tremor ataxia syndrome. Brain Res 1693:43–54

  14. Hagerman PJ, Hagerman RJ (2004) The fragile-X premutation: a maturing perspective. Am J Hum Genet 74:805–816

  15. Hukema RK, Buijsen RA, Raske C, Severijnen LA, Nieuwenhuizen-Bakker I, Minneboo M, Maas A, de Crom R, Kros JM, Hagerman PJ et al (2014) Induced expression of expanded CGG RNA causes mitochondrial dysfunction in vivo. Cell Cycle 13:2600–2608

  16. Jacquemont S, Pacini L, Jønch AE, Cencelli G, Rozenberg I, He Y, D'Andrea L, Pedini G, Eldeeb M, Willemsen R et al (2018) Protein synthesis levels are increased in a subset of individuals with fragile X syndrome. Hum Mol Genet 27:3825

  17. Kaplan ES, Cao Z, Hulsizer S, Tassone F, Berman RF, Hagerman PJ, Pessah IN (2012) Early mitochondrial abnormalities in hippocampal neurons cultured from Fmr1 pre-mutation mouse model. J Neurochem 123:613–621

  18. Klemmer P, Meredith RM, Holmgren CD, Klychnikov OI, Stahl-Zeng J, Loos M, van der Schors RC, Wortel J, de Wit H, Spijker S et al (2011) Proteomics, ultrastructure, and physiology of hippocampal synapses in a fragile X syndrome mouse model reveal presynaptic phenotype. J Biol Chem 286:25495–25504

  19. Lanni S, Goracci M, Borrelli L, Mancano G, Chiurazzi P, Moscato U, Ferrè F, Helmer-Citterich M, Tabolacci E, Neri G (2013) Role of CTCF protein in regulating FMR1 locus transcription. PLoS Genet 9:e1003601

  20. Leboucher A, Pisani DF, Martinez-Gili L, Chilloux J, Bermudez-Martin P, Van Dijck A, Ganief T, Macek B, Becker JAJ, Le Merrer J, Kooy RF, Amri EZ, Khandjian EW, Dumas ME, Davidovic L (2019) The translational regulator FMRP controls lipid and glucose metabolism in mice and humans. Mol Metab 21:22–35

  21. Lemasters JJ (2014) Variants of mitochondrial autophagy: types 1 and 2 mitophagy and micromitophagy (Type 3). Redox Biol 2:749–754

  22. Liao L, Park SK, Xu T, Vanderklish P, Yates JR 3rd (2008) Quantitative proteomic analysis of primary neurons reveals diverse changes in synaptic protein content in fmr1 knockout mice. Proc Natl Acad Sci USA 105:15281–15286

  23. Lin MT, Beal MF (2006) Mitochondrial dysfunction and oxidative stress in neurodegenerative diseases. Nature 443:787–795

  24. Loesch DZ, Annesley SJ, Trost N, Bui MQ, Lay ST, Storey E, De Piazza SW, Sanislav O, Francione LM, Hammersley EM et al (2017) Novel blood biomarkers are associated with white matter lesions in fragile X-associated tremor/ataxia syndrome. Neurodegener Dis 17:22–30

  25. Matic K, Eninger T, Bardoni B, Davidovic L, Macek B (2014) Quantitative phosphoproteomics of murine Fmr1-KO cell lines provides new insights into FMRP-dependent signal transduction mechanisms. J Proteome Res 13:4388–4397

  26. Matilainen O, Quirós PM, Auwerx J (2017) Mitochondria and epigenetics-crosstalk in homeostasis and stress. Trends Cell Biol 27:453–463

  27. Maulucci G, Labate V, Mele M, Panieri E, Arcovito G, Galeotti T, Østergaard H, Winther JR, De Spirito M, Pani G (2008) High-resolution imaging of redox signaling in live cells through an oxidation-sensitive yellow fluorescent protein. Sci Signal 1:pl3

  28. Misgeld T, Schwarz TL (2017) Mitostasis in neurons: maintaining mitochondria in an extended cellular architecture. Neuron 96:651–666

  29. Monzo K, Dowd SR, Minden JS, Sisson JC (2010) Proteomic analysis reveals CCT is a target of fragile X mental retardation protein regulation in Drosophila. Dev Biol 340:408–418

  30. Napoli E, Ross-Inta C, Wong S, Omanska-Klusek A, Barrow C, Iwahashi C, Garcia-Arocena D, Sakaguchi D, Berry-Kravis E, Hagerman R et al (2011) Altered zinc transport disrupts mitochondrial protein processing/import in fragile X-associated tremor/ataxia syndrome. Hum Mol Genet 20:3079–3092

  31. Napoli E, Song G, Wong S, Hagerman R, Giulivi C (2016) Altered bioenergetics in primary dermal fibroblasts from adult carriers of the FMR1 premutation before the onset of the neurodegenerative disease fragile X-associated tremor/ataxia syndrome. Cerebellum 15:552–564

  32. Pasciuto E, Bagni C (2014) SnapShot: FMRP mRNA targets and diseases. Cell 158:1446–1446

  33. Pietrobono R, Tabolacci E, Zalfa F, Zito I, Terracciano A, Moscato U, Bagni C, Oostra BA, Chiurazzi P, Neri G (2005) Molecular dissection of the events leading to inactivation of the FMR1 gene. Hum Mol Genet 14:267–277

  34. Primerano B, Tassone F, Hagerman RJ, Hagerman P, Amaldi F, Bagni C (2002) Reduced FMR1 mRNA translation efficiency in fragile X patients with premutations. RNA 8:1482–1488

