Characterization of boar sperm cytoskeletal cylicin II as an actin-binding protein

Cryopreservation, in addition to protein tyrosine phosphorylation, alters the distribution of phosphatidyl inositol bisphosphate and the localization of cytoskeletal and signaling proteins (gelsolin, tyrosine kinase c-SRC and phospholipase C-ζ) in the perinuclear theca of boar sperm

Cryopreservation of boar spermatozoa affects the perinuclear theca (PT) and involves several proteins and molecules that play important roles during capacitation and the acrosomal reaction. The objective of the present study was to evaluate whether the deleterious effects of cryopreservation in addition to protein tyrosine phosphorylation are accompanied by changes in the distribution of phosphatidyl inositol bisphosphate (PIP2) and the localization of cytoskeletal and signaling proteins in the perinuclear theca of cryopreserved boar spermatozoa. For this purpose, by immunocytochemistry (IC) the changes in localization of phosphorylated proteins in tyrosine residues, gelsolin, c-SRC kinase and PLC-ζ, as well as in the distribution of phosphatidyl inositol bisphosphate were analyzed in thawed spermatozoa (T) non capacitated (NC), capacitated (C) and in those with acrosomal reaction (AR) and compared with fresh spermatozoa (F) under the same physiological status. Western blotting (WB) and co-immunoprecipitation were performed to confirm the presence of these proteins in PT and to determine the interaction between these molecules. IC showed that immunostaining for phosphorylated proteins significantly increased in the acrosomal region and flagellum in TNC spermatozoa (p < 0.05). The proportion of cells displaying immunolabeling for gelsolin in the acrosomal region decreased after capacitation in cryopreserved spermatozoa; the same change was found (p < 0.05) in the proportion of spermatozoa immunoreactive to PIP2 in the sperm head. c-SRC was observed in the equatorial segment and acrosomal region, subdomains that coincide with the site where phosphorylated proteins were detected. PLC-ζ immunolocalization in fresh spermatozoa underwent changes after capacitation and acrosomal reaction, with a significant increase in the equatorial segment and post-acrosomal region in cryopreserved spermatozoa (p < 0.05). WB analysis indicated the presence of gelsolin, c-SRC and PLC-ζ in PT; besides, we confirmed that gelsolin co-immunoprecipitated with c-SRC and PLC-ζ, which changes according to the physiological state of spermatozoa. As a conclusion, cryopreservation together with increased immunodetection of tyrosine phosphorylated proteins decreases the detection of PIP2 and alters the immunolocalization patterns of gelsolin, c-SRC and PLC-ζ in the PT in boar spermatozoa.

Cylicins are a structural component of the sperm calyx being indispensable for male fertility in mice and human

Cylicins are testis-specific proteins, which are exclusively expressed during spermiogenesis. In mice and humans, two Cylicins, the gonosomal X-linked Cylicin 1 (Cylc1/CYLC1) and the autosomal Cylicin 2 (Cylc2/CYLC2) genes, have been identified. Cylicins are cytoskeletal proteins with an overall positive charge due to lysine-rich repeats. While Cylicins have been localized in the acrosomal region of round spermatids, they resemble a major component of the calyx within the perinuclear theca at the posterior part of mature sperm nuclei. However, the role of Cylicins during spermiogenesis has not yet been investigated. Here, we applied CRISPR/Cas9-mediated gene editing in zygotes to establish Cylc1- and Cylc2-deficient mouse lines as a model to study the function of these proteins. Cylc1 deficiency resulted in male subfertility, whereas Cylc2-/-, Cylc1-/yCylc2+/-, and Cylc1-/yCylc2-/- males were infertile. Phenotypical characterization revealed that loss of Cylicins prevents proper calyx assembly during spermiogenesis. This results in decreased epididymal sperm counts, impaired shedding of excess cytoplasm, and severe structural malformations, ultimately resulting in impaired sperm motility. Furthermore, exome sequencing identified an infertile man with a hemizygous variant in CYLC1 and a heterozygous variant in CYLC2, displaying morphological abnormalities of the sperm including the absence of the acrosome. Thus, our study highlights the relevance and importance of Cylicins for spermiogenic remodeling and male fertility in human and mouse, and provides the basis for further studies on unraveling the complex molecular interactions between perinuclear theca proteins required during spermiogenesis.

