A CASSETTE FOR HIGH-LEVEL EXPRESSION IN THE MOUSE SALIVARY-GLANDS

Expression in the mouse salivary glands may be used as a model system for studies involving oral cavity delivery of gene products. Previousl y, sequences from the mouse Psp gene were used to build a minigene con struct denoted 'Lama'. This construct was used as a cassette for expre ssion of human factor VIII light chain in mouse saliva. However, where as the endogenous Psp mRNA is the most abundant protein-coding transcr ipt in the parotid glands, the Lama mRNA was expressed below 1% of the level of Psp mRNA in these glands. Here, we show that a 25-kb cosmid- derived DNA fragment (PspX25) carrying the structural gene and large f lanking areas of Psp is expressed in all 14 analysed lines in the paro tid glands. The average level of transgene expression was estimated to be 45% of that of the endogenous Psp gene. More importantly, it was p ossible to transfer PspX25's ability for high-level parotid gland expr ession to the Lama construct. (C) 1997 Elsevier Science B.V.