  35. Reid MA, Dai Z, Locasale JW (2017) The impact of cellular metabolism on chromatin dynamics and epigenetics. Nat Cell Biol 19:1298–1306

  36. Rizzo G, Pizza F, Scaglione C, Tonon C, Lodi R, Barbiroli B, Ambrosetto P, Martinelli P (2006) A case of fragile X premutation tremor/ataxia syndrome with evidence of mitochondrial dysfunction. Mov Disord 21:1541–1542

  37. Ross-Inta C, Omanska-Klusek A, Wong S, Barrow C, Garcia-Arocena D, Iwahashi C, Berry-Kravis E, Hagerman RJ, Hagerman PJ, Giulivi C (2010) Evidence of mitochondrial dysfunction in fragile X-associated tremor/ataxia syndrome. Biochem J 429:545–552

  38. Rueden CT, Schindelin J, Hiner MC, DeZonia BE, Walter AE, Arena ET, Eliceiri KW (2017) Image J2: ImageJ for the next generation of scientific image data. BMC Bioinform 18:529

  39. Sellier C, Freyermuth F, Tabet R, Tran T, He F, Ruffenach F, Alunni V, Moine H, Thibault C, Page A et al (2013) Sequestration of DROSHA and DGCR8 by expanded CGG RNA repeats alters microRNA processing in fragile X-associated tremor/ataxia syndrome. Cell Rep 3:869–880

  40. Shevchenko A, Tomas H, Havlis J, Olsen JV, Mann M (2006) In-gel digestion for mass spectrometric characterization of proteins and proteomes. Nat Protoc 1:2856–2860

  41. Smeets HJ, Smits AP, Verheij CE, Theelen JP, Willemsen R, van de Burgt I, Hoogeveen AT, Oosterwijk JC, Oostra BA (1995) Normal phenotype in two brothers with a full FMR1 mutation. Hum Mol Genet 4:2103–2108

  42. Song G, Napoli E, Wong S, Hagerman R, Liu S, Tassone F, Giulivi C (2016) Altered redox mitochondrial biology in the neurodegenerative disorder fragile X-tremor/ataxia syndrome: use of antioxidants in precision medicine. Mol Med 22:548–559.

  43. Tabolacci E, Moscato U, Zalfa F, Bagni C, Chiurazzi P, Neri G (2008) Epigenetic analysis reveals a euchromatic configuration in the FMR1 unmethylated full mutations. Eur J Hum Genet 16:1487–1498

  44. Tassone F, Hagerman RJ, Taylor AK, Gane LW, Godfrey TE, Hagerman PJ (2000) Elevated levels of FMR1 mRNA in carrier males: a new mechanism of involvement in the fragile-X syndrome. Am J Hum Genet 66:6–15

  45. Todd PK, Oh SY, Krans A, Pandey UB, Di Prospero NA, Min KT, Taylor JP, Paulson HL (2010) Histone deacetylases suppress CGG repeat-induced neurodegeneration via transcriptional silencing in models of fragile X tremor ataxia syndrome. PLoS Genet 6:e1001240

  46. Todd PK, Oh SY, Krans A, He F, Sellier C, Frazer M, Renoux AJ, Chen KC, Scaglione KM, Basrur V et al (2013) CGG repeat-associated translation mediates neurodegeneration in fragile X tremor ataxia syndrome. Neuron 78:440–455

  47. Usdin K, Kumari D (2015) Repeat-mediated epigenetic dysregulation of the FMR1 gene in the fragile X-related disorders. Front Genet 6:192

  48. Valente S, Mellini P, Spallotta F, Carafa V, Nebbioso A, Polletta L, Carnevale I, Saladini S, Trisciuoglio D, Gabellini C et al (2007) 1,4-Dihydropyridines active on the SIRT1/AMPK pathway ameliorate skin repair and mitochondrial function and exhibit inhibition of proliferation in cancer cells. J Med Chem 59:1471–1491

  49. Xu B, Zhang Y, Zhan S, Wang X, Zhang H, Meng X, Ge W (2018) Proteomic profiling of brain and testis reveals the diverse changes in ribosomal proteins in fmr1 knockout mice. Neuroscience 371:469–483

  50. Zhang YQ, Matthies HJ, Mancuso J, Andrews HK, Woodruff E 3rd, Friedman D, Broadie K (2004) The Drosophila fragile X-related gene regulates axoneme differentiation during spermatogenesis. Dev Biol 270:290–307

  51. Zhang YQ, Friedman DB, Wang Z, Woodruff E 3rd, Pan L, O'Donnell J, Broadie K (2005) Protein expression profiling of the drosophila fragile X mutant brain reveals up-regulation of monoamine synthesis. Mol Cell Proteomics 4:278–290

Download references


We gratefully acknowledge families, who spontaneously participate supporting our research.


This work was supported by Telethon Foundation grant (GGP15257A) and PRIN (Prot. 201789LFKB)to E.T.,and by the Italian Association for Fragile X syndrome.

Author information

Correspondence to Elisabetta Tabolacci.

Ethics declarations

Conflict of interest

The authors declare no conflict of interest.

Additional information

Publisher's Note

Springer Nature remains neutral with regard to jurisdictional claims in published maps and institutional affiliations.

Electronic supplementary material

Rights and permissions

Reprints and Permissions

About this article

Verify currency and authenticity via CrossMark

Cite this article

Nobile, V., Palumbo, F., Lanni, S. et al. Altered mitochondrial function in cells carrying a premutation or unmethylated full mutation of the FMR1 gene. Hum Genet 139, 227–245 (2020).

Download citation