Incorporating Mitochondrial Gene Expression Changes Within a Testable Mathematical Model for Alzheimer's Disease: Stress Response Modulation Predicts Potential Therapeutic Targets.

Background: Alzheimer's disease is a specific form of dementia characterized by the aggregation of amyloid-β plaques and tau tangles. New research has found that the formation of these aggregates occurs after dysregulation of cellular respiration and the production of radical oxygen species. Proteomic data shows that these changes are also related to unique gene expression patterns.

Expression Changes in Mitochondrial Genes Affecting Mitochondrial Morphology, Transmembrane Potential, Fragmentation, Amyloidosis, and Neuronal Cell Death Found in Brains of Alzheimer's Disease Patients.

Background: Alzheimer's disease (AD) is a neurological disease that has both a genetic and non-genetic origin. Mitochondrial dysfunction is a critical component in the pathogenesis of AD as deficits in oxidative capacity and energy production have been reported.

Objective: Nuclear-encoded mitochondrial genes were studied in order to understand the effects of mitochondrial expression changes on mitochondrial function in AD brains.

The T9861C Mutation in the mtDNA-Encoded Cytochrome C Oxidase Subunit III Gene Occurs in High Frequency but with Unequal Distribution in the Alzheimer's Disease Brain.

Mitochondrial dysfunction is recognized as a critical component in the pathogenesis of neurodegenerative diseases, including Alzheimer's disease (AD). Deficits in oxidative capacity and, specifically, cytochrome c oxidase (CO) activity have been reported in AD brains and platelets. We previously identified a point mutation at np 9861 in AD brain mitochondrial DNA (mtDNA) that alters amino acid 219 of subunit III of CO from phenylalanine to leucine.

Mitochondrial function and abnormalities implicated in the pathogenesis of ASD.

Mitochondria are the powerhouse that generate over 90% of the ATP produced in cells. In addition to its role in energy production, the mitochondrion also plays a major role in carbohydrate, fatty acid, amino acid and nucleotide metabolism, programmed cell death (apoptosis), generation of and protection against reactive oxygen species (ROS), immune response, regulation of intracellular calcium ion levels and even maintenance of gut microbiota. With its essential role in bio-energetic as well as non-energetic biological processes, it is not surprising that proper cellular, tissue and organ function is dependent upon proper mitochondrial function.

Reproductive competency and mitochondrial variation in aged Syrian hamster oocytes.

The hamster is a useful model of human reproductive biology because its oocytes are similar to those in humans in terms of size and structural stability. In the present study we evaluated fecundity rate, ovarian follicular numbers, ova production, mitochondrial number, structure and function, and cytoplasmic lamellae (CL) in young (2-4 months) and old (12-18 months) Syrian hamsters (Mesocricetus auratus). Young hamsters had higher fertilisation rates and larger litters than old hamsters (100 vs 50% and 9.

Endometriosis may be associated with mitochondrial dysfunction in cumulus cells from subjects undergoing in vitro fertilization-intracytoplasmic sperm injection, as reflected by decreased adenosine triphosphate production.

Objective: To determine whether endometriosis is associated with mitochondrial dysfunction in cumulus (granulosa [GC]) cells of subjects undergoing IVF-intracytoplasmic sperm injection (ICSI).

Design: Prospective cohort study.

Setting: An IVF clinic in a tertiary academic care center.

Age-associated metabolic and morphologic changes in mitochondria of individual mouse and hamster oocytes.

Background: In human oocytes, as in other mammalian ova, there is a significant variation in the pregnancy potential, with approximately 20% of oocyte-sperm meetings resulting in pregnancies. This frequency of successful fertilization decreases as the oocytes age. This low proportion of fruitful couplings appears to be influenced by changes in mitochondrial structure and function.

The association of reproductive senescence with mitochondrial quantity, function, and DNA integrity in human oocytes at different stages of maturation.

Objective: To determine the impact of reproductive aging on oocyte mitochondrial quantity, function, and DNA (mtDNA) integrity.

Design: Prospective observational study.

Setting: IVF clinic in a tertiary academic care center.

Estrogen receptor alpha (ERalpha) phospho-serine-118 is highly expressed in human uterine leiomyomas compared to matched myometrium.

