Spermatogenesis of mice lacking CK2alpha': failure of germ cell survival and characteristic modifications of the spermatid nucleus

Prevalence and Morphological Appearance of Sperm Nuclear Defects Using Feulgen Reaction in Beef Bulls

The objective of this study was to assess the prevalence and compare the morphological aspects of sperm nuclei abnormalities in beef bulls submitted to breeding soundness evaluation (BSE). Semen samples were collected by electroejaculation from 649 beef bulls (Bos indicus, n = 515 and Bos indicus × Bos taurus crossbreed, n = 134) ranging from 2 to 12 years of age. Following a clinical evaluation and semen assessment, a slide was prepared with fresh semen and stained by using the Feulgen-stain for the purpose of evaluating sperm and nuclear morphology. Abnormal sperm nuclei were classified into three categories: A, multiple vacuoles in a pouch-like formation; B, a single vacuole such as the nuclear crater/diadem defect; and C, abnormal chromatin condensation. In accordance with the BSE criteria, the animals were classified as either satisfactory or unsatisfactory potential breeders. The prevalence of nuclear defects was comparable between satisfactory bulls of both genotypes. Unsatisfactory Bos indicus bulls exhibited a higher frequency of A and B nuclear defect categories. A category presented an odds ratio of 7.14 (0.012) for unsatisfactory bulls. A low percentage of the C category (2.3%) was observed in both BSE classifications. Vacuoles or craters were predominantly observed in the post-acrosomal and mid-subacrosomal regions, with minimal occurrence in the apical ridge region. Our findings provide the baseline for nuclear defects in B. indicus and its crossbreeds. The Feulgen reaction thus enables a simple yet comprehensive analysis of nuclear sperm head defects during BSE. In addition, stain retention facilitates a practical evaluation and an accurate account of the nuclear lesion types.

Bovine Spermatogenesis

The intent of this chapter is to provide a morphological foundation in the normal cellular process of bovine gamete development so that abnormalities occurring are recognizable. The knowledge gained here is essential to begin to understand the significance of many of the common bull sperm abnormalities encountered in the clinics. Spermatogenesis is divided into three phases (i. e., Mitosis, Meiosis and Spermiogenesis) all happening in the seminiferous epithelium. The 'Cycle of the Bovine Seminiferous Epithelium' is explained in relation to these phases. Information is provided as to how to identify the stages of the bovine cycle and the steps of spermiogenesis at the histological and ultrastructural levels in preparation to recognize where and when in the cycle a spermatid abnormality arises. Spermiogenesis, the last phase of spermatogenesis, is the most revealing phase to recognize gamete abnormalities as this is where spermatid head and tail differentiation take place and spermatid compartments materialize. The formation of the nucleus, acrosome, manchette, perinuclear theca, axoneme, outer dense fibers, fibrous sheath, connecting piece and mitochondrial sheath occur during this phase and are evaluated. The origins and assembly of a number of essential proteins compartmentalizing the sperm head and tail as well as defects arising during spermiogenesis are reviewed.

In Skeletal Muscle Fibers, Protein Kinase Subunit CSNK2A1/CK2α Is Required for Proper Muscle Homeostasis and Structure and Function of Neuromuscular Junctions

CSNK2 tetrameric holoenzyme is composed of two subunits with catalytic activity (CSNK2A1 and/or CSNK2A2) and two regulatory subunits (CSNK2B) and is involved in skeletal muscle homeostasis. Up-to-date, constitutive Csnk2a2 knockout mice demonstrated mild regenerative impairments in skeletal muscles, while conditional Csnk2b mice were linked to muscle weakness, impaired neuromuscular transmission, and metabolic and autophagic compromises. Here, for the first time, skeletal muscle-specific conditional Csnk2a1 mice were generated and characterized. The ablation of Csnk2a1 expression was ensured using a human skeletal actin-driven Cre reporter. In comparison with control mice, first, conditional knockout of CSNK2A1 resulted in age-dependent reduced grip strength. Muscle weakness was accompanied by impaired neuromuscular transmission. Second, the protein amount of other CSNK2 subunits was aberrantly changed. Third, the number of central nuclei in muscle fibers indicative of regeneration increased. Fourth, oxidative metabolism was impaired, reflected by an increase in cytochrome oxidase and accumulation of mitochondrial enzyme activity underneath the sarcolemma. Fifth, autophagic processes were stimulated. Sixth, NMJs were fragmented and accompanied by increased synaptic gene expression levels. Altogether, knockout of Csnk2a1 or Csnk2b results in diverse impairments of skeletal muscle biology.

