Spag16 is the murine orthologue of Chlamydomonas reinhardtii PF20, a protein known to be essential to the structure and function of the “9+2” axoneme. In Chlamydomonas, the PF20 gene encodes a single protein present in the central pair of the axoneme. Loss of PF20 prevents central pair assembly/integrity and results in flagellar paralysis. Here we demonstrate that the murine Spag16 gene encodes two proteins: 71 kDa SPAG16L, which is found in all murine cells with motile cilia or flagella, and 35 kDa SPAG16S, representing the C terminus of SPAG16L, which is expressed only in male germ cells, and is predominantly found in specific regions within the nucleus that also contain SC35, a known marker of nuclear speckles enriched in pre-mRNA splicing factors. SPAG16S expression precedes expression of SPAG16L. Mice homozygous for a knockout of SPAG16L alone are infertile, but show no abnormalities in spermatogenesis. Mice chimeric for a mutation deleting the transcripts for both SPAG16L and SPAG16S have a profound defect in spermatogenesis. We show here that transduction of SPAG16S into cultured dispersed mouse male germ cells and BEAS-2B human bronchial epithelial cells increases SPAG16L expression, but has no effect on the expression of several other axoneme components. We also demonstrate that the Spag16L promoter shows increased activity in the presence of SPAG16S. The distinct nuclear localization of SPAG16S and its ability to modulate Spag16L mRNA expression suggest that SPAG16S plays an important role in the gene expression machinery of male germ cells. This is a unique example of a highly conserved axonemal protein gene that encodes two protein products with different functions.
Primary ciliary dyskinesia (PCD), resulting from defects in cilia assembly or motility, is caused by mutations in a number of genes encoding axonemal proteins. PCD phenotypes are variable, and include recurrent respiratory tract infections, bronchiectasis, hydrocephaly, situs inversus, and male infertility. We generated knockout mice for the sperm-associated antigen–17 (Spag17) gene, which encodes a central pair (CP) protein present in the axonemes of cells with “9 + 2” motile cilia or flagella. The targeting of Spag17 resulted in a severe phenotype characterized by immotile nasal and tracheal cilia, reduced clearance of nasal mucus, profound respiratory distress associated with lung fluid accumulation and disruption of the alveolar epithelium, cerebral ventricular expansion consistent with emerging hydrocephalus, failure to suckle, and neonatal demise within 12 hours of birth. Ultrastructural analysis revealed the loss of one CP microtubule in approximately one quarter of tracheal cilia axonemes, an absence of a C1 microtubule projection, and other less frequent CP structural abnormalities. SPAG6 and SPAG16 (CP proteins that interact with SPAG17) were increased in tracheal tissue from SPAG17-deficient mice. We conclude that Spag17 plays a critical role in the function and structure of motile cilia, and that neonatal lethality is likely explained by impaired airway mucociliary clearance.
primary ciliary dyskinesia; axoneme; central pair; Spag17; cilia
Gene targeting was used to create mice lacking sperm-associated antigen 6 (Spag6), the murine orthologue of Chlamydomonas PF16, an axonemal protein containing eight armadillo repeats predicted to be important for flagellar motility and stability of the axoneme central apparatus. Within 8 weeks of birth, approximately 50% of Spag6-deficient animals died with hydrocephalus. Spag6-deficient males surviving to maturity were infertile. Their sperm had marked motility defects and was morphologically abnormal with frequent loss of the sperm head and disorganization of flagellar structures, including loss of the central pair of microtubules and disorganization of the outer dense fibers and fibrous sheath. We conclude that Spag6 is essential for sperm flagellar motility and that it is important for the maintenance of the structural integrity of mature sperm. The occurrence of hydrocephalus in the mutant mice also implicates Spag6 in the motility of ependymal cilia.
cDNAs were cloned for the murine and human orthologues of Chlamydomonas PF20, a component of the alga axoneme central apparatus that is required for flagellar motility. The mammalian genes encode transcripts of 1.4 and 2.5 kb that are highly expressed in testis. The two transcripts appear to arise from alternative transcription start sites. The murine Pf20 gene was mapped to chromosome 1, syntenic with the location of the human gene on chromosome 2. An antibody generated against an N-terminal sequence of mouse Pf20 recognized a 71-kDa protein in sperm and testis extracts. Immunocytochemistry localized Pf20 to the tails of permeabilized sperm; electron microscope immunocytochemistry showed that Pf20 was located in the axoneme central apparatus. A murine Pf20-green fluorescent protein fusion protein expressed in Chinese hamster ovary cells accumulated in the cytoplasm. When coexpressed with Spag6, the mammalian orthologue of Chlamydomonas PF16, Pf20 was colocalized with Spag6 on polymerized microtubules. Yeast two-hybrid assays demonstrated interaction of the Pf20 WD repeats with Spag6. Pf20 was markedly reduced in sperm collected from mice lacking Spag6, which are infertile due to a motility defect. Our observations provide the first evidence for an association between mammalian orthologues of two Chlamydomonas proteins known to be critical for axoneme structure and function.
