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The gene encoding the opioid peptide precursor preproenkephalin is expressed at high levels in the initial segment of the adult rat epididymis. Expression is localized to principal cells, the secretory epithelial cells lining the epididymal duct. During development, epididymal proenkephalin mRNA levels show a pronounced increase at about 44 days of age, coincident with the initial entry of spermatozoa into the epididymal lumen. Hypophysectomy leads to a 60-fold decrease in epididymal proenkephalin mRNA levels. Testosterone replacement can prevent this decline in a manner consistent with an effect upon spermatogenesis. Castration studies demonstrate that a gonadal factor other than testosterone directly regulates epididymal proenkephalin expression, and the results of efferent duct ligation suggest that this factor must be supplied through an intact connection of the testis and epididymis. Proenkephalin mRNA levels in the epididymis correlate with the decline and reappearance of spermatozoa induced by the alkylating agent busulphan. Thus, the developmental profile of proenkephalin expression, coupled with the results of both surgical and pharmacological manipulations of the reproductive tract, indicate that spermatozoa, or a spermatozoa-associated factor, regulate proenkephalin gene expression in the epididymis.  相似文献   

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Calspermin is a heat-stable, acidic calmodulin-binding protein predominantly found in mammalian testis. The cDNA representing the rat form of this protein has been cloned from a rat testis lambda gt11 library. Sequence analysis of two overlapping clones revealed a 232-nucleotide 5'-nontranslated region, 510 nucleotides of open reading frame, a 148-nucleotide 3'-untranslated region, and a poly(A) tail. Authenticity of the clones was confirmed by comparison of a portion of the deduced amino acid sequence with the sequence of a tryptic peptide obtained from the rat testis protein. The lambda gt11 fusion protein was recognized by affinity purified antibodies to pig testis calspermin and bound 125I-calmodulin in a Ca2+-dependent manner. Calspermin cDNA encodes a 169-residue protein with a calculated Mr of 18,735. The putative calmodulin-binding domain is very close to the amino terminus of the protein. This region shows 46% identity with the calmodulin-binding region of rat brain Ca2+/calmodulin-dependent protein kinase II and 32% identity with the equivalent region of chicken smooth muscle myosin light chain kinase. The 5'-nontranslated region reveals significant homology with a portion of the catalytic region of the calmodulin-dependent protein kinase family. Calspermin contains a stretch of 17 contiguous glutamic acid residues in the central region of the molecule. Computer analysis predicts calspermin to be 81% alpha-helix and 14% random coil. Analysis of genomic DNA indicates calspermin to be the product of a unique gene. Northern blot analysis of rat testis RNA reveals a 1.1-kilobase mRNA. This RNA is restricted to testis among several rat tissues examined and could not be identified in total RNA isolated from testes of other mammals. Analysis of cells isolated from rat testis reveals calspermin mRNA to be predominantly expressed in postmeiotic cells indicating that it may be specific to haploid cells.  相似文献   

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