Effects of water-soluble curcuminoid-rich extract in a solid dispersion form (CRE-SD) on the sperm characteristics, longevity and casein kinase II catalytic subunit alpha protein stability in chilled goat semen

The present study evaluated the effects of water-soluble curcuminoid-rich extract in a solid dispersion form (CRE-SD) on goat sperm qualities and sperm protein CSNK2A2 expression during liquid storage. Semen was collected from five fertile goats, using an artificial vagina. Ejaculates with a motility above 70% were cooled to 4 °C using TRIS-citric acid-fructose diluent with 10% egg yolk containing various concentrations of CRE-SD (0, 0.1, 1, 10 and 100 μg/mL). Chilled sperm were evaluated for sperm characteristics, casein kinase II catalytic subunit alpha (CSNK2A2) protein level and oxidative status up to 15 days. After 12 days of preservation, sperm motility, viability, acrosomal integrity and mitochondrial activity were significantly higher in the group preserved with 10 μg/mL CRE-SD as compared with the control group. Supplementation of CRE-SD at this concentration was also able to conserve the CSNK2A2 a significantly higher than that in control group until 9 days of cold storage, possibly by reducing oxidative stress. The molecular mass of the sperm CSNK2A2 protein detected in this study was 37 kDa; it was mostly located in the post-acrosomal region, midpiece and flagellum. These results demonstrate the possibility to use the CRE-SD as a natural antioxidant during liquid semen storage in goats.

The Role of Protein Kinase CK2 in Development and Disease Progression: A Critical Review

Protein kinase CK2 (CK2) is a ubiquitous holoenzyme involved in a wide array of developmental processes. The involvement of CK2 in events such as neurogenesis, cardiogenesis, skeletogenesis, and spermatogenesis is essential for the viability of almost all organisms, and its role has been conserved throughout evolution. Further into adulthood, CK2 continues to function as a key regulator of pathways affecting crucial processes such as osteogenesis, adipogenesis, chondrogenesis, neuron differentiation, and the immune response. Due to its vast role in a multitude of pathways, aberrant functioning of this kinase leads to embryonic lethality and numerous diseases and disorders, including cancer and neurological disorders. As a result, CK2 is a popular target for interventions aiming to treat the aforementioned diseases. Specifically, two CK2 inhibitors, namely CX-4945 and CIBG-300, are in the early stages of clinical testing and exhibit promise for treating cancer and other disorders. Further, other researchers around the world are focusing on CK2 to treat bone disorders. This review summarizes the current understanding of CK2 in development, the structure of CK2, the targets and signaling pathways of CK2, the implication of CK2 in disease progression, and the recent therapeutics developed to inhibit the dysregulation of CK2 function in various diseases.

Zona Pellucida sperm-binding protein 3 receptor distribution during Gopc-/- globozoospermic spermatogenesis

Globozoospermia is a type of teratozoospermia characterized by round morphology of the sperm head. Gopc^-/- infertile globozoospermic murine model has failures during spermiogenesis, such as the incorrect biogenesis of the acrosome, disorganized acroplaxome and manchette, round nuclei and spiral flagella. In this study, Western blot, RT-PCR, immunohistochemistry and immunogold were done for the localization of the acrosome protein Zona Pellucida sperm-binding protein 3 receptor (ZP3R), also called sp56, in wild type and Gopc^-/- mice testis. The ZP3R protein was located in the acrosome and pseudo-acrosome vesicles of wild type and Gopc^-/- mice, respectively. Also, it is distributed through the cytoplasm of the haploid spermatids only. The incorrect spermiogenesis of Gopc^-/- mice causes a deregulation in the expression of ZP3R in the globozoospermic spermatids. Our results suggest that although the lack of GOPC causes a failure during the transport of the pre-acrosomal vesicles, the acrosome protein ZP3R is localized in the acrosome and is distributed through the cytoplasm only during spermiogenesis. Furthermore, the failure in spermiogenesis does not impair the synthesis of ZP3R and its localization in the pre-acrosomal vesicles.