SOX5 is a transcription factor with homology to the high mobility group box region of the testis-determining factor, SRY. Both the mouse and human SOX5 genes encode a 48-kDa SOX5 protein (S-SOX5) that is only present in tissues containing cells with motile cilia/flagella. The mammalian sperm-associated antigen 6 gene (SPAG6) encodes an axoneme central apparatus protein. Because human and mouse SPAG6 gene promoters contain multiple potential binding sites for SOX5, SPAG6 gene regulation by S-SOX5 was investigated in BEAS-2B cells, a line derived from human bronchial cells. Like FOXJ1, a transcription factor known to be essential for motile ciliogenesis, S-SOX5 stimulated mouse and human SPAG6 promoter function in BEAS-2B cells, but the effect was abrogated when the SOX5 binding sites were mutated or deleted. S-SOX5 and FOXJ1 functioned cooperatively in stimulating SPAG6 promoter activity. The SPAG6 message was up-regulated when S-SOX5 was overexpressed in BEAS-2B cells, and silencing of S-SOX5 by RNA interference down-regulated SPAG6 transcripts. Chromatin immunoprecipitation and EMSA experiments demonstrated that S-SOX5 associates with the SPAG6 promoter directly. The present study demonstrates that SPAG6 is a S-SOX5 target gene, indicating a key role for S-SOX5 in the formation and function of motile cilia.
DNA-Protein Interaction; Gene Regulation; Promoters; Site-directed Mutagenesis; Sperm; Central Apparatus; Motile Cilia; SOX5; SPAG6; Transcription Regulation
Sperm binding proteins and their C-terminal peptides of the Sperm Associated Antigen 11 (SPAG11) family were found to play an important role in epididymal innate immunity in addition to their role in sperm maturation. However, the expression of Spag11 transcripts in rodents is not well documented.
Computational analysis was employed to identify novel Spag11 isoforms in the rat. RT-PCR analyses were carried out on RNAs isolated from the male reproductive tract tissues of rat using gene specific primers for Spag11c and Spag11t. The identities of PCR products were confirmed by sequencing. Tissue distribution, developmental expression and androgen regulation of Spag11t and Spag11c were studied using RT-PCR. The antimicrobial activities of recombinant Spag11t and Spag11c were tested against E coli in a colony forming unit assay.
In this study, we identified two novel Spag11 transcripts, namely, Spag11t and Spag11c derived from the long arm of chromosome 16 in the rat (Rattus norvegicus), using both in silico and molecular biology approaches. Spag11c is expressed in all three regions of the epididymis, in testis and in ovary but is absent from the seminal vesicle. Spag11t expression is confined to the caput and it is not expressed in the testis, seminal vesicle or ovary. Age dependent expression of Spag11t and Spag11c was observed in the epididymides of rats (10–60 day old). Their expression was found to be most abundant in the adult rat (60 day) suggesting roles in mature reproductive function. Further, both Spag11t and Spag11c expression was down regulated in castrated rat epididymides and the expression was maintained in the testosterone replaced castrated rats. SPAG11C is a potent antibacterial agent. SPAG11T also displayed bactericidal capacity although weaker than SPAG11C and SPAG11E.
The abundant expression of Spag11t and Spag11c in the male reproductive tract suggests an important role in male reproductive tract immunity. Their expression is developmentally regulated and androgen dependent. Characterization of novel SPAG11 isoforms will contribute to our understanding of the role of epididymal proteins in sperm maturation and innate immunity.
Mammalian SPAG6 protein is localized to the axoneme central apparatus, and it is required for normal flagella and cilia motility. Recent studies demonstrated that the protein also regulates ciliogenesis and cilia polarity in the epithelial cells of brain ventricles and trachea. Motile cilia are also present in the epithelial cells of the middle ear and Eustachian tubes, where the ciliary system participates in the movement of serous fluid and mucus in the middle ear. Cilia defects are associated with otitis media (OM), presumably due to an inability to efficiently transport fluid, mucus and particles including microorganisms. We investigated the potential role of SPAG6 in the middle ear and Eustachian tubes by studying mice with a targeted mutation in the Spag6 gene. SPAG6 is expressed in the ciliated cells of middle ear epithelial cells. The orientation of the ciliary basal feet was random in the middle ear epithelial cells of Spag6-deficient mice, and there was an associated disrupted localization of the planar cell polarity (PCP) protein, FZD6. These features are associated with disordered cilia orientation, confirmed by scanning electron microscopy, which leads to uncoordinated cilia beating. The Spag6 mutant mice were also prone to develop OM. However, there were no significant differences in bacterial populations, epithelial goblet cell density, mucin expression and Eustachian tube angle between the mutant and wild-type mice, suggesting that OM was due to accumulation of fluid and mucus secondary to the ciliary dysfunction. Our studies demonstrate a role for Spag6 in the pathogenesis of OM in mice, possibly through its role in the regulation of cilia/basal body polarity through the PCP-dependent mechanisms in the middle ear and Eustachian tubes.
