Expression of a sperm protein gene during spermatogenesis in mammalian testis: an in situ hybridization study

Antisperm antibodies associated with infertility: properties and encoding genes of target antigens

Infertility among couples of reproductive age is a perplexing condition when the cause is indeterminate. These cases are classified as unexplained infertility. In a subset of subjects, antisperm antibodies with sperm agglutinating and/or immobilizing activities have been detected in the blood or fluids of the reproductive tract. These cases are designated as immunologic infertility although a cause and effect relationship of the antibodies to infertility has not been established. In this review, seven target sperm antigens to antibodies associated with infertility and their encoding genes are described. The antisperm antibodies (ASAs) examined were obtained from infertile women or were monoclonal antibodies (mAb) raised against human sperm proteins. All the ASAs studied possessed potent sperm agglutinating and/or immobilizing activities. The target antigens were isolated from human and other mammalian sperm, and the encoding genes identified. The seven antigens are YWK-II, BE-20, rSMP-B, BS-63 (nucleoporin-related), BS-17 (calpastatin), HED-2 (zyxin), and 75- kDa. Each antigen is a distinct and separate entity and is produced by different cells of the reproductive tract, (e.g., germ cells, epididymal epithelial cells, and Sertoli cells). No single predominant target component has been found to interact with the ASAs. It is proposed that immunologic infertility is the consequence of the combined actions of multiple ASAs in immobilizing and/or agglutinating spermatozoa, blocking spermegg interaction, preventing implantation, and/or arresting embryo development.

Molecular cloning and characterization of a novel testis-specific nucleoporin-related gene

A 20-kDa sperm membrane protein cDNA, designated as RSD-1, was isolated by epitope selection from a rat testis lambda gtll expression library. RSD-1 was used as a probe to screen a human testis lambda ZAPII cDNA expression library. A cDNA designated as BS-63 was isolated and found to consist of 1933 bp with an open reading frame of 1824 bp and assigned the accession number U64675 by GenBank. The deduced polypeptide consisted of 608 amino acid residues containing XFXFG or FG motifs that are characteristic of nuclear pore complex (NPC) proteins and act as potential binding sites for Ran. The N-terminal region has high homology with RanBP2/Nup358, a nucleoporin component, showing that BS-63 is a member of the NPC family. Northern blot analysis of mRNAs prepared from various human tissues shows that BS-63 is transcribed in two forms: 6.0 and 8.5 kb. The 8.5-kb transcript was present in low amounts in several somatic tissues, whereas the 6.0-kb transcript is expressed only in testis. In situ hybridization analysis of human testis sections showed that BS-63 mRNA is expressed only in germ cells at all stages of spermatogenesis. Sertoli cells did not transcribe the gene.

Expression of the BE-20 epididymal protein gene: in situ hybridization

A protein designated as BE-20 was purified from cauda epididymal fluid of male rabbits and the amino acid sequence of the N-terminus was determined. A 23-mer oligonucleotide coding the N-terminal eight amino acids of the BE-20 protein was synthesized. The oligonucleotide was used as sense primer with rabbit epididymal mRNA as template in the RT-PCR system. The BE-20 cDNA consisted of 499 bp with an open reading frame of 285 bp encoding a deduced polypeptide composed of 95 amino acids. Digoxigenin-labeled BE-20 cDNA was prepared and used as a hybridization probe to detect the specific mRNA. The probe interacted with a 1.2-kb mRNA prepared from rabbit epididymis; mRNAs prepared from rabbit testis gave negative reaction. Using tissue sections, the BE-20 mRNA was located in the epithelial cells of the cauda epididymis and proximal segment of the ductus deferens by in situ hybridization method. Sections of the corpus and caput epididymis, testis, and liver gave negative reaction. Polyclonal anti-BE-20 antibodies were raised and found to inhibit in vitro the capacity of human sperm to penetrate zona-free hamster ova. The results suggest that BE-20 protein may influence maturation of spermatozoa during its movement through the epididymis and/or the capacity of sperm to fertilize ova.

Gene expression and tissue localization of the two isoforms of angiotensin I converting enzyme

Angiotensin converting enzyme exists in two different isoforms, somatic and germinal, whose respective distributions and intracellular localizations have not been precisely determined. The differing biochemical and molecular characteristics of the two isozymes allowed the preparation of antibodies specific for each of the two angiotensin converting enzyme isoforms and of two nucleic acid probes, one of which was specific for the germinal isoform. Immunohistochemistry and in situ hybridization were used to determine the cell distribution of, respectively, the two isoforms and their corresponding messenger RNAs in the classically studied tissues of male adult humans and marmosets. Results provided by the two different methods were always concordant and were identical in the two species. The somatic angiotensin converting enzyme form was expressed uniquely in somatic tissues (vascular endothelial cells and at the brush border of renal proximal convoluted tubule, jejunal villus, and epididymal duct epithelia), and the germinal form was expressed uniquely in germinal cells with a precise stage-specific pattern, starting in round spermatids and finishing in spermatozoa. In situ hybridization documented the presence of somatic angiotensin converting enzyme messenger RNA in renal tubule epithelium, jejunal enterocytes, and epididymal epithelium and demonstrated that there was no direct correlation between the levels of angiotensin converting enzyme messenger RNA and the enzyme it encodes for, i.e., angiotensin converting enzyme, in a given epithelium. The significance of the ultraselective expression of germinal angiotensin converting enzyme and of its specific messenger RNA at a very precise stage of spermatogenesis remains uncertain.

Two-dimensional electrophoresis and densitometric analysis of solubilized bovine sperm plasma membrane proteins detected by silver staining and radioiodination

Bovine sperm plasma membranes were extracted with deoxycholate and subjected to two-dimensional gel electrophoresis. Proteins were visualized either by silver staining or autoradiography using 125I. When 1.5-2.0 micrograms of protein extract was applied to the first-dimension get, 250 spots could be detected by autoradiography. Thirty micrograms of protein was required to obtain spot visualization using silver strain, revealing more than 500 spots on the gel. These data establish the limit under which two-dimensional electrophoresis can be used in conjunction with flow cytometric sorting of sperm for the analysis of possible sex-specific membrane differences. The necessity of orienting sperm as they past the laser in the cell sorting system reduces throughput; thus, the number of sperm sorted within a given time is limited. It is suggested that autoradiography will allow the flow cytometer to be used in a time-efficient manner. Longer sorting times would be required to obtain sufficient sample to analyze total protein composition.

Expression of a gene encoding a rabbit sperm membrane protein in mammalian cells

A general mammalian expression vector designated pSV2-EP was reconstructed by inserting an oligonucleotide fragment into pSV2-dhfr. This vector allowed insertion of cDNAs with EcoRI cohesive ends. The pSV2-EP contains a simian virus 40 (SV40) early promoter, origin for DNA replication, SV40 poly-A site, splicing site, an initiator ATG downstream from the promoter and an EcoRI site for the insertion of cDNA fragment screened from lambda gt11 expression libraries. A recombinant plasmid (pS-VRS-1) was constructed by inserting RSD-1, a cDNA encoding a rabbit sperm tail protein, into the EcoRI site of the pSV2-EP vector. Chinese hamster ovarian (CHO) dhfr-negative cells were cotransformed with pSV2-dhfr and pSVRS-1 by the calcium phosphate method. In selective culture medium without thymidine and hypoxanthine, several cell lines were obtained containing mRNA and DNA that hybridized with RSD-1. One of these transformed cell lines stained intensely with anti-rSMP-B antibodies, demonstrating that the RSD-1 was expressed in the transformed CHO cells.