Molecular cloning and analysis of the Catsper1 gene promoter

Abstract

CatSper channels are essential for hyperactivity of sperm flagellum, progesterone-mediated chemotaxis and oocyte fertilization. Catsper genes are exclusively expressed in the testis during spermatogenesis, but the function and regulation of the corresponding promoter regions are unknown. Here, we report the cloning and characterization of the promoter regions in the human and murine Catsper1 genes. These promoter regions were identified and isolated from genomic DNA, and transcriptional activities were tested in vitro after transfection into human embryonic kidney 293, mouse Sertoli cells 1 and GC-1spg cell lines as well as by injecting plasmids directly into mouse testes. Although the human and murine Catsper1 promoters lacked a TATA box, a well-conserved CRE site was identified. Both sequences may be considered as TATAless promoters because their transcriptional activity was not affected after deletion of TATA box-like sites. Several transcription initiation sites were revealed by RNA ligase-mediated rapid amplification of the cDNA 5'-ends. We also found that the immediate upstream region and the first exon in the human CATSPER1 gene negatively regulate transcriptional activity. In the murine Catsper1 promoter, binding sites for transcription factors SRY, SOX9 and CREB were protected by the presence of nuclear testis proteins in DNAse degradation assays. Likewise, the mouse Catsper1 promoter exhibited transcriptional activity in both orientations and displayed significant expression levels in mouse testis in vivo, whereas the suppression of transcription signals in the promoter resulted in low expression levels. This study, thus, represents the first identification of the transcriptional control regions in the genes encoding the human and murine CatSper channels.