The Spag16L gene codes for a protein that is localized to the central apparatus which is essential for normal sperm motility and male fertility. Sperm from mice homozygous for a targeted deletion of the Spag16L gene were examined to assess their flagellar motor functions compared with age- and strain-matched control sperm. Sperm were also demembranated with Triton X-100 and examined for their ability to respond to free calcium, as well as for their ability to undergo microtubule sliding driven by dynein action. In addition, the passive flagella, inhibited by sodium metavanadate to disable the dyneins, were examined for mechanical abnormalities. Live Spag16L-null sperm exhibited much less bending of the flagellum during the beat. The amount of microtubule sliding in the R-bend direction of the beat was selectively restricted, which suggests that there is limited activation of the dyneins on one side of the axoneme in the live cells. This is corroborated by the results on detergent-extracted sperm models. The flagellar response to calcium is greatly reduced. The calcium response requires the activation of the dyneins on outer doublets 1, 2, 3, and 4. These are the same dyneins required for R-bend formation. In axonemes prepared to disintegrate by microtubule sliding, we observed little or no extrusion of doublets 1 and 2, consistent with a reduced activity of their dyneins. This deficit in motor function, and an increased rigidity of the midpiece region which we detected in the passive flagella, together can explain the observed motility characteristics of the Spag16L-null sperm.
Mouse sperm lacking SPAG16L have altered motility and a reduced response to calcium.
axoneme; calcium; central pair; ciliopathies; dynein; hyperactivation
Mammalian SPAG16L, the orthologue of Chlamydomonas Pf20, is an axoneme central apparatus protein necessary for flagellar motility. The SPAG16L protein sequence contains multiple potential phosphorylation sites and the protein was confirmed to be phosphorylated in vivo. A yeast-two-hybrid screen identified the testis-specific kinase, TSSK2, to be a potential SPAG16L binding partner. SPAG16L and TSSK2 interactions were confirmed by co-immunoprecipitation of both proteins from testis extracts and cell lysates expressing these proteins, and their co-localization was also noted by confocal microscopy in CHO cells where they were co-expressed. TSSK2 associates with SPAG16L via its C terminal domain bearing WD repeats. The N-terminal domain containing a coiled coil motif does not associate with TSSK2. SPAG16L can be phosphorylated by TSSK2 in vitro. Finally, TSSK2 is absent or markedly reduced from the testes in most of the SPAG16L null mice. These data support the conclusion that SPAG16L is a TSSK2 substrate.
SPAG16L; kinase; phosphorylation; sperm motility
SPAG6, an axoneme central apparatus protein, is essential for function of ependymal cell cilia and sperm flagella. A significant number of Spag6-deficient mice die with hydrocephalus, and surviving males are sterile because of sperm motility defects. In further exploring the ciliary dysfunction in Spag6-null mice, we discovered that cilia beat frequency was significantly reduced in tracheal epithelial cells, and that the beat was not synchronized. There was also a significant reduction in cilia density in both brain ependymal and trachea epithelial cells, and cilia arrays were disorganized. The orientation of basal feet, which determines the direction of axoneme orientation, was apparently random in Spag6-deficient mice, and there were reduced numbers of basal feet, consistent with reduced cilia density. The polarized epithelial cell morphology and distribution of intracellular mucin, α-tubulin, and the planar cell polarity protein, Vangl2, were lost in Spag6-deficient tracheal epithelial cells. Polarized epithelial cell morphology and polarized distribution of α-tubulin in tracheal epithelial cells was observed in one-week old wild-type mice, but not in the Spag6-deficient mice of the same age. Thus, the cilia and polarity defects appear prior to 7 days post-partum. These findings suggest that SPAG6 not only regulates cilia/flagellar motility, but that in its absence, ciliogenesis, axoneme orientation, and tracheal epithelial cell polarity are altered.
Epididymal sperm maturation occurs via interactions between sperm and proteins secreted by the epididymal epithelium. Although this is an important process, the genes that encode the involved proteins remain largely uncharacterized. Previous studies have demonstrated that the genes involved in sperm maturation are regulated by androgen. Spag11a is an epididymal gene that is influenced by androgen. However, little is known about the putative role of this gene in the sperm maturation process. The objective of this study was to characterize Spag11a in the mouse epididymis.
In silico analyses were performed to predict signal peptides and functional domains. Spag11a expression was measured by quantitative real-time RT-PCR. Western blots and immunocytochemistry were performed to determine protein expression.
