EXPRESSION OF MAL IS ASSOCIATED WITH UROTHELIAL DIFFERENTIATION IN-VITRO - IDENTIFICATION BY DIFFERENTIAL DISPLAY REVERSE-TRANSCRIPTASE POLYMERASE CHAIN-REACTION

We have developed an in vitro urothelial differentiation model. In thi s model, differentiated urothelial cells assemble desmosomes and E-cad herin at cell-cell junctions and stratify and show antigenic and funct ional evidence for tight junctions. Using this urothelial differentiat ion model with the differential display reverse-transcriptase polymera se chain reaction (ddRT-PCR), we identified two independently isolated gene fragments that showed near identity with the reported sequence f or a human cDNA clone named mal. Differential expression of mal mRNA d uring urothelial differentiation was confirmed by RT-PCR using two oth er sets of PCR primers. Furthermore, uncultured urothelial cells from tissues also express mal mRNA, as indicated by RT-PCR. Mal was origina lly identified in a subtracted cDNA library as a human T-cell differen tiation-associated gene and was thought to be T-cell specific. Our res ults identify mal as a gene also expressed in urothelial cells during differentiation and demonstrate the power of ddRT-PCR for analysis of gene expression under these controlled conditions.