Coordinate expression of the PRM1, PRM2, and TNP2 multigene locus in human testis

Developmental validation of an mRNA kit: A 5-dye multiplex assay designed for body-fluid identification

Identifying the sources of biosamples found at crime scenes is crucial for forensic investigations. Among the markers used for body fluid identification (BFI), mRNA has emerged as a well-studied marker because of its high specificity and remarkable stability. Despite this potential, commercially available mRNA kits specifically designed for BFI are lacking. Therefore, we developed an mRNA kit that includes 21 specific mRNA markers of body fluids, along with three housekeeping genes for BFI, to identify four forensic-relevant fluids (blood, semen, saliva, and vaginal fluids). In this study, we tested 451 single-body-fluid samples, validated the universality of the mRNA kit, and obtained a gene expression profile. We performed the validation studies in triplicates and determined the sensitivity, specificity, stability, precision, and repeatability of the mRNA kit. The sensitivity of the kit was found to be 0.1 ng. Our validation process involved the examination of 59 RNA mixtures, 60 body fluids mixtures, and 20 casework samples, which further established the reliability of the kit. Furthermore, we constructed five classifiers that can handle single-body fluids and mixtures using this kit. The classifiers output possibility values and identify the specific body fluids of interest. Our results showed the reliability and suitability of the BFI kit, and the Random Forest classifier performed the best, with 94% precision. In conclusion, we developed an mRNA kit for BFI which can be a promising tool for forensic practice.

Efficient isolation and purification of spermatogonia, spermatocytes, and spermatids from mice, piglets, and adult boars using an optimized STA-PUT method

Spermatogenesis is a delicate and complex biological process in which spermatogonial stem cells continue to proliferate and differentiate into mature spermatozoa, maintaining sperm production in male mammals throughout the lifetime. To study the molecular mechanism of spermatogenesis, researchers had to isolate different germ cell subpopulations for in vitro culture and characterization. However, due to the existence of several stages of germ cells and a variety of populations of somatic cells in the testis of male mammals, it is a challenge for us to obtain high-purity germ cell subpopulations for further research. Here, we optimized the STA-PUT device and successfully applied it to isolate and purify spermatogonia populations in piglets, and multiple germ cell populations at different developmental stages in testes of adult mice and boars. This work provides a simple platform for germ cell fractionation to facilitate the molecular mechanistic study of animal spermatogenesis in vitro.

Sequence variability of CatSper1 and TNP2 gene in indigenous and crossbred cattle in Bangladesh

CatSper1 and TNP2 genes are known to affect semen quality and fertility parameters, including sperm motility and maturation. However, studies are yet to examine the genes in indigenous and crossbred cattle in Bangladesh. Therefore, this study was conducted to determine the genetic variants of CatSper1 and TNP2 in indigenous and crossbred cattle in Bangladesh. Blood samples were collected from 130 indigenous and 70 crossbred (Holstein Friesian × indigenous) cattle. Nucleotide variation was evaluated by PCR-RFLP and sequencing. The results of the study showed that the indigenous cattle possessed only TT genotype (1.0), whereas the crossbreds possessed both TT (0.91) and CT (0.09) genotypes, which was validated by gene sequencing. Additionally, the CatSper1 was conserved in both the indigenous and crossbred cattle, suggesting good semen quality and fertility. However, the TNP2 was conserved in the indigenous breeds and mostly conserved in the crossbreds. The findings of this study reveal the diversity of CatSper1 and TNP2 genes in indigenous and crossbred cattle.

Transcriptomic analysis of testis and epididymis tissues from Banna mini-pig inbred line boars with single-molecule long-read sequencing†

In mammals, testis and epididymis are critical components of the male reproductive system for androgen production, spermatogenesis, sperm transportation, as well as sperm maturation. Here, we report single-molecule real-time sequencing data from the testis and epididymis of the Banna mini-pig inbred line (BMI), a promising laboratory animal for medical research. We obtained high-quality full-length transcriptomes and identified 9879 isoforms and 8761 isoforms in the BMI testis and epididymis, respectively. Most of the isoforms we identified have novel exon structures that will greatly improve the annotation of testis- and epididymis-expressed genes in pigs. We also found that 3055 genes (over 50%) were shared between BMI testis and epididymis, indicating widespread expression profiles of genes related to reproduction. We characterized extensive alternative splicing events in BMI testis and epididymis and showed that 96 testis-expressed genes and 79 epididymis-expressed genes have more than six isoforms, revealing the complexity of alternative splicing. We accurately defined the transcribed isoforms in BMI testis and epididymis by combining Pacific Biotechnology Isoform-sequencing (PacBio Iso-Seq) and Illumina RNA Sequencing (RNA-seq) techniques. The refined annotation of some key genes governing male reproduction will facilitate further understanding of the molecular mechanisms underlying BMI male sterility. In addition, the high-confident identification of 548 and 669 long noncoding RNAs (lncRNAs) in these two tissues has established a candidate gene set for future functional investigations. Overall, our study provides new insights into the role of the testis and epididymis during BMI reproduction, paving the path for further studies on BMI male infertility.

A viral histone-like protein exploits antagonism between linker histones and HMGB proteins to obstruct the cell cycle

Virus infection necessarily requires redirecting cellular resources toward viral progeny production. Adenovirus encodes the histone-like protein VII, which causes catastrophic global reorganization of host chromatin to promote virus infection. Protein VII recruits the family of high mobility group box (HMGB) proteins to chromatin along with the histone chaperone SET. As a consequence of this recruitment, we find that protein VII causes chromatin depletion of several linker histone H1 isoforms. The relationship between linker histone H1 and the functionally opposite HMGB proteins is critical for higher-order chromatin structure. However, the physiological consequences of perturbing this relationship are largely unknown. Here, we employ complementary systems in Saccharomyces cerevisiae and human cells to demonstrate that adenovirus protein VII disrupts the H1-HMGB balance to obstruct the cell cycle. We find that protein VII causes an accumulation of G2/M cells both in yeast and human systems, underscoring the high conservation of this chromatin vulnerability. In contrast, adenovirus E1A and E1B proteins are well established to override cell cycle regulation and promote transformation of human cells. Strikingly, we find that protein VII obstructs the cell cycle, even in the presence of E1A and E1B. We further show that, in a protein-VII-deleted infection, several cell cycle markers are regulated differently compared to wild-type infection, supporting our model that protein VII plays an integral role in hijacking cell cycle regulation during infection. Together, our results demonstrate that protein VII targets H1-HMGB1 antagonism to obstruct cell cycle progression, revealing an unexpected chromatin vulnerability exploited for viral benefit.