SPAG11A is a member of the beta defensin protein family and constitutes a secretory protein. Spag11a was expressed exclusively in the epididymis. Moreover, it exhibited region-specific expression in the caput, which is typical for genes that are involved in creating a suitable microenvironment for sperm maturation. Mouse Spag11a was regulated by androgen. A significant decrease of Spag11a expression was observed at third day following a gonadectomy (P < 0.001). Interestingly, testosterone replacement therapy was able to maintain the expression almost at the normal level, indicating a dependency on androgen. Besides androgen, testicular factors influenced Spag11a expression in a different way. This was revealed by efferent duct ligation in which Spag11a was transiently up-regulated at the third day following the ligation before returning to the normal level at day 5. Spag11a regional expression was also observed at protein level detected by western immunoblotting which revealed a clear band in the caput but not in other regions. The prediction that SPAG11A is a secretory protein was confirmed by immunocytochemical analyses indicating cell-specific expression mainly in the caput principal cells and detection of the protein in epididymal luminal fluid and spermatozoa.
Based on the characteristics of Spag11a, it is likely that this gene has a specific role in epididymal sperm maturation. Further studies using functional assays are necessary to confirm this finding.
Spag11a; Epididymis; Androgen; Secretory protein; Principal cells
Majority of bladder cancer deaths are caused due to transitional cell carcinoma (TCC) which is the most prevalent and chemoresistant malignancy of urinary bladder. Therefore, we analyzed the role of Sperm associated antigen 9 (SPAG9) in bladder TCC.
Methodology and Findings
We examined SPAG9 expression and humoral response in 125 bladder TCC patients. Four bladder cancer cell lines were assessed for SPAG9 expression. In addition, we investigated the effect of SPAG9 ablation on cellular proliferation, cell cycle, migration and invasion in UM-UC-3 bladder cancer cells by employing gene silencing approach. Our SPAG9 gene and protein expression analysis revealed SPAG9 expression in 81% of bladder TCC tissue specimens. High SPAG9 expression (>60% SPAG9 positive cells) was found to be significantly associated with superficial non-muscle invasive stage (P = 0.042) and low grade tumors (P = 0.002) suggesting SPAG9 putative role in early spread and tumorigenesis. Humoral response against SPAG9 was observed in 95% of patients found positive for SPAG9 expression. All four bladder cancer cell lines revealed SPAG9 expression. In addition, SPAG9 gene silencing in UM-UC-3 cells resulted in induction of G0–G1 arrest characterized by up-regulation of p16 and p21 and consequent down-regulation of cyclin E, cyclin D and cyclin B, CDK4 and CDK1. Further, SPAG9 gene silencing also resulted in reduction in cellular growth, and migration and invasion ability of cancer cells in vitro.
Collectively, our data in clinical specimens indicated that SPAG9 is potential biomarker and therapeutic target for bladder TCC.
Human sperm-associated antigen 11 (SPAG11) is closely related to beta-defensins in structure, expression, and function. Like the beta-defensins, SPAG11 proteins are predominantly expressed in the male reproductive tract, where their best-known major roles are in innate host defense and reproduction. Although several hypotheses have emerged to describe the evolution of beta-defensin and SPAG11 multifunctionality, few describe these multiple functions in terms of defensin interactions with specific proteins. To gain insight into the protein interaction potentials of SPAG11 and the signaling pathways that SPAG11 may influence, we used a yeast two-hybrid screening of a human testis-epididymis library. The results reveal human SPAG11B isoform D (SPAG11B/D) interactions with tryptase alpha/beta 1 (TPSAB1), tetraspanin 7 (TSPAN7), and attractin (ATRN). These interactions were confirmed by coimmunoprecipitation and glutathione S-transferase affinity matrix binding. SPAG11B/D and the three interacting proteins are expressed in the proximal epididymis, and all function in immunity and fertility pathways. We analyzed the functional consequences of SPAG11B/D interaction with TPSAB1 and showed that SPAG11B/D is both a substrate and a potent inhibitor of TPSAB1 activity. Furthermore, we show that (like SPAG11B/D) TSPAN7 and ATRN are associated with spermatozoa.
Human sperm associated antigen SPAG11B (isoform D) is both a substrate and a potent inhibitor of tryptase alpha/beta 1 activity, and interacts with tetraspanin 7 and attractin in the proximal epididymis and spermatazoa..
attractin; beta-defensin; epididymis; gene regulation; male reproductive tract; signal transduction; sperm; spermatozoa; tetraspanin; tryptase
Recently, we reported an association of a novel cancer testis (CT) antigen, sperm-associated antigen 9 (SPAG9) expression in breast cancer clinical samples, indicating its potential role in carcinogenesis. Around 15% breast cancers are designated as triple-negative for which treatment modalities are limited. Therefore, in the present study, we assessed the role of SPAG9 in triple-negative breast cancer cells.
