Mature Human Sperm Research Articles

DNA and total protamine masses in individual sperm from fertile mammalian subjects

The total amount of phosphorus and sulfur inside the nuclei of individual bull, stallion, hamster, human, and mouse sperm from fertile subjects has been measured using Particle Induced X-ray Emission (PIXE). Using the sulfur masses, we determined the total protamine (protamine 1 plus protamine 2) mass within the sperm nuclei of each species. Using the phosphorus masses, we determined the DNA mass present within the sperm nuclei of each species. The results reveal that although the relative proportion of protamine 1 to protamine 2 varies among the species examined, the total protamine mass to DNA mass ratio is similar in bull, stallion, hamster, and mouse sperm nuclei. In contrast, mature human sperm nuclei were found to contain significantly less protamine. This observation is consistent with other studies, which suggest that as much as 15% of the DNA in human sperm remain packaged by histones. Using the data obtained for bull sperm, the length of DNA that could be covered by each protamine 1 molecule in bull sperm has been estimated. Making the assumption that the size of the protamine 1 binding site on DNA is similar in the sperm of these species, the length of DNA covered by a single protamine 2 molecule also has been estimated. © 1996 Wiley-Liss, Inc.

Double and triple in situ chromosomal labeling of human spermatozoa by PRINS.

The PRimed IN Situ (PRINS) labeling method allows rapid, specific detection of human chromosomes in situ. We have adapted the PRINS protocol to mature human sperm in combination with a 3 M NaOH protocol for simultaneous in situ decondensation and denaturation of sperm nuclei. Using fluorochrome-labeled dNTPs in a sequential PRINS reaction, the direct detection of two or three distinct chromosomes must be performed within a timespan of 3 h. The method was tested with primers specific for chromosomes 8, 9, 12, 13, 16, 18, and 21 and the X. The frequencies of disomy ranged from 0.11% to 0.34%. Chromosome-specific primers have been defined for most of the human chromosomes, including some that are indistinguishable by fluorescence in situ hybridization (FISH) with centromeric probes. Consequently, this new strategy constitutes a rapid and efficient alternative to FISH for detecting nondisjunction in human sperm.

Presence of Endogenous Nicks in DNA of Ejaculated Human Spermatozoa and its Relationship to Chromomycin A3 Accessibility1

During spermiogenesis, mammalian chromatin undergoes replacement of nuclear histones by protamines, resulting in a DNA that is highly condensed in the mature sperm. We have previously demonstrated that a percentage of human spermatozoa exhibit 1) positivity to the guanine-cylosine-specific chromomycin A3 (CMA3) fluorochrome and 2) the presence of endogenous nicks in their DNA. In situ protamination of mature human sperm limits the percentage of sperm positive to CMA3 and exhibiting endogenous nicks. In this study, we report further investigations that aim to clarify the relationship existing between levels of CMA3 stainability and the presence of endogenous nicks in the DNA of mature human spermatozoa. Human spermatozoa from 25 different samples showed values of sensitivity to the CMA3 fluorochrome ranging from 13% to 75%. The same samples showed a percentage of sensitivity to endogenous nick translation ranging from 1% to 38%. A strong correlation (r = 0.86) was evident between these two parameters. Prior staining of sperm with the CMA3 fluorochrome drastically reduced sensitivity to nick translation. In contrast, previously nick-translated sperm stained with CMA3 showed very little difference from samples that had not been pretreated. The presence of nicked sperm in the ejaculate may indicate anomalies during spermiogenesis and be an indicator of male infertility.

Fluorescent in situ hybridization evaluation of human Y-bearing spermatozoa separated by albumin density gradients

Fluorescent in situ hybridization of decondensed sperm nuclei was employed to evaluate the effectiveness of the Ericsson albumin gradient enrichment technique of Y-bearing sperm. Mature human spermatozoa were separated from donor- and randomly selected patient semen using three different albumin density layers. Sperm nuclei, in the albumin layer with highest density, were decondensed and the percentage Y-bearing sperm was determined by fluorescent in situ hybridization. A slight, although statistically significant, increase in percentage Y-bearing sperm was observed. Although statistically significant, the clinical relevance of the small increase in Y-bearing sperm remains uncertain. A randomized controlled clinical study should help to clarify the above laboratory results.

