Detection of mRNA transcripts of beta 1 integrins in ejaculated human spermatozoa by nested reverse transcription-polymerase chain reaction

Molecules involved in the sperm interaction in the human uterine tube: a histochemical and immunohistochemical approach

In humans, even where millions of spermatozoa are deposited upon ejaculation in the vagina, only a few thousand enter the uterine tube (UT). Sperm transiently adhere to the epithelial cells lining the isthmus reservoir, and this interaction is essential in coordinating the availability of functional spermatozoa for fertilization. The binding of spermatozoa to the UT epithelium (mucosa) occurs due to interactions between cell-adhesion molecules on the cell surfaces of both the sperm and the epithelial cell. However, in humans, there is little information about the molecules involved. The aim of this study was to perform a histological characterization of the UT focused on determining the tissue distribution and deposition of some molecules associated with cell adhesion (F-spondin, galectin-9, osteopontin, integrin αV/β3) and UT's contractile activity (TNFα-R1, TNFα-R2) in the follicular and luteal phases. Our results showed the presence of galectin-9, F-spondin, osteopontin, integrin αV/β3, TNFα-R1, and TNFα-R2 in the epithelial cells in ampullar and isthmic segments during the menstrual cycle. Our results suggest that these molecules could form part of the sperm-UT interactions. Future studies will shed light on the specific role of each of the identified molecules.

Evaluation of α5β1 integrin as a candidate marker for fertility in bull sperm samples

With the progressive increase in the use of reproductive biotechnologies in the cattle industry, like artificial insemination and in vitro embryo production, the accurate determination of fertilizing competence of cryopreserved sperm samples is an essential issue. The routine methodology to assess bull sperm quality relies primarily on count, viability and motility of spermatozoa. However, these parameters do not tightly predict the reproductive success of samples. Therefore, identification of complementary markers of sperm functionality to strengthen the predictability of traditional spermogram is desirable to improve livestock reproduction practices. Previous results from our laboratory indicated that α5β1 integrin plays a key role in bovine sperm function and mediates their interaction with the female reproductive tract. Thus, this study aimed to investigate whether the localization of α5β1 held a correlation with fertilizing ability of bovine cryopreserved semen samples. Firstly, we assessed the quality of samples from six different bulls (A-F). We determined motility and viability of sperm samples after thawing and selection. Additionally, we measured the capacitation state of the samples by chlortetracycline (CTC) assay in the presence or absence of heparin, as an indicator of their responsiveness to a capacitating stimulus. Based on these assays, samples were classified being A the bull with the lowest quality and F the bull with the highest quality. Then, we studied the presence and localization of α5β1 integrin. This protein showed a distribution pattern in the acrosomal (A), post-acrosomal (P) and acrosomal + post-acrosomal (A + P) regions with different localization percentages among the studied samples. Next, we determined the fertilizing ability of the samples in in vitro fertilization (IVF) assays and performed correlation analyses between IVF outcome and the routine spermogram parameters or α5β1 integrin localization patterns. When the percentage of cells showing α5β1 integrin was compared to fertilization rate, no correlation was observed. However, the presence of α5β1 integrin in P and A + P regions (PA pattern), positively correlated with IVF rate (p < 0.05). These results suggest that while routine semen analyses failed to predict sperm reproductive competence, integrin localization in post-acrosomal region (PA pattern) showed a positive correlation with IVF outcome, thus posing an attractive marker to predict more accurately the reproductive performance of an individual.