The molecular mechanisms underlying acrosome biogenesis elucidated by gene-manipulated mice

Sexual reproduction requires the fusion of two gametes in a multistep and multifactorial process termed fertilization. One of the main steps that ensures successful fertilization is acrosome reaction. The acrosome, a special kind of organelle with a cap-like structure that covers the anterior portion of sperm head, plays a key role in the process. Acrosome biogenesis begins with the initial stage of spermatid development, and it is typically divided into four successive phases: the Golgi phase, cap phase, acrosome phase, and maturation phase. The run smoothly of above processes needs an active and specific coordination between the all kinds of organelles (endoplasmic reticulum, trans-golgi network and nucleus) and cytoplasmic structures (acroplaxome and manchette). During the past two decades, an increasingly genes have been discovered to be involved in modulating acrosome formation. Most of these proteins interact with each other and show a complicated molecular regulatory mechanism to facilitate the occurrence of this event. This Review focuses on the progresses of studying acrosome biogenesis using gene-manipulated mice and highlights an emerging molecular basis of mammalian acrosome formation.

Identification of ceRNA and candidate genes related to fertility conversion of TCMS line YS3038 in wheat

Previous studies have indicated that noncoding RNAs are important factors in gene functions. To explore the mechanism of male sterility of YS3038, the sterile genes were mapped, and based on previous work, the expression of long noncoding RNAs (lncRNAs), circular RNAs (circRNAs), and their target genes was studied. Weighted gene coexpression network analysis (WGCNA) and competitive endogenous RNA (ceRNA) analysis were further performed for differentially expressed noncoding RNAs and target genes. At last, the candidate genes were silenced by barley stripe mosaic virus-induced gene silencing (BSMV-VIGS) to prove their function. The sterile genes were mapped on chromosomes 1B and 6B based on chip mix pool analysis, and one major effect QTL (27.3190% variation) was found based on SSR primers. The WGCNA analysis revealed that the dark turquoise and steel blue modules were highly correlated with anther development and fertility conversion, respectively. The ceRNA analysis showed that a total of 184 RNAs interacted with each other, including 115 mRNAs, 55 microRNAs (miRNAs), eight circRNAs, and six lncRNAs. Finally, the seed setting rate of the plant was significantly decreased after fatty acyl-CoA reductase 5 silencing. This study provides breeders with a new option for the development of thermosensitive cytoplasmic male-sterile (TCMS) wheat lines, which will favor the sustainable development of two-line hybrid wheat.

Biophysical Characterization and Anticancer Activities of Photosensitive Phytoanthraquinones Represented by Hypericin and Its Model Compounds

Photosensitive compounds found in herbs have been reported in recent years as having a variety of interesting medicinal and biological activities. In this review, we focus on photosensitizers such as hypericin and its model compounds emodin, quinizarin, and danthron, which have antiviral, antifungal, antineoplastic, and antitumor effects. They can be utilized as potential agents in photodynamic therapy, especially in photodynamic therapy (PDT) for cancer. We aimed to give a comprehensive summary of the physical and chemical properties of these interesting molecules, emphasizing their mechanism of action in relation to their different interactions with biomacromolecules, specifically with DNA.

Protein kinase 2 (CK2): a potential regulator of immune cell development and function in cancer

Protein kinase CK2, formally known as casein kinase II, is ubiquitously expressed and highly conserved serine/threonine or tyrosine kinase enzyme that regulates diverse signaling pathways responsible for cellular processes (i.e., cell proliferation and apoptosis) via interactions with over 500 known substrates. The enzyme's physiological interactions and cellular functions have been widely studied, most notably in the blood and solid malignancies. CK2 has intrinsic role in carcinogenesis as overexpression of CK2 subunits (α, α`, and β) and deregulation of its activity have been linked to various forms of cancers. CK2 also has extrinsic role in cancer stroma or in the tumor microenvironment (TME) including the immune cells. However, very few research studies have focused on extrinsic role of CK2 in regulating immune responses as a therapeutic alternative for cancer. The following review discusses CK2's regulation of key signaling events [Nuclear factor kappa B (NF-κB), Janus kinase/signal transducer and activators of transcription (JAK/STAT), Hypoxia inducible factor-1alpha (HIF-1α), Cyclooygenase-2 (COX-2), Extracellular signal-regulated kinase/mitogen-activated protein kinase (ERK/MAPK), Notch, Protein kinase B/AKT, Ikaros and Wnt] that can influence the development and function of immune cells in cancer. Potential clinical trials using potent CK2 inhibitors will facilitate and improve the treatment of human malignancies.

