Browsing by Subject "DEFECT"

Sort by: Order: Results:

Now showing items 1-3 of 3
  • Garone, Caterina; Taylor, Robert W.; Nascimento, Andres; Poulton, Joanna; Fratter, Carl; Dominguez-Gonzalez, Cristina; Evans, Julie C.; Loos, Mariana; Isohanni, Pirjo; Suomalainen, Anu; Ram, Dipak; Hughes, M. Imelda; McFarland, Robert; Barca, Emanuele; Gomez, Carlos Lopez; Jayawant, Sandeep; Thomas, Neil D.; Manzur, Adnan Y.; Kleinsteuber, Karin; Martin, Miguel A.; Kerr, Timothy; Gorman, Grainne S.; Sommerville, Ewen W.; Chinnery, Patrick F.; Hofer, Monika; Karch, Christoph; Ralph, Jeffrey; Camara, Yolanda; Madruga-Garrido, Marcos; Dominguez-Carral, Jana; Ortez, Carlos; Emperador, Sonia; Montoya, Julio; Chakrapani, Anupam; Kriger, Joshua F.; Schoenaker, Robert; Levin, Bruce; Thompson, John L. P.; Long, Yuelin; Rahman, Shamima; Donati, Maria Alice; DiMauro, Salvatore; Hirano, Michio (2018)
    Background Thymine kinase 2 (TK2) is a mitochondrial matrix protein encoded in nuclear DNA and phosphorylates the pyrimidine nucleosides: thymidine and deoxycytidine. Autosomal recessive TK2 mutations cause a spectrum of disease from infantile onset to adult onset manifesting primarily as myopathy. Objective To perform a retrospective natural history study of a large cohort of patients with TK2 deficiency. Methods The study was conducted by 42 investigators across 31 academic medical centres. Results We identified 92 patients with genetically confirmed diagnoses of TK2 deficiency: 67 from literature review and 25 unreported cases. Based on clinical and molecular genetics findings, we recognised three phenotypes with divergent survival: (1) infantile-onset myopathy (42.4%) with severe mitochondrial DNA (mtDNA) depletion, frequent neurological involvement and rapid progression to early mortality (median post-onset survival (POS) 1.00, CI 0.58 to 2.33 years); (2) childhood-onset myopathy (40.2%) with mtDNA depletion, moderate-to-severe progression of generalised weakness and median POS at least 13 years; and (3) late-onset myopathy (17.4%) with mild limb weakness at onset and slow progression to respiratory insufficiency with median POS of 23 years. Ophthalmoparesis and facial weakness are frequent in adults. Muscle biopsies show multiple mtDNA deletions often with mtDNA depletion. Conclusions In TK2 deficiency, age at onset, rate of weakness progression and POS are important variables that define three clinical subtypes. Nervous system involvement often complicates the clinical course of the infantile-onset form while extraocular muscle and facial involvement are characteristic of the late-onset form. Our observations provide essential information for planning future clinical trials in this disorder.
  • Richter, Uwe; Evans, Molly E.; Clark, Wesley C.; Marttinen, Paula; Shoubridge, Eric A.; Suomalainen, Anu; Wredenberg, Anna; Wedell, Anna; Pan, Tao; Battersby, Brendan J. (2018)
    Post-transcriptional RNA modifications play a critical role in the pathogenesis of human mitochondrial disorders, but the mechanisms by which specific modifications affect mitochondrial protein synthesis remain poorly understood. Here we used a quantitative RNA sequencing approach to investigate, at nucleotide resolution, the stoichiometry and methyl modifications of the entire mitochondrial tRNA pool, and establish the relevance to human disease. We discovered that a N-1 -methyladenosine (m(1)A) modification is missing at position 58 in the mitochondrial tRNA(LYs) of patients with the mitochondrial DNA mutation m.8344 A > G associated with MERRF (myoclonus epilepsy, ragged-red fibers). By restoring the modification on the mitochondrial tRNA(LYs), we demonstrated the importance of the m(1)A58 to translation elongation and the stability of selected nascent chains. Our data indicates regulation of post-transcriptional modifications on mitochondrial tRNAs is finely tuned for the control of mitochondrial gene expression. Collectively, our findings provide novel insight into the regulation of mitochondrial tRNAs and reveal greater complexity to the molecular pathogenesis of MERRF.
  • Vakkilainen, Svetlana; Skoog, Tiina; Einarsdottir, Elisabet; Middleton, Anna; Pekkinen, Minna; Öhman, Tiina; Katayama, Shintaro; Krjutškov, Kaarel; Kovanen, Panu E.; Varjosalo, Markku; Lindqvist, Arne; Kere, Juha; Mäkitie, Outi (2019)
    RMRP was the first non-coding nuclear RNA gene implicated in a disease. Its mutations cause cartilage-hair hypoplasia (CHH), an autosomal recessive skeletal dysplasia with growth failure, immunodeficiency, and a high risk for malignancies. This study aimed to gain further insight into the role of RNA Component of Mitochondrial RNA Processing Endoribonuclease (RMRP) in cellular physiology and disease pathogenesis. We combined transcriptome analysis with single-cell analysis using fibroblasts from CHH patients and healthy controls. To directly assess cell cycle progression, we followed CHH fibroblasts by pulse-labeling and time-lapse microscopy. Transcriptome analysis identified 35 significantly upregulated and 130 downregulated genes in CHH fibroblasts. The downregulated genes were significantly connected to the cell cycle. Multiple other pathways, involving regulation of apoptosis, bone and cartilage formation, and lymphocyte function, were also affected, as well as PI3K-Akt signaling. Cell-cycle studies indicated that the CHH cells were delayed specifically in the passage from G2 phase to mitosis. Our findings expand the mechanistic understanding of CHH, indicate possible pathways for therapeutic intervention and add to the limited understanding of the functions of RMRP.