MALE GERM-CELL EXPRESSION OF MURINE BETA-4-GALACTOSYLTRANSFERASE - A 796-BASE PAIR GENOMIC REGION, CONTAINING 2 CAMP-RESPONSIVE ELEMENT (CRE)-LIKE ELEMENTS, MEDIATES MALE GERM CELL-SPECIFIC EXPRESSION IN TRANSGENIC MICE

In murine somatic cells, transcription of the single gene encoding bet a 4-galactosyltransferase results in two transcripts of 4.1 and 3.9 ki lobases (kb), as a consequence of the use of two transcriptional start sites that are located on exon one separated by 200 base pairs (bp). In early male germ cell development, spermatogonia use only the 4.1-kb start site to yield a transcript that is identical to its somatic cel l counterpart. As these cells enter meiosis, there is a switch from th e use of this somatic cell start site to the exclusive use, beginning in pachytene spermatocytes, of a male germ cell-specific start site. G erm cell specific transcripts are distinguished from their somatic cou nterparts by an additional similar to 560 nucleotides of 5'-untranslat ed sequence that is located immediately upstream and contiguous with t he transcriptional start site defined for the 4.1-kb mRNA (Harduin-Lep ers, A., Shaper, N. L., Mahoney, J. A., and Shaper, J. H. (1992) Glyco biology 2, 361-368). This observation predicts the use of a different upstream male germ cell-specific promoter. In this study we show that a 796-bp fragment containing 543 bp of genomic sequence upstream of th e germ cell specific transcriptional start site and 253 bp of flanking downstream sequence, directs expression of the reporter gene, beta-ga lactosidase, exclusively to the pachytene spermatocytes and round sper matids of transgenic mice. This pattern of cell type-specific expressi on of the transgene is comparable with that of the endogenous beta 4-g alactosyltransferase gene.