Molecular cloning of complementary deoxyribonucleic acid for an androgen-regulated epididymal protein: sequence homology with metalloproteins

Acidic epididymal glycoprotein (AEG) is a 31,000 molecular weight secretory protein of the rat epididymis. Screening of a rat epididymal cDNA library with affinity-purified AEG antiserum yielded cDNA for AEG. Identity of the clones was verified by comparison of amino acid sequence of the purified protein with the sequence derived from the nucleotide sequence of the cDNA isolates. Two classes of AEG cDNA, approximately 1500 base pairs (bp) and 950 bp in length, differed by 538 bp in the 3'-untranslated region and by four single nucleotide mismatches, one of which was in the coding region. Northern blot hybridization of epididymal RNA revealed two species of AEG mRNA, corresponding in length to each type of cDNA. Analysis of RNA from individual animals provided evidence that the two mRNA species are the products of allelic genes. In vivo studies demonstrated that the level of total AEG mRNA is regulated by androgen. Amino acid sequence homology of AEG with metal-binding domains of several proteins suggests that AEG is a metalloprotein.     

Novel sperm-binding proteins of epididymal origin contain four fibronectin type II-modules

Novel fibronectin type II (Fn2)-module proteins were cloned from human and canine epididymal cDNA libraries. cDNA sequences predicted a highly conserved protein family, related but not homologous to ungulate seminal plasma proteins (approximately 50% sequence identity), and the first known examples of proteins with four tandemly arranged Fn2-domains. By Northern blot and in situ hybridization analyses the encoding mRNAs were shown to be abundant products of the epididymal duct epithelium, but not detectable in other tissues. Homologous mRNAs were identified in the epididymides of various mammals, representing members of this novel protein family of epididymal origin. Within the Fn2-module-encoding stretches, species homologues displayed >85% sequence identity, but showed high variability at their predicted N-termini. An antipeptide antiserum in Western blot analyses detected 30-35 kDa immunoreactive protein bands in epididymal tissue, cauda epididymidal fluid, and sperm membrane protein preparations. The tandem arrangement of increasing numbers of Fn2-modules might functionally correspond to the tendency to form oligomers that has been described for lipid-binding proteins.     

Identification and characterization of novel and unknown mouse epididymis-specific genes by complementary DNA microarray technology

To examine epididymal function, we attempted to identify highly expressed genes in mouse epididymis using a cDNA microarray containing PCR products amplified from a mouse epididymal cDNA library. We isolated one novel and four known genes-lymphocyte cytosolic protein 1 (Lcp1), complement subcomponents C1r/C1s, Uegf protein, and bone morphogenetic protein and zona pellucida-like domains 1 (Cuzd1), transmembrane epididymal protein 1 (Teddm1), and whey acidic protein 4-disulfide core domain 16 (Wfdc16)-with unknown functions in the epididymis. The novel gene, designated Serpina1f (serine peptidase inhibitor [SERPIN], clade A, member 1f), harbors an open reading frame of 1 233 bp encoding a putative protein of 411 amino acids, including a SERPIN domain. These five genes were predominantly expressed in the epididymis as compared to other organs. In situ hybridization analysis revealed their epididymal region-specific expression patterns. Real-time RT-PCR analysis revealed a significant increase in mRNA expression of these genes around puberty. Castration decreased their expression, except forLcp1. Testosterone (T) restored these reduced expressions, except forTeddm1; however, this restoration was not observed with 17 beta-estradiol (E2). Administration of T and E2 combination recovered the Serpina1f mRNA concentration; this recovery was also observed with T alone. However, the recovery of Cuzd1and Wfdc16mRNA concentrations was inadequate. Neonatal diethylstilbestrol treatment suppressed the Cuzd1, Wfdc16, and Serpina1f mRNA expression in the epididymis of 8-week-old mice; this was not observed with E2. These results suggest that our microarray system can provide a novel insight into the epididymal function on a molecular basis, and the five genes might play important roles in the epididymis.