Male germ cell expression of murine beta 4-galactosyltransferase. A 796-base pair genomic region, containing two 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 beta 4-galactosyltransferase results in two transcripts of 4.1 and 3.9 kilobases (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 cell counterpart. As these cells enter meiosis, there is a switch from the use of this somatic cell start site to the exclusive use, beginning in pachytene spermatocytes, of a male germ cell-specific start site. Germ cell-specific transcripts are distinguished from their somatic counterparts by an additional approximately 560 nucleotides of 5'-untranslated sequence that is located immediately upstream and contiguous with the transcriptional start site defined for the 4.1-kb mRNA (Harduin-Lepers, A., Shaper, N.L., Mahoney, J.A., and Shaper, J.H. (1992) Glycobiology 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 the germ cell specific transcriptional start site and 253 bp of flanking downstream sequence, directs expression of the reporter gene, beta-galactosidase, exclusively to the pachytene spermatocytes and round spermatids of transgenic mice. This pattern of cell type-specific expression of the transgene is comparable with that of the endogenous beta 4-galactosyltransferase gene.