Distinct Regions of the Mouse Cyclin A1 Gene, Ccna1, Confer Male Germ-Cell Specific Expression and Enhancer Function Expression of Ccna1 Reporter Genes in Mice cyclin, spermatogenesis, meiosis, gene regulation, testis

1 The gene encoding mouse cyclin A1, Ccna1, is expressed at highest levels in late 2 pachytene-diplotene spermatocytes, where it is required for meiotic cell division. To 3 begin to understand the mechanisms responsible for its highly restricted pattern of 4 expression, transgenic mouse lines carrying constructs consisting of the cyclin A1 5 regulatory region fused with the reporter gene lacZ were generated. Analysis of tissue6 specific and testicular cell type-specific transgene expression indicated that sequences 7 within -1.3 kb of the cyclin A1 putative transcriptional start site were sufficient to direct 8 transgene expression uniquely to late spermatocytes while maintaining repression in other 9 tissues. However, sequences located between -4.8 kb and -1.3 kb of the putative 10 transcriptional start site were apparently required to transcribe the reporter at levels 11 needed for consistent X-gal staining. Comparison of the mouse, rat and human proximal 12 promoters revealed regions of high sequence conservation and consensus sequences both 13 for known transcripton factors, some of which are co-expressed with Ccna1, such as A14 myb and Hsf2, and for elements that control expression of genes in somatic cell cycles, 15 such as CDE, CHR, and CCAAT elements. Thus, the promoter region within 1.3 kb 16 upstream of the putative Ccna1 transcriptional start can direct expression of lacZ to 17 spermatocytes, while sequences located between -4.8 kb and -1.3 kb of the putative 18 transcriptional start site may enhance expression of lacZ. 19 20