bims-cytox1 Biomed news
on Cytochrome oxidase subunit 1
Issue of 2018‒12‒23
eight papers selected by
Gavin McStay
Staffordshire University

  1. Proc Natl Acad Sci U S A. 2018 Dec 21. pii: 201811938. [Epub ahead of print]
    Spinazzi M, Radaelli E, Horré K, Arranz AM, Gounko NV, Agostinis P, Maia TM, Impens F, Morais VA, Lopez-Lluch G, Serneels L, Navas P, De Strooper B.
      The mitochondrial intramembrane rhomboid protease PARL has been implicated in diverse functions in vitro, but its physiological role in vivo remains unclear. Here we show that Parl ablation in mouse causes a necrotizing encephalomyelopathy similar to Leigh syndrome, a mitochondrial disease characterized by disrupted energy production. Mice with conditional PARL deficiency in the nervous system, but not in muscle, develop a similar phenotype as germline Parl KOs, demonstrating the vital role of PARL in neurological homeostasis. Genetic modification of two major PARL substrates, PINK1 and PGAM5, do not modify this severe neurological phenotype. Parl -/- brain mitochondria are affected by progressive ultrastructural changes and by defects in Complex III (CIII) activity, coenzyme Q (CoQ) biosynthesis, and mitochondrial calcium metabolism. PARL is necessary for the stable expression of TTC19, which is required for CIII activity, and of COQ4, which is essential in CoQ biosynthesis. Thus, PARL plays a previously overlooked constitutive role in the maintenance of the respiratory chain in the nervous system, and its deficiency causes progressive mitochondrial dysfunction and structural abnormalities leading to neuronal necrosis and Leigh-like syndrome.
    Keywords:  Leigh syndrome; mitochondria; neurodegeneration; respiratory chain; rhomboid protease
  2. Adv Exp Med Biol. 2018 ;1085 161-162
    Tsang SH, Aycinena ARP, Sharma T.
      Mitochondrial diseases are multisystem disorders: anemia, myopathy, lactic acidosis, CNS abnormality, endocrine abnormalities, renal disease, sensorineural deafness, and retinal involvement. The clinical abnormalities are heterogeneous, and they usually begin in childhood. Premature death occurs because of cardiac conduction defects. The onset is usually before 20 years of age. The fundus shows pigmentary retinopathy, with a salt-and-pepper appearance (Fig. 30.1), but vision remains good in most patients. Systemic involvement includes chronic progressive external ophthalmoplegia (CPEO), with ptosis being the most common complaint, and cardiomyopathy. Other variable features are short stature; cerebellar symptoms; weakness of muscles of the face, pharynx, trunk, or extremities; and progressive hearing loss. Full-field ERG does show evidence of generalized retinal dysfunction, involving both rods and cones. Skeletal muscle biopsy shows ragged red fibers and abnormal mitochondria.
    Keywords:  KSS; Kearns-Sayre syndrome; Mitochondrial disorder
  3. J Assist Reprod Genet. 2018 Dec 15.
    Pompei M, Pompei F.
      The purpose of the paper is to explore novel means to overcome the controversial ban in the USA against mitochondrial replacement therapy, a form of IVF, with the added step of replacing a woman's diseased mutated mitochondria with a donor's healthy mitochondria to prevent debilitating and often fatal mitochondrial diseases. Long proven effective in non-human species, MRT recently performed in Mexico resulted in the birth of a healthy baby boy. We explore the ethics of the ban, the concerns over hereditability of mitochondrial disease and its mathematical basis, the overlooked role of Mitochondrial Eve, the financial burden of mitochondrial diseases for taxpayers, and a woman's reproductive rights. We examine applicable court cases, particularly protection of autonomy within the reproductive rights assured by Roe v Wade. We examine the consequences of misinterpreting MRT as genetic engineering in the congressional funding prohibitions causing the MRT ban by the FDA. Allowing MRT to take place in the USA would ensure a high standard of reproductive medicine and safety for afflicted women wishing to have genetically related children, concurrently alleviating the significant financial burden of mitochondrial diseases on its taxpayers. Since MRT does not modify any genome, it falls outside the "heritable genetic modification" terminology of concern to Congress and the FDA. Correcting this terminology, the IOM's conclusion that MRT is ethical, the continuing normalcy of the first MRT recipient, and increasing public awareness of the promising benefits might be all that is required to modify the FDA's position on MRT.