Chronic arsenic exposure lowered sperm motility via impairing ultra-microstructure and key proteins expressions of sperm acrosome and flagellum formation during spermiogenesis in male mice

Arsenic (As) poisoning and its potential reproductive functional lesions are a global environmental concern. Recent studies shown that spermiogenesis tends to be a major target process in arsenic-induced male infertility, however, the underlying mechanisms are not fully illuminated. In the present study, 32 fertility related indices including sperm motility, dynamic acrosome formation and sperm flagellum during spermiogenesis in testes were evaluated in adult male mice treated with 0, 0.2, 2, and 20 ppm As₂O₃ via drinking water for 180 consecutive days. The results showed that out of 32 indices, 11, 25, and 29 indicators were changed statistically by 0.2-, 2-, and 20- ppm As₂O₃ treatment compared to the controls (0 ppm As₂O₃), respectively, which reveals a significant dose-dependent relationship. For details, sperm motilities were significantly decreased by 18.85%, 32.47% and 29.53% in three As₂O₃ treatment groups compared to the control group. Meanwhile, the ultra-structures of acrosome formation and sperm flagellum in testes have been altered by chronic arsenic exposure. Furthermore, arsenic decreased the mRNA expressions of 11 out of 13 genes associated with acrosome biosynthesis and 11 out of 12 genes related to flagellum formation in testes, particularly, down-regulated DPY19L2, AKAP3, AKAP4, CFAP44 and SPAG16 were further confirmed at the protein levels by western blotting. Taken together, chronic arsenic exposure declines male fertility by disorganizing dynamic acrosome and flagellum formation in testes. Especially, DPY19L2, AKAP3, AKAP4, CFAP44, and SPAG16 maybe the potential targets in this process. These results may offer not only a new insight to the mechanism of arsenic-induced male reproductive toxicity, but also provide a clue for the diagnosis and therapy of arseniasis.

Casein kinase 2 modulates the spindle assembly checkpoint to orchestrate porcine oocyte meiotic progression

Background

CK2 (casein kinase 2) is a serine/threonine-selective protein kinase that has been involved in a variety of cellular processes such as DNA repair, cell cycle control and circadian rhythm regulation. However, its functional roles in oocyte meiosis have not been fully determined.

Results

We report that CK2 is essential for porcine oocyte meiotic maturation by regulating spindle assembly checkpoint (SAC). Immunostaining and immunoblotting analysis showed that CK2 was constantly expressed and located on the chromosomes during the entire oocyte meiotic maturation. Inhibition of CK2 activity by its selective inhibitor CX-4945 impaired the first polar body extrusion and arrested oocytes at M I stage, accompanied by the presence of BubR1 at kinetochores, indicative of activated SAC. In addition, we found that spindle/chromosome structure was disrupted in CK2-inhibited oocytes due to the weakened microtubule stability, which is a major cause resulting in the activation of SAC. Last, we found that the level DNA damage as assessed by γH2A.X staining was considerably elevated when CK2 was inhibited, suggesting that DNA damage might be another critical factor leading to the SAC activation and meiotic failure of oocytes.

Conclusions

Our findings demonstrate that CK2 promotes the porcine oocyte maturation by ensuring normal spindle assembly and DNA damage repair.

HIPK4 is essential for murine spermiogenesis

Mammalian spermiogenesis is a remarkable cellular transformation, during which round spermatids elongate into chromatin-condensed spermatozoa. The signaling pathways that coordinate this process are not well understood, and we demonstrate here that homeodomain-interacting protein kinase 4 (HIPK4) is essential for spermiogenesis and male fertility in mice. HIPK4 is predominantly expressed in round and early elongating spermatids, and Hipk4 knockout males are sterile, exhibiting phenotypes consistent with oligoasthenoteratozoospermia. Hipk4 mutant sperm have reduced oocyte binding and are incompetent for in vitro fertilization, but they can still produce viable offspring via intracytoplasmic sperm injection. Optical and electron microscopy of HIPK4-null male germ cells reveals defects in the filamentous actin (F-actin)-scaffolded acroplaxome during spermatid elongation and abnormal head morphologies in mature spermatozoa. We further observe that HIPK4 overexpression induces branched F-actin structures in cultured fibroblasts and that HIPK4 deficiency alters the subcellular distribution of an F-actin capping protein in the testis, supporting a role for this kinase in cytoskeleton remodeling. Our findings establish HIPK4 as an essential regulator of sperm head shaping and potential target for male contraception.

