| Budget Amount *help |
¥13,800,000 (Direct Cost: ¥13,800,000)
Fiscal Year 2006: ¥6,300,000 (Direct Cost: ¥6,300,000)
Fiscal Year 2005: ¥7,500,000 (Direct Cost: ¥7,500,000)
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| Research Abstract |
Our purpose was to generate conditional mutant mice lacking genes that are essential for kidney development, and to analyze renal functions of these mice at an adult stage. As Sall1 is expressed in the metanephric mesenchyme (renal progenitors) and in the adult kidney, we planned to generate mice harboring CreER, which is a fusion protein of Cre recombinase and a mutated estrogen receptor, in the Sall1 locus. When this mouse is crossed with floxed mice of a variety of developmental genes and is stimulated with tamoxifen, a ligand for ER, we could theoretically delete the genes at desired temporal stages. We succeeded in inserting CreER in the Sall1 locus by homologous recombination in embryonic stem cells, generated chimeric mice, and subsequently obtained Sall1 CreER mouse. To test the efficiency of gene excision using this mouse strain, it was crossed with lacZ indicator mouse and was stimulated with tamoxifen. The lacZ staining, however, was faint, indicating the low rate of excision. We then obtained ROSA26CreER mouse which expresses CreER ubiquitously, and crossed with the indicator mouse, but the lacZ staining was still weak. Though it is possible that our protocol of tamoxifen treatment was not optimal, it is likely that the CreER activity was not high enough to efficiently delete genes, because mice expressing unmodified Cre in the Sall1 locus or ubiquitously showed potent gene excision activity as assessed by the lacZ staining. Thus CreER may not be suitable to generate conditional knockout mice. To achieve the initial purpose that is the analysis of renal functions at the adult stage, we are now generating mice in which Sall1 activity is partially restored.
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