It is thought that the growth of uterine leiomyomas may be mediated by the interaction of estrogen receptor alpha (ERalpha) and growth factor pathways and that phosphorylation of ERalpha at serine 118 (ERalpha-phospho-Ser118) is important in this interaction. In this study, immunoblotting and immunohistochemistry were used to investigate the expression of ERalpha-phospho-Ser118, phosphorylated p44/42 mitogen-activated protein kinase (phospho-p44/42 MAPK), and proliferating cell nuclear antigen (PCNA) in human leiomyoma and myometrial tissues during the proliferative and secretory phases of the menstrual cycle. We found that tumors taken from the proliferative phase expressed significantly higher levels of ERalpha-phospho-Ser118, phospho-p44/42 MAPK, and PCNA compared to patient-matched myometria and had significantly higher ERalpha-phospho-Ser118 and PCNA expression compared to secretory phase tumors.

Mutations in mitochondrial-encoded cytochrome c oxidase subunits I, II, and III genes detected in Alzheimer's disease using single-strand conformation polymorphism.

A "mitochondrial hypothesis" of late onset Alzheimer's disease (AD) has been proposed. Biochemical studies indicate that there is a significant decrease in cytochrome oxidase (CO) activity as well as perturbed CO I and CO III mRNA levels in platelets and brain tissue from Alzheimer's patients. Using the electrophoretic mutation detection technique SSCP and DNA sequencing, we have identified 20 point mutations in the mitochondrial-encoded CO subunits (CO I, II, and III) in AD and age-matched control brain samples.

Mitochondrial disorders: a clinician's primer.

Mitochondrial disorders represent an extremely challenging set of conditions, partly due to the complexities of the mitochondrial genetic system. Nurses must be prepared with knowledge about genetic conditions so that they can participate fully in early identification of affected individuals and assist them in accessing the most current genetic diagnostic and treatment therapeutics. This knowledge will be critical as nurses collect family history data, provide current and accurate genetic information and support to individuals and families, and refer to and collaborate with genetic specialists in their communities.

Elevated levels of the Kearns-Sayre syndrome mitochondrial DNA deletion in temporal cortex of Alzheimer's patients.

A mitochondrial hypothesis of Alzheimer's disease (AD) has been proposed based on a number of studies which establish altered oxidative phosphorylation (OXPHOS) and ATP synthesis in AD tissue. Four out of five complexes in the OXPHOS pathway are partly encoded by mitochondrial DNA (mtDNA); thus, this may be a crucial site of lesions that alter brain activity. We examined temporal cortex autopsy tissue for deleted mtDNA by PCR-based methods and Southern analysis.

Association of mitochondrial DNA deletions and cochlear pathology: a molecular biologic tool.

The purpose of these experiments was to develop a method of isolation, amplification, and identification of cochlear mitochondrial DNA (mtDNA) from minute quantities of tissue. Additionally, studies were designed to detect mtDNA deletions (mtDNA del) from the cochlea that previously have been amplified from other organ systems and tissues. MtDNA del have been associated with many pathologies, including neurological disorders, sensorineural hearing loss, ischemia, cardiomyopathies, and aging.

Mammalian mitochondrial DNA topoisomerase I preferentially relaxes supercoils in plasmids containing specific mitochondrial DNA sequences.

Selected regions of mammalian mitochondrial DNA (mtDNA) were inserted into pGEM plasmid vectors and used as substrates in a kinetic analysis of the highly purified bovine mitochondrial type I topoisomerase. Recombinant plasmids containing the bovine mtDNA heavy and light strand origins of replication (pZT-Hori and pZT-Lori, respectively), a major transcription termination region (pZT-Term) and a portion of cytochrome b gene (pZT-Cytb) were prepared. Southern hybridization using probes specific for either control or mtDNA-containing plasmid indicated a relative preference by the mitochondrial topoisomerase I to relax supercoils in pZT-Hori and pZT-Term.

Response of purified mitochondrial DNA topoisomerase I from bovine liver to camptothecin and m-AMSA.

The type I DNA topoisomerase isolated from bovine liver mitochondria is demonstrated here to be inhibited by camptothecin, a plant alkaloid previously shown to target the nuclear type I topoisomerase in mammalian cells. The antitumor drug reduces the ability of the mitochondrial enzyme to relax positive as well as negative supercoils although the inhibition of the former process requires more than 60-fold more drug than the latter process. A similar response is seen with the nuclear topoisomerase I.

Rett syndrome studies of natural history and search for a genetic marker.

The commonly held notion that Rett syndrome (RS) is a neurodegenerative disorder with normal early development was examined by an epidemiological survey and review of medical records and serial neurological and development evaluations. In some subjects, deviance from normal development was evident from the perinatal period, and gradually became more prominent with age. These findings are convincing when seen in conjunction with a reduction in velocity of brain growth, as early as 2-4 months of life, well before the recognition of gross neurological deficits.

Mitochondrial DNA deletion analysis: a comparison of PCR quantitative methods.