Epigenetics and the dynamics of chromatin during adenovirus infections

The DNA genome of eukaryotic cells is compacted by histone proteins within the nucleus to form chromatin. Nuclear-replicating viruses such as adenovirus have evolved mechanisms of chromatin manipulation to promote infection and subvert host defenses. Epigenetic factors may also regulate persistent adenovirus infection and reactivation in lymphoid tissues. In this review, we discuss the viral proteins E1A and protein VII that interact with and alter host chromatin, as well as E4orf3, which separates host chromatin from sites of viral replication. We also highlight recent advances in chromatin technologies that offer new insights into virus-directed chromatin manipulation. Beyond the role of chromatin in the viral replication cycle, we discuss the nature of persistent viral genomes in lymphoid tissue and cell lines, and the potential contribution of epigenetic signals in maintaining adenovirus in a quiescent state. By understanding the mechanisms through which adenovirus manipulates host chromatin, we will understand new aspects of this ubiquitous virus and shed light on previously unknown aspects of chromatin biology.

DNA Flow cytometric analysis of the human testicular tissues to investigate the status of spermatogenesis in azoospermic patients

A single, rapid and reproducible diagnostic test to predict the type of azoospermia and outcome of sperm retrieval is not yet available. So the feasibility of employing DNA flow cytometry for rapid investigation of the status of spermatogenesis in the patients with azoospermia was investigated. Testicular biopsies of 44 patients with azoospermia undergoing sperm-retrieval surgery and 4 controls were analyzed by flow cytometry to ascertain their testicular germ-cell patterns. The observed germ-cell pattern was further confirmed by RT-PCR analysis of the cell-specific markers and histology for some patients. The patients with Obstructive Azoospermia (OA) exhibited normal spermatogenesis similar to the control fertile patients showing the presence of diploid, double-diploid and haploid cells. The non-obstructive azoospermia (NOA) patients exhibited disrupted spermatogenesis with arrest at the pre-meiotic (only diploid cells present) or meiotic (diploid and double-diploid cells present) stages. The germ-cell pattern, as ascertained by flow cytometry, provided a clear picture of the intra-testicular spermatogenesis and the presence of spermatozoa in the patients’ testes, which was prognostic of their sperm-retrieval. DNA flow cytometry test to ascertain the testicular germ-cell pattern is simple in execution, analysis and interpretation, requires small amount of tissue and provides quantitative data about the status of spermatogenesis in patients. This test would allow comparable analysis of the status of spermatogenesis in patients across clinics and may form the basis for deciding future treatment and intervention strategies.

Comparative expression profiling of testis-enriched genes regulated during the development of spermatogonial cells

The testis has been identified as the organ in which a large number of tissue-enriched genes are present. However, a large portion of transcripts related to each stage or cell type in the testis still remains unknown. In this study, databases combined with confirmatory measurements were used to investigate testis-enriched genes, localization in the testis, developmental regulation, gene expression profiles of testicular disease, and signaling pathways. Our comparative analysis of GEO DataSets showed that 24 genes are predominantly expressed in testis. Cellular locations of 15 testis-enriched proteins in human testis have been identified and most of them were located in spermatocytes and round spermatids. Real-time PCR revealed that expressions of these 15 genes are significantly increased during testis development. Also, an analysis of GEO DataSets indicated that expressions of these 15 genes were significantly decreased in teratozoospermic patients and polyubiquitin knockout mice, suggesting their involvement in normal testis development. Pathway analysis revealed that most of those 15 genes are implicated in various sperm-related cell processes and disease conditions. This approach provides effective strategies for discovering novel testis-enriched genes and their expression patterns, paving the way for future characterization of their functions regarding infertility and providing new biomarkers for specific stages of spematogenesis.

Regeneration of Leydig cells in ectopically autografted adult mouse testes

Ectopic autografting of testis tissue is a promising approach for studying testicular development, male germline preservation and restoration of male fertility. In this study, we examined the fate of various testicular cells in adult mouse testes following ectopic autografting at 1, 2, 4 and 8 weeks post grafting. Histological examination showed no evidence of re-establishment of spermatogenesis in autografts, and progressive degeneration of seminiferous tubules was detected. Expression of germ cell-specific proteins such as POU5F1, DAZL, TNP1, TNP2, PRM1 and PRM2 revealed that, although proliferating and differentiating spermatogenic germ cells such as spermatogonia, spermatocytes and spermatids could survive in autografts until 4 weeks, only terminally differentiated germ cells such as sperm persisted in autografts until 8 weeks. The presence of Sertoli and peritubular myoid cells, as indicated by expression of WT1 and ACTA2 proteins, respectively, was evident in the autografts until 8 weeks. Interestingly, seminal vesicle weight and serum testosterone level were restored in autografted mice by 8 weeks post grafting. The expression of Leydig cell-specific proteins such as CYP11A1, HSD3B2 and LHCGR showed revival of Leydig cell (LC) populations in autografts over time since grafting. Elevated expression of PDGFRA, LIF, DHH and NEFH in autografts indicated de novo regeneration of LC populations. Autografted adult testis can be used as a model for investigating Leydig cell regeneration, steroidogenesis and regulation of the intrinsic factors involved in Leydig cell development. The success of this rodent model can have therapeutic applications for adult human males undergoing sterilizing cancer therapy.

