| Budget Amount *help |
¥54,860,000 (Direct Cost: ¥42,200,000、Indirect Cost: ¥12,660,000)
Fiscal Year 2004: ¥10,790,000 (Direct Cost: ¥8,300,000、Indirect Cost: ¥2,490,000)
Fiscal Year 2003: ¥10,790,000 (Direct Cost: ¥8,300,000、Indirect Cost: ¥2,490,000)
Fiscal Year 2002: ¥16,120,000 (Direct Cost: ¥12,400,000、Indirect Cost: ¥3,720,000)
Fiscal Year 2001: ¥17,160,000 (Direct Cost: ¥13,200,000、Indirect Cost: ¥3,960,000)
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| Research Abstract |
1.Studies on the molecular pathogenesis of autosomal-dominant type nephrogenic diabetes insipidus (AD-NDI).
We found five families of AD-NDI. Sequencing of AQP2 gene revealed that there were heterozygous frame-shift mutations in all patients, which resulted in the addition of 61 amino acids to the carboxy terminus of AQP2. In contrast to the apical localization of the wild-type AQP2 expressed in MDCK cells, the disease-causing mutants were localized to the basolateral membranes. Furthermore, the mutants recruited the wild-type AQP2 to the basolateral membrane when co-expressed, showing dominant-negative effect. We also found that a di-luecine motif in the mutant was responsible for the basolateral sorting. To confirm whether the above mentioned mechanism really worked in vivo, we generated by gene targeting a knock-in mouse that expressed the mutant AQP2. As expected, the knock-in mice showed AD-NDI. Apical localization of the wild-type AQP2 was significantly impaired by the mutant AQP2
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expression. Further analysis of this mouse model will help to clarify the molecular mechanisms of AD-NDI in vivo and to develop strategy for the treatment of AD-NDI.
2.Generation of AQP11 and AQP12 knockout mice.
AQP11 and AQP12 were identified by us using database search. Although AQP11 was ubiquitously expressed, AQP 12 was found to be a pancreas-specific AQP. They were also identified as intracellular AQPs by transient expression studies in cultured cells and Xenopus oocytes. To identify their physiological roles in vivo, we generated AQP11 and AQP12 knock-out mice by targeted gene disruption. At present, renal and pancreatic functions are analyzed in AQP11 and AQP12 knockout-mice, respectively.
3.Analysis of a disease-causing mutant WNK4.
Mutations of WNK1 and WNK4 kinases were reported to be responsible for pseudohypoaldosteronism type II (PHAII) by positional cloning strategy. However, the molecular pathogenesis of PHAII by these mutations was not clarified. We demonstrated that the mutant WNK4 increased paracellular chloride permeability and claudin phosphorylation in MDCK cells. These results supported the previously postulated "chloride shunt" hypothesis in PHAII and clarified the molecular mechanisms of PHAII. Less
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