| Research Abstract |
In the present project, we have investigated the molecular regulation of heme metabolism and its genetic disorder.
1) Genetic disorder of heme biosynthesis. We have reported molecular analyzes of two types of porphyria : hereditary coproporphyria (HCP) and hepatoerythropoietic porphyria (HEP). Three mutations were identified in coproporphyrinogen oxydase (CPO) from a patient with HCP.A G172H substitution was observed in one allele, while G89S as well as V194I substitutions were demonstrated in the other allele. Further analysis indicated that CPO with G172H has little activity. The other substitutions were revealed to be polymorphism.
We have also identified two mutations in uroporphyrinogen decarboxylase (UROD) from a patient with HEP.A T^<417>G^<418>T^<419> to CCA mutation was existed in one allele, whereas A^<677> to C mutation was investigated in the other allele. Using Chinese hamster ovary cells, we have elucidated that the former and the latter mutation decreased UROD activity by
… More
20% and by 80%, respectively.
Now, we continued our effort on hereditary sideroblastic anemia, variegate porphyria, and delta-aminolevulinate dehydratase deficient porphyria.
2) Molecular regulation of heme metabolism. To understand the factor (s) that might influence the hereditary heme disorder, we have started the project on erythroid type of heme synthesis. Until today, we have elucidated that a erythroid transcriptional factor, GATA-1, is expressed not only in erythroid cells but also in the testis, that the large subunit as well as the small subunit of NF-E2 is necessary for erythroid specific gene activation, and that the large subunit of NF-E2 is regulated by heme. We also demonstrated that heme is necessary for ferrochelatase mRNA.Thus, the insufficient supply of heme by genetic disorder will result in not only the abnormal level of ferrochelatase mRNA but also the abnormal regulation of erythroid heme biosynthesis.
Using a cell line, UT-7, we also investigated the mechanisms to undergo megakaryocytic maturation as well as to undergo erythroid differentiation. These findings are important for the better understanding of heme metabolism in patients with genetic disorder of the pathway. Less
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