Rapid and diverse changes of gene expression in the kidneys of protein-overload proteinuria mice detected by microarray analysis

Background. Microarray is a method that allows the analysis of a large numb er of genes at the same time. We applied this method to show the difference of gene expression in the kidney caused by proteinuria. Methods. An experimental mouse model of protein overload was prepared by bo vine serum albumin injection. The mRNAs of kidneys isolated after 0, 1, 2, 3 and 4 weeks loading were analysed by Northern blotting. We analysed about 18000 genes by microarray. The expression patterns of the microarray were displayed on control, 1 and 3 weeks of protein overload using the clusterin g procedure. A clone showing the greatest changes of up-regulation in the k idney was cloned and analysed by in situ hyrbridization and immunohistochem istry. Results. Over 1600 kinds of gene expression were confirmed in control kidne ys. Proteinuria caused systematic changes of gene expression demonstrated b y the cluster analysis. The up-regulation of osteopontin mRNA was shown and confirmed by Northern blot analysis. One of the clones showing the largest changes, AA275245, was isolated and characterized. It revealed that AA2752 45 was an unreported 3' noncoding region of vinculin mRNA which was associa ted with cytoskeleton proteins (e.g. alpha1-actinin, talin, F-actin). Immun ohistochemistry and in situ hybridization showed that this clone was identi fied in glomeruli as a mesangial pattern. The detected signal intensity usi ng both methods, however, was virtually identical in control and disease ki dney models. All data including images and analysed signal intensities are accessible on the web site. Conclusion. The microarray analysis revealed that the renal gene expression pattern was changed dynamically in mice with experimentally induced protei nuria within a few weeks.