An analysis of expression patterns of genes encoding proteins with catalytic activities

The expression patterns of 662 genes that encode enzymes were determined by ISH in the mid-gestation mouse embryo, a stage that models the complexity of the adult organism. Forty-five percent of transcripts encoding metabolic enzymes (n = 297) showed a regional expression pattern. A similar percentage was found for the 190 kinases that were also analyzed. Many mRNAs encoding glycolytic and TCA cycle enzymes exhibited a characteristic expression pattern. The annotated expression patterns were deposited on the Genepaint database and are retrievable by user-defined queries including gene name and sites of expression.The 662 expression patterns discussed here comprised gene products with activities associated with catalysis. Preliminary analysis of these data revealed that a significant number of genes encoding housekeeping functions such as biosynthesis and catabolism were expressed regionally, so they could be used as tissue-specific gene markers. We found no difference in tissue specificity between mRNAs encoding housekeeping functions and those encoding components of signal transduction pathways, as exemplified by the kinases.When and where genes are expressed provides useful information about their function. This view forms the basis of several genome-scale projects that attempt the systematic localization of mRNAs and/or proteins expressed in tissues and cells [1,2]. When the products of genes remain within the cells that transcribe and translate them, localizing mRNAs is especially informative. Cell-autonomously acting proteins include transcription factors, transmembrane proteins and also the majority of metabolic enzymes. Although the expression patterns of many genes that encode enzymes have been determined on a gene-by-gene basis, the systematic effort used in the present study stands out because it not only provides a significant coverage of enzymes encoded in the genome but is conducted in a standardized fashion. In addition, expression sites are annotated