Deletion of Ck2β gene causes germ cell development arrest and azoospermia in male mice

Objectives

In humans, non‐obstructive azoospermia (NOA) is a major cause of male infertility. However, the aetiology of NOA is largely unknown. Previous studies reported that protein CK2β was abundantly and broadly expressed in spermatogenic cells. Here, we investigate whether protein CK2β participates in spermatogenesis.

Materials and Methods

In this study, we separated spermatogenic cells using STA‐PUT velocity sedimentation, analysed the expression pattern of protein CK2β by immunoblotting, specifically deleted Ck2β gene in early‐stage spermatogenic cells by crossing Ck2β^fl mice with Stra8‐Cre⁺ mice and validated the knockout efficiency by quantitative RT‐PCR and immunoblotting. The phenotypes of Ck2β^fl/Δ;SCre⁺ mice were studied by immunohistochemistry and immunofluorescence. The molecular mechanisms of male germ cell development arrest were elucidated by immunoblotting and TUNEL assay.

Results

Ablation of Ck2β gene triggered excessive germ cell apoptosis, germ cell development arrest, azoospermia and male infertility. Inactivation of Ck2β gene caused distinctly reduced expression of Ck2α′ gene and CK2α′ protein.

Conclusions

Ck2β is a vital gene for germ cell survival and male fertility in mice.

Increase of germ cell nuclear factor expression in globozoospermic Gopc-/- knockout mice

BACKGROUND

Golgi-associated PDZ and coiled-coil motif-containing protein (GOPC) is a Golgi protein that plays a role in vesicular transport and intracellular protein trafficking and degradation. Mice deficient in GOPC protein have globozoospermia and are infertile. The germ cell nuclear factor (GCNF) is a member of the nuclear receptor superfamily which is expressed in male germ cells, from spermatocytes and spermatids, both in the nucleus and the acrosomal region. It is not known if its expression could be altered in Gopc^-/- mice with defective acrosomes.

OBJECTIVES

The aim of the present work was to analyze the distribution of GCNF protein in spermatids of Gopc^-/- knockout mice.

MATERIALS AND METHODS

We have analyzed the expression and distribution during spermatogenesis of GCNF and its deregulation in Gopc^-/- mutant mice by RT-qPCR, Western blot, immunohistochemistry and immunogold.

RESULTS

Germ cell nuclear factor was localized in the nucleus of all the cell types in the seminiferous tubules. Despite being a nuclear protein, it was also located in the acrosome and in the manchette of elongating spermatids. We have found that in the absence of GOPC, the expression of GCNF was increased in the nucleus of spermatocytes, mainly in leptotene, and in the nucleus and the manchette during the spermatid elongation.

DISCUSSION AND CONCLUSION

Gopc^-/- mice have defective acrosome and manchette. The manchette is involved in the transport of proteins through the cytoplasm and the nucleus. Considering that the GCNF protein is normally transported to the acrosome and the nucleus, it can be thought that transport deficiencies in Gopc^-/- mice are responsible for the increased expression of this protein.

m6A mRNA modification regulates mammalian spermatogenesis

Mammalian spermatogenesis is a highly specialized differentiation process involving precise regulatory mechanisms at the transcriptional, posttranscriptional, and translational levels. Emerging evidence has shown that N⁶-methyladenosine (m⁶A), an epitranscriptomic regulator of gene expression, can influence pre-mRNA splicing, mRNA export, turnover, and translation, which are controlled in the male germline to ensure coordinated gene expression. In this review, we summarize the typical features of m⁶A RNA modification on mRNA during male germline development, and highlight the function of writers, erasers, and readers of m⁶A during mouse spermatogenesis.