PLIN1 deficiency affects testicular gene expression at the meiotic stage in the first wave of spermatogenesis

PLIN1, a lipid droplet associated protein, has been implicated in playing a key role in the regulation of lipolysis and lipid storage in adipocytes. PLIN1 is found to be highly expressed in Leydig cells of testis, suggesting a potential role in steroidogenesis and spermatogenesis. In this study, we showed that PLIN1 was expressed in testis and that its mRNA levels declined significantly with development. To investigate the role of PLIN1, we take advantage of PLIN1-null mice. We found that the number of seminiferous tubules containing round spermatids was significantly increased at P21 (postnatal day 21). Furthermore, microarray analysis showed that there were 538 differentially expressed genes between PLIN1-null and wild-type mice at P21. The up-regulated genes in knockout mice were enriched in spermatogenesis by Gene Ontology classification. Among them, Prm1 and Wbp2nl are important for spermatogenesis which were confirmed by real-time PCR. Unexpectedly, the levels of serum testosterone and serum 17β-estradiol as well as steroidogenic genes are not altered in the PLIN1-null mice. Compared to the wild-type mice, no significant difference of fertility was found in the PLIN1-null mice. Therefore, these findings indicated that PLIN1 disruption leads to the increase of round spermatid-containing seminiferous tubules at the meiotic stage of the first wave of spermatogenesis through regulating spermatogenic related genes.

The human testis-specific proteome defined by transcriptomics and antibody-based profiling

The testis' function is to produce haploid germ cells necessary for reproduction. Here we have combined a genome-wide transcriptomics analysis with immunohistochemistry-based protein profiling to characterize the molecular components of the testis. Deep sequencing (RNA-Seq) of normal human testicular tissue from seven individuals was performed and compared with 26 other normal human tissue types. All 20 050 putative human genes were classified into categories based on expression patterns. The analysis shows that testis is the tissue with the most tissue-specific genes by far. More than 1000 genes show a testis-enriched expression pattern in testis when compared with all other analyzed tissues. Highly testis enriched genes were further characterized with respect to protein localization within the testis, such as spermatogonia, spermatocytes, spermatids, sperm, Sertoli cells and Leydig cells. Here we present an immunohistochemistry-based analysis, showing the localization of corresponding proteins in different cell types and various stages of spermatogenesis, for 62 genes expressed at >50-fold higher levels in testis when compared with other tissues. A large fraction of these genes were unexpectedly expressed in early stages of spermatogenesis. In conclusion, we have applied a genome-wide analysis to identify the human testis-specific proteome using transcriptomics and antibody-based protein profiling, providing lists of genes expressed in a tissue-enriched manner in the testis. The majority of these genes and proteins were previously poorly characterised in terms of localization and function, and our list provides an important starting point to increase our molecular understanding of human reproductive biology and disease.

Association of TNP2 gene polymorphisms of the bta-miR-154 target site with the semen quality traits of Chinese Holstein bulls

Transition protein 2 (TNP2) participates in removing nucleohistones and the initial condensation of spermatid nucleus during spermiogenesis. This study investigated the relationship between the variants of the bovine TNP2 gene and the semen quality traits of Chinese Holstein bulls. We detected three single nucleotide polymorphisms (SNPs) of the TNP2 gene in 392 Chinese Holstein bulls, namely, g.269 G>A (exon 1), g.480 C>T (intron 1), and g.1536 C>T (3′-UTR). Association analysis showed that the semen quality traits of the Chinese Holstein bulls was significantly affected by the three SNPs. The bulls with the haplotypic combinations H6H4, H6H6, and H6H8 had higher initial semen motility than those with the H7H8 and H8H4 haplotypic combinations (P<0.05). SNPs in the microRNA (miRNA) binding region of the TNP2 gene 3′-UTR may have contributed to the phenotypic differences. The phenotypic differences are caused by the altered expression of the miRNAs and their targets. Bioinformatics analysis predicted that the g.1536 C>T site in the TNP2 3′-UTR is located in the bta-miR-154 binding region. The quantitative real-time polymerase chain reaction results showed that the TNP2 mRNA relative expression in bulls with the CT and CC genotypes was significantly higher than those with the TT genotype (P<0.05) in the g.1536 C>T site. The luciferase assay also indicated that bta-miR-154 directly targets TNP2 in a murine Leydig cell tumor cell line. The SNP g.1536 C>T in the TNP2 3′-UTR, which altered the binding of TNP2 with bta-miR-154, was found to be associated with the semen quality traits of Chinese Holstein bulls.

The mouse cytosine-5 RNA methyltransferase NSun2 is a component of the chromatoid body and required for testis differentiation

Posttranscriptional regulatory mechanisms are crucial for protein synthesis during spermatogenesis and are often organized by the chromatoid body. Here, we identify the RNA methyltransferase NSun2 as a novel component of the chromatoid body and, further, show that NSun2 is essential for germ cell differentiation in the mouse testis. In NSun2-depleted testes, genes encoding Ddx4, Miwi, and Tudor domain-containing (Tdr) proteins are repressed, indicating that RNA-processing and posttranscriptional pathways are impaired. Loss of NSun2 specifically blocked meiotic progression of germ cells into the pachytene stage, as spermatogonial and Sertoli cells were unaffected in knockout mice. We observed the same phenotype when we simultaneously deleted NSun2 and Dnmt2, the only other cytosine-5 RNA methyltransferase characterized to date, indicating that Dnmt2 was not functionally redundant with NSun2 in spermatogonial stem cells or Sertoli cells. Specific NSun2- and Dnmt2-methylated tRNAs decreased in abundance when both methyltransferases were deleted, suggesting that RNA methylation pathways play an essential role in male germ cell differentiation.

