CellMontage is a system for searching gene expression databases for cells or tissues similar to the query gene expression profile. The similarity of two profiles is computed by comparing the order of genes ranked by expression. Although this is a simple measure we have observed that it is sufficient to characterize cell types across different microarray platforms.

Gene sets and expression value ranges differ between platforms, making direct comparison impossible. Given this situation, we use "gene expression ranks" as a way to compare expression data across platforms.

Spearman's rank correlation coefficient Spearman's method uses the correlation coefficient &rho between two rank numbers.

Under construction.

We investigated the top hits obtained by searches using queries from seven normal cell types. The precentage of top hits from each cell type increased rapidly as the number of genes used in the query increased. The number of randomly chosen genes required to retrieve seven normal cell types is only 64-128 (on the same platform).