SPAG9 mRNA and protein expression was investigated in various breast cancer cells of different hormone receptor status and different subtypes by employing reverse transcriptase-polymerase chain reaction (RT-PCR), real time PCR, Western blotting, indirect immunofluorescence (IIF) and fluorescence activated cell sorting (FACS). Employing plasmid-based small interfering RNA (siRNA) approach, knockdown of SPAG9 was carried out in triple-negative breast cancer cells, MDA-MB-231, to assess its role on various malignant properties in vitro and in vivo.
SPAG9 mRNA and protein expression was detected in all breast cancer cells. Further, IIF results showed that SPAG9 was predominantly localized in the cytoplasm of breast cancer cells. FACS analysis revealed distinct SPAG9 surface localization in breast cancer cells. Gene silencing of SPAG9 resulted in significant reduction in cellular proliferation, colony forming ability, migration, invasion and cellular motility of MDA-MB-231 cells. Further, ablation of SPAG9 expression resulted in reduction in the tumor growth of human breast cancer xenograft in nude mice in vivo.
In summary, our data indicated that down regulation of SPAG9 reduces growth and invasive potential of triple-negative breast cancer cells, suggesting that SPAG9 may be a potential target for therapeutic use.
Migration; Invasion; CT antigens; SPAG9; Gene silencing
Mutations in the gene for Usher syndrome 2A (USH2A) are causative for non-syndromic retinitis pigmentosa and Usher syndrome, a condition that is the most common cause of combined deaf-blindness. To gain insight into the molecular pathology underlying USH2A-associated retinal degeneration, we aimed to identify interacting proteins of USH2A isoform B (USH2AisoB) in the retina.
We identified the centrosomal and microtubule-associated protein sperm-associated antigen (SPAG)5 in the retina. SPAG5 was also found to interact with another previously described USH2AisoB interaction partner: the centrosomal ninein-like protein NINLisoB. Using In situ hybridization, we found that Spag5 was widely expressed during murine embryonic development, with prominent signals in the eye, cochlea, brain, kidney and liver. SPAG5 expression in adult human tissues was detected by quantitative PCR, which identified expression in the retina, brain, intestine, kidney and testis. In the retina, Spag5, Ush2aisoB and NinlisoB were present at several subcellular structures of photoreceptor cells, and colocalized at the basal bodies.
Based on these results and on the suggested roles for USH proteins in vesicle transport and providing structural support to both the inner ear and the retina, we hypothesize that SPAG5, USH2AisoB and NINLisoB may function together in microtubule-based cytoplasmic trafficking of proteins that are essential for cilium formation, maintenance and/or function.
The majority of beta-defensin family members are exclusively expressed in the epididymis, and some members have been shown to play essential roles in sperm maturation and fertility in rats, mice and humans. Therefore, beta-defensins are hypothesized to be potential targets for contraception and infertility diagnosis and treatment. Clarifying the regulatory mechanisms for the expression of these genes is necessary. Androgen/androgen receptor (AR) signaling plays an important regulatory role in epididymal structure and function. However, very little is known about the androgenic regulation on the production and secretion of the epididymal beta-defensins.
The expression of beta-defensins was detected by quantitative RT-PCR. The androgen dependence of beta-defensins was determined by bilateral orchiectomy and androgen supplementation. The androgen response elements (AREs) in the promoters of beta-defensins were identified using the MatInspector software. The binding of AR to AREs was assayed by ChIP-PCR/qPCR.
We demonstrated that 23 mouse caput epididymal beta-defensins were differentially regulated by androgen/androgen receptor. Six genes, Defb18, 19, 20, 39, 41, and 42, showed full regulation by androgens. Ten genes, Defb15, 30, 34, 37, 40, 45, 51, 52, 22 and Spag11a, were partially regulated by androgens. Defb15, 18, 19, 20, 30, 34, 37, 39, 41, 42, 22 and Spag11a were associated with androgen receptor binding sites in their promoter or intronic regions, indicating direct regulation of AR. Six genes, Defb1, 12, 13, 29, 35, and spag11b/c, exhibited an androgen-independent expression pattern. One gene, Defb25, was highly dependent on testicular factors rather on androgens.
The present study provides novel insights into the mechanisms of androgen regulation on epididymal beta-defensins, enabling a better understanding of the function of beta-defensins in sperm maturation and fertility.
Androgen; Androgen receptor; Epididymis; Beta-defensins
Sperm-associated antigen 9 (SPAG9) has been suggested as a possible biomarker in several malignancies including thyroid cancer. We investigated the expression of SPAG9 mRNA in fine needle aspiration (FNA) material from papillary thyroid carcinoma (PTC) and benign thyroid nodules.
