Maternally inherited

Mitochondria are unique organelles in that they contain their own DNA (mtDNA), which, in addition to ribosomal RN A (rRNA) and transfer RN A (tRNA)-coding sequences, also encodes 13 polypeptides which are components of complexes I, III, IV, and V (Anderson et al., 1981). This fact has important implications for both the genetics and the etiology of the respiratory chain disorders. Since mtDNA is maternally-inherited, a defect of a respiratory complex due to a mtDNA deletion would be expected to show a pattern of maternal transmission. However the situation is complicated by the fact that the majority of the polypeptide subunits of complexes I, III, IV, and V, and all subunits of complex II, are encoded by nuclear DNA. A defect in a nuclear-coded subunit of one of the respiratory complexes would be expected to show classic Mendelian inheritance. A further complication exists in that it is now established that some respiratory chain disorders result from defects of communication between nuclear and mitochondrial genomes (Zeviani et al., 1989). Since many mitochondrial proteins are synthesized in the cytosol and require a sophisticated system of posttranslational processing for transport and assembly, it is apparent that a diversity of genetic errors is to be expected. 

Myoclonic epilepsy with ragged-red fibers (MERPF) is a rare syndrome which shows clear maternal inheritance and a variable clinical pattern including progressive myoclonus, cerebellar ataxia, dementia, and muscle weakness. It is associated with an A-to-G transition at position 8344 of the tRNA Lys gene in the mtDNA. The mutation is heteroplasmic and produces similar multicomplex deficiencies as are seen in KSS. 

In the formation of the zygote, all mitochondria are contributed by the ovum. Therefore, mtDNA is transmitted by maternal inheritance in a vertical, nonmendelian fashion. Strictly maternal transmission of mtDNA has been documented in humans by studies of restriction fragment length polymorphisms (RFLPs) in DNA from platelets. As exemplified by the disorders outlined above,... 

As described above, maternal inheritance has been documented in diseases due to point mutations of mtDNA, while most diseases due to mtDNA deletions or duplications are sporadic. 

This type of inheritance, also known as maternal inheritance, applies to genes in mitochondrial DNA. Mitochondria, which are structures in each cell that convert molecules into energy, each contain a small amount of DNA. Because only egg cells contribute mitochondria to the developing embryo, only females can pass on mitochondrial conditions to their children. Mitochondrial disorders can appear in every generation of a family and can affect both males and females, but fathers do not pass mitochondrial traits to their children. 

The circular mitochondrial chromosome encodes 13 of the more than 80 proteins that comprise the major complexes of oxidative phosphorylation as well as 22 tRNAs and 2 rRNAs. Mutations in these genes affect highly aerobic tissues (nerves, muscle), and the diseases exhibit characteristic mitochondrial pedigrees (maternal inheritance). 

F. Mitochondrial disorders exhibit a maternal inheritance pattern. 

Bohman, M., Sigvardsson, S., and Cloninger, C.R. (1981) Maternal inheritance of alcohol abuse cross-fostering analysis of adopted women. Arch Gen Psychiatry 38 965-969. 

Gene containment Natural gene containment due to maternal inheritance Potential outcrossing among weeds... 

Rapid rearrangement of a polymorphic minisatellite within the D-loop/control region of the 5. mansoni mitochondrial genome has also been reported by various authors (Minchella et al., 1994 Bieberich and Minchella, 2001 Jannolti-Passos et al., 2001). These observations are discussed in detail in the section entitled Maternal Inheritance. ... 

Transmission by Maternal Inheritance and Random Segregation of mtDNA during... 

Although DNA mutations in nuclear DNA may cause mitochondrial dysfunction, the majority of genetically defined mitochondrial diseases are caused by mutations in mtDNA (M15, PI, S4). Point mutations and deletions of mtDNA have been reported to be associated with or responsible for mitochondrial myopathies and/or encephalomyopathies (M15, PI, S4). Patients with such diseases usually manifest major clinical symptoms early in life and at a later stage may develop additional multisystem disorders such as encephalopathy and/or peripheral neuropathy. Most of the mitochondrial myopathies occur sporadically and are often caused by large-scale mtDNA deletions (PI). However, there are several reports on maternally inherited mitochondrial myopathy and familial mitochondrial myopathy. These patients usually harbor a specific mtDNA mutation and often exhibit defects in NADH-CoQ reductase and/or cytochrome c oxidase. 

A1555G Aminoglycoside-induced deafness or maternally inherited deafness... 

Cl. Casali, C., Santorelli, F. M., D Amati, G., Bemucci, P., DeBiase, L., and DiMauro, S., A novel mtDNA point mutation in maternally inherited mitochondrial myopathy. Biochem. Biophys. Res. Common. 213, 588-593 (1995). 

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