Determining the detailed expression profiles of specific microRNAs (miRNAs)is an important part of the study of miRNA biology. Negative sensor systems to visualize miRNA expression patterns have already been described; for example, in a 2004 study by Mansfield et al miRNA complementary sequences were placed in the 3' UTR of the B-galactosidase gene. When this construct was ubiquitously expressed in mice, areas of high target miRNA expression appeared white instead of blue after staining. While negative systems succeed in giving an indication of the presence or absence of target miRNAs, it is difficult to visualize the finer details of their expression patterns. It would be much easier to visualize a positive sensor; i.e., a system in which blue staining or fluorescence indicated the presence of a miRNA as opposed to its absence. We are currently working to develop such positive sensor systems, first in tissue culture and eventually in mice
The staining pattern in the mouse embryos above is Hox-like because the miR-10 and miR-196 Hox genes are located in Hox-clusters and are expressed in a manner that is overall consistent with their relative locations in the Hox cluster (see figure below).