Proteomic alterations underlie an association with teratozoospermia in obese mice sperm

BACKGROUND

Obesity is a worldwide crisis impairing human health. In this condition, declines in sperm quality stem from reductions in sperm concentration, motility and increase in sperm deformity. The mechanism underlying these alterations remains largely unknown. This study, determined if obesity-associated proteomic expression patterns in mice sperm parallel those in spermatozoa obtained from obese humans.

METHODS

An obese mouse model was established via feeding a high-fat diet (HFD). Histological analysis identified testicular morphology and a computer assisted semen analyzer (CASA) evaluated sperm parameters. Proteome analysis was performed using a label-free quantitative LC-MS/MS system. Western blot, immunohistochemical and immunofluorescent analyses characterized protein expression levels and localization in testis, sperm and clinical samples.

RESULTS

Bodyweight gains on the HFD induced hepatic steatosis. Declines in sperm motility accompanied sperm deformity development. Differential proteomic analysis identified reduced cytoskeletal proteins, centrosome and spindle pole associated protein 1 (CSPP1) and Centrin 1 (CETN1), in sperm from obese mice. In normal weight mice, both CSPP1 and CETN1 were localized in the spermatocytes and spermatids. Their expression was appreciable in the post-acrosomal region parallel to the microtubule tracks of the manchette structure in spermatids, which affects spermatid head shaping and morphological maintenance. Moreover, CSPP1 was localized in the head-tail coupling apparatus of the mature sperm, while CETN1 expression was delimited to the post-acrosomal region within the sperm head. Importantly, sperm CSPP1 and CETN1 abundance in both the overweight and obese males decreased in comparison with that in normal weight men.

CONCLUSION

These findings show that regionally distinct expression and localization of CETN1 and CSPP1 is strongly related to spermiogenesis and sperm morphology maintaining. Obesity is associated with declines in the CETN1 and CSPP1 abundance and compromise of both sperm morphology in mice and relevant clinical samples. This parallelism between altered protein expression in mice and humans suggests that these effects may contribute to poor sperm quality including increased deformity.

Comparative proteomic identification buffalo spermatozoa during in vitro capacitation

To investigate the proteomic profiling in buffalo spermatozoa before and after capacitation, a liquid chromatography-tandem mass spectrometry (LC-MS/MS) combined with Tandem Mass Tag (TMT) labeling strategy was applied. As a result, 1461 proteins were identified, 93 of them were found to be differentially expressed (>1.5-fold), including 52 up-regulated proteins and 41 down-regulated proteins during sperm capacitation. 88 out of 93 proteins were annotated and classified. Gene ontology (GO) analysis revealed that most of the differently expressed proteins (DEPs) were involved in the Biological Process of transport, cytoskeleton organization, sexual reproduction, and spermatogenesis. Kyoto Encyclopedia of Genes and Genomes (KEGG) analysis indicated that DEPs were mainly involved in the pathways of metabolic pathways, PPAR signaling pathway, and oxidative phosphorylation. Western blot (WB) assay confirmed the expressional variation of VAMP4 and APOC3 proteins. Our date provided a foundation for studying the changes in protein expression during sperm capacitation, which contributing to identifying marker proteins that may be associated with sperm capacitation.