A history of why fathers' RNA matters

Having been debated for many years, the presence and role of spermatozoal RNAs is resolving, and their contribution to development is now appreciated. Data from different species continue show that sperm contain a complex suite of coding and noncoding RNAs that play a role in an individual's life course. Mature sperm RNAs provide a retrospective of spermatogenesis, with their presence and abundance reflecting sperm maturation, fertility potential, and the paternal contribution to the developmental path the offspring may follow.Sperm RNAs delivered upon fertilization provide some of the initial contacts with the oocyte, directly confront the maternal with the paternal contribution as a prelude to genome consolidation. Following syngamy, early embryo development may in part be modulated by paternal RNAs that can include epidydimal passengers. This provides a direct path to relay an experience and then initiate a paternal response to the environment to the oocyte and beyond. Their epigenetic impact is likely felt prior to embryonic genome activation when the population of sperm delivered transcripts markedly changes. Here, we review the insights gained from sperm RNAs over the years, the subtypes, and the caveats of the RNAs described. We discuss the role of sperm RNAs in fertilization and embryo development, and their possible mechanism(s) influencing offspring phenotype. Approaches to meet the future challenges as the study of sperm RNAs continues, include, elucidating the potential mechanisms underlying how paternal allostatic load, the constant adaptation of health to external conditions, may be relayed by sperm RNAs to affect future generations.

Laminin-111 Inhibits Bovine Fertilization but Improves Embryonic Development in vitro, and Receptor Integrin-β1 is Involved in Sperm-Oocyte Binding

This study detected the distribution of laminin during embryonic formation by immunofluorescence. To determine the possible function of laminin on developmental ability of in vitro fertilized embryos, the presumptive zygotes were divided and transferred to CR1aa medium supplemented with different concentrations (0 μg/ml, 5 μg/ml, 10 μg/ml and 20 μg/ml) of laminin. To explore the association with sperm-oocyte fusion, oocytes and/or sperm were pre-incubated with laminin or anti-β1 antibody before insemination. Laminin was absent in mature oocytes and could be detected first at the 8-cell stage and then displayed an increasing tendency. Adding 10 μg/ml laminin to the culture medium improved embryonic development including cleavage rate, blastocyst rate, total cell numbers in the blastocyst and cell numbers in the inner cell mass. Laminin inhibited sperm-oocyte fusion when incubated with oocytes and/or sperm before in vitro fertilization, and only integrin-β1 of sperm was involved in sperm-oocyte binding. Inhibition may be caused by blocking β1, but why laminin inhibits fertilization is still unknown. The results suggest that laminin plays an important role during embryonic formation and has a negative function in sperm-oocyte fusion, but improves embryonic development. However, only integrin-β1 is involved in sperm-oocyte binding.

The small RNA content of human sperm reveals pseudogene-derived piRNAs complementary to protein-coding genes

At the end of mammalian sperm development, sperm cells expel most of their cytoplasm and dispose of the majority of their RNA. Yet, hundreds of RNA molecules remain in mature sperm. The biological significance of the vast majority of these molecules is unclear. To better understand the processes that generate sperm small RNAs and what roles they may have, we sequenced and characterized the small RNA content of sperm samples from two human fertile individuals. We detected 182 microRNAs, some of which are highly abundant. The most abundant microRNA in sperm is miR-1246 with predicted targets among sperm-specific genes. The most abundant class of small noncoding RNAs in sperm are PIWI-interacting RNAs (piRNAs). Surprisingly, we found that human sperm cells contain piRNAs processed from pseudogenes. Clusters of piRNAs from human testes contain pseudogenes transcribed in the antisense strand and processed into small RNAs. Several human protein-coding genes contain antisense predicted targets of pseudogene-derived piRNAs in the male germline and these piRNAs are still found in mature sperm. Our study provides the most extensive data set and annotation of human sperm small RNAs to date and is a resource for further functional studies on the roles of sperm small RNAs. In addition, we propose that some of the pseudogene-derived human piRNAs may regulate expression of their parent gene in the male germline.

Detection of a Short CCR5 Messenger RNA Isoform in Human Spermatozoa

It has recently been reported that the Regulated upon Activation of Normal T-cells Expressed and Secreted (RANTES) chemokine may exhibit a chemotactic effect on sperm. The RANTES chemokine acts on target cells by binding to the CCR5 receptor, which is present on the surface of various cells. Spermatozoa contain a complex repertoire of messenger RNAs (mRNAs) that may provide an insight into past events of spermatogenesis. The type and amount of CCR5 chemokine receptor transcript were investigated in spermatozoa that were isolated by the swim-up method from semen samples of men with normozoospermia. Using reverse transcription and real-time quantitative polymerase chain reaction (RQ-PCR) analysis, we found that the CCR5 mRNA isoform in human spermatozoa consists of exons 3 and 4, and is shorter than the transcript in leukocytes. This CCR5 transcript may represent a more stable mRNA isoform; one that is used to biosynthesize the CCR5 receptor in spermatogenesis or the early stages of embryonic development.