Ablation of beta subunit of protein kinase CK2 in mouse oocytes causes follicle atresia and premature ovarian failure

Premature ovarian failure (POF), a major cause of female infertility, is a complex disorder, but the molecular mechanisms underlying the disorder are only poorly understood. Here we report that protein kinase CK2 contributes to maintaining follicular survival through PI3K/AKT pathway and DNA damage response pathway. Targeted deletion of CK2β in mouse oocytes from the primordial follicle stage resulted in female infertility, which was attributed to POF incurring by massive follicle atresia. Downregulated PI3K/AKT signaling was found after CK2β deletion, indicated by reduced level of phosphorylated AKT (S473, T308, and S129) and altered AKT targets related to cell survival. Further studies discovered that CK2β-deficient oocytes showed enhanced γH2AX signals, indicative of accumulative unrepaired DSBs, which activated CHK2-dependant p53 and p63 signaling. The suppressed PI3K/AKT signaling and failed DNA damage response signaling probably contribute to large-scale oocyte loss and eventually POF. Our findings provide important new clues for elucidating the mechanisms underlying follicle atresia and POF.

The protein kinase CK2 substrate Jabba modulates lipid metabolism during Drosophila oogenesis

Lipid metabolism plays a critical role in female reproduction. During oogenesis, maturing oocytes accumulate high levels of neutral lipids that are essential for both energy production and the synthesis of other lipid molecules. Metabolic pathways within the ovary are partially regulated by protein kinases that link metabolic status to oocyte development. Although the functions of several kinases in this process are well established, the roles that many other kinases play in coordinating metabolic state with female germ cell development are unknown. Here, we demonstrate that the catalytic activity of casein kinase 2 (CK2) is essential for Drosophila oogenesis. Using an unbiased biochemical screen that leveraged an unusual catalytic property of the kinase, we identified a novel CK2 substrate in the Drosophila ovary, the lipid droplet-associated protein Jabba. We show that Jabba is essential for modulating ovarian lipid metabolism and for regulating female fertility in the fly. Our findings shed light on a CK2-dependent signaling pathway governing lipid metabolism in the ovary and provide insight into the long-recognized but poorly understood association between energy metabolism and female reproduction.

Ablation of Protein Kinase CK2β in Skeletal Muscle Fibers Interferes with Their Oxidative Capacity

The tetrameric protein kinase CK2 was identified playing a role at neuromuscular junctions by studying CK2β-deficient muscle fibers in mice, and in cultured immortalized C2C12 muscle cells after individual knockdown of CK2α and CK2β subunits. In muscle cells, CK2 activity appeared to be at least required for regular aggregation of nicotinic acetylcholine receptors, which serves as a hallmark for the presence of a postsynaptic apparatus. Here, we set out to determine whether any other feature accompanies CK2β-deficient muscle fibers. Hind limb muscles gastrocnemius, plantaris, and soleus of adult wildtype and CK2β-deficient mice were dissected, cross-sectioned, and stained histochemically by Gomori trichrome and for nicotinamide adenine dinucleotide (NADH) dehydrogenase and succinate dehydrogenase (SDH) enzymatic activities. A reduction of oxidative enzymatic activity was determined for CK2β-deficient muscle fibers in comparison with wildtype controls. Importantly, the CK2β-deficient fibers, muscle fibers that typically exhibit high NADH dehydrogenase and SDH activities, like slow-type fibers, showed a marked reduction in these activities. Altogether, our data indicate additional impairments in the absence of CK2β in skeletal muscle fibers, pointing to an eventual mitochondrial myopathy.

Protein kinase CK2 in development and differentiation

Among the human kinomes, protein kinase CK2 (formerly termed casein kinase II) is considered to be essential, as it is implicated in the regulation of various cellular processes. Experiments with pharmacological inhibitors of the kinase activity of CK2 provide evidence that CK2 is essential for development and differentiation. Therefore, the present review addresses the role of CK2 during embryogenesis, neuronal, adipogenic, osteogenic and myogenic differentiation in established model cell lines, and in embryonic, neural and mesenchymal stem cells. CK2 kinase activity appears to be essential in the early stages of differentiation, as CK2 inhibition at early time points generally prevents differentiation. In addition, the present review reports on target proteins of CK2 in embryogenesis and differentiation.

