Distinct Regions of the Mouse Cyclin A1 Gene, Ccna1, Confer Male Germ-Cell Specific Expression and Enhancer Function1

Abstract

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

A Conserved E2F6-Binding Element in Murine Meiosis-Specific Gene Promoters1

“…These studies have demonstrated that short proximal promoter regions of meiotic genes are sufficient to specify their silencing in somatic cells and activation in germ cells [8][9][10][11][12][13]. A more detailed analysis of these minimal promoter regions revealed DNA regulatory elements harboring transcription factor binding sites.…”

Function of the A-Type Cyclins During Gametogenesis and Early Embryogenesis

“…The essential role of Ccna1 in male germ cell development and the concurrent expression of cyclin A1 mRNA and protein suggested the importance of understanding mechanisms controlling transcription of the Ccna1 gene. The lack of cell lines derived from male germ cells made it necessary to analyze the Ccna1 promoter in these cells in vivo in transgenic mice (Lele and Wolgemuth 2004). Serial deletions in the Ccna1 upstream sequence allowed us to define two functional segments of the promoter.…”

“…Analysis of transgenes carrying the genomic fragment of mouse Ccna1 spanning −1.3 kb to +0.8 kb (designated 1.3cyA1lacZ) of the putative transcriptional start site, using a combination of X-gal staining and in situ hybridization, revealed expression specifically in spermatocytes at stages IX to XII of the cycle of the seminiferous epithelium (Lele and Wolgemuth 2004). No expression was observed in spermatogonia or earlier meiotic stages, a pattern that is similar to the narrow window of expression during spermatogenesis seen for the endogenous mouse gene.…”

Regulating mitosis and meiosis in the male germ line: critical functions for cyclins

“…Transcriptional regulatory factors such as E2F, Rb, CDF-1 and perhaps the SWI/SNF chromatin remodelling complex have all been implicated in the function of these elements (Schulze et al 1995;Liu et al 1998b;Philips et al 1999;Coisy et al 2004), but they remain poorly characterized. It is of interest that the CDE/CHR elements are also found in the promoter proximal region of both the human and mouse cyclin A1 gene (Lele & Wolgemuth 2004). …”