SPAG9 expression was assessed in 36 FNA samples corresponding to 16 PTC and 20 benign nodules using the original method detecting the SPAG9 transcript containing intron 21 (NCBI X91879). The presence of the BRAF V600E point mutation was also analyzed by pyrosequencing.
Six of 16 (38%) PTC samples were positive for X91879 SPAG9 transcript compared to 8 of 20 (40%) benign samples (p = 0.88). Out of 12 BRAF-positive PTC, 3 (25%) also expressed the SPAG9 transcript compared to 3 out of 4 BRAF-negative PTC (75%; p = 0.12).
The X91879 SPAG9 transcript originally described does not appear to be overexpressed in FNA material from PTC or to be clinically relevant in the diagnosis of thyroid nodules.
Sperm-associated antigen 9; Fine needle aspiration; Thyroid; Diagnosis; Cancer
The ultrastructure of normal human cilia and flagella was examined and quantitatively assessed to determine the normal variations in the structure of the axoneme. Ciliated respiratory epithelial cells and spermatozoa from 10 normal, nonsmoking male volunteers who had normal semen parameters were fixed for electron microscopy. Tannic acid and MgSO4 were included during fixation to enhance, in particular, axonemal components. In 75 axonemal cross sections per sample, the number of outer doublet and central singlet microtubules, outer and inner dynein arms, and radial spokes were recorded. Statistical analysis of the results showed a marked reduction, from the expected value of nine, in the numbers of inner dynein arms (mean +/- SE, cilia, 5.31 +/- 0.13; sperm, 5.38 +/- 0.16) and radial spokes (cilia, 4.95 +/- 0.22; sperm, 5.80 +/- 0.19). The ideal axoneme with all its structural components was seen in only 0.13% of cilia and 0.80% of sperm tails. Significantly more doublet microtubules (P less than 0.05) and less central microtubules (P less than 0.01) and radial spokes (P less than 0.01) were seen in cilia than in sperm tail axonemes. Between subjects there was little variation in the mean number of a structure seen per axoneme. However, within each sample, the variation was considerably higher, particularly for the inner and outer dynein arms and radial spokes. The doublet microtubules had significantly greater standard deviations in the sperm tails compared with the cilia (P less than 0.01), and furthermore, a significantly greater number of sperm tails compared with cilia showed the incorrect number of doublet microtubules (P less than 0.02). In one semen sample, with normal semen analysis, 20% of the sperm tails showed incorrect numbers of doublet microtubules, ranging from 12 + 2 to 5 + 2 compared with only 1.3% in cilia from this subject. This study has demonstrated that the ideal axoneme is rarely seen even in normal samples, probably because of the technical difficulties in resolution and visualization, and stresses the need for thorough documentation of axonemal ultrastructure. This work provides a normal data base for comparison with patients who have chronic respiratory disease and suspected infertility.
Primary ciliary dyskinesia (PCD) results from defects in motile cilia function. Mice homozygous for the mutation big giant head (bgh) have several abnormalities commonly associated with PCD, including hydrocephalus, male infertility, and sinusitis. In the present study, we use a variety of histopathological and cell biological techniques to characterize the bgh phenotype, and we identify the bgh mutation using a positional cloning approach. Histopathological, immunofluorescence, and electron microscopic analyses demonstrate that the male infertility results from shortened flagella and disorganized axonemal and accessory structures in elongating spermatids and mature sperm. In addition, there is a reduced number of elongating spermatids during spermatogenesis and mature sperm in the epididymis. Histological analyses show that the hydrocephalus is characterized by severe dilatation of the lateral ventricles and that bgh sinuses have an accumulation of mucus infiltrated by neutrophils. In contrast to the sperm phenotype, electron microscopy demonstrates that mutant respiratory epithelial cilia are ultrastructurally normal, but video microscopic analysis shows that their beat frequency is lower than that of wild-type cilia. Through a positional cloning approach, we identified two sequence variants in the gene encoding sperm flagellar protein 2 (SPEF2), which has been postulated to play an important role in spermatogenesis and flagellar assembly. A causative nonsense mutation was validated by Western blot analysis, strongly suggesting that the bgh phenotype results from the loss of SPEF2 function. Taken together, the data in this study demonstrate that SPEF2 is required for cilia function and identify a new genetic cause of PCD in mice.
Sperm flagellar protein 2 is required for spermatogenesis and regulation of ciliary motility in mice.
cilia; flagella; genetics; hydrocephalus; male infertility; primary ciliary dyskinesia; sinusitis; SPEF2; spermatogenesis
In an effort to define the molecular basis for morphogenesis of major sperm tail structures, including outer dense fibers, we recently cloned the Spag5 gene by virtue of its strong and specific leucine-zipper-mediated interaction with Odf1, the 27-kDa major outer dense fiber protein. Spag5 is expressed during meiosis and in round spermatids and is similar, if not identical, to Deepest, a putative spindle pole protein. Here we report the disruption of the Spag5 gene by homologous recombination. Spag5-null mice lack Spag5 mRNA and protein. However, male mice are viable and fertile. Analysis of the process of spermatogenesis and sperm produced in Spag5-null mice did not reveal a major phenotype as a consequence of the knockout event. This result suggests that if Spag5 plays a role in spermatogenesis it is likely compensated for by unknown proteins.
