Mitochondrial disease: maintenance of mitochondrial genome and molecular diagnostics

Detection of Human Papillomavirus Genotypes and Major BRCA Mutations in Familial Breast Cancer

Breast cancer is a multistep disease and infection with a DNA virus could play a role in one or more of the steps in this pathogenic process. High-risk human papillomaviruses (HPVs) are the causative agents of several cancers. In this study, we investigated HPV genotypes associated with breast cancer and its relationship with BRCA mutation for the detection of familial breast cancer. We analyzed 84 formalin-fixed, paraffin-embedded tissue blocks from 38 familial breast cancer and 46 nonfamilial breast cancer samples by multiplex polymerase chain reaction and clinical parameters. Overall prevalence of HPV infection was 27 of 84: 10 (37.03%) HPV-16, 9 (29.62%) HPV-18, 4 (14.81%) HPV-11, 1 (3.7%) HPV-31, 1 (3.7%) HPV-33, and 2 (7.4%) HPV35. Furthermore, 17 mtDNA4977 deletions and 5 5382insC mutations were detected from 38 familial breast cancer samples. Our results demonstrate that infection with HPV was prevalent among Iranian women with familial breast cancer and the testing of mtDNA4977 deletions and 5382insC mutations in combination with clinical parameters as major risk factors can serve in the identification of familial breast cancer.

Delivery of drugs and macromolecules to mitochondria

Mitochondria is where the bulk of the cell's ATP is produced. Mutations occur to genes coding for members of the complexes involved in energy production. Some are a result of damages to nuclear coded genes and others to mitochondrial coded genes. This review describes approaches to bring small molecules, proteins and RNA/DNA into mitochondria. The purpose is to repair damaged genes as well as to interrupt mitochondrial function including energy production, oxygen radical formation and the apoptotic pathway.

False Positive Results of Mitochondrial DNA Depletion/Deletion due to Single Nucleotide Substitutions Causing Appearance of Additional PvuII Restriction Sites

Human mitochondrial diseases are usually caused by dysfunction of mitochondrial DNA (mtDNA), particularly by point mutations, deletions, or depletions. In commonly used procedures for molecular diagnostics of mitochondrial dysfunction, one of the first steps is linearization of circular mitochondrial genomes with either BamHI or PvuII restriction endonulease, which cuts human mtDNA at a unique site. Here, we describe a case of false positive results, which suggested mtDNA depletion or a large deletion in a patient's tissue sample. More detailed analysis (mtDNA sequencing) revealed that these false positive results were caused by the presence of the 12753A>G substitution in the gene coding for NADH dehydrogenase subunit 5 (ND5). This substitution results in no change in amino acid sequence of the gene product but creates an additional PvuII site. Investigating a population of 200 patients not affected by mitochondrial diseases, we found an additional case of 12753A>G, and also another substitution, 12804T>C, which also results in no change in amino acid sequence of ND5 but creates an additional PvuII site. A few cases of 12753A>G and 12804T>C substitutions were found previously in Asian, American, African, and European populations (though they were not reported to date in the MITOMAP), but those samples were used in population studies and not tested for mtDNA deletion or depletion. Therefore, we present a cautionary report indicating that these mtDNA polymorphisms exist in various human populations (and thus, they are panethnic) and may cause false positive results of standard molecular analyses, including molecular diagnostics, of human mtDNA.