A cytokine gene screen uncovers SOCS1 as genetic risk factor for multiple sclerosis

Cytokine and cytokine receptor genes, including IL2RA, IL7R and IL12A, are known risk factors for multiple sclerosis (MS). Excitotoxic oligodendroglial death mediated by glutamate receptors contributes to demyelinating reactions. In the present study, we screened 368 single-nucleotide polymorphisms (SNPs) in 55 genes or gene clusters coding for cytokines, cytokine receptors, suppressors of cytokine signaling (SOCS), complement factors and glutamate receptors for association with MS in a Spanish-Basque resident population. Top-scoring SNPs were found within or nearby the genes coding for SOCS-1 (P=0.0005), interleukin-28 receptor, alpha chain (P=0.0008), oncostatin M receptor (P=0.002) and interleukin-22 receptor, alpha 2 (IL22RA2; P=0.003). The SOCS1 rs243324 variant was validated as risk factor for MS in a separate cohort of 3919 MS patients and 4003 controls (combined Cochran-Mantel-Haenszel P=0.00006; odds ratio (OR)=1.13; 95% confidence interval (CI)=1.07-1.20). In addition, the T allele of rs243324 was consistently increased in relapsing-remitting/secondary progressive versus primary-progressive MS patients, in each of the six data sets used in this study (P(CMH)=0.0096; OR=1.24; 95% CI 1.05-1.46). The association with SOCS1 appears independent from the chr16MS risk locus CLEC16A.

Translational control of the AZFa gene DDX3Y by 5'UTR exon-T extension

The human DEAD-box Y (DBY) RNA helicase (aka DDX3Y) gene is thought to be the major azoospermia factor a (AZFa) gene in proximal Yq11. Although it is transcribed in many tissues, the protein is expressed only in spermatogonia. In this study, we demonstrate that this translational control mechanism is probably germ cell-specific because of its association with expression of a distinct class of DDX3Y testis transcripts present only in pre- and post-meiotic male germ cells. They are initiated from a second distal DDX3Y promoter domain at two distinct start sites in the gene's 5' untranslated region (UTR) exon-T sequence. With the aid of an EGFP-3xFLAG reporter cassette cloned downstream of DDX3Y minigenes containing exons 1-4 and two different exon-T extensions, we discovered that DDX3Y translation is influenced by the presence of several ATG triplets located in exon-T, thus upstream of the main translational ATG start codon in exon 1. Strong translational repression of the DDX3Y minigene transcripts was observed when they contained the longest exon-T sequence with five upstream ATG triplets (uATGs). The potential formation of complex distinct stem-loop structures serve here as additional repressor element. Only minor translational attenuation was seen for the DDX3Y minigene transcripts when containing the shortest exon-T sequence, that is, starting at first transcriptional start site (coined 'T-TSS-I'). It was completely released after its single uATG was abolished by mutation. As we found DDX3Y transcripts with the longest exon-T sequence predominantly in spermatids, our results suggest that the amount of DDX3Y protein in pre-meiotic germ cells and its absence in post-meiotic germ cells are tightly controlled by the different extensions of exon-T in this germ cell-specific DDX3Y transcript class.

In vitro culture and differentiation of buffalo (Bubalus bubalis) spermatogonia

The objective of this study was to develop a culture system which could support buffalo spermatogonia differentiation into spermatids in vitro. Testes from 3- to 5-month-old buffaloes were decapsulated and seminiferous tubules were enzymatically dissociated to recover spermatogonia and sertoli cells. The cells were cultured in modified Dulbecco modified Eagle medium supplemented with different concentrations of foetal bovine serum, retinol, testosterone for 2 months at 37 degrees C. Spermatogonia and sertoli cells were identified with an antibody against c-kit or GATA4, respectively. The viability of spermatogonia in the media supplemented with different concentrations of serum was all significantly higher (p < 0.05) compared with that in the medium without serum. A-paired or A-aligned spermatogonia and spermatogonial colonies (AP-positive) were observed after 7-10 days of culture and spermatid-like cells with a flagellum (6-8 microm) appeared after 30 days of culture. For cultured conditions, retinol could not significantly promote the formation of spermatid-like cells (p > 0.05), whereas supplementation of testosterone could significantly promote (p < 0.05) the formation of spermatid-like cells after 41 days of culture. The expression of the spermatid-specific marker gene (PRM2) was identified after 30 days of culture by RT-PCR. Yet, the transition protein 1 (TP1, a haploid makers) was not detected. Meanwhile, spermatids developed in vitro were also confirmed by Raman spectroscopy. These results suggest that buffalo spermatogonia could differentiate into spermatids in vitro based on the analysis of their morphology, PRM2 expression and Raman spectroscopy. Yet, the normality of the spermatid-like cells was not supported by TP1 expression.

The protamine family of sperm nuclear proteins

An overview of the vertebrate members of a diverse family of basic DNA-binding proteins that are synthesized in the late-stage spermatids of many animals and plants and condense the spermatid genome into a genetically inactive state.

The protamines are a diverse family of small arginine-rich proteins that are synthesized in the late-stage spermatids of many animals and plants and bind to DNA, condensing the spermatid genome into a genetically inactive state. Vertebrates have from one to 15 protamine genes per haploid genome, which are clustered together on the same chromosome. Comparison of protamine gene and amino-acid sequences suggests that the family evolved from specialized histones through protamine-like proteins to the true protamines. Structural elements present in all true protamines are a series of arginine-rich DNA-anchoring domains (often containing a mixture of arginine and lysine residues in non-mammalian protamines) and multiple phosphorylation sites. The two protamines found in mammals, P1 and P2, are the most widely studied. P1 packages sperm DNA in all mammals, whereas protamine P2 is present only in the sperm of primates, many rodents and a subset of other placental mammals. P2, but not P1, is synthesized as a precursor that undergoes proteolytic processing after binding to DNA and also binds a zinc atom, the function of which is not known. P1 and P2 are phosphorylated soon after their synthesis, but after binding to DNA most of the phosphate groups are removed and cysteine residues are oxidized, forming disulfide bridges that link the protamines together. Both P1 and P2 have been shown to be required for normal sperm function in primates and many rodents.

