Although no longer in operation, the Expression Project has proved a rich source of genetic information.

An objective of the project was to define the RNA expression profiles in specific tissues and cells, and developmental stages of C. elegans. Two complementary approaches were applied: serial analysis of gene expression (SAGE), and the construction of promoter::GFP fusions for in vivo analysis of gene expression.
Another objective was the development of a protein expression baseline for specific tissues during development.

Project breakdown:
1)Promoter::GFP fusions
2) SAGE

1) Monitoring in vivo expression of the fusion constucts in transgenic worms allows the determination of the developmental stage, tissue, and in some cases, the cells where a particular gene is expressed. Our goal was to build promoter::GFP fusion constructs for C. elegans genes that have human orthologues. We analyzed approximately 2000 of the 5000 genes that fall into this category. When coupled with SAGE and knockout data, this provides valuable and more complete expression profiles for cells, tissues, and developmental stages.

2) SAGE is a sensitive and specific method for obtaining qualitative and quantitative information on expressed RNAs. SAGE also allowed us to identify non-protein-coding genes, and provided insight into alternatively spliced mRNA isoforms and their relative abundance between tissues.

We examined total mRNA populations in all developmental stages, both in whole worms and in specific cells and tissues. We have generated 17 SAGE libraries, which include all developmental stages, mutation-specific populations, and specific tissues and cells, totalling approximately 1.8 million observed tags. Tissue- and cell-specific libraries were generated from FACS-sorted cells marked by expression of specific promoter::GFP fusions. To date, we have SAGE libraries for purified embryonic muscle, gut, and a subset of neurons.

GFP fusion database
SAGE database