Diversity of human and mouse homeobox gene expression in development and adult tissues.

The homeobox genes comprise a large superclass and their expression patterns are correspondingly diverse, although in a broad sense related to an evolutionarily-based classification. The ubiquitous expression of some genes suggests roles in general cellular processes; in contrast, most human homeobox genes have greater tissue specificity and we compile useful homeobox datasets for particular tissues, organs and developmental stages. The identification of a set of eutherian-specific homeobox genes peaking from human 8-cell to morula stages suggests co-option of new genes to new developmental roles in evolution.