A global but stable change in HeLa cell morphology induces reorganization of DNA structural loop domains within the cell nucleus

DNA of higher eukaryotes is organized in supercoiled loops anchored to a nuclear matrix (NM). The DNA loops are attached to the NM by means of non-coding sequences known as matrix attachment regions (MARs). Attachments to the NM can be subdivided in transient and permanent, the second type is considered to represent the attachments that subdivide the genome into structural domains. As yet very little is known about the factors involved in modulating the MAR-NM interactions. It has been suggested that the cell is a vector field in which the linked cytoskeleton-nucleoskeleton may act as transducers of mechanical information. We have induced a stable change in the typical morphology of cultured HeLa cells, by chronic exposure of the cells to the polar compound dimethylsulfoxide (DMSO). Using a PCR-based method for mapping the position of any DNA sequence relative to the NM, we have monitored the position relative to the NM of sequences corresponding to four independent genetic loci located in separate chromosomes representing different territories within the cell nucleus. Here, we show that stable modification of the NM morphology correlates with the redefinition of DNA loop structural domains as evidenced by the shift of position relative to the NM of the c-myc locus and the multigene locus PRM1 --> PRM2 --> TNP2, suggesting that both cell and nuclear shape may act as cues in the choice of the potential MARs that should be attached to the NM.

Analysis of gene expression in normal and neoplastic human testis: new roles of RNA

Large-scale methods for analysing gene expression, such as microarrays, have yielded a wealth of information about gene expression at the mRNA level. However, expression of alternative transcripts, together with the presence of a wide range of largely undescribed RNA transcripts combined with regulation from the RNA interference pathway, may cause misinterpretations when trying to base conclusions from expression data derived from studies at the mRNA level. With HLXB9, PRM1, DICER and E2F1 as examples, we here show a range of situations that can occur when investigating gene expression, and give recommendations for the complementary methods that can verify gene expression data from large-scale studies, as well as give new information regarding the regulation of specific genes. Especially, we show that the absence of a protein despite high expression of the corresponding mRNA can be caused by expression of miRNAs targeting the mRNA. Additionally, we show through cloning the presence of both known and new miRNAs in the testis emphasizing the necessity for following up mRNA expression data by investigating expression at the protein level.

An SNP in protamine 1: a possible genetic cause of male infertility?

Gene targeting of the sperm nuclear proteins, the protamines, in mice leads to haploinsufficiency, abnormal chromatin compaction, sperm DNA damage, and male infertility. In order to investigate whether changes in amount or structure of the protamines could be a cause of human infertility, we sequenced the protamine genes of infertile men whose sperm appeared phenotypically similar to those of protamine deficient mice. We identified a heterozygous single nucleotide polymorphism (SNP) in the protamine (PRM1) gene in three infertile men (10% of the total infertile men analysed). This SNP disrupts one of the highly conserved arginine clusters needed for normal DNA binding. To rapidly screen for this SNP in infertile patients, we developed a simple PCR restriction fragment length polymorphism assay. This is the first report of a SNP in the PRM1 gene that appears associated with human male infertility.

Cellular expression of protamine 1 and 2 transcripts in testicular spermatids from azoospermic men submitted to TESE-ICSI

Testicular sperm extraction (TESE) combined with ICSI is used to treat azoospermia. However, the factors that influence the outcome of ICSI in this situation are ill-defined. We sought to investigate the expression of protamine 1 (PRM1) and protamine 2 (PRM2) transcripts in testicular spermatids from obstructive and non-obstructive azoospermic men with impaired spermatogenesis. The relationship between PRM1 and PRM2 transcript levels and the TESE-ICSI outcome was evaluated. The cellular expression of PRM1 and PRM2 mRNAs in single testicular spermatids from 41 azoospermic patients (in whom testicular spermatozoa were subsequently recovered and submitted for TESE-ICSI) was determined by radioactive in situ hybridization. Group I contained seven men with congenital, obstructive azoospermia and whose testicular biopsies indicated quantitatively normal spermatogenesis. Group II consisted of 18 azoospermic men with moderately impaired spermatogenesis. Sixteen men with non-obstructive azoospermia and severely deranged spermatogenesis (i.e. mixed atrophy with small foci of spermatids and spermatozoa) constituted group III. The spermatids of men with severely deranged spermatogenesis exhibited significant lower PRM1 mRNA expression than in the other patient groups. There were no significant inter-group differences in PRM2 mRNA expression. Spermatid PRM1 expression was lower in non-pregnant couples than in pregnant couples. The low number of spermatids in cases of mixed atrophy with small spermatogenic foci is associated with significantly lower PRM1 expression and a lower pregnancy rate. These results emphasize the role of PRM1 as a potentially critical factor in post-ICSI embryonic development.

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.

Type II gonadotropin-releasing hormone receptor transcripts in human sperm

GnRH regulates reproduction via the well-characterized mammalian pituitary GnRH receptor (type I). In addition, two homologous genes for a second form of the GnRH receptor (type II) are present in the human genome, one on chromosome 14 and the second on chromosome 1. The chromosome 14 gene is ubiquitously transcribed at high levels in the antisense orientation but lacks exon 1, required to encode a full-length receptor. In comparison, the chromosome 1 gene contains all three exons. The issue of whether this gene is transcribed in any human tissue(s), and whether these transcripts encode a functional receptor protein, remains unresolved. We have directly addressed this by screening a panel of human RNAs by hybridization and RT-PCR. These analyses showed that, unlike the chromosome 14 gene, chromosome 1 gene expression is limited and of low abundance. Exon 1-containing transcripts were detected by in situ hybridization in mature sperm and in human postmeiotic testicular cells. Further sequence analysis revealed that although all the potential coding segments were present, the human transcripts, like the gene, contain a stop codon within the coding region and a frame-shift relative to other mammalian GnRH receptors. Although this suggests that the human gene may be a transcribed pseudogene, a functional type II GnRH receptor cDNA has recently been cloned from monkeys. Given the well-established role of GnRH in spermatogenesis and reported evidence of type II GnRH receptor immunoreactivity in human tissues, it is possible that the chromosome 1 gene is functional.

