Protein domains enriched in mammalian tissue-specific or widely expressed genes.

In multicellular organisms some genes are expressed in essentially all tissues, whereas others are expressed predominantly in only one or a few tissues. In this study, we investigate the relationship between the tissue-specificity of gene expression and the type of protein encoded. We find that many protein domains are found to be enriched in either tissue-specific or widely expressed genes. Domains enriched in tissue-specific genes tend to be metazoan-specific; these same domains are also enriched in genes that are not essential for cell viability. These findings identify families of proteins that are probably used in the development or terminal differentiation of many different tissue types.