An Expression Profile of Active Genes in Human Colonic Mucosa

An expression profile of genes active in the human colonic mucosawas obtained by collecting 959 partial sequences from a 3'-directedcDNA library. Seven genes were found to produce mRNA each ofwhich comprized more than 1% of total mRNA. Four of these genesare novel, and are likely to be uniquely expressed in the colonicmucosa, and the other three have been identified as genes forfatty acid binding protein, immunoglobulin lambda chain, andcarcinoma-associated antigen GA733-2. In the remaining 952 clones,310 were composed of 118 species occurred recurrently but lessthan 1%, and 533 clones appeared only once. Because the 3'-directedcDNA library faithfully represents the mRNA population in thesource tissue, these numbers represent the relative activitiesof the gene expression. Altogether 156 gene species were identified in GenBank, anda significant portion of these genes encode proteins found inGolgi apparatus and lysosomes, chromosome-encoded mitochondrialproteins, cell surface proteins, and components in the proteinsynthesis machinery. The types and proportions of genes identifiedis consistent with the known major activities of the colonicmucosa such as mucous protein production, energy-dependent waterabsorption, and rapid cell proliferation and turnover.