Novel insights into the genetic and epigenetic paternal contribution to the human embryo

The integrity of the sperm genome and epigenome are critical for normal embryonic development. The advent of assisted reproductive technology has led to an increased understanding of the role of sperm in fertilization and embryogenesis. During fertilization, the sperm transmits not only nuclear DNA to the oocyte but also activation factor, centrosomes, and a host of messenger RNA and microRNAs. This complex complement of microRNAs and other non-coding RNAs is believed to modify important post-fertilization events. Thus, the health of the sperm genome and epigenome is critical for improving assisted conception rates and the birth of healthy offspring.

RETRACTED ARTICLE: Transcriptome profile alterations in asthenozoospermic and idiopathic infertile spermatozoa uncovered by microarray

This article has been retracted at the request of the Editor-in- Chief. The original submission was made without the approval of the previously listed co-author Dr. Rajender Singh. In addition, the article is being retracted because the corresponding author is not the owner of the data and has no right to publication.

Spermatozoal RNAs: what about their functions?

The profound architectural changes that transform spermatids into spermatozoa result in a high degree of DNA packaging within the sperm head. However, the mature sperm chromatin that harbors imprinted genes exhibits a dual nucleoprotamine/nucleohistone structure with DNase-sensitive regions, which could be implicated in the establishment of efficient epigenetic information in the developing embryo. Despite its apparent transcriptionally inert state, the sperm nucleus contains diverse RNA populations, mRNAs, antisense and miRNAs, that have been transcribed throughout spermatogenesis. There is also an endogenous reverse transcriptase that may be activated under certain circumstances. It is now commonly accepted that sperm can deliver some RNAs to the ovocyte at fertilization. This review presents potential links between male-specific genomic imprinting, chromatin organization, and the presence of diverse RNA populations within the sperm nucleus and discusses the functional significance of these RNAs in the spermatozoon itself and in the early embryo following fertilization. Some recent data are provided, supporting the view that analyzing the profile of spermatozoal RNAs could be useful for assessment of male fertility.

QUANTITATIVE ANALYSIS OF CCR5 CHEMOKINE RECEPTOR AND CYTOCHROME P450 AROMATASE TRANSCRIPTS IN SWIM-UP SPERMATOZOA ISOLATED FROM FERTILE AND INFERTILE MEN

We determined the CCR5 chemokine receptor and cytochrome P450 aromatase (P450arom) transcript copies number in swim-up sperm isolated from fertile and infertile men. The ejaculates were purified by centrifugation through discontinuous Percoll density gradient and swim-up techniques. RNA was isolated from sperm, treated with DNase I and reverse-transcribed into cDNA. Quantitative analysis of CCR5 and P450arom cDNA were performed by real-time quantitative (RQ-PCR) SYBR Green I analysis. There was a higher content of CCR5 and P450arom transcripts copy number in swim-up sperm of fertile than from infertile donors. The decrease in CCR5 and P450arom transcripts in swim-up sperm may be associated with male infertility.

Expression of cytochrome P450 aromatase transcripts in buffalo (Bubalus bubalis)-ejaculated spermatozoa and its relationship with sperm motility