    Keywords:  MRT; Mitochondrial Eve; Mitochondrial replacement therapy; Reproductive autonomy; Three-parent babies
  4. PLoS One. 2018 ;13(12): e0209489
    Jackson M, Serada N, Sheehan M, Srinivasan S, Mason N, Guha M, Avadhani N.
      Osteosarcoma (OSA) is an aggressive mesenchymal tumor of the bone that affects children and occurs spontaneously in dogs. Human and canine OSA share similar clinical, biological and genetic features, which make dogs an excellent comparative model to investigate the etiology and pathogenesis of OSA. Mitochondrial (mt) defects have been reported in many different cancers including OSA, although it is not known whether these defects contribute to OSA progression and metastasis. Taking a comparative approach using canine OSA cell lines and tumor tissues we investigated the effects of mtDNA content and dysfunction on OSA biology. OSA tumor tissues had low mtDNA contents compared to the matched non-tumor tissues. We observed mitochondrial heterogeneity among the OSA cell lines and the most invasive cells expressing increased levels of OSA metastasis genes contained the highest amount of mitochondrial defects (reduced mtDNA copies, mt respiration, and expression of electron transport chain proteins). While mitochondria maintain a filamentous network in healthy cells, the mitochondrial morphology in OSA cells were mostly "donut shaped", typical of "stressed" mitochondria. Moreover the expression levels of mitochondrial retrograde signaling proteins Akt1, IGF1R, hnRNPA2 and NFkB correlated with the invasiveness of the OSA cells. Furthermore, we demonstrate the causal role of mitochondrial defects in inducing the invasive phenotype by Ethidium Bromide induced-mtDNA depletion in OSA cells. Our data suggest that defects in mitochondrial genome and function are prevalent in OSA and that lower mtDNA content is associated with higher tumor cell invasiveness. We propose that mt defects in OSA might serve as a prognostic biomarker and a target for therapeutic intervention in OSA patients.
  5. Biochim Biophys Acta Mol Cell Biol Lipids. 2018 Dec 12. pii: S1388-1981(18)30369-X. [Epub ahead of print]
    Cirigliano A, Macone A, Bianchi MM, Oliaro-Bosso S, Balliano G, Negri R, Rinaldi T.
      Sterols are essential lipids, involved in many biological processes. In Saccharomyces cerevisiae, the enzymes of the ergosterol biosynthetic pathway (Erg proteins) are localized in different cellular compartments. With the aim of studying organelle interactions, we discovered that Erg27p resides mainly in Lipid Droplets (LDs) in respiratory competent cells, while in absence of respiration, is found mostly in the ER. The results presented in this paper demonstrate an interplay between the mitochondrial respiration and ergosterol production: on the one hand, rho° cells show lower ergosterol content when compared with wild type respiratory competent cells, on the other hand, the ergosterol biosynthetic pathway influences the mitochondrial status, since treatment with ketoconazole, which blocks the ergosterol pathway, or the absence of the ERG27 gene, induced rho° production in S. cerevisiae. The loss of mitochondrial DNA in the ∆erg27 strain is fully suppressed by exogenous addition of ergosterol. These data suggest the notion that ergosterol is essential for maintaining the mitochondrial DNA attached to the inner mitochondrial membrane.
    Keywords:  Ergosterol; Lipid droplets; Mitochondria; Rho° cells; S. cerevisiae; Sterols
  6. Adv Exp Med Biol. 2018 ;1085 163-165
    Tsang SH, Aycinena ARP, Sharma T.