Detection of human leukocyte antigen class I messenger ribonucleic acid transcripts in human spermatozoa via reverse transcription-polymerase chain reaction

To determine by reverse transcription-polymerase chain reaction (PCR) whether human leukocyte antigen (HLA) class I messenger RNA (mRNA) is present in mature human spermatozoa. Mature human spermatozoa was isolated from donor semen using a swim-up technique. Total RNA was extracted via guanidinium isothiocyanate-cesium chloride ultracentrifugation. By the method previously validated in our laboratory, reverse transcription-PCR was performed using primers specific for HLA class I transcripts. Positive control cells included a choriocarcinoma cell line (JEG) and human fetal tissue. Transformed peripheral blood lymphocytes (PBL) were used as a negative control for somatic cellular contamination. Human spermatozoa were positive for HLA class I (-G and -B) mRNA by reverse transcription-PCR, consistent with the positive controls. We did not detect any mRNA for beta-actin, retinoblastoma (RB), CD4, or kappa light chain genes in the sperm complementary DNA samples, verifying that the class I mRNA detected was not due to somatic cellular contamination of the purified sperm samples. These experiments provide the first evidence that mRNA for HLA class I molecules are present in mature human spermatozoa. The physiological role of these transcripts is unknown at present. Further experiments characterizing the expression of HLA class I (-G and -B) mRNA in oocytes and preimplantation embryos are in progress.

Incidence of chromosome 3, 7, 10, 11, 17 and X disomy in mature human sperm nuclei as determined by nonradioactive in situ hybridization.

In situ hybridizations were performed on mature human sperm cells with biotin-labeled alpha-satellite DNA probes specific for chromosomes 3, 7, 10, 11, 17, and X in order to reveal the disomy rate for each of these chromosomes. A total of 76,253 sperm nuclei from seven healthy probands aged 23-57 years were analyzed. An average of 12,000 sperm nuclei (at least 1500 per donor) showing hybridization were scored with each probe. The disomy rate as indicated by two distinct hybridization signals turned out to be similar for all chromosomes, ranging from 0.31% to 0.34%. There were no significant interindividual differences and no age correlation in the frequency of disomic sperm cells between the donors.

Organization of centromeres in the decondensed nuclei of mature human sperm

The localization of centromeres in mature human sperm was shown by immunofluorescent labeling and nonisotopic in situ hybridization. In the decondensed nucleus structural elements (dimers, tetramers, linear arrays and V shape structures) formed by individual centromeres of nonhomologous chromosomes were observed. They organize the compact chromocenter, which was shown for nuclei decondensed to a low extent. The chromocenter is buried inside the nucleus; in contrast, telomeric regions of chromosomes were tentatively localized on the periphery. Thus, a gross architecture, which can influence selective unpackaging of the paternal genome upon fertilization, exists in human sperm.

Stimulation of protein tyrosine phosphorylation by a progesterone receptor on the cell surface of human sperm

Mature human sperm initiate a rapid Ca2+ influx and the acrosomal exocytosis in response to progesterone. Recent evidence indicates that both events can be induced by antibody-mediated cross-linking of a sperm surface progesterone receptor. In many other systems in which signal is generated by receptor cross-linking, protein phosphorylation on tyrosine residues is involved in the signal transduction across the plasma membrane. In this study we examined whether tyrosine phosphorylation is implicated in the function of the sperm surface progesterone receptor, too. The effect of progesterone on the phosphorylation of proteins from a sperm membrane lysate was evaluated by in vitro kinase assay and by phosphoamino acid analysis using [gamma-32P]ATP as precursor. These experiments revealed a selective increase in the tyrosine phosphorylation of a 94-kilodalton phosphoprotein in the presence of progesterone. To decide whether the progesterone-induced increase in protein tyrosine phosphorylation is actually due to the hormone action on the cell surface, living sperm were treated with a cell-impermeant progesterone receptor agonist, and the resulting changes in the cellular level of phosphotyrosine proteins were examined. These experiments showed a clear relationship between the agonist binding and an increase in the phosphotyrosine concentration in the respective cells. This relationship was lost in the presence of genistein, which also efficiently inhibited the phosphorylation of the 94-kilodalton protein and the progesterone-induced acrosomal exocytosis. These results lead to the hypothesis that protein tyrosine phosphorylation is involved in signal transduction through the sperm surface progesterone receptor and may be implicated in nongenomic steroid effects in other cell types.

Stimulation of protein tyrosine phosphorylation by a progesterone receptor on the cell surface of human sperm.

