Prosaposin: promoter analysis and central-nervous-system-preferential elements for expression in vivo

The expression of prosaposin is temporally and spatially regulated at the t ranscriptional and post-translational levels. In vitro, the mouse prosaposi n promoter contains functional RORE [retinoic acid-receptor-related orphan receptor alpha subunit (ROR alpha)-binding element], Sp1 and U (unknown) si tes within 310 bp directly 5' to the transcription start site and additiona l elements within 2400 bp 5' to the transcription start site. To elucidate promoter regions important to tissue-preferential expression in vivo, trans genic mice were created with 5'-flanking deletions of the prosaposin gene f used to a luciferase reporter. Nearly exclusive expression was observed in cerebrum, cerebellum and eyes of adult transgenic mice containing construct s with 234-310 bp of 5'-flanking DNA. This central nervous system (CNS) exp ression was due to the presence of RORE and overlapping Sp1 sites in this r egion. Internal deletion of RORE and the Sp1 cluster from the longer constr ucts with 2400 bp of 5'-flanking DNA significantly diminished expression in the CNS. The appearance of substantial visceral tissue (e.g. liver, spleen , lung, kidney, thymus and heart) expression was obtained with transgenic m ice bearing constructs with 742-2400 bp of 5'-flanking DNA. The cellular lo calization of luciferase reporter-gene expression from these constructs cor responded closely with that for prosaposin. These results define important CNS and visceral regulatory regions in the promoter in vivo and may be suff icient to account for the majority of prosaposin's tissue-preferential expr ession.