Kazutoshi Nakano

Positive Contribution of Pathogenic Mutations in the Mitochondrial Genome to the Promotion of Cancer by Prevention from Apoptosis

The role of mitochondrial dysfunction in cancer has been a subject of great interest and much ongoing investigation. Although most cancer cells harbor somatic mutations in mitochondrial DNA (mtDNA), the question of whether such mutations contribute to the promotion of carcinomas remains unsolved. Here we used trans-mitochondrial hybrids (cybrids) containing a common HeLa nucleus and mtDNA of interest to compare the role of mtDNA against the common nuclear background. We constructed cybrids with or without a homoplasmic pathogenic point mutation at nucleotide position 8,993 or 9,176 in the mtDNA ATP synthase subunit 6 gene (MTATP6) derived from patients with mitochondrial encephalomyopathy. When the cybrids were transplanted into nude mice, the MTATP6 mutations conferred an advantage in the early stage of tumor growth. The mutant cybrids also increased faster than wild type in culture. To complement the mtDNA mutations, we transfected a wild-type nuclear version of MTATP, whose codons were converted to the universal genetic codes containing a mitochondrial target sequence, into the nucleus of cybrids carrying mutant MTATP6. The restoration of MTATP slowed down the growth of tumor in transplantation. Conversely, expression of a mutant nuclear version of MTATP6 in the wild-type cybrids declined respiration and accelerated the tumor growth. These findings showed that the advantage in tumor growth depended upon the MTATP6 function but was not due to secondary nuclear mutations caused by the mutant mitochondria. Because apoptosis occurred less frequently in the mutant versus wild-type cybrids in cultures and tumors, the pathogenic mtDNA mutations seem to promote tumors by preventing apoptosis.

TRH therapy in a patient with juvenile Alexander disease

Alexander disease is a rare disorder of the central nervous system caused by a de novo mutation in the glial fibrillary acidic protein (GFAP) gene. Unlike the much more common infantile form, the juvenile form is slowly progressive with bulbar, pyramidal and cerebellar signs. Herein, we report a 9-year old Japanese girl suffering from frequent vomiting, slurred speech and truncal ataxia. Juvenile Alexander disease was diagnosed by genetic analysis, which detected a novel GFAP mutation, D360V. We also describe our clinical success in treating this patient with thyrotropin releasing hormone (TRH).

Creatine monohydrate therapy in a Leigh syndrome patient with A8344G mutation

Mitochondrial encephalomyopathies, including Leigh syndrome (subacute necrotizing encephalomyelopathy), are progressive degenerative disorders that often involve multiple organs. 1 A number of treatments have been tried with mitochondrial encephalomyopathies, including vitamins B 1 , B 2 , C, and E, 2 coenzyme Q 10 , 2 dichloroacetate 3 and l-arginine, 4 but there is still no defi nitive therapy. Creatine monohydrate supplementation has been reported to give clinical improvement in some diseases with gyrate atrophy, in guanidinoacetate methyltransferase defi ciency 5

Familial antiphospholipid antibody in a child with involuntary movement and deterioration

Antiphospholipid antibody syndrome (APS) is a thrombotic disorder characterized by the association of arterial and venous thrombosis with antibodies against phospholipids. APS in children has diverse clinical features including involuntary movements similar to those in adults. We present here a case that showed deterioration in addition to chorea and ballistic involuntary movements. The patient had high antiphospholipid antibody titers, which is compatible with APS and he had a family history of APS. However, the clinical course was clearly distinguishable from that of classic APS.

Continuous culture of novel mitochondrial cells lacking nuclei

We isolated stable cell lines, designated as mitochondrial cells, from cybrids obtained by fusing mitochondria-less HeLa cells with platelets from patients with Leigh syndrome, a subtype of mitochondrial encephalomyopathy. The cells contain a pathogenic point mutation, T9176C, in the mitochondrial DNA. Hematoxylin-eosin staining, confocal fluorescent microscopy and flow cytometry in fixed or living cells showed that the majority of these mitochondrial cells lack nuclear DNA and nuclei, but contain active mitochondria. Despite the absence of nuclear DNA, these cells can be continuously generated in culture. Therefore, it is likely that they arise from the minority of cells which possess a nucleus.