Mature human sperm initiate a rapid Ca2+ influx and the acrosomal exocytosis in response to progesterone. Recent evidence indicates that both events can be induced by antibody-mediated cross-linking of a sperm surface progesterone receptor. In many other systems in which signal is generated by receptor cross-linking, protein phosphorylation on tyrosine residues is involved in the signal transduction across the plasma membrane. In this study we examined whether tyrosine phosphorylation is implicated in the function of the sperm surface progesterone receptor, too. The effect of progesterone on the phosphorylation of proteins from a sperm membrane lysate was evaluated by in vitro kinase assay and by phosphoamino acid analysis using [gamma-32P]ATP as precursor. These experiments revealed a selective increase in the tyrosine phosphorylation of a 94-kilodalton phosphoprotein in the presence of progesterone. To decide whether the progesterone-induced increase in protein tyrosine phosphorylation is actually due to the hormone action on the cell surface, living sperm were treated with a cell-impermeant progesterone receptor agonist, and the resulting changes in the cellular level of phosphotyrosine proteins were examined. These experiments showed a clear relationship between the agonist binding and an increase in the phosphotyrosine concentration in the respective cells. This relationship was lost in the presence of genistein, which also efficiently inhibited the phosphorylation of the 94-kilodalton protein and the progesterone-induced acrosomal exocytosis. These results lead to the hypothesis that protein tyrosine phosphorylation is involved in signal transduction through the sperm surface progesterone receptor and may be implicated in nongenomic steroid effects in other cell types.

The culture of human epididymal epithelium and in vitro maturation of epididymal spermatozoa

To promote human sperm maturation in vitro.Spermatozoa from the proximal epididymis were coincubated with epididymal epithelial fragments.Hospital and research institute.Tissue samples were obtained from men undergoing epididymovasostomy procedures or vasectomy.Fragments of epididymal epithelium formed everted epithelial spheres that in the presence of androgen maintained cell integrity. Coincubation for up to 48 hours of caput epididymal spermatozoa with 3-day-old epithelial cultures from the cauda epididymis was undertaken.Morphology of epididymal epithelium was assessed by light and electron microscopy. Pulse labeling of tissue in vitro with 35S-methionine was performed with analysis by sodium dodecyl sulfate-polyacrylamide gel electrophoresis technique and fluorography. Spermatozoa were assessed for progressive motility and their capacity to bind to salt-stored human zona pellucidae.Epididymal fragments formed everted epithelial spheres that maintained cell integrity and functional morphology for 5 to 7 days. Specific proteins were synthesized in culture, in particular, proteins of 20, 22, 40, and 66 kd. Coincubation of caput epididymal spermatozoa with cultures from the cauda epididymis induced a significant increase in progressive sperm motility and sperm binding to salt-stored human zona pellucidae compared with control cultures of epithelium incubated in the absence of androgens or overgrown with fibroblasts.Aspects of human sperm maturation processes can be mimicked in vitro using coculture techniques with epididymal epithelium. This method may be valuable for improving the fertilizing capacity of human spermatozoa retrieved from the proximal region of the excurrent ducts.

Characterization of fibronectin as a marker for human epididymal sperm maturation.

Fertilization involves adhesive interactions between gametes similar to those mediated by fibronectin (FN) in other cellular systems. Fibronectin has been found on the equatorial segment of ejaculated human serum. As sperm capacity to interact with the oocyte is acquired during epididymal transit, the possible participation of FN in human sperm maturation was studied. The presence of FN in both epididymal sperm and fluid was demonstrated by the detection of a major component of 220 kD in immunoblot studies using anti-FN antisera. The concentration of FN in soluble tissue extracts of epididymis was determined by enzyme-linked immunosorbent assay (ELISA). A gradual increase along the length of the organ, averaging 12-fold from proximal caput to distal corpus, was detected. Immunocytochemistry assays indicated that the number of spermatozoa with immunoreactive FN over the equatorial segment increased from 18% in caput to 64% in distal corpus epididymis. Immunoprecipitation of medium from epididymal explants culture with anti-FN antiserum demonstrated the de novo synthesis of FN in vitro. The greater number of FN-positive sperm coincident with FN accumulation in distal regions of the epididymis supports the role of FN in sperm maturation.

Human sperm proteins from testicular and epididymal origin that participate in fertilization: modulation of sperm binding to zona-free hamster oocytes, using monoclonal antibodies.

In order to identify human sperm surface proteins involved in the gamete recognition process, mouse monoclonal antibodies were directed against human spermatozoa and screened with live spermatozoa by enzyme-linked immunosorbent assay (ELISA). Immunoperoxidase staining of human testis showed the early presence of four corresponding proteins on germinal cells, while six were detected primarily in testis fluid. The presence of 17 proteins was evidenced in the epididymis. Eight were detected with a decreasing gradient from the beginning to the end of the organ, including vasa efferentia for three of them. The other nine were observed in only one defined segment, usually the caput epididymis, which was found to be the most active region. Comparison of spermatozoa patterns from testis, vasa efferentia, and the three regions of epididymis pointed out a progressive coating. By contrast, three antibodies displayed a migration of spermatozoa surface domains in the course of epididymal transit. Six antibodies were found to inhibit human spermatozoa adherence to zona-free hamster oocytes, while nine promoted it. Molecular weights of antigens corresponding to nine of the antibodies ranged from 11 to 215 kDa. No correlation could be established with previously described human proteins. These observations emphasize the role of epididymis in human sperm maturation.

