Identification and isolation of differentially expressed genes in osmotically stressed human oral keratinocytes

Complementary DNA fragments which showed differential expression relative t o unstressed controls were identified and isolated from human oral keratino cytes exposed to hyperosmotic stress. The up- or downregulation of the expr ession of nine of these cDNAs in response to osmotic stress was determined by Northern blotting. Sequence analysis showed that clones K-5 and K-46 con tained identical sequences. Homology searches revealed that K-13 and K-33 w ere fragments of unknown genes. Among the upregulated cDNAs, K-16 and K-32 were 94 and 83% identical to chromosome 16 bacterial artificial chromosome (CIT987K-A-418G10) and a cDNA (ai49b01.s1) clone, respectively. Another clo ne, K-34, encoded a protein 73% identical to Bare. Among the downregulated genes, K-5/46 and K-45 were 99% identical to the og24d08.s1 cDNA clone and to mitochondrial genes for tRNAs and 12S and 16S ribosomal RNAs, respective ly, while K-50 was 100% identical to KIAA0905 protein. The gene expression induced by osmotic stress occurred in parallel with the induction of apopto sis and a reduction in protein biosynthesis. This observation, together wit h the characteristics of the some of the differentially expressed genes, su ggests that among the major events induced in oral keratinocytes by hyperos motic stress are the induction of apoptosis and a decrease in protein biosy nthesis, brought about by upregulation of pro-apoptotic genes and downregul ation of genes involved in protein biosynthesis. (C) 2001 Elsevier Science Ltd. All rights reserved.