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Namasivayam S, Baptista RP, Xiao W, Hall EM, Doggett JS, Troell K, Kissinger JC. A novel fragmented mitochondrial genome in the protist pathogen Toxoplasma gondii and related tissue coccidia. Genome Res 2021; 31:852-865. [PMID: 33906963 PMCID: PMC8092004 DOI: 10.1101/gr.266403.120] [Citation(s) in RCA: 9] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/24/2020] [Accepted: 03/09/2021] [Indexed: 12/19/2022]
Abstract
Mitochondrial genome content and structure vary widely across the eukaryotic tree of life, with protists displaying extreme examples. Apicomplexan and dinoflagellate protists have evolved highly reduced mitochondrial genome sequences, mtDNA, consisting of only three cytochrome genes and fragmented rRNA genes. Here, we report the independent evolution of fragmented cytochrome genes in Toxoplasma and related tissue coccidia and evolution of a novel genome architecture consisting minimally of 21 sequence blocks (SBs) totaling 5.9 kb that exist as nonrandom concatemers. Single-molecule Nanopore reads consisting entirely of SBs ranging from 0.1 to 23.6 kb reveal both whole and fragmented cytochrome genes. Full-length cytochrome transcripts including a divergent coxIII are detected. The topology of the mitochondrial genome remains an enigma. Analysis of a cob point mutation reveals that homoplasmy of SBs is maintained. Tissue coccidia are important pathogens of man and animals, and the mitochondrion represents an important therapeutic target. The mtDNA sequence has been elucidated, but a definitive genome architecture remains elusive.
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Affiliation(s)
- Sivaranjani Namasivayam
- Department of Genetics, University of Georgia, Athens, Georgia 30602, USA.,Center for Tropical and Emerging Global Diseases, University of Georgia, Athens, Georgia 30602, USA
| | - Rodrigo P Baptista
- Center for Tropical and Emerging Global Diseases, University of Georgia, Athens, Georgia 30602, USA.,Institute of Bioinformatics, University of Georgia, Athens, Georgia 30602, USA
| | - Wenyuan Xiao
- Department of Genetics, University of Georgia, Athens, Georgia 30602, USA.,Center for Tropical and Emerging Global Diseases, University of Georgia, Athens, Georgia 30602, USA
| | - Erica M Hall
- Department of Genetics, University of Georgia, Athens, Georgia 30602, USA
| | - Joseph S Doggett
- Division of Infectious Diseases, Oregon Health Sciences University, Portland, Oregon 97239, USA.,Division of Infectious Diseases, Veterans Affairs Portland Health Care System, Portland, Oregon 97239, USA
| | - Karin Troell
- Department of Microbiology, National Veterinary Institute, SE-751 89 Uppsala, Sweden
| | - Jessica C Kissinger
- Department of Genetics, University of Georgia, Athens, Georgia 30602, USA.,Center for Tropical and Emerging Global Diseases, University of Georgia, Athens, Georgia 30602, USA.,Institute of Bioinformatics, University of Georgia, Athens, Georgia 30602, USA
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Enhanced Protective Effect of the Combination of Uncaria and Semen Raphani on Vascular Endothelium in Spontaneously Hypertensive Rats. EVIDENCE-BASED COMPLEMENTARY AND ALTERNATIVE MEDICINE 2015; 2015:358352. [PMID: 26539222 PMCID: PMC4619921 DOI: 10.1155/2015/358352] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 02/13/2015] [Revised: 05/20/2015] [Accepted: 05/28/2015] [Indexed: 02/02/2023]
Abstract
Endothelial dysfunction and low-grade inflammation are closely associated with hypertension and other cardiovascular diseases. The combination of Uncaria (U) and Semen Raphani (R) is common in traditional Chinese medicine for the treatment of hypertension and heart diseases. We aimed to investigate the therapeutic effect of the combination of Uncaria and Semen Raphani on spontaneously hypertensive rats (SHRs), and valsartan was used as a positive control. In the present study, all extracts decreased systolic pressure, diastolic pressure, and mean arterial pressure. U alone showed antihypertensive efficacy and effectively decreased CECs count, while R alone showed efficacy in relieving inflammatory level. The combination of U and R showed enhanced effectiveness at lowering activated CECs and improving endothelial integrity of thoracic aorta and mesenteric artery and normalized the level of plasma biomarkers of endothelial damage. The combination of U and R decreased the mRNA level of VCAM-1, Sel-L, TFPI, and Sel-P, while it elevated mRNA expression of FGF-1 and THBD of the thoracic aorta, which may be, at least in part, involved in the mechanism of protective effect on hypertensive endothelial injury.
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Formation of Mitochondrial Genome Concatemers as an Alternative Mechanism Promoting Oncogenic Transformation of Lymphoid Cells. ACTA ACUST UNITED AC 2009; 2:310-312. [PMID: 20046889 DOI: 10.1016/j.bihy.2009.07.003] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
We have previously shown that AIDS-associated lymphomas and lymphoma cell lines contain mitochondrial genome concatemers not present in normal T-lymphocytes. Since cellular homeostasis and energy production rely heavily on mitochondrial DNA (mtDNA) stability, mutations in the mtDNA have long been linked to the development of various types of cancers. In most of the cases, however, neoplastically transformed cells harbor non-mutated mtDNA. Herein, we propose an alternative mechanism that shows how the formation of mitochondrial genome concatemers may promote oncogenic transformation of normal lymphoid progenitor cells when no mtDNA mutations or chromosomal aberrations are present. We detected high reactive oxygen species (ROS) levels in the lymphoma samples tested despite no identification of putative mutations in the coding mtDNA. We propose that the formation of atypical mtDNA configurations (i.e. dimers and concatemers) interferes with normal mitochondrial function. Unstable mitochondria lead to abnormal assembly and dysfunction of the oxidative phosphorylation (OXPHOS) complexes, eventually leading to oxidative stress from elevated production of intracellular ROS. ROS have been reported to activate transcription factors associated with cellular proliferation and apoptosis inhibition. Therefore, we hypothesize that formation of mitochondrial genome concatemers can augment endogenous ROS levels capable of promoting oncogenic transformation of normal lymphoid progenitor cells.
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