Method to purify mitochondrial DNA directly from yeast total DNA

A comparison of mitochondrial DNA isolation methods in frozen post-mortem human brain tissue—applications for studies of mitochondrial genetics in brain disorders

Given that many brain disorders are characterized by mitochondrial dysfunction, there is a growing interest in investigating genetic and epigenetic variation in mitochondrial DNA (mtDNA). One major caveat for such studies is the presence of nuclear-mitochondrial pseudogenes (NUMTs), which are regions of the mitochondrial genome that have been inserted into the nuclear genome over evolution and, if not accounted for, can confound genetic studies of mtDNA. Here we provide the first systematic comparison of methods for isolating mtDNA from frozen post-mortem human brain tissue. Our data show that a commercial method from Miltenyi Biotec, which magnetically isolates mitochondria using antibodies raised against the mitochondrial import receptor subunit TOM22, gives significant mtDNA enrichment and should be considered the method of choice for mtDNA studies in frozen brain tissue.

Identification of RNase-resistant RNAs in Saccharomyces cerevisiae extracts: Separation from chromosomal DNA by selective precipitation

High-quality chromosomal DNA is a requirement for many biochemical and molecular biological techniques. To isolate cellular DNA, standard protocols typically lyse cells and separate nucleic acids from other biological molecules using a combination of chemical and physical methods. After a standard chemical-based protocol to isolate chromosomal DNA from Saccharomyces cerevisiae and then treatment with RNase A to degrade RNA, two RNase-resistant bands persisted when analyzed using gel electrophoresis. Interestingly, such resistant bands did not appear in preparations of Escherichia coli bacterial DNA after RNase treatment. Several enzymatic, chemical, and physical methods were employed in an effort to remove the resistant RNAs, including use of multiple RNases and alcohol precipitation, base hydrolysis, and chromatographic methods. These experiments resulted in the development of a new method for isolation of S. cerevisiae chromosomal DNA. This method utilizes selective precipitation of DNA in the presence of a potassium acetate/isopropanol mixture and produces high yields of chromosomal DNA without detectable contaminating RNAs.

The mitochondrial epigenome: a role in Alzheimer's disease?

Considerable evidence suggests that mitochondrial dysfunction occurs early in Alzheimer's disease, both in affected brain regions and in leukocytes, potentially precipitating neurodegeneration through increased oxidative stress. Epigenetic processes are emerging as a dynamic mechanism through which environmental signals may contribute to cellular changes, leading to neuropathology and disease. Until recently, little attention was given to the mitochondrial epigenome itself, as preliminary studies indicated an absence of DNA modifications. However, recent research has demonstrated that epigenetic changes to the mitochondrial genome do occur, potentially playing an important role in several disorders characterized by mitochondrial dysfunction. This review explores the potential role of mitochondrial epigenetic dysfunction in Alzheimer's disease etiology and discusses some technical issues pertinent to the study of these processes.