The cytochrome P450 aromatase (aromP450) deficient mice are infertile due to an impairment of spermatogenesis associated with a decrease in sperm motility and inability to fertilize oocytes. The sperm analysis showed decreased sperm motility in humans, having Cyp19 gene mutations. Further, in human, it was hypothesized that aromatase could be used as marker of sperm quality, particularly in the acquisition of its motility. However, there is no information regarding the expression of aromP450 in spermatozoa of farm animals including cattle and buffalo. In the present study, the expression of aromP450 in ejaculated buffalo spermatozoa and its relationship with sperm motility of ejaculated spermatozoa was studied by RT-PCR using total RNA isolated from buffalo-ejaculated spermatozoa. The results showed that conventional RT-PCR could not amplify aromatase transcript, while a nested PCR detected the presence of P450arom mRNA in buffalo-ejaculated spermatozoa. RT reaction followed by nested PCR was performed to compare the expression of aromatase transcripts in buffalo-ejaculated spermatozoa of two category semen graded on the basis of mass motility and motile and non-motile spermatozoa separated by swim-up. A higher (P<0.01) expression of aromP450 transcript was found in spermatozoa obtained from the good quality semen (higher mass motility) to that in spermatozoa of poor quality semen (low mass motility). Similarly, higher (P<0.01) expression of aromP450 mRNA was observed in the motile spermatozoa as compared to non-motile spermatozoa separated from good quality semen by swim-up. It is concluded that the present study demonstrates a positive relation between aromatase transcript and mass motility of buffalo-ejaculated spermatozoa, which could be a putative marker for the quality of semen in farm animals, particularly the acquisition of sperm motility.

Protein synthesis in sperm: dialog between mitochondria and cytoplasm

Ejaculated sperm are capable of using mRNAs transcripts for protein translation during the final maturation steps before fertilization. In a capacitation-dependent process, nuclear-encoded mRNAs are translated by mitochondrial-type ribosomes while the cytoplasmic translation machinery is not involved. Our findings suggest that new proteins are synthesized to replace degraded proteins while swimming and waiting in the female reproductive tract before fertilization, or produced due to the specific needs of the capacitating spermatozoa. In addition, a growing number of articles have reported evidence for the correlation of nuclear-encoded mRNA and protein synthesis in somatic mitochondria. It is known that all of the proteins necessary for the replication, transcription and translation of the genes encoded in mtDNA are now encoded in the nuclear genome. This genetic investment is far out of proportion to the number of proteins involved, as there have been multiple movements and duplications of genes. However, the evolutionary retention (or secondary uptake) of the mitochondrial machinery for translation of nuclear-encoded mRNAs may shed light on this paradox.

Effect of fibronectin on proteasome activity, acrosome reaction, tyrosine phosphorylation and intracellular calcium concentrations of human sperm

BACKGROUND

Previously we showed that the human sperm proteasome plays significant roles during mammalian fertilization. Here we studied the effect of fibronectin (Fn), an extracellular matrix protein present in the cumulus oophorus of the oocyte, on proteasome activity, acrosome reaction, intracellular calcium concentration ([Ca(2+)](i)) and protein tyrosine phosphorylation of human sperm.

METHODS

Aliquots of motile sperm were incubated for 15 min (T0), 5 h (T5) and 18 h (T18), at 37 degrees C, 5% CO(2) and 95% air with Fn (0-100 microg/ml). The chymotrypsin- and trypsin-like activity of the proteasome was measured using the fluorogenic substrates, Suc-Leu-Leu-Val-Tyr-AMC and Boc-Gln-Ala-Arg-AMC, respectively. At T18, sperm aliquots were incubated for 15 min with Fn and/or progesterone in the presence or absence of epoxomicin (a proteasome inhibitor). The percentage of viable acrosome reacted sperm was evaluated using the Fluorescein isothiocyanate (FITC)-labeled Pisum sativum agglutinin. Tyrosine phosphorylation was evaluated by western blot and [Ca(2+)](i) using fura 2.

RESULTS

Fn stimulated both enzymatic activities of the proteasome and the acrosome reaction of human sperm. Progesterone enhanced and epoxomicin drastically inhibited the effect of Fn. Fn treatment also increased the [Ca(2+)](i). Western blot analysis revealed that Fn increased tyrosine protein phosphorylation and that some proteasome subunits became tyrosine phosphorylated upon Fn treatment.

CONCLUSIONS

These results suggest that Fn activates the proteasome and induces the acrosome reaction in human sperm. This effect may involve binding with specific receptors (integrins) on the sperm surface and the activation of tyrosine kinases.

Characterization and quantification of mRNA transcripts in ejaculated spermatozoa of fertile men by serial analysis of gene expression

BACKGROUND

Accumulated evidence proves that mature spermatozoa contain a complex yet specific array of mRNA, which could provide information on the past events of spermatogenesis.

