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Stroke
Published in Henry J. Woodford, Essential Geriatrics, 2022
Mitochondria were originally symbiotic bacteria that migrated into animal cells with the advantage of being able to perform aerobic metabolism. They possess their own DNA and are inherited by the division of the mitochondria contained with the maternal egg cell. Various disorders have been described relating to mutations in mitochondrial DNA.128 One of these is ‘mitochondrial encephalomyopathy, lactic acidosis and stroke-like episodes' (MELAS). This disorder is very rare and usually presents in children or young adults with focal neurological deficits, seizures and progressive cognitive impairment. There may be an associated history of exercise intolerance, deafness, diabetes, migraine and/or learning disability. Fasting plasma and CSF lactate levels are elevated. Muscle biopsy may demonstrate ragged red fibres or abnormal mitochondria. There is no treatment for this condition.
Basic Cell Biology
Published in Kedar N. Prasad, Handbook of RADIOBIOLOGY, 2020
Mitochondria contain DNA, which, like bacteria, is circular in shape. The mitochondrial DNA is capable of coding the information for the biosynthesis of some mitochondrial proteins.22b Indeed, it has been shown that mitochondria synthesize RNA and protein in vitro. These studies indicate that mitochondria occupy semiautonomous status within the cell. Further work is being done to elucidate the role of mitochondrial DNA in cellular metabolism.
Myoclonic epilepsy and ragged red fiber (MERRF) disease
Published in William L. Nyhan, Georg F. Hoffmann, Aida I. Al-Aqeel, Bruce A. Barshop, Atlas of Inherited Metabolic Diseases, 2020
William L. Nyhan, Georg F. Hoffmann, Aida I. Al-Aqeel, Bruce A. Barshop
Mitochondrial genetics differs from nuclear genetics in that the mitochondrial genome is inherited exclusively from the mother. The mitochondrial DNA is transmitted via the cytoplasm of the egg. A cell may contain hundreds of mitochondria; during ovum formation, the number of mitochondria increases while the number of DNAs per mitochondrion decreases to one from two [55]. With growth and development, differences emerge among tissues in mitochondrial content and amounts of mitochondrial DNA. The latter is highest in brain, the organ most vulnerable to diseases of oxidative phosphorylation [56]. Cells may contain more than one sequence of mitochondrial DNA; this is referred to as heteroplasmy.
Laboratory testing for mitochondrial diseases: biomarkers for diagnosis and follow-up
Published in Critical Reviews in Clinical Laboratory Sciences, 2023
Abraham J. Paredes-Fuentes, Clara Oliva, Roser Urreizti, Delia Yubero, Rafael Artuch
The mitochondrial metabolism is probably the most intricate within cellular metabolism. The double genetic origin that controls oxidative phosphorylation (OXPHOS), in which proteins are codified by either nuclear or mitochondrial genomes (mitochondria are the only organelles with such double genetic regulation), and the fundamental pathways that occur in mitochondria partially explain this complexity [1,2]. All clinical presentations, ages of disease onset and inheritance types (e.g. maternal, X-linked, dominant, recessive, or sporadic) are possible in mitochondrial diseases (MDs), which are a group of rare genetic disorders that impair different mitochondrial biological functions [2,3]. When mutations are detected in nuclear genes (nDNA), they follow Mendelian inheritance and exhibit dominant, recessive or X-linked patterns. However, when mutations are localized in mitochondrial DNA (mtDNA), maternal inheritance, or sporadic mutations occur along with other genetic features such as heteroplasmy, mitotic segregation, or random distributions of mutated mtDNA among cells. Thus, the pathophysiological mechanisms of MDs are heterogeneous, and the diagnostic and treatment monitoring aspects present challenges to health professionals and researchers working in this field [3–5]. This group includes clinical laboratory professionals, because the lack of specificity and sensitivity of the currently available biomarkers used in clinical laboratories for both diagnostic and patient follow-up purposes is generally recognized [6–8].
Mitochondria targeting molecular transporters: synthesis, lipophilic effect, and ionic complex
Published in Drug Delivery, 2022
Akula S. N. Murthy, Sanket Das, Tejinder Singh, Tae-Wan Kim, Nasim Sepay, Seob Jeon, Jungkyun Im
Mitochondria generate ATP by oxidative phosphorylation and are thus regarded as cell powerhouses. They also engage in a wide range of cellular processes including homeostasis of calcium concentration, regulation of cellular redox states, and metabolism of carbohydrates, fatty acids, and amino acids (Wallace et al., 2010; Murphy et al., 2016). Additionally, mitochondria are involved in the modulation of cellular apoptosis (Wang & Youle, 2009). However, pathological events and the free radicals generated by the mitochondrial respiratory system can damage mitochondria. Genetic mutation of mitochondrial DNA or nuclear DNA can also create defects in mitochondrial components (Smith et al., 2012). Since mitochondria are linked to several biological processes, any such negative features in mitochondria can lead to mitochondrial dysfunction, causing other diverse human diseases including cancers, type 2 diabetes, obesity, ischemia-reperfusion injury, and neurodegenerative diseases, such as Alzheimer’s disease, Parkinson’s disease, and Huntington’s disease (Lin & Beal, 2006; Prime et al., 2009; Lu et al., 2016; Intihar et al., 2019).
Forensic evaluation of mitochondrial DNA heteroplasmy in Gujarat population, India
Published in Annals of Human Biology, 2022
Mohammed H. M. Alqaisi, Molina Madhulika Ekka, Bhargav C. Patel
The mitochondrial DNA is homoplasmic when all mitochondrial DNA molecules are identical. On the other hand, if mutant mtDNA coexists alongside wild-type mtDNA and has two distinct populations of mtDNA, it is called heteroplasmy (Melton 2004; Wallace and Chalkia 2013; Li et al. 2016). Heteroplasmy is primarily caused by the higher mutation rates observed in mitochondrial genomes compared to nuclear genomes (Brown et al. 1982; Wallace et al. 1987; Wallace and Chalkia 2013). Moreover, hypervariable regions are more susceptible to having heteroplasmies than other mitochondrial genome regions (Greenberg et al. 1983; Li et al. 2015). In mtDNA sequences, two forms of heteroplasmy may be found: point heteroplasmy (PH) and length/C-stretch heteroplasmy (LH). PH is the most common type of heteroplasmy used in forensic analysis. It is possible to detect two nucleotides as two peaks at a single position in an electropherogram, indicating the presence of PH (Figure 1). However, LH (Figure 2) is generally triggered when C residues are inserted or when thymine is substituted for cytosine (Bendall and Sykes 1995; Bendall et al. 1997; Lutz-Bonengel et al. 2008; Parson et al. 2014).