Previously uncharacterized histone acetyltransferases implicated in mammalian spermatogenesis

During spermiogenesis (the maturation of spermatids into spermatozoa) in many vertebrate species, protamines replace histones to become the primary DNA-packaging protein. It has long been thought that this process is facilitated by the hyperacetylation of histone H4. However, the responsible histone acetyltransferase enzymes are yet to be identified. CDY is a human Y-chromosomal gene family expressed exclusively in the testis and implicated in male infertility. Its mouse homolog Cdyl, which is autosomal, is expressed abundantly in the testis. Proteins encoded by CDY and its homologs bear the "chromodomain," a motif implicated in chromatin binding. Here, we show that (i) human CDY and mouse CDYL proteins exhibit histone acetyltransferase activity in vitro, with a strong preference for histone H4; (ii) expression of human CDY and mouse Cdyl genes during spermatogenesis correlates with the occurrence of H4 hyperacetylation; and (iii) CDY and CDYL proteins are localized to the nuclei of maturing spermatids where H4 hyperacetylation takes place. Taken together, these data link human CDY and mouse CDYL to the histone-to-protamine transition in mammalian spermiogenesis. This link offers a plausible mechanism to account for spermatogenic failure in patients bearing deletions of the CDY genes.

Protamine 1: protamine 2 stoichiometry in the sperm of eutherian mammals

We have compared the relative proportion of protamine 1 (P1) and protamine 2 (P2) bound to DNA in the sperm of a variety of eutherian mammals to obtain insight into how these two proteins interact in sperm chromatin. Gel electrophoresis (combined with microdensitometry) and high performance liquid chromatography (HPLC) were used to determine the content of the two protamines, and the identity of each protein was confirmed by amino-terminal sequencing or amino acid analysis. The sperm of all species examined contained P1, but P2 was found to be present only in certain species. Unlike the fixed ratio of core histones that package DNA into nucleosomes in all somatic cells, the proportion of P2 present in mature sperm was found to be continuously variable from 0 to nearly 80%. These results show that P1 and P2 do not interact with each other or DNA to form a discrete complex or subunit structure that is dependent upon particular P1/P2 stoichiometries. Data obtained from a number of closely and distantly related species also indicate that while the P2 content of sperm chromatin is allowed to vary over a wide range during the course of evolution, the relative proportion of P1 and P2 are tightly regulated within a genus.

In vitro production of haploid germ cells from fresh or frozen-thawed testicular cells of neonatal bulls

Improved methods for culturing spermatogenic cells will facilitate the study of spermatogenesis, treatment of male factor infertility, and genetic modification of the male germ line. The objective of this study was to develop a procedure for achieving male germ cell progression through meiosis in vitro. Testes from 3-day-old bulls were decapsulated and seminiferous tubules were dissociated enzymatically to recover Sertoli and germ cells. Dissociated cells were reaggregated by phytohemagglutinin and encapsulated by calcium alginate, then cultured for up to 14 wk in modified Dulbecco modified Eagle medium/F12 (32 degrees C, 5% CO(2) in air). At 2, 5, and 10 wk, cultured cells were examined and evaluated by reverse transcription-polymerase chain reaction (RT-PCR) and Northern blot analysis for protamine-2 (PRM-2) and transition protein-1 (TP-1) mRNA, expressed specifically in round spermatids. Ploidy was characterized by flow cytometric analysis of DNA content of cultured cells. Only Sertoli cells and gonocytes were observed in seminiferous tubules of 3-day-old testes. By 10 wk of culture, small spherical cells (7-10 microm) were apparent at the margin of cell associations in culture. Following RT-PCR and Northern blot analysis, specific bands corresponding to PRM-2 and TP-1 were detected only in adult testis RNA or after 10 wk of culture. Based on flow cytometry, a haploid population of cells appeared in vitro that was not in 3-day-old bull testis. The novel culture system developed in this study is the first to promote differentiation of gonocytes to presumptive spermatids in vitro based on the expression of spermatid-specific genes.

Round spermatids from infertile men exhibit decreased protamine-1 and -2 mRNA

During spermiogenesis, histone-to-protamine exchange causes chromatin condensation. Spermatozoa from infertile men are known to exhibit an increased protamine-1 (PRM1) to protamine-2 (PRM2) protein ratio. Since patients undergoing testicular sperm extraction (TESE) followed by intracytoplasmic sperm injection (ICSI) reveal low fertilization rates, whether the outcome of ICSI could be related to the percentage of round spermatids expressing PRM1-mRNA and PRM2-mRNA was investigated. Applying in-situ hybridization, 55 testicular biopsies from men undergoing TESE/ICSI were investigated. The percentage of PRM1-mRNA and PRM2-mRNA positive spermatids was significantly (P < 0.0001) decreased in men with at least qualitatively normal spermatogenesis (PRM1-mRNA: 58.4 +/- 13.8%; PRM2-mRNA: 56.4 +/- 11.3%) and impaired spermatogenesis (PRM1-mRNA: 32.6 +/- 10.8%; PRM2-mRNA: 31.7 +/- 11.1%) compared with men with obstructive azoospermia and quantitatively normal spermatogenesis (PRM1-mRNA: 79.9 +/- 4.6%; PRM2-mRNA: 78.1 +/- 5.7%). A positive correlation (r(PRM1) = 0.733; r(PRM2) = 0.784; P < 0.001) was demonstrated between the score and the percentage of PRM1-mRNA and PRM2-mRNA positive spermatids. While successful fertilization was neither related to the score, nor to the percentage of PRM1-mRNA and PRM2-mRNA positive spermatids, a significant (P < 0.05) relationship was demonstrated between successful fertilization and the PRM1-mRNA to PRM2-mRNA ratio. Therefore, the PRM1-mRNA to PRM2-mRNA ratio in round spermatids may serve as a possible predictive factor for the outcome of ICSI.