Toward selective CK2alpha and CK2alpha' inhibitors: Development of a novel whole-cell kinase assay by Autodisplay of catalytic CK2alpha'

Human protein kinase CK2 is an emerging target for the development of novel anti-cancer therapeutics. CK2 is a tetramer composed of two catalytically active α- and/or α'-subunits, bound to a dimer of the regulatory β-subunit. Inhibitors targeting one of the two isoforms of the catalytically active CK2-subunit (α- and α') are important to study the distinct functions of these isoforms toward different CK2 associated pathologies. The present study for the first time describes the successful Autodisplay of the CK2α'-subunit, the paralogous isoform of CK2α. Expression on the cell surface of E. coli of CK2α' alone and in combination with the regulatory CK2β-subunit was confirmed by outer membrane isolation and protease accessibility test. Kinase activity of surface displayed CK2 could be detected with a CE-based assay and was found to be 3.06×10(-6) μmol/min for CK2α' alone and 1.02×10(-5) μmol/min when expressed in combination with CK2β. The comparison of the influence of NaCl on activity of the α'-subunit alone and in combination with the non-catalytically active β-subunit indicated interaction of both subunits on the cell surface. TMCB (4,5,6,7-tetrabromo-2-(dimethylamino)-1H-benzo[d]imidazol-1-yl)acetic acid), a known CK2 inhibitor described with distinct Ki values of 83 nM and 21 nM for the two different catalytic CK2 subunits α and α' was used for testing. First, inhibition of TMCB toward the purified CK2 holoenzyme CK2α2β2 was determined and resulted in a Ki value of 10.1 nM. Second, Ki values were determined with the surface displayed isoform CK2 holoenzymes and turned out to be of 31.1 nM for CK2α2β2 and 19.6 nM for CK2α'2β2. The inhibition data as obtained represented the distinct affinities of TMCB toward the two isoform holoenzymes. This indicated, that the surface display of CKα and CK2α', in the context of the corresponding holoenzymes, can be used to identify selective compounds. A set of twelve ATP competitive CK2 inhibitors with an indeno[1,2-b]indole scaffold was tested in order to demonstrate suitability for this application.

Ultrastructural Morphology of Sperm from Human Globozoospermia

Globozoospermia is a rare disorder characterized by the presence of sperm with round head, lacking acrosome. Coiling tail around the nucleus has been reported since early human studies, but no specific significance has conferred it. By contrast, studies on animal models suggest that coiling tail around the nucleus could represent a crucial step of defective spermatogenesis, resulting in round-headed sperm. No observations, so far, support the transfer of this hypothesis to human globozoospermia. The purpose of this work was to compare ultrastructural morphology of human and mouse model globozoospermic sperm. Sperm have been investigated by using scanning and transmission electron microscopy. The images that we obtained show significant similarities to those described in GOPC knockout mice, an animal model of globozoospermia. By using this model as reference, we were able to identify the probable steps of the tail coiling process in human globozoospermia. Although we have no evidence that there is the same pathophysiology in man and knocked-out mouse, the similarities between these ultrastructural observations in human and those in the experimental model are very suggestive. This is the first demonstration of the existence of relevant morphological homologies between the tail coiling in animal model and human globozoospermia.

Accumulation of glucosylceramide in the absence of the beta-glucosidase GBA2 alters cytoskeletal dynamics

Glycosphingolipids are key elements of cellular membranes, thereby, controlling a variety of cellular functions. Accumulation of the simple glycosphingolipid glucosylceramide results in life-threatening lipid storage-diseases or in male infertility. How glucosylceramide regulates cellular processes is ill defined. Here, we reveal that glucosylceramide accumulation in GBA2 knockout-mice alters cytoskeletal dynamics due to a more ordered lipid organization in the plasma membrane. In dermal fibroblasts, accumulation of glucosylceramide augments actin polymerization and promotes microtubules persistence, resulting in a higher number of filopodia and lamellipodia and longer microtubules. Similar cytoskeletal defects were observed in male germ and Sertoli cells from GBA2 knockout-mice. In particular, the organization of F-actin structures in the ectoplasmic specialization and microtubules in the sperm manchette is affected. Thus, glucosylceramide regulates cytoskeletal dynamics, providing mechanistic insights into how glucosylceramide controls signaling pathways not only during sperm development, but also in other cell types.