OBJECTIVE

To quantitatively microdissect these mRNA transcripts by a digital approach.

METHODS

Serial analysis of gene expression (SAGE) was used to study the mRNA transcripts from ejaculate of a fertile individual and of a pool of 10 fertile men. Online DAVID software suite was also utilized to cluster the UniGene data.

RESULTS

A SAGE library from the individual produced 20,237 raw tags representing 2459 unique tags and that from pooled 10 men generated 21,052 raw tags representing 2712 unique tags. When the unique tags occurring > or = 4 times were analysed, 564 overlapping tags were produced by 638 unique tags from the individual and 682 from the pooled library. Fifty-four of these overlapped tags were considered to be novel genes. Online analysis of the overlapping tags revealed 25 functional gene groups, with the dominant one comprising 96 nuclear protein genes involving transcription and transcription regulation and also a group with 84 ribosomal subunit genes involving protein synthesis.

CONCLUSION

A SAGE analysis of ejaculate from fertile men has revealed a large number of transcripts, which occur in steady frequencies and probably have important roles in spermatogenesis and fertilization.

The controversy, potential and roles of spermatozoal RNA

The majority of cellular and molecular andrologists endorse the view that the sperm is a vessel for transporting the paternal genome to the waiting egg and nothing more. Any requirement for additional spermatozoal components that enter the ooplasm apart from the paternal centriole and the soluble egg-activating factor is generally dismissed. Many studies, however, have reported RNAs in ejaculate spermatozoa and we now know that mRNAs are delivered to the egg on fertilisation. The function and utility of sperm mRNA remains essentially unexplored. Here, we examine the controversy surrounding spermatozoal mRNA carriage, the evidence refuting its presence as an artefact and how spermatozoal mRNA is leading us to suspect that, quite apart from its undoubted diagnostic potential, it might have an important role in the establishment and maintenance of a viable paternal genome.

RNA in human sperm

We have yet to develop a fundamental understanding of the molecular complexities of human spermatozoa. This encompasses the unique packaging and structure of the sperm genome along with their paternally derived RNAs in preparation for their delivery to the egg. The diversity of these transcripts is vast, including several anti-sense molecules resembling known regulatory micro-RNAs. The field is still grasping with its delivery to the oocyte at fertilization and possible significance. It remains tempting to analogize them to maternally-derived transcripts active in early embryo patterning. Irrespective of their role in the embryo, their use as a means to assess male factor infertility is promising.

Identification of transcripts by macroarrays, RT–PCR and in situ hybridization in human ejaculate spermatozoa

Round spermatids contain high levels of extremely varied mRNAs that are synthesized either throughout early spermatogenesis or during spermiogenesis from the haploid genome. Concomitantly, with major changes in the chromatin organization, arrest of transcription occurs at midspermiogenesis. However, previous investigations using RT-PCR have revealed the persistence of numerous and different transcripts in ejaculated spermatozoa. In the present study, a step-by-step analysis by means of macroarray hybridization, RT-PCR and in situ hybridization was performed to identify more accurately the different mRNA species found in the human ejaculated spermatozoa. The data showed an extended pattern of various transcripts encoding a diverse range of proteins involved in signal transduction and cell proliferation. For the first time, they demonstrated that mRNAs coding for the transcription factors NFkappaB, HOX2A, ICSBP, protein kinase JNK2, growth factor HBEGF and receptors RXRbeta and ErbB3 accumulate within the sperm nucleus. The origin and fate of the sperm transcripts remain subject to discussion.

Transcription in haploid male germ cells

Major modifications in chromatin organization occur in spermatid nuclei, resulting in a high degree of DNA packaging within the spermatozoon head. However, before arrest of transcription during midspermiogenesis, high levels of mRNA are found in round spermatids. Some transcripts are the product of genes expressed ubiquitously, whereas some are generated from male germ cell-specific gene homologs of somatic cell genes. Others are transcript variants derived from genes with expression regulated in a testis-specific fashion. The haploid genome of spermatids also initiates the transcription of testis-specific genes. Various general transcription factors, distinct promoter elements, and specific transcription factors are involved in transcriptional regulation. After meiosis, spermatids are genetically but not phenotypically different, because of transcript and protein sharing through cytoplasmic bridges connecting spermatids of the same generation. Interestingly, different types of mRNAs accumulate in the sperm cell nucleus, raising the question of their origin and of a possible role after fertilization.