During spermiogenesis, haploid round spermatids undergo dramatic cell differentiation and morphogenesis to give rise to mature spermatozoa for fertilization, including nuclear elongation, chromatin remodeling, acrosome formation, and development of flagella. The molecular mechanisms underlining these fundamental processes remain poorly understood. Here, we report that MNS1, a coiled-coil protein of unknown function, is essential for spermiogenesis. We find that MNS1 is expressed in the germ cells in the testes and localizes to sperm flagella in a detergent-resistant manner, indicating that it is an integral component of flagella. MNS1–deficient males are sterile, as they exhibit a sharp reduction in sperm production and the remnant sperm are immotile with abnormal short tails. In MNS1–deficient sperm flagella, the characteristic arrangement of “9+2” microtubules and outer dense fibers are completely disrupted. In addition, MNS1–deficient mice display situs inversus and hydrocephalus. MNS1–deficient tracheal motile cilia lack some outer dynein arms in the axoneme. Moreover, MNS1 monomers interact with each other and are able to form polymers in cultured somatic cells. These results demonstrate that MNS1 is essential for spermiogenesis, the assembly of sperm flagella, and motile ciliary functions.
Cilia are microtubule-based structures present in virtually all cells in vertebrates. Cilia have diverse functions in development, growth, signaling, and fertilization. Primary ciliary dyskinesia (PCD) affects one in 16,000 individuals. PCD is characterized by bronchiectasis and chronic sinusitis, and is often associated with situs inversus and male infertility. The genetic cause of PCD is heterogeneous. Some cases of PCD in humans and animals are caused by single genic mutations such as mutations in genes encoding microtubule-based dynein arm components. We have characterized a protein called MNS1 and found that it plays an essential role in ciliary functions in mice. MNS1 is a novel and integral component of sperm flagella. Mice lacking MNS1 exhibit male sterility as evidenced by abnormal assembly of sperm flagella. MNS1–deficient mice also display defects in left–right asymmetry patterning of internal organs and hydrocephalus. Therefore, mutations in MNS1 may contribute to male infertility and PCD in humans.
Semen samples collected from 28 male partners of infertile couples were divided into three equal aliquots and prepared with three selected media, such as PureSperm® (Nidacon, Gothenburg, Sweden), Sil-Select Plus™ (Fertipro, Beernem, Belgium) and SpermGrad™ (Vitrolife, Gothenburg, Sweden). The differences in mean percentages of semen parameters were assessed by repeated measures analysis. Correlations of sperm DNA damage, as measured by terminal deoxynucleotidyl transferase dUTP nick end labeling (TUNEL) assay, and of protamine deficiency, as measured by chromomycin A3 (CMA3) staining with sperm parameters, were determined by Pearson's correlation. After preparation with all three media, sperm concentrations decreased (P < 0.05) while percentages of sperm with normal morphology increased (P < 0.05). Percentages of sperm motility, rapid motility and progressive motile concentration (PMC) increased (P < 0.05) for each of these parameters, PureSperm preparation gave the best results (P < 0.05). The percentage of DNA damage decreased in the PureSperm and Sil-Select Plus preparations (17.9% and 31.3%, respectively, P < 0.05) and increased in the SpermGrad preparation (56.3%, P < 0.05). Protamine deficiency also decreased in all three kinds of media, 59.3%, 47.7% and 40.3% for PureSperm, Sil-Select Plus and SpermGrad preparations, respectively (P < 0.05). The percentage of DNA-damaged sperm was negatively correlated with the percentages of sperm motility, rapid motility and PMC, but was positively correlated with static motility (P < 0.05). This comparative study and correlation analysis revealed that PureSperm preparation yielded sperm with the best motility and the lowest percentage of protamine deficiency. The Sil-Select Plus preparation yielded sperm with the lowest amount of DNA damage. The SpermGrad preparation had a high percentage of sperm with normal morphology, but also had the highest percentage of sperm with DNA damage. Sperm DNA damage was correlated with percentages of sperm motility, rapid motility, static motility and PMC.
semen parameters; sperm DNA damage; sperm preparation media; sperm protamine deficiency
Sperm DNA damage is associated with male infertility, lower pregnancy rates and pregnancy loss.
The primary aim of our study was to evaluate the prevalence of sperm DNA damage in younger and older men with normozoospermia.