Divergent N-terminal sequences target an inducible testis deubiquitinating enzyme to distinct subcellular structures

Ubiquitin-specific processing proteases (UBPs) presently form the largest enzyme family in the ubiquitin system, characterized by a core region containing conserved motifs surrounded by divergent sequences, most commonly at the N-terminal end. The functions of these divergent sequences remain unclear. We identified two isoforms of a novel testis-specific UBP, UBP-t1 and UBP-t2, which contain identical core regions but distinct N termini, thereby permitting dissection of the functions of these two regions. Both isoforms were germ cell specific and developmentally regulated. Immunocytochemistry revealed that UBP-t1 was induced in step 16 to 19 spermatids while UBP-t2 was expressed in step 18 to 19 spermatids. Immunoelectron microscopy showed that UBP-t1 was found in the nucleus while UBP-t2 was extranuclear and was found in residual bodies. For the first time, we show that the differential subcellular localization was due to the distinct N-terminal sequences. When transfected into COS-7 cells, the core region was expressed throughout the cell but the UBP-t1 and UBP-t2 isoforms were concentrated in the nucleus and the perinuclear region, respectively. Fusions of each N-terminal end with green fluorescent protein yielded the same subcellular localization as the native proteins, indicating that the N-terminal ends were sufficient for determining differential localization. Interestingly, UBP-t2 colocalized with anti-gamma-tubulin immunoreactivity, indicating that like several other components of the ubiquitin system, a deubiquitinating enzyme is associated with the centrosome. Regulated expression and alternative N termini can confer specificity of UBP function by restricting its temporal and spatial loci of action.

Human spermatogenesis as a model to examine gene potentiation

The first tier of control over the expression of genic domains utilizes chromatin structure. Before the onset of transcription, the chromatin domain that encompasses the gene(s) must assume an open conformation. This renders large segments of the genome available to the tissue-specific and ubiquitous trans-factors necessary for proper expression of the genes present. This process has been termed potentiation. It is a necessary obligate, but alone it is not sufficient for gene expression. Spermatogenesis, the development of a viable fertile male gamete, provides a unique model to begin to address the underlying mechanism(s) governing differentiation and tissue-specific gene expression. Male gametogenesis is typified by the activation of numerous genes whose products have novel functions, as well as testis-specific forms of constitutively expressed somatic genes. We have shown that mouse spermatogenesis represents a selective potentiative process (Kramer et al., 1998: Development 125:4749-4655), but little is known about its human counterpart. To fill this void we have examined the potentiative state of several spermatid-expressed genes during the latter stages of human spermatogenesis. We have shown that spermatidexpressed genes are potentiated by the pachytene stage of differentiation. Furthermore, we establish that a chromatin domain functions as a discrete structural unit during differentiation. Interestingly, some of these open structures are maintained in the mature spermatozoon.

Expression of protamine-1 and -2 mRNA during human spermiogenesis

During spermiogenesis, the histone-to-protamine replacement causes the compaction of the spermatid chromatin. The genes for protamines, PRM-1 and PRM-2, are transcribed in round and elongating spermatids. The transcripts are stored in a translationally-repressed state by the binding of protein repressors before being translated in elongating and elongated spermatids. RNA extracts from homogenized whole testis samples supply only average data, and cell-specific and stage-specific expression cannot be addressed. Therefore, we used UV-laser-assisted cell-picking (UV-LACP) to select spermatids of defined differentiation steps. Subsequent reverse transcription-polymerase chain reaction (RT-PCR) with intron-spanning primer pairs allowed the detection of DNA-free and pseudogene-free PRM-1 and PRM-2 cDNA. Additional in-situ hybridization with digoxygenin-labelled cRNA probes exhibited PRM-1 and PRM-2 mRNA from step 1/2 spermatids to step 4 spermatids, but not in elongated spermatids. RT-PCR revealed amplicons for PRM-1 and PRM-2 in all spermatids except step 3 round spermatids. Applying proteinase K digestion, PRM-1 and PRM-2 transcripts were also detected in step 3 spermatids indicating that protein repressors may bind to both PRM-1 and PRM-2 mRNA in step 3 round spermatids. These data demonstrate that the combination of UV-LACP and non-radioactive in-situ hybridization appear to be a suitable approach for the study of cell-specific and stage-specific gene expression during spermiogenesis.

Differences in the DNA-stainability of spermatozoa from fertile and suspected infertile men

The aim of this work was to determine whether it is possible to distinguish between fertile (control group, already fathers) and infertile men (suspected infertility), by comparing the fluorescence intensity of the sperm-DNA after incubation with appropriate dyes. First we examined two different DNA-specific dyes (DAPI and YOYO-1) using bull spermatozoa. Based on good results in immunohistochemical applications, YOYO-1 was chosen for further work. The fluorescence-intensity of 200 single, morphologically normal spermatozoa in each semen sample were measured in a cytophotometer, means + SD determined and histograms delineated. Of 20 samples from the control group, 17 had markedly higher fluorescence-intensity than did 7/15 of the suspected infertile men. It is concluded that the DNA of the latter seven samples was less accessible to the dye than was the DNA of the control group. There are cases of infertility known in which there is loss of one or more of the DNA-binding proteins, which in spermatozoa are mainly (85%) protamines. The relationship between the stainability of the sperm-DNA and the packaging with DNA-binding proteins is discussed. Two of the histograms showed abnormalities in the distribution of the fluorescence-intensities, one sample was extremely fragile and most of the sperm lysed during the staining-procedure. Five samples showed normal histograms in comparison with the control group.

Co-localization of HP1 and TP1 transcripts in human spermatids by double electron microscopy in situ hybridization

Nuclear changes in the basic nucleoprotein complement occur during spermiogenesis in man. Somatic type histones are displaced by transition proteins which are replaced themselves by protamines, the major nuclear proteins present in late spermatids and sperm nuclei. Sense and antisense 35S-labelled riboprobes, coding respectively for human transition protein 1 (TP1) and protamine 1 (HP1), were synthesized with modified specific oligonucleotides and were used for light microscopy in situ hybridization. A double EM in situ hybridization was performed using a digoxigenin-labelled probe for TP1 and a biotin-labelled probe for HP1, and hybrids were revealed, respectively, with specific antibodies coupled to colloidal gold particles of different sizes (10 nm and 15 nm). For both types of transcripts, histological study revealed a specific distribution of the silver grains in the adluminal region of the seminiferous tubules where spermatids are localized. Quantitative ultrastructural analysis of the nuclear and cytoplasmic labelling densities for the mRNAs coding for TP1 and HP1 showed that the transcripts were found in both the nucleus and cytoplasm of round spermatids and persisted until the elongation phase. Transcripts accumulated in the spermatid cytoplasm without any particular cellular compartmentalization. At the end of the spermatid elongation phase, the disappearance of TP1 and HP1 transcripts may be related to the arrest of transcriptional activity, while the deposition of transition proteins and protamines occurs successively within spermatid nuclei.