      Patients with maternally inherited diabetes and deafness (MIDD) have insulin-dependent diabetes with relatively low BMI; usually the onset of the diabetes is during the third or fourth decade of life and it is associated with progressive neurosensory deafness. The fundus shows circumferentially oriented but discontinuous patches of RPE and choriocapillaris (CC) atrophy around the macula, within the arcades (Figs. 31.1 and 31.2). Sometimes even hyperpigmentation can be seen, also around the optic nerve, or pattern-like dystrophy may occur. Vision is usually good, about 20/40 or better. Fundus autofluorescence (FAF) shows decreased AF in the areas of RPE atrophy, surrounded by a zone of speckled AF. No generalized retinal dysfunction is seen on full-field electroretinography (ERG), but pattern ERG or multifocal ERG shows abnormal function. Asymptomatic maternal relatives harboring the mutation may show pigmentary changes, hearing loss, and in some, diabetes. Another disorder associated with the same A3243G mitochondrial DNA (mtDNA) mutation as MIDD is Mitochondrial Encephalomyopathy with Lactic Acidosis and Stroke-like episodes (MELAS). The stroke-like episode (such as hemiplegia) occurs at about 5-15 years of age, and severe encephalopathy may cause death at a young age. Patients may also experience headache, vomiting, visual field defects, or cortical blindness.
    Keywords:  MIDD; Mitochondrial disorder; Mitochondrial inherited diabetes and deafness
  7. Hum Mol Genet. 2018 Dec 19.
    Pulman J, Ruzzenente B, Bianchi L, Rio M, Boddaert N, Munnich A, Rötig A, Metodiev MD.
      Mitochondria contain a dedicated translation system, which is responsible for the intramitochondrial synthesis of 13 mtDNA-encoded polypeptides essential for the biogenesis of oxidative phosphorylation (OXPHOS) complexes I and III to V. Mutations in nuclear genes encoding factors involved in mitochondrial translation result in isolated or multiple OXPHOS deficiencies and mitochondrial disease. Here, we report the identification of disease-causing variants in the MRPS28 gene, encoding the small mitoribosomal subunit (mtSSU) protein bS1m in a patient with intrauterine growth retardation, craniofacial dysmorphism and developmental delay. Whole exome sequencing helped identify a seemingly homozygous missense variant NM_014018.2:c.356A>G, p.(Lys119Arg) which affected a highly conserved lysine residue. The variant was present in the mother in a heterozygous state, but not in the father who likely carried a large deletion spanning exon 2 and parts of introns 1 and 2 that could account for the apparent homozygosity of the patient. PCR amplification and Sanger sequencing of MRPS28 cDNA from patient fibroblasts revealed the presence of a truncated MRPS28 transcript, which lacked exon 2. Molecular and biochemical characterization of patient fibroblasts revealed a decrease in the abundance of the bS1m protein, decreased abundance of assembled mtSSU and inhibited mitochondrial translation. Consequently, OXPHOS biogenesis and cellular respiration were compromised in these cells. Expression of wild-type MRPS28 restored mitoribosomal assembly, mitochondrial translation and OXPHOS biogenesis, thereby demonstrating the deleterious nature of the identified MRPS28 variants. Thus, MRPS28 joins the increasing number of nuclear genes encoding mitoribosomal structural proteins linked to mitochondrial disease.
  8. BMC Res Notes. 2018 Dec 20. 11(1): 911
    Bianco A, Valletti A, Longo G, Bisceglia L, Montoya J, Emperador S, Guerriero S, Petruzzella V.
      OBJECTIVES: Leber's hereditary optic neuropathy (LHON) is a mitochondrial genetic disease characterized by a variable and reduced penetrance. Individuals carrying a primary LHON-causing mitochondrial DNA (mtDNA) mutation may either remain asymptomatic lifelong, as unaffected carriers, or develop sudden central visual loss that rapidly aggravates over some weeks. Over the years several genetic/environmental triggers able to modulate the risk of developing LHON have been proposed. We provided data supporting a possible correlation between LHON penetrance and the mtDNA copy number, a raw index of mitochondrial mass, whose increase could represent a compensatory response that cells implement to alleviate the pathogenic effect of the primary LHON-causing mtDNA mutations.DATA DESCRIPTION: We collected Italian and Spanish subjects harboring one of the three common LHON primary mutations, either in heteroplasmic or homoplasmic status. For each population we were able to discriminate between affected subjects presenting typical clinical tracts of LHON and LHON-causing mutation carriers showing no symptoms correlated with vision loss. Each subject has been characterized for the presence of a LHON primary mutation, for its status of homoplasmy or heteroplasmy, and for the mtDNA content per cell, expressed as relative mtDNA/nDNA ratio respect to controls. Additional clinical information is present for all the Italian subjects.
    Keywords:  Incomplete penetrance; Leber’s hereditary optic neuropathy; Mitochondrial genome; mtDNA copy number