| Summary: | 碩士 === 國立陽明大學 === 生物化學研究所 === 93 === To study kidney-specific gene targeting, it is necessary to generate a mouse strain that expresses Cre recombinase under the control of a tissue-specific gene promoter. To direct the expression of Cre, we used the promoter of the kidney-specific cadherin gene (Ksp-cadherin, cadherin 16). This gene is uniquely expressed in the basolateral membrane of tubular epithelial cells in the kidney. Transgenic mice carrying the Ksp promoter linked to the Cre recombinase gene were produced by pronuclear microinjection. RT-PCR and immunoblot analysis showed that Ksp-Cre mice expressed Cre only in the kidney and not in any other tissues examined. We observed the mice to have polyuria and polydipsia that are the primary symptoms of diabetes insipidus (DI). This disorder is characterized by a urinary concentrating defect resulting from resistance of the collecting duct to the antidiuretic action of vasopressin (AVP). In Ksp-Cre transgenic mice, water intake increased about two-fold and urine volume increased about eight-fold compared with wild-type mice. An analysis of urine and serum information in the Ksp-Cre transgenic mice showed that urine osmolality decreased to approximately 500 mOsm/l. In contrast, the osmolality of urine in wild-type mice was about 2000 mOsm/l. The urine gravity was lower in the Ksp-Cre transgenic mice than in the wild-type mice. Furthermore, BUN , creatinine, calcium, potassium, and magnesium were a little higher in Ksp-Cre transgenic mice than in wild-type mice. Moreover, histology showed that the epithelial cells of the collecting ducts had degenerated. Taken together, these results demonstrate that Ksp-Cre transgenic mice had problems in their collecting ducts. Therefore, Ksp-Cre transgenic mice may be yet another mouse model for nephrogenic diabetes insipidus.
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