Figure 1.

Microarrays of gene expression in mouse embryos. (a) A typical single microarray comparison, using mouse embryos as an example, illustrating some of the issues that arise concerning the use of microarrays to study development. The whole-mount in situ hybridization shown in the top panels demonstrates the complexity of gene expression during development, with tissue-specific expression in a small number of areas. Studying the consequences of altering normal gene expression requires dissection of the tissues that gene is expressed in, or sorting of the specific cell populations of interest. A consequence of this is that the extracted RNA will probably need to be amplified to generate sufficient cDNA for a microarray probe. (b) Detail of a microarray hybridization comparing gene expression in a single mouse neural progenitor cell (red) with that in total brain (green). One issue for developmental biologists is whether arrays can be used to profile gene expression in small numbers of cells. We and others have found that it is possible to reproducibly profile gene expression from single cells, using current cDNA amplification technologies.