RAPID COMMUNICATION: A haplotype information theory method reveals genes of evolutionary interest in European vs. Asian pigs

Asian and European wild boars were independently domesticated ca. 10,000 yr ago. Since the 17th century, Chinese breeds have been imported to Europe to improve the genetics of European animals by introgression of favorable alleles, resulting in a complex mosaic of haplotypes. To interrogate the structure of these haplotypes further, we have run a new haplotype segregation analysis based on information theory, namely compression efficiency (CE). We applied the approach to sequence data from individuals from each phylogeographic region (n = 23 from Asia and Europe) including a number of major pig breeds. Our genome-wide CE is able to discriminate the breeds in a manner reflecting phylogeography. Furthermore, 24,956 nonoverlapping sliding windows (each comprising 1,000 consecutive SNP) were quantified for extent of haplotype sharing within and between Asia and Europe. The genome-wide distribution of extent of haplotype sharing was quite different between groups. Unlike European pigs, Asian pigs haplotype sharing approximates a normal distribution. In line with this, we found the European breeds possessed a number of genomic windows of dramatically higher haplotype sharing than the Asian breeds. Our CE analysis of sliding windows captures some of the genomic regions reported to contain signatures of selection in domestic pigs. Prominent among these regions, we highlight the role of a gene encoding the mitochondrial enzyme LACTB which has been associated with obesity, and the gene encoding MYOG a fundamental transcriptional regulator of myogenesis. The origin of these regions likely reflects either a population bottleneck in European animals, or selective targets on commercial phenotypes reducing allelic diversity in particular genes and/or regulatory regions.

Identification of microtubule growth deceleration and its regulation by conserved and novel proteins

Live imaging of microtubule dynamics in Caenorhabditis elegans muscle cells reveals a novel microtubule behavior characterized by an abrupt change in growth rate, named “microtubule growth deceleration.” The conserved protein ZYG-9^TOGp and two novel ORFs, cylc-1 and cylc-2, are involved in the regulation of this novel microtubule behavior.

Microtubules (MTs) are cytoskeletal polymers that participate in diverse cellular functions, including cell division, intracellular trafficking, and templating of cilia and flagella. MTs undergo dynamic instability, alternating between growth and shortening via catastrophe and rescue events. The rates and frequencies of MT dynamic parameters appear to be characteristic for a given cell type. We recently reported that all MT dynamic parameters vary throughout differentiation of a smooth muscle cell type in intact Caenorhabditis elegans. Here we describe local differences in MT dynamics and a novel MT behavior: an abrupt change in growth rate (deceleration) of single MTs occurring in the cell periphery of these cells. MT deceleration occurs where there is a decrease in local soluble tubulin concentration at the cell periphery. This local regulation of tubulin concentration and MT deceleration are dependent on two novel homologues of human cylicin. These novel ORFs, which we name cylc-1 and -2, share sequence homology with stathmins and encode small, very basic proteins containing several KKD/E repeats. The TOG domain–containing protein ZYG-9^TOGp is responsible for the faster polymerization rate within the cell body. Thus we have defined two contributors to the molecular regulation for this novel MT behavior.

Proteomic pattern changes associated with obesity-induced asthenozoospermia

Obesity, an increasingly frequent societal disease can also be accompanied by declines in spermatozoa quality and male subfecundity. To determine if there are obesity-associated proteomic changes potentially affecting sperm quality and motility, differential proteomic analysis was performed on spermatozoa from both obesity-associated asthenozoospermia and clinically healthy individuals, using a label-free quantitative LC-MS/MS approach. We resolved 1975 proteins in the human sperm proteome, amongst which, 105 proteins were less abundant, whereas 22 other proteins increased in obesity-associated asthenozoospermia. Functional category analyses indicated that the differentially expressed proteins are mainly related to cytoskeletal regulation, vesicle biogenesis, metabolism, and protein degradation involved in spermiogenesis and sperm motility. Furthermore, declines in endoplasmic reticulum protein 57 (ERp57) and actin-binding-related protein T2 (ACTRT2) expression were verified by immunofluorescence, Western blot, and flow cytometry analyses. It is evident that ERp57 is localized in the acrosome region, neck and principal piece of human spermatozoa, whereas ACTRT2 is localized in the post-acrosomal region and middle piece. Thus, these differences in protein expression in asthenozoospermia may contribute to the underlying sperm quality defects afflicting these individuals. Notably, declines in ERp57 and ACTRT2 expression in obesity-associated asthenozoospermia may play critical roles in reducing sperm motility.