The human SPANX multigene family: genomic organization, alignment and expression in male germ cells and tumor cell lines

Multigenicity is one of the features of cancer/testis-associated genes. In the present study we analyzed the number and expression of genes of the SPANX(CTp11) family of cancer/testis-associated genes. Genomic database analysis, next to the four previously described SPANX genes, revealed the presence of a novel gene: SPANXE. Moreover, we detected an allelic variant of SPANXB resulting in one amino acid substitution in the encoded protein: SPANXB'. Most SPANX genes are present on contig NT_011574 located at Xq26.3-Xq27.1. Based on expressed sequence tag databases and RT-PCR analysis three additional novel SPANX sequences were identified, though not represented so far in the human genome sequence. Sequence alignments justify a subdivision of this gene family based on the absence (SPANXA-likes) or presence (SPANXB) of an 18 base pair sequence stretch in the open reading frame. The alignments also reveal an unusually high level (99%) of intron homology. Furthermore, the nucleotide variations in the open reading frame almost all lead to amino acid substitutions. Southern blot and database analyses indicate that SPANX sequences are exclusively present in primates. With RT-PCR analysis on human sperm cell precursors and tumor cell lines most family members could be detected. SPANXB was only found in sperm cell precursors and could not be detected in the tumor cell lines tested. Overall SPANXA was the most frequently expressed SPANX variant in melanoma and glioblastoma cell lines.

Estrogen receptor, calcium mobilization and rat sperm motility

Oral treatment with 0.4 mg/kg/day of tamoxifen citrate, an antiestrogen, has been reported to reduce the fertility of adult male rat, presumably through estrogen receptors expressed throughout the male reproductive tract. During the course of these studies, tamoxifen was observed to gradually alter the pattern of sperm motility in the cauda epididymides without reducing sperm counts. Studies were carried out to understand the mechanism involved in tamoxifen induced change in the sperm motility pattern. In order to study the direct effects of tamoxifen on motility, biochemical levels/activities of sperm calcium, cAMP, phosphodiesterase and dynein ATPase, normally implicated in sperm motility were studied In view of the fact that tamoxifen is a ligand of estrogen receptor, estrogen receptor alpha protein and transcript were localized on rat sperm membrane and the effect of tamoxifen studied. The present study demonstrated presence of estrogen receptor protein and mRNA in the rat sperm by immunofluorescence, western blotting and in situ hybridization respectively. Specificity of sperm estrogen receptors was confirmed by conventional binding studies using [3H]-estradiol. There was no effect of tamoxifen treatment on estrogen receptors in rat sperms. Biochemical analysis of the sperms from tamoxifen treated cauda epididymides revealed a significant increase in the levels of calcium and cAMP. A significant reduction was also apparent in the activity of dynein ATPase. Tamoxifen treatment did not alter phosphodiesterase activity. Estrogen receptors could be identified both in the control as well as tamoxifen treated rat sperms. It was concluded that tamoxifen treatment mobilized calcium from the intra- or extra-cellular pools with a concomitant increase in cAMP and presumably activation of PKA (protein kinase A). Tamoxifen altered the pattern of sperm motility through a calcium induced block in the activity of dynein ATPase, presumably through the activation of sperm phosphatase. The putative estrogen receptor mediated signal transduction pathway appears to be directly affected in the tamoxifen treated, sub-motile rat sperm.

