Cloning and characterization of the rat Crisp-1 gene

Rat androgen-regulated acidic epididymal glycoprotein (AEG), also known as Protein DE, is a product of the Crisp-1 gene. Protein DE is secreted into the epididymal lumen and binds to sperm heads during their transit through the epididymis. In experiments reported here, the rat Crisp-1 gene has been cloned and its structure determined. The rat Crisp-1 gene spans 38kb and contains nine exons encoding an 1120bp epididymal Protein DE mRNA. The boundaries of the protein-coding exons are structurally organized similar to the mouse Crisp-1 gene, except for the 5' untranslated sequence, which is encoded by one exon in the mouse Crisp-1 gene and two exons in the rat gene. All the introns are flanked by AG/GT consensus splice sequences. Crisp-1 is a single-copy gene as shown by the presence of single bands by Southern blot analysis and PCR using rat genomic DNA as template. Recognition sites for steroid hormone receptors are present in the 5' flanking region and in intron 1, consistent with the known regulation of Protein DE expression by androgens. RT-PCR experiments demonstrate three splice variant mRNAs involving the non-coding exon 2. The Crisp-1 gene also produces an mRNA without an exon 1 sequence by utilizing a transcription start site in intron 1, 5' of the start of exon 2. All forms of the Crisp-1 mRNA are predicted to encode Protein DE.