Leber's optic atrophy: a possible example of vertical transmission of a slow virus in man

The neurodegenerative mitochondriopathies

Mitochondria are physically or functionally altered in many neurodegenerative diseases. This is the case for very rare neurodegenerative disorders as well as extremely common age-related ones such as Alzheimer's disease and Parkinson's disease. In some disorders very specific patterns of altered mitochondrial function or systemic mitochondrial dysfunction are demonstrable. Some disorders arise from mitochondrial DNA mutation, some from nuclear gene mutation, and for some the etiology is not definitively known. This review classifies neurodegenerative diseases using mitochondrial dysfunction as a unifying feature, and in doing so defines a group of disorders called the neurodegenerative mitochondriopathies. It discusses what mitochondrial abnormalities have been identified in various neurodegenerative diseases, what is currently known about the mitochondria-neurodegeneration nexus, and speculates on the significance of mitochondrial function in some disorders not classically thought of as mitochondriopathies.

Cytochrome oxidase deficiency in Alzheimer's disease

Alzheimer's disease (AD) is a degenerative neurologic disorder that may be familial but is usually sporadic and not easily analyzable in terms of conventional Mendelian genetics. The mitochondrial electron transport chain contains 13 proteins that are encoded by mitochondrial genes rather than nuclear (chromosomal) genes. Disorders resulting from heteroplasmic mutations of mitochondrial genes may appear to be sporadic rather than familial. We evaluated electron transport chain activity in platelet mitochondria prepared from patients with AD and found a specific defect in cytochrome oxidase in five of six patients studied. The mitochondrial genome may play a role in the pathogenesis of AD.

Restriction endonuclease analysis of leukocyte mitochondrial DNA in Leber's optic atrophy

In order to test the hypothesis that Leber's optic atrophy may be caused by mutation of the mitochondrial (mt) genome, restriction fragment length polymorphism in leukocyte mt DNA was studied in 16 patients with Leber's optic atrophy, 28 of their unaffected matrilineal relatives, and 35 normal control subjects. No differences in restriction fragment patterns were observed between affected and unaffected individuals in the same maternal line, and there was no evidence of major deletion of mt DNA in patients. This study provides no positive evidence of mitochondrial inheritance in Leber's optic atrophy but does not exclude it.

Leber's optic neuropathy--a cytogenetic study of a family

The present report describes a family with Leber's optic neuropathy. The cytogenetic findings in this family, as well as some clinical features, are suggestive of a slow viral infection with vertical transmission as a possible cause of the disease.

Analysis of family history data for evidence of non-Mendelian inheritance resulting from vertical transmission

A number of infections of man, as well as of other animal and plant species, are heavily dependent upon 'vertical transmission'--that is direct parent-to-progeny transfer--for their maintenance in host populations. Such vertical transmission may be considered as a form of inheritance. It is usually non-Mendelian. This paper discusses the implications of such inheritance for the distribution of disease in families. A method is described for making quantitative predictions of prevalence rates of infection and of disease within different classes of relatives of either infected or uninfected probands. It is pointed out that, whereas a maternal line excess is to be expected among relatives of positive probands, the opposite should be found in families of negative probands. Expected differences between maternal and paternal line prevalence rates of observable disease decline rapidly with distance of relationship from the proband, and are greatly reduced by diagnostic insensitivity (analogous to penetrance). The implications of this analytic method for the design of family history studies are discussed. Published data on familial breast cancer are reviewed, and found to show no evidence that this condition is associated with a non-integrated vertically transmitted agent.