Profiling gene expression using onto-express

Gene expression profiles obtained through microarray or data mining analyses often exist as vast data strings. To interpret the biology of these genetic profiles, investigators must analyze this data in the context of other information such as the biological, biochemical, or molecular function of the translated proteins. This is particularly challenging for a human analyst because large quantities of less than relevant data often bury such information. To address this need we implemented an automated routine, called Onto-Express (http://vortex.cs.wayne.edu:8080), to systematically translate genetic fingerprints into functional profiles. Using strings of accession or cluster identification numbers, Onto-Express searches the public databases and returns tables that correlate expression profiles with the cytogenetic locations, biochemical and molecular functions, biological processes, cellular components, and cellular roles of the translated proteins. The profiles created by Onto-Express fundamentally increase the value of gene expression analyses by facilitating the translation of quantitative value sets to records that contain biological implications.

Human leukocyte antigen II expression in sperm cells: comparison between fertile and infertile men

Human leukocyte antigens (HLA) class II transcripts in mature spermatozoa of healthy volunteers have recently been demonstrated using reverse transcription polymerase chain reaction (RT-PCR). HLA II expression was investigated on ejaculated sperm cells in fertile and infertile men by RT-PCR and flow cytometry. Among 22 fertile and 20 infertile men, 18 were selected for the study because they showed no contamination with non-sperm cells. HLA II mRNA transcripts were expressed in all but 1 of 8 infertile subjects and in only 2 of 10 fertile ones. The cytofluorometric analysis on three RT-PCR positive samples confirmed the presence of class II antigens on cell surfaces. These data clearly confirm the presence of both HLA II mRNA and surface molecules on human sperm cells. In addition, an interesting nonrandom distribution of positivity among fertile and infertile samples regarding HLA II expression (p < .025) suggests a possible correlation with infertility.

A novel chimeric mitochondrial RNA localized in the nucleus of mouse sperm

Six identical cDNA clones corresponding to an RNA of 1685 nucleotides that is enriched in mouse sperm compared with testis were isolated from a mouse testis cDNA library. The sequence of these clones corresponds to the 16S mitochondrial RNA plus an inverted repeat of 120 bp covalently joined to the 5' end of the RNA. By RT-PCR, it was demonstrated that this transcript, referred to as chimeric RNA, was present in mouse sperm, testis, liver, kidney, brain, and spleen. The absence of an equivalent sequence in mitochondrial DNA or as a mitochondrial pseudogene in total DNA extracted from sperm, testis, and somatic tissues suggests that the chimeric RNA is a post-transcriptional product, maybe resulting from a trans splicing reaction. The chimeric RNA was found by RT-PCR in total RNA extracted from purified sperm heads. This result was confirmed by in situ hybridization, which showed clear staining of the sperm nucleus with probes corresponding to sequences of the mitochondrial 16S RNA and the inverted repeat.

The causes of reduced fertility with cryopreserved semen

Cryopreserved mammalian semen is generally acknowledged to have an impaired fertility by comparison with fresh semen. The reduction arises from both a lower viability post-thaw and sublethal dysfunction in a proportion of the surviving subpopulation. The reasons for the loss of fertility are various. In this paper, factors affecting the proportion of survivors (e.g., cold shock susceptibility, cooling rate, diluent composition and osmotic stress) and factors influencing functional status of survivors (e.g., membrane stability, oxidative damage, membrane receptor integrity, nuclear structure) are briefly reviewed. The possible effects of cryopreservation on the role of spermatozoa in the early stages of embryogenesis are considered. In the light of this review, indications for new approaches for improving the performance of cryopreserved semen are offered.

Expression of the platelet-activating factor receptor in human spermatozoa: differences in messenger ribonucleic acid content and protein distribution between normal and abnormal spermatozoa

OBJECTIVE

To determine the expression and distribution of the platelet-activating factor (PAF) receptor in normal and abnormal specimens of human spermatozoa.

DESIGN

Prospective analysis of membrane-bound PAF receptors by immunofluorescence and PAF receptor messenger RNA by quantitated reverse transcription-polymerase chain reaction in normal and abnormal spermatozoa.

SETTING

University-based reproductive genetics laboratory.

PATIENT(S)

Men undergoing routine semen analysis.

INTERVENTION(S)

Normal and abnormal spermatozoa were exposed to rabbit anti-PAF receptor antibody, fluorescein isothiocyanate-conjugated goat anti-rabbit antibody, and fluorescent microscopy or subjected to RNA isolation by acid-phenol extraction and quantitated (MIMIC Construction Kit [Clontech Laboratories, Inc., Palo Alto, CA]) reverse transcription-polymerase chain reaction.