Genome-wide association study for poor sperm motility in Holstein-Friesian bulls

The aim of the study was to screen the whole bull genome to identify markers and candidate genes underlying poor sperm motility. The analyzed data set originates from the Polish Holstein-Friesian bull population and consists of 41 Case and 279 Control bulls (selected from 1581 bulls). The most distinguishing trait of case group was very poor sperm motility (average 25.61%) when compared to control samples (average 72.95%). Each bull was genotyped using the Illumina BovineSNP50 BeadChip. Genome-wide association analysis was performed with the use of GoldenHelix SVS7 software. An additive model with a Cohran-Armitage test, Correlation/Trend adjusted by Bonferroni test were used to estimate the effect of Single Nucleotide Polymorphism (SNP) marker for poor sperm motility. Markers (n=34) reached genome-wide significance. The most significant SNP were located on chromosome 24 (rs110876480), 5 (rs110827324 and rs29011704), and 1 (rs110596818), in the close vicinity of melanocortin 4 receptor (MC4R), PDZ domain containing ring finger 4 (PDZRN4) and ethanolamine kinase 1 (ETNK1), olfactory receptor 5K3-like (LOC785875) genes, respectively. For five other candidate genes located close to significant markers (in distance of ca. 1 Mb), namely alkaline phosphatase, liver/bone/kidney (ALPL), tripartite motif containing 36 (TRIM36), 3-hydroxyisobutyrate dehygrogenase (HIBADH), kelch-like 1 (KLHL1), protein kinase C, beta (PRKCB), their potential role in sperm motility was confirmed in the earlier studies. Five additional candidate genes, cystic fibrosis transmembrane conductance regulator (CFTR), insulin-like growth factor 1 receptor (IGF1R), steroid-5-alpha-reductase, alpha polypeptide 2 (SRD5A2), cation channel, sperm associated 1 (CATSPER1) calpain 1 (mu/I) large subunit (CAPN1) were suggested to be significantly associated with sperm motility or semen biochemistry. Results of the present study indicate there is a genetic complexity of poor sperm motility but also indicate there might be a causal polymorphism useful in marker-assisted selection. Identifying genomic regions associated with poor sperm motility may be very important for early recognition of a young sire as unsuitable for effective semen production in artificial insemination centers.

The postacrosomal assembly of sperm head protein, PAWP, is independent of acrosome formation and dependent on microtubular manchette transport