Design, Setting and Participants
We obtained semen from 277 consecutive non-azoospermic men presenting for sperm DNA testing.
Outcome Measurements and Statistical Analysis
The main outcome measures included sperm % DNA fragmentation index (%DFI, using sperm chromatin structure assay), sperm concentration, motility and morphology, and, paternal age.
Results and Limitations
Sperm % DFI was positively correlated with paternal age (r = 0.20, P < 0.001) and inversely correlated % progressive motility (r = −0.16, P = 0.01). Sperm %DFI was significantly higher in older (≥40 years) compared to younger (<40 years) normozoospermic men (17 ± 13 vs. 12 ± 8, respectively P = 0.008), whereas, sperm concentration, progressive motility and morphology were not significantly different in these two groups. Moreover, the prevalence of high levels of sperm DNA damage (>30 % DFI) was significantly higher in older compared to younger normozoospermic men (17 % vs. 3 %, respectively, P < 0.001).
The data indicate that a conventional semen analysis can often fail to detect a defect in spermatogenesis (high %DFI) in older men and suggest that infertile couples with advanced paternal age, including those with normal semen parameters, should consider sperm DNA testing as part of the couple evaluation.
Sperm; DNA fragmentation; Age; Normozoospermia; Infertility
To understand role of mitochondrial (mt) mutations in genes regulating oxidative phosphorylation (OXPHOS) in pathogenesis of male infertility. Infertility affects approximately 15% of couples trying to conceive. Infertility is frequently attributed to defects of sperm motility and number. Mitochondrion and mitochondrial DNA (mtDNA) play an important role in variety of physiological process. They control the oxidative energy supply and thus are central to growth, development and differentiation. Mitochondrial function is controlled by a fine-tuned crosstalk between mtDNA and nuclear DNA (nDNA). As mitochondria supply energy by OXPHOS, any mutation in mtDNA disrupts adenosine triphosphate (ATP) production and thus result in an impaired spermatogenesis and impaired flagellar movement. As sperm midpiece has few mtDNA copies, thus enhanced number of mutant mtDNA results in early phenotypic defect which manifest as spermatogenic arrest or asthenozoospermia. Oxidative stress and mtDNA mutations are positively correlated and mutations in mitochondrial genome (mt genome) are implicated in the lowered fertilising capacity of the sperm and affects the reproductive potential of an individual.
Materials and Methods
A thorough review of articles in the last 15 years was cited with reference to the below-mentioned keywords. The articles considered discuss the role of mt genome in the normal functioning of sperm and the factors associated with mt mutations and impact of these mutations on the reproductive potential.
Sperm motility is a very important factor for the fertilisation of ova. The energy requirements of sperm are therefore very critical for sperm. Mutations in the mitochondrial genes as COX II, ATPase 6 and 8 play an important role and disrupts ATP production affecting the spermatogenesis and sperm motility. Therefore, the aberrations in mt genome are an important etiopatholgy of male infertility.
In the context of male infertility, mt mutations, generation of reactive oxygen species and lowered antioxidant capacity are interlinked and constitute a unified pathogenic molecular mechanism. In the era of assisted reproduction technique (ART), it is very important to distinguish between mutations in nuclear and mitochondrial genomes in sperm, as mtDNA mutations are better diagnostic and prognostic markers in infertile men opting for ART.
Assisted reproduction techniques; asthenozoospermia; infertility; Mitochondrion and mitochondrial DNA mutations; mt genome
Outer dense fiber protein 2, Odf2, is a major component of the outer dense fibers, ODF, in the flagellum of spermatozoa. ODF are associated with microtubule doublets that form the axoneme. We recently demonstrated that tyrosine phosphorylation of Odf2 is important for sperm motility. In the course of a study of Odf2 using Odf2 mouse knockout lines we observed that males of a high percentage chimaerism, made using XL169 embryonic stem cells, were infertile, whereas mice of low-medium percentage chimaerism were fertile.
XL169 ES cells have a β-geo gene trap cassette inserted in the Odf2 gene. To determine possible underlying mechanisms resulting in infertility we analyzed epididymal sperm and observed that >50% displayed bent tails. We next performed ultrastructural analyses on testis of high percentage XL169 chimaeric mice. This analysis showed that high percentage XL169 chimaeric mice produce elongating spermatids that miss one or more entire outer dense fibers in their midpiece and principal piece. In addition, we observed elongating spermatids that show thinning of outer dense fibers. No other obvious abnormalities or defects are present in elongating spermatids. Spermatozoa from the caput and cauda epididymis of XL169 mice of high percentage chimaerism show additional tail defects, including absence of one or more axonemal microtubule doublets and bent tails. Sperm with bent tails display abnormal motility.
Our results document the possible impact of loss of one Odf2 allele on sperm tail structure and function, resulting in a novel sperm tail phenotype.