MAIN OUTCOME MEASURE(S)

Fluorescent intensities at six locations along spermatozoa (end piece, principal tail, midpiece, neck, proximal head, and acrosomal region) and PAF receptor expression (messenger RNA) levels.

RESULT(S)

Immunofluorescence demonstrated a significant difference in PAF receptor distribution between normal and abnormal human spermatozoa, specifically at the neck region. Additionally, abnormal spermatozoa were found to have statistically significantly more PAF receptor messenger RNA than normal spermatozoa.

CONCLUSION(S)

Platelet-activating factor receptor expression and distribution are significantly altered in abnormal spermatozoa and this may be the result of some defect in gene transcription.

Presence of ribonucleic acid in human spermatozoa: differences in content between normal and abnormal spermatozoa

OBJECTIVE

Our purpose was to determine whether there are any differences in total ribonucleic acid content between normal and abnormal human spermatozoa.

STUDY DESIGN

Spermatozoa were obtained from men undergoing routine semen analysis at a university-based reproductive genetics laboratory. Specimens were classified as normal or abnormal according to World Health Organization criteria. Total ribonucleic acid was removed by acid-phenol extraction, and ribonucleic acid expression levels were determined by spectrophotometric analysis.

RESULTS

Abnormal spermatozoa were found to have significantly more ribonucleic acid (0.14 +/- 0.02 mg/10(6) spermatozoa) than normal spermatozoa (0.05 +/- 0.01 mg/10(6) spermatozoa; P <.001).

CONCLUSION

Ribonucleic acid content is significantly altered in abnormal spermatozoa, and this alteration may be the result of some defect in the posttranscriptional pathway.

Expression of the integrin subunits alpha 5, alpha 6 and beta 1 in the testes of the common marmoset

Integrin subunits alpha 5, alpha 6 and beta 1 were localized in the testis of pre-pubertal or adult non-human primates (Callithrix jacchus) by immunofluorescence staining and in situ hybridization. In animals of all ages subunits alpha 5 and beta 1 were localized in cells of the lamina propria of the seminiferous epithelium. In prepubertal animals, the integrin subunits alpha 5, alpha 6, as well as beta 1, were distributed all over the plasma membrane of Sertoli cells. In adult animals the integrin subunits were confined to those plasma membrane regions of Sertoli cells which are assigned to the basal compartment, including the basement membrane of the seminiferous tubules. Protein expression of integrin subunits alpha 6 and beta 1 was most pronounced in tubular stages in which elongated spermatids were not yet present in the adluminal compartment of the epithelium, suggesting that these integrin subunits are particularly essential at certain developmental stages of spermatogenesis. Non-radioactive in situ hybridization revealed that the mRNA for integrin subunits alpha 5, alpha 6 and beta 1 was expressed by Sertoli cells. In situ hybridization, together with immunofluorescence data, shows that these integrin subunits were exclusively synthesized in Sertoli cells. As to functional aspects, it is concluded that during primate spermatogenesis. Sertoli cell integrins may be involved in both cell matrix as well as cell-cell interactions, particularly during early spermatogenesis.

Adhesion molecules and matrix proteins on human spermatozoa

Ejaculated spermatozoa and spermatogenic cells express alpha- and beta-chains of beta 1, 3 and 4 integrins as well as their ligands fibronectin and laminin in an extended intra- and interindividual variation and in different patterns of location. The mRNA transcripts of these molecules were detectable by nested polymerase chain reaction in the spermatozoa. The conclusion of a functional competence of these adhesion molecules (AM) was supported by their relation to the results of the zona-free hamster oocyte penetration (HOP) test, the in vitro fertilization of human oocytes and cell attachment assays. AM labelling was influenced by the disintegration of the sperm plasma membrane, especially in seminal plasma, by progesterone, human follicular fluid and microorganisms, but was barely modified by sperm cryopreservation. Despite substantial advances in the knowledge about sperm adhesion molecules, many questions remain to be answered.