PAWP (postacrosomal sheath WW domain-binding protein) exclusively resides in the postacrosomal sheath (PAS) of the sperm perinuclear theca (PT). Because of the importance of this region in initiating oocyte activation during mammalian fertilization [Sutovsky, P., Manandhar, G., Wu, A., Oko, R., 2003. Interactions of sperm perinuclear theca with the oocyte: implications for oocyte activation, anti-polyspermy defense, and assisted reproduction. Microsc. Res. Tech. 61, 362-378; Wu, A., Sutovsky, P., Manandhar, G., Xu, W., Katayama, M., Day, B.N., Park, K.W., Yi, Y.J., Xi, Y.W., Prather, R.S., Oko, R., 2007. PAWP, A sperm specific ww-domain binding protein, promotes meiotic resumption and pronuclear development during fertilization. J. Biol. Chem. 282, 12164-12175], we were interested in resolving the origin and assembly of its proteins during spermatogenesis, utilizing PAWP as a model. Based on previous PT developmental studies, we predicted that the assembly of PAWP is dependent on microtubule-manchette protein transport and manchette descent and independent of subacrosomal PT formation. Consequently, we hypothesized that PAWP will colocalize with manchette microtubules during spermiogenesis. Utilizing specific antibodies, PAWP was first detected in the cytoplasmic lobe of spermatids beginning to undergo elongation and became most prominent in this region just prior to and during manchette descent. During this peak period, PAWP was concentrated over the manchette and colocalized with alpha- and beta-tubulin. It was then assembled as part of the PAS in the wake of manchette descent over the caudal half of the elongated spermatid nucleus. PAWP mRNA, on the other hand, was first detected in mid-pachytene spermatocytes, peaked by early round spermatids, and declined during spermatid elongation. In order to confirm that PAWP-PAS assembly was independent of subacrosomal PT development, PAWP immunolocalization was performed on the testes of NB-DNJ-treated mice which fail to form an acrosome and subacrosomal layer during spermiogenesis [van der Spoel, A.C., Jeyakumar, M., Butters, T.D., Charlton, H.M., Moore, H.D., Dwek, R.A., Platt, F.M., 2002. Reversible infertility in male mice after oral administration of alkylated imino sugars: a nonhormonal approach to male contraception. Proc. Natl. Acad. Sci. U.S.A. 99, 17173-17178] but whose elongated spermatids still retain egg-activating ability [Suganuma, R., Walden, C.M., Butters, T.D., Platt, F.M., Dwek, R.A., Yanagimachi, R., and van der Spoel, A.C., 2005. Alkylated imino sugars, reversible male infertility-inducing agents, do not affect the genetic integrity of male mouse germ cells during short-term treatment despite induction of sperm deformities. Biol. Reprod. 72, 805-813]. The same temporal and manchette-based pattern of PAWP-PAS assembly during spermiogenesis was evident as in controls supporting our hypothesis that PAS assembly is independent of subacrosomal PT formation and that egg-activating ability resides within the PAS.

PAWP, a sperm-specific WW domain-binding protein, promotes meiotic resumption and pronuclear development during fertilization

We report a novel alkaline extractable protein of the sperm head that exclusively resides in the post-acrosomal sheath region of the perinuclear theca (PT) and is expressed and assembled in elongating spermatids. It is a protein that shares sequence homology to the N-terminal half of WW domain-binding protein 2, while the C-terminal half is unique and rich in proline. A functional PPXY consensus binding site for group-I WW domain-containing proteins, and numerous unique repeating motifs, YGXPPXG, are identified in the proline-rich region. Considering these molecular characteristics, we designated this protein PAWP for postacrosomal sheath WW domain-binding protein. Microinjection of recombinant PAWP or alkaline PT extract into metaphase II-arrested porcine, bovine, macaque, and Xenopus oocytes induced a high rate of pronuclear formation, which was prevented by co-injection of a competitive PPXY motif containing peptide derived from PAWP but not by co-injection of the point-mutated peptide. Intracytoplasmic sperm injection (ICSI) of porcine oocytes combined with co-injection of the competitive PPXY peptide or an anti-recombinant PAWP antiserum prevented pronuclear formation and arrested fertilization. Conversely, co-injection of the modified PPXY peptide, when the tyrosine residue of PPXY was either phosphorylated or substituted with phenylalanine, did not prevent ICSI-induced fertilization. This study uncovers a group I WW domain module signal transduction event within the fertilized egg that appears compulsory for meiotic resumption and pronuclear development during egg activation and provides compelling evidence that a PPXY motif of sperm-contributed PAWP can trigger these events.