The role of mitochondrial DNA (mtDNA) deletions in aging and in neurodegenerative diseases is often determined by measuring the amount of deleted mtDNA in the affected tissue. Upon examining brain autopsy tissue from a 59 year old individual with lung cancer we determined by serial dilution PCR and kinetic PCR that a greater ratio of deleted mtDNA was present in the caudate than in the parietal cortex. However, the magnitude difference for these two brain regions appeared to be technique dependent; by serial dilution PCR the caudate had 10 times more deleted mtDNA than the parietal cortex (0.

Heat stress induces hsc70/nuclear topoisomerase I complex formation in vivo: evidence for hsc70-mediated, ATP-independent reactivation in vitro.

We previously demonstrated that in murine T cells thermotolerance correlated with heat shock protein 70 (hsp70) synthesis and protection of nuclear type I topoisomerase (topo I). Topo I activity returned to normal levels following heat stress even in cells not rendered thermotolerant by a prior heat shock. Recovery of topo I activity was not dependent on de novo protein synthesis, suggesting that the cell possesses a pathway(s) for refolding this nuclear protein.

Mammalian mitochondrial DNA sequences can function as in vivo bacterial transcription terminators.

We have used a prokaryotic terminator identification vector, pDR721, to isolate regions from rat mitochondrial DNA (mtDNA) that can act as transcription terminators in vivo. Three independent fragments having terminator capability have been mapped to three general regions of the mitochondrial genome. Two terminators, pRMT1 and pRMT3, are found within and around the D-loop and cytochrome b gene, respectively, while the third, pRMT5, is located at the 3'-end of the 16S ribosomal RNA gene.

PCR amplification using a single cell allows the detection of the mtDNA lesion associated with Leber's hereditary optic neuropathy.

The development of the polymerase chain reaction (PCR), which routinely can amplify specific target sequences more than one billion-fold, has made it possible to produce readily detectable amounts of DNA from a few copies of very rare sequences. We have begun a study of mitochondrial myopathies with the purpose of developing a diagnostic test using PCR to amplify appropriate mitochondrial DNA (mtDNA) target sequences from small amounts of sample. We have developed a 15-min procedure for recovering mtDNA which can be amplified by PCR to detectable levels, from as little as 30 microliters of blood or 5 microliters of amniotic fluid.

Induction of thermotolerance in T cells protects nuclear DNA topoisomerase I from heat stress.

In this study, we have demonstrated that topoisomerase I DNA relaxing activity is protected against a severe heat shock in T cells made thermotolerant by a prior modest heat treatment. However, following a severe heat-shock challenge and incubation at 37 degrees C, topoisomerase activity in the control population eventually returned to levels similar to those detected in thermotolerant cells. This recovery of topoisomerase activity appears to result from the renaturation of heat-inactivated enzyme rather than from synthesis of new protein because the rate of recovery of catalytic activity was not inhibited by the presence of the protein synthesis inhibitor, cycloheximide.

DNA topoisomerase I from calf thymus mitochondria is associated with a DNA binding, inner membrane protein.

During purification of the type I DNA topoisomerase from calf thymus mitochondria, two polypeptides, p78 and p63, cofractionate with the enzymatic activity (Lazarus et al., (1987) Biochemistry 26, 6195-6203). The two polypeptides are released from a mitochondrial inner membrane preparation by nonionic detergent lysis and both adsorb strongly to a single-stranded DNA agarose column.

2',5'-oligoadenylates inhibit relaxation of supercoiled DNA by calf thymus DNA topoisomerase I.

DNA topoisomerases interconvert various topological isomers of DNA and play key roles in replication and gene expression. The possible involvement of the 2',5'-oligoadenylates (2-5A) system in cell growth, regulation, and cell differentiation led us to investigate the effects of 2-5A on mammalian topoisomerases. We found that the calf thymus type I topoisomerase was inhibited by a variety of 2-5A compounds.

DNA topoisomerase II from mammalian mitochondria is inhibited by the antitumor drugs, m-AMSA and VM-26.

A type II DNA topoisomerase has been partially purified from calf thymus mitochondria by a combination of differential centrifugation and column chromatography. The mitochondrial enzyme was inhibited by amsacrine (m-AMSA) slightly at 0.5 microM, significantly at 5.

Identification of transcription promoter regions from rat mtDNA that are utilized in vivo by the bacterial RNA polymerase.

We have used a prokaryotic promoter-identification vector, pKO-1, to isolate rat mitochondrial DNA (mtDNA) sequences that can act as bacterial transcription promoters. Three putative promoter-containing clones that hydridized to mtDNA probes were identified. The strength of the promoters was quantitated by measuring galactokinase activity.