Temporal expression of the transgenic human protamine gene cluster

OBJECTIVE

To ascertain the fidelity of expression of the genes from the transgenic human sperm-specific nuclear packaging protamine-1-->protamine-2-->transition protein-2 (PRM1-->PRM2-->TNP2) locus.

DESIGN

Controlled human transgene study.

SETTING

Basic science laboratory.

ANIMAL(S)

Age-matched transgenic and nontransgenic mice.

INTERVENTION(S)

Transgenic mice containing the human protamine locus were mated. One testis from each offspring was frozen at -80 degrees C and the other was preserved in formalin.

MAIN OUTCOME MEASURE(S)

The temporal expression of the human and mouse protamines was evaluated by Northern blot analysis. Orientation of the transgenic locus was determined by Southern blot analysis. Tissue morphology was assessed histologically.

RESULT(S)

Conservation of transgenic morphology was confirmed. Head-to-tail integration of the PRM1--> PRM2-->TNP2 locus was shown. Temporal expression of the mouse and human protamine genes was maintained in the transgenic state.

CONCLUSION(S)

These results show that the head-to-tail concatomer of the PRMI-->PRM2-->TNP2 locus contains all the necessary elements for appropriate temporal expression while maintaining testicular structure and function.

Differentiation: the selective potentiation of chromatin domains

Potentiation is requisite for the expression of our genome. It is the mechanism of opening chromatin domains to render genes accessible to tissue-specific and ubiquitous transacting-factors that enables transcription. The results presented in this study demonstrate that modulation of stage- and cell-type-specific gene expression during mammalian spermatogenesis involves selective potentiation of testis-expressed genes that reverses their repressive state when present in the spermatogonial stem cell. This directly contrasts hematopoiesis, which acts to selectively restrict lineage potential during differentiation from its permissive stem cell. These results are key to understanding how differentiative pathways are controlled and cellular phenotypes determined. A window to their modulation is presented.

Expression of ciliary tektins in brain and sensory development

Many types of neural tissues and sensory cells possess either motile or primary cilia. We report the first mammalian (murine testis) cDNA for tektin, a protein unique to cilia, flagella, and centrioles, which we have used to identify related proteins and genes in sensory tissues. Comparison with the sequence database reveals that tektins are a gene family, spanning evolution from Caenorhabditis elegans (in which they correlate with touch receptor cilia) and Drosophila melanogaster, to Mus musculus and Homo sapiens (in which they are found in brain, retina, melanocytes, and at least 13 other tissues). The peptide sequence RPNVELCRD, or a variant of it, is a prominent feature of tektins and is likely to form a functionally important protein domain. Using the cDNA as a probe, we determined the onset, relative levels, and locations of tektin expression in mouse for several adult tissues and embryonic stages by Northern blot analysis and in situ hybridization. Tektin expression is significant in adult brain and in the choroid plexus, the forming retina (primitive ependymal zone corresponding to early differentiating photoreceptor cells), and olfactory receptor neurons of stage embryonic day 14 embryos. There is a striking correlation of tektin expression with the known presence of either motile or primary cilia. The evolutionary conservation of tektins and their association with tubulin in cilia and centriole formation make them important and useful molecular targets for the study of neural development.

Nucleosome positioning in the rat protamine 1 gene in vivo and in vitro

The positions of the nucleosomes along the rat protamine 1 gene have been determined in vivo through micrococcal nuclease digestion of isolated nuclei followed by Southern analysis and indirect end labeling with a protamine 1 gene probe. Several strong positioning signals are detected in rat liver nuclei where the gene is repressed. In vitro reconstitution of nucleosomes along the cloned rat protamine 1 gene results in a precisely positioned nucleosome with a dyad axis at -109 bp upstream from the transcriptional start site. The position of this nucleosome reconstituted in vitro coincides with the position of one of the nucleosomes present in vivo in rat liver nuclei. Two important regulatory elements of the expression of the protamine 1 gene, the serum response element (CArG box) and the protamine 1 consensus (cAMP response element), are positioned over the -109 nucleosome with potential functional implications for transcriptional activation.

Characterization of germ cell-specific expression of the orphan nuclear receptor, germ cell nuclear factor

Nuclear receptors, such as those for androgens, estrogens, and progesterones, control many reproductive processes. Proteins with structures similar to these receptors, but for which ligands have not yet been identified, have been termed orphan nuclear receptors. One of these orphans, germ cell nuclear factor (GCNF), has been shown to be germ cell specific in the adult and, therefore, may also participate in the regulation of reproductive functions. In this paper, we examine more closely the expression patterns of GCNF in germ cells to begin to define spatio-temporal domains of its activity. In situ hybridization showed that GCNF messenger RNA (mRNA) is lacking in the testis of hypogonadal mutant mice, which lack developed spermatids, but is present in the wild-type testis. Thus, GCNF is, indeed, germ cell specific in the adult male. Quantitation of the specific in situ hybridization signal in wild-type testis reveals that GCNF mRNA is most abundant in stage VII round spermatids. Similarly, Northern analysis and specific in situ hybridization show that GCNF expression first occurs in testis of 20-day-old mice, when round spermatids first emerge. Therefore, in the male, GCNF expression occurs postmeiotically and may participate in the morphological changes of the maturing spermatids. In contrast, female expression of GCNF is shown in growing oocytes that have not completed the first meiotic division. Thus, GCNF in the female is expressed before the completion of meiosis. Finally, the nature of the two different mRNAs that hybridize to the GCNF complementary DNA was studied. Although both messages contain the DNA binding domain, only the larger message is recognized by a probe from the extreme 3' untranslated region. In situ hybridization with these differential probes demonstrates that both messages are present in growing oocytes. In addition, the coding region and portions of the 3' untranslated region of the GCNF complementary DNA are conserved in the rat.