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Yasutoshi Koga

Publications and source records attributed to Yasutoshi Koga.

8 recordsLinked to original sources
PubMed2005

A novel Myc-target gene, mimitin, that is involved in cell proliferation of esophageal squamous cell carcinoma.

Myc is a ubiquitous mediator of cell proliferation that transactivates the expression of various genes through E-box sites. Here we report a novel gene, mimitin (Myc-induced mitochondrial protein), that encodes a mitochondrial protein with a molecular mass of 20 kDa. We demonstrated that the transcription of mimitin is directly stimulated by c-Myc. To investigate the role of Mimitin, its expression was suppressed by the RNA interference (RNAi) technique. Whereas specific inhibition of mimitin expression did not affect cell proliferation in human cervical carcinoma, colon adenocarcinoma, and hepatocarcinoma cell lines, it did suppress cell proliferation in human glioblastoma, esophageal squamous cell carcinoma (ESCC), and embryonic lung fibroblastic cells, with the greatest suppression efficiency in ESCC cells. To investigate whether mimitin is related to tumorigenesis in ESCC in vivo, the expression of Mimitin protein in ESCC tissues was studied. Mimitin was highly expressed in 80% (28 of 35) of ESCC tumors, suggesting that high expression of Mimitin is a characteristic feature of ESCC. The expression level of Mimitin was found to be correlated with that of c-Myc and cell proliferation, but not with the histopathological grade, stage of cancer, or age of patients. Taken together, these results suggest that the novel gene mimitin is a direct transcriptional target of c-Myc, and is involved in Myc-dependent cell proliferation at least in ESCC cells.

Amino Acid Sequence↗
PubMed2005

A new sequence variant in mitochondrial DNA associated with high penetrance of Russian Leber hereditary optic neuropathy.

We have analyzed mitochondrial DNA sequence in 15 Russian LHON patients and found the new mtDNA sequence variant in one family (2 patients) who showed 100% penetrance of the disease in men. This family has a T14484C primary mutation, and four secondary mutations (T4216C, G13708A, G15812A, G15257A), which belong to the European haplogroup J. The new sequence variant of A9016G in the ATPase 6 gene changed highly conserved amino acid of isoleucine to valine, has not been found in the rest of 13 LHON patients and controls. This novel sequence variant may contribute to the 100% penetration of LHON disorder in men of this family.

Amino Acid Substitution↗
PubMed2005

[Migraine headache and mitochondrial DNA abnormality].

Migraine headache is a heterogenous group of neurologic disorders with high prevalence in the general population and strong familial aggregation. Epidemiologic evidence for frequent maternal transmission has long suggested a role for an altered mitochondrial genetic background. This is supported by the observation of impaired energy metabolism and mitochondrial function in migraine patients as well as by the frequent association of migraine headache in MELAS. In the literature, some patients having migraine headache are reported to have mitochondrial DNA abnormalities, however, systematic screening studies have failed to demonstrate the clear relationship between migraine headache and mitochondrial DNA abnormalities. Migraine may be associated with mutations of nuclear genes which encode respiratory chain enzymes.

DNA, Mitochondrial↗
PubMed2004

Noonan syndrome, moyamoya-like vascular changes, and antiphospholipid syndrome.

This reports describes a 12-year-old Japanese female with Noonan syndrome who had antiphospholipid syndrome and moyamoya-like vascular changes. She presented choreic movements in her face and extremities. She manifested phenotypic features of Noonan syndrome with short stature, mental retardation, and a webbed neck. Magnetic resonance angiography revealed occlusion of bilateral internal carotid arteries and moyamoya-like vascular changes around the basal ganglion region. Pimozide completely resolved the patient's choreic movements. Tests for anticardiolipin antibody and lupus anticoagulant were positive. The patient has manifested no symptoms for 2 years with pimozide, aspirin, and growth hormone treatment, without further aggravation of moyamoya-like vascular changes. This article is the first report of Noonan syndrome with antiphospholipid syndrome and moyamoya-like vascular lesions.

Antiphospholipid Syndrome↗
PubMed2003

Increased mitochondrial processing intermediates associated with three tRNA(Leu(UUR)) gene mutations.

Accumulation of RNA 19 has been associated with mitochondrial myopathy, encephalopathy, lactic acidosis and stroke-like episodes. We analyzed total RNA in muscle specimens from six patients who had one of three pathogenetic point mutations in the mitochondrial tRNA(Leu(UUR)) gene, including A3243G, T3271C, and T3303C. Mitochondrial processing intermediates were identified and quantitated by Northern blotting. The percentage of DNA with the mutation also was determined in each patient. The intermediate (RNA 19) was significantly increased in all patients. The proportion of mutation-carrying RNA in processing intermediates was always higher than in the DNA fraction, suggesting that these mutations may have dominant-negative effects on mitochondrial RNA processing events at the tRNA(Leu(UUR)) gene boundary.

Blotting, Northern↗
PubMed2002

[Complex II].

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Diagnosis, Differential↗
PubMed2002

[Complex III].

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Diagnosis, Differential↗