During mammalian spermatogenesis, sperm with a head and a tail are formed from a round cell. This process is tightly regulated and involves the close interaction of somatic Sertoli cells and germ cells. Accumulation of the glycosphingolipid glucosylceramide in the absence of the beta-glucosidase GBA2 has been proposed to disturb sperm development, leading to morphological defects. However, the underlying mechanism is not known. Here, we demonstrate that accumulation of glucosylceramide in GBA2 knockout-mice controls the dynamics of the actin and microtubule cytoskeleton, which are crucial for sperm development. In particular, cytoskeletal structures at the interface between Sertoli and germ cells are disorganized, leading to malformation of the sperm head and a defect in acrosome formation. In summary, we provide mechanistic insights into how glucosylceramide controls cellular signaling and dysregulation of this essential glycosphingolipid leads to male infertility.

Synthesis, biological activity and structural study of new benzotriazole-based protein kinase CK2 inhibitors

A new series of TBB-derivatives was synthesized and characterized as CK2 inhibitors. Crystallographic analysis and docking studies were used to understand the mode of binding.

A mutation study of sperm head shape and motility in the mouse: lessons for the clinic

Mouse mutants that show effects on sperm head shape, the sperm tail (flagellum), and motility were analysed in a systematic way. This was achieved by grouping mutations in the following classes: manchette, acrosome, Sertoli cell contact, chromatin remodelling, and mutations involved in complex regulations such as protein (de)phosphorylation and RNA stability, and flagellum/motility mutations. For all mutant phenotypes, flagellum function (motility) was affected. Head shape, including the nucleus, was also affected in spermatozoa of most mouse models, though with considerable variation. For the mutants that were categorized in the flagellum/motility group, generally normal head shapes were found, even when the flagellum did not develop or only poorly so. Most mutants are sterile, an occasional one semi-sterile. For completeness, the influence of the sex chromosomes on sperm phenotype is included. Functionally, the genes involved can be categorized as regulators of spermiogenesis. When extrapolating these data to human sperm samples, in vivo selection for motility would be the tool for weeding out the products of suboptimal spermiogenesis and epididymal sperm maturation. The striking dependency of motility on proper sperm head development is not easy to understand, but likely is of evolutionary benefit. Also, sperm competition after mating can never act against the long-term multi-generation interest of genetic integrity. Hence, it is plausible to suggest that short-term haplophase fitness i.e., motility, is developmentally integrated with proper nucleus maturation, including genetic integrity to protect multi-generation fitness. We hypothesize that, when the prime defect is in flagellum formation, apparently a feedback loop was not necessary as head morphogenesis in these mutants is mostly normal. Extrapolating to human-assisted reproductive techniques practice, this analysis would supply the arguments for the development of tools to select for motility as a continuous (non-discrete) parameter.

Emodin inhibits human sperm functions by reducing sperm [Ca(2+)]i and tyrosine phosphorylation

Emodin, a bioactive anthraquinone widely used in Chinese traditional medicine, disrupts mouse testicular gene expression in vivo. In this study, we investigated the toxicity of emodin to human sperm in vitro. Different doses of emodin (25, 50, 100, 200 and 400μM) were applied to ejaculated human sperm. The results indicated that 100, 200 and 400μM emodin significantly inhibited the total motility, progressive motility and linear velocity of human sperm. In addition, sperm's ability to penetrate viscous medium together with progesterone induced capacitation and acrosome reaction was also adversely affected by emodin. In contrast, emodin did not affect sperm viability. Furthermore, intracellular Ca(2+) concentration ([Ca(2+)]i) and tyrosine phosphorylation, which serve as key regulators of sperm function, were dose-dependently reduced by emodin (50-400μM). These results suggest that emodin inhibits human sperm functions by reducing sperm [Ca(2+)]i and suppressing tyrosine phosphorylation in vitro.

Iqcg is essential for sperm flagellum formation in mice

Mammalian spermatogenesis comprises three successive phases: mitosis phase, meiosis phase, and spermiogenesis. During spermiogenesis, round spermatid undergoes dramatic morphogenesis to give rise to mature spermatozoon, including the condensation and elongation of nucleus, development of acrosome, formation of flagellum, