An expression profile of active genes in cultured human keratinocytes

An expression profile of genes active in cultured human keratinocytes was obtained by collecting 770 partial sequences from a 3′-directed cDNA library that faithfully represents the mRNA population in the source cells. Ninety-four species composed of 258 clones occurred recurrently, and 512 clones appeared only once. The gene which showed the most abundant expression codes for type I keratin 14, the major keratin that is known to be strongly expressed in the basal layer of the epidermis. Altogether 242 gene species were identified in GenBank, 9.5% of which encode cytoskeletal proteins and 14.5% the components of protein synthesis. Keratin synthesis, the unique property of the keratinocyte, has been measured by elevating the level of transcription of several keratin genes. However, there was no expression of the differentiation markers, type II keratin 1 (K1) or type I keratin 10 (K10), indicating that the cells used for our cDNA library construction were in the pre-differentiation stage. By comparing this expression profile with seven expression profiles from other tissues/cells, four clones, including a novel clone were tentatively identified as specific to keratinocytes.