Acrosome-specific gene AEP1: identification, characterization and roles in spermatogenesis

Spermatogenesis is a tightly regulated process leading to the development of spermatozoa. To elucidate the molecular spermatogenic mechanisms, we identified an acrosome-specific gene AEP1 in spermatids, which is located in rat chromosome 17p14 with a transcript size of 3,091 bp encoding a signal peptide, zinc finger-like motif, coiled-coil region, several predicted glycosylation and phosphorylation sites. Northern blot and RT-PCR analyses revealed the restricted expression of AEP1 to the testis only. In postnatal rat testes, AEP1 mRNA became detectable from postnatal 25 dpp (round spermatids) and onwards. By using in situ hybridization (ISH) and flow cytometry-fluorescent ISH, only the haploid spermatids yielded the positive AEP1 signal. Immunohistochemistry showed that AEP1 was expressed in the acrosomal cap of late-staged germ cells in rat testis, and co-localized with the acrosomal marker, peanut agglutinin. The spatial expression of AEP1 immunoreactivity in testis was conserved among diverse mammalian species (rat, pig, monkey, human). To further study its roles in spermatogenesis, we showed AEP1 and beta-actin was associated together in complex by co-immunoprecipitation in adult germ cells and by immunofluorescence assay in isolated spermatozoon. In human testes diagnosed with hypospermatogenesis, lower expression of AEP1 was observed, whereas there was no detectable signal in undescended testes. In short, AEP1 is an evolutionary-conserved acrosome-specific gene and likely functions in acrosome-cap formation.

Novel aspect of perinuclear theca assembly revealed by immunolocalization of non-nuclear somatic histones during bovine spermiogenesis

The perinuclear theca (PT) is an important accessory structure of the sperm head, yet its biogenesis is not well defined. To understand the developmental origins of PT-derived somatic histones during spermiogenesis, we used affinity-purified antibodies against somatic-type histones H3, H2B, H2A, and H4 to probe bovine testicular tissue using three different immunolocalization techniques. While undetectable in elongating spermatid nuclei, immunoperoxidase light microscopy showed all four somatic histones remained associated to the caudal head region of spermatids from steps 11 to 14 of the 14 steps in bovine spermiogenesis. Immunogold electron microscopy confirmed the localization of somatic histones on two nonnuclear structures, namely transient manchette microtubules of step-9 to step-11 spermatids and the developing postacrosomal sheath of step-13 and -14 spermatids. Immunofluorescence demonstrated somatic histone immunoreactivity in the developing postacrosomal sheath, and on anti-beta-tubulin decorated manchette microtubules of step-12 spermatids. Focal antinuclear pore complex labeling on the base of round spermatid nuclei was detected by electron microscopy and immunofluorescence, occurring before the nucleoprotein transition period during spermatid elongation. This indicated that, if nuclear histone export precedes their degradation, this process could only occur in this region, thereby questioning the proposed role of the manchette in nucleocytoplasmic trafficking. Somatic histone immunodetection on the manchette during postacrosomal sheath formation supports a role for the manchette in PT assembly, signifying that some PT components have origins in the distal spermatid cytoplasm. Furthermore, these findings suggest that somatic histones are de novo synthesized in late spermiogenesis for PT assembly.

Formation and organization of the mammalian sperm head

The formation and organization of a mammalian sperm head occurs through diverse cellular and molecular processes during spermiogenesis. Such cellular events include sequential changes in the nucleus and the acrosome-which is derived from the Golgi apparatus-in concert with prominent bundles of microtubules, the manchette. However, these complex processes are readily impaired by a variety of intrinsic and extrinsic factors, eventually causing various types of male infertility--such as teratozoospermia--which include the deformation of the acrosome and nucleus. In order to comprehend such idiopathic male infertility syndromes, it is important to clarify the mechanism involved in sperm head formation and organization. In addition to the manchette, two key structures in these events are the acroplaxome and the perinuclear theca. The acroplaxome forms the acrosome plate with periodic intermediate filament bundles of the marginal ring at the leading edge of the acrosome, and its nature has recently been characterized. The perinuclear theca, which is located in the perinuclear region in the sperm head, contains not only a cytoskeletal element to maintain the shape of the sperm head but also functional molecules leading to oocyte activation during fertilization. This review discusses recent developments regarding the formation and organization of the mammalian sperm head in relation to its relevant functions.