The culture of human epididymal epithelium and in vitro maturation of epididymal spermatozoa

To promote human sperm maturation in vitro. Spermatozoa from the proximal epididymis were coincubated with epididymal epithelial fragments. Hospital and research institute. Tissue samples were obtained from men undergoing epididymovasostomy procedures or vasectomy. Fragments of epididymal epithelium formed everted epithelial spheres that in the presence of androgen maintained cell integrity. Coincubation for up to 48 hours of caput epididymal spermatozoa with 3-day-old epithelial cultures from the cauda epididymis was undertaken. Morphology of epididymal epithelium was assessed by light and electron microscopy. Pulse labeling of tissue in vitro with 35S-methionine was performed with analysis by sodium dodecyl sulfate-polyacrylamide gel electrophoresis technique and fluorography. Spermatozoa were assessed for progressive motility and their capacity to bind to salt-stored human zona pellucidae. Epididymal fragments formed everted epithelial spheres that maintained cell integrity and functional morphology for 5 to 7 days. Specific proteins were synthesized in culture, in particular, proteins of 20, 22, 40, and 66 kd. Coincubation of caput epididymal spermatozoa with cultures from the cauda epididymis induced a significant increase in progressive sperm motility and sperm binding to salt-stored human zona pellucidae compared with control cultures of epithelium incubated in the absence of androgens or overgrown with fibroblasts. Aspects of human sperm maturation processes can be mimicked in vitro using coculture techniques with epididymal epithelium. This method may be valuable for improving the fertilizing capacity of human spermatozoa retrieved from the proximal region of the excurrent ducts.

The Ability of Dehydrated Hamster and Human Sperm Nuclei to Develop into Pronuclei1

To determine whether the nuclei of mature mammalian spermatozoa are resistant to dehydrated conditions, nuclei of hamster and human spermatozoa were freeze-dried or treated with various dehydrating agents before injection into hamster oocytes. Freeze-dried nuclei remained capable of developing into pronuclei even after 12 mo of storage at 4 degrees C. The level of DNA synthetic activity in the sperm (male) pronucleus was comparable to that in the egg (female) pronucleus. Sperm nuclei that had been stored in 100% ethanol, 100% methanol, or chloroform-methanol (2:1) mixture for 20 days were also capable of developing into pronuclei. Even the nuclei that had been dehydrated ("fixed") with Carnoy's fluid could develop into morphologically normal pronuclei. However, the level of DNA synthesis in the pronuclei derived from these chemically dehydrated nuclei was generally lower than that in the female pronuclei. Although the genetic integrity of the dehydrated sperm nuclei is yet to be determined, nuclei of mature hamster and human spermatozoa appear to be fairly resistant to dehydrated conditions.

Expression and function of ras proto-oncogene proteins in human sperm cells.

The presence and role of c-ras proteins were investigated in mature human sperm cells. The v-H-ras monoclonal antibody (mAb) against the c-ras protein, p21, reacted specifically with the acrosomal region of methanol-fixed as well as unfixed-live capacitated and non-capacitated human sperm cell in the indirect immunofluorescence technique. The v-H-ras mAb predominantly recognized c-ras protein of 21 kDa on the Western blot of lithium diiodosalicylate (LIS)-solubilized human sperm preparation. The incubation of sperm cells with v-H-ras mAb affected the sperm cell function in the human sperm penetration assay. The antibody significantly reduced the acrosome reaction and release of acrosin activity from the sperm cells. There was no effect of the mAb on percentage motility, although the mAb significantly affected various motility characteristics such as linearity, amplitude of lateral head displacement (ALH) and beat frequency, the motility parameters involved in the hyperactivation phenomenon of sperm cells leading to capacitation and acrosome reaction. These results suggest that the c-ras or c-ras-like proteins are present in mature sperm cell and may have a role in capacitation and/or acrosome reaction of human sperm cell.

Isolation of four core histones from human sperm chromatin representing a minor subset of somatic histones

Using high performance liquid chromatography we have successfully purified four core histones from mature human sperm chromatin. The H2A variants present in sperm (H2A.X and limited H2A.Z) have been shown previously to be minor variants in somatic chromatin. The histones are highly modified as evidenced by extensive acetylation and an as yet uncharacterized multicharge modification of H2B. Based on our data, we conclude that histone proteins are a minor component of each mature spermatozoa. Given the unique nature of the histone variants present in sperm, we propose that this chromatin component has a specific function and may possibly facilitate the programming of genes which will be active in early development.

Localization of cytoplasmic lactate dehydrogenase-X in spermatozoa.

Cytoplasmic lactate dehydrogenase-X (LDH-X) has been localized in the tail sheath of mature intact mouse, human, and rat spermatozoa by histochemical and immunological techniques. The isozyme is also found within the mitochondria. Intact sperm demonstrate a mitochondrial LDH-X but cytoplasmic localization in mature sperm cells has been inconclusive. The presence of LDH-X in the sperm tail supports in vitro biochemical data for the existence of a cytosol/mitochondria shuttle of reducing equivalents mediated by LDH-X.

Replacement of protamine by F1 histone during reactivation of fused human sperm nuclei

Rabbit antisera, specific for the histones F1, F2a2, F2b, F3 and for protamine were used to monitor a possible transition from protamine towards somatic-type histones during sperm nucleus reactivation, following human sperm fusion with mouse fibroblasts. Mature human sperm nuclei were shown to contain the histones F2a2, F2b, F3 and protamine, but were missing F1 histone by immuno cytochemistry using the indirect fluorescence method. However, a gradual disappearance of protamine from fused sperm nuclei, could be observed during the first 24 h of reactivation. Subsequently, F1 histone could be detected in increasing concentrations in 60% of reactivated sperm nuclei, during the next four days. The shift from protamine towards F1 histone could also be visualized cytochemically via staining with brilliant sulphaflavine, which appears to discriminate between sperm nuclei on the basis of their F1 histone content.

Inhibition of Sperm Maturation Through Intervention of the Carnitine System

Carnitine, acetylcarnitine and carnitine acetyltransferase (E.C.2.2.1.7) are present in 6–120 fold higher concentrations in human spermatozoa than in seminal plasma. Carnitine uptake by epididymal tissue in vitro in the rat is most active in the same segments of epididymis where the highest concentrations of carnitine are found in man. Radiolabelled carnitine is not taken up by mature human spermatozoa. Carnitine suppresses oxygen uptake in bovine ejaculated spermatozoa but not in human ejaculated or in rat or bovine epididymal spermatozoa. These findings indicate that the epididymis contributes to the accumulation of carnitine in caput spermatozoa and that carnitine may not be primarily responsible for the quiescent state of the spermatozoa in the cauda epididymis.Extensive changes in carnitine uptake in the epididymis can be encouraged by a hormonal treatment which has no effect on the carnitine uptake by the heart. This raises the possibility of interference with the carnitine balance in the epididymis without effecting the pattern of carnitine uptake in other tissues.

F-bodies as Y chromosome markers in mature human sperm heads: a quantitative approach.

It is generally accepted that at least some Y chromosomes in human mature sperm heads are represented in preparations by fluorescent F-bodies. From data consisting solely of F-body scorings and the visually estimated size of sperm heads from normal donors, a quantitative model is developed which permits simultaneous estimation of six parameters representing biological factors (the proportions of ploidy classes and of their sex-chromosome complements) and biassing factors (not all Y chromosomes represented by F-bodies, not all F-bodies representing Y chromosomes, and error in scoring ploidy from visual size). The analysis is statistically adequate and succeeds in predicting a variety of independently validated phenomena. The work may be regarded as a contribution to the integration of qualitative and quantitative evidence in the study of F-bodies. In all, 21,700 one-headed spermatozoa from 12 donors were scored. A mean of 54% spermatozoa lacking F-bodies was subject to a standard deviation between donors of 4.8, over and above binomial error. Analysis yielded the following estimates: 83.3% of diploid spermatozoa are XY, the remainder XX and YY in assumed equal number (this information assists analysis of the origin of embryonic triploidy); 2.4% of spermatozoa are diploid (this estimate does not compete in accuracy with direct estimates from DNA absorbance); only 83% of Y chromosomes are represented by F-bodies; 7% of haploid heads and 14% of diploids contain one or more "adventitious bodies" indistinguishable from true F-bodies. The visually scored head sizes "Small" and "Medium" correspond approximately with haploidy and diploidy; nearly all haploids are scored as Small, and 72% of the Medium are diploid. F-bodies are not thought at present to give a useful basis for estimating the presumably low incidence of sex-chromosome aneuploidy and nondisjunction. No such estimate has been attempted. The problem is overshadowed by not fully understood complicating factors of greater magnitude, which now appear to be a major subject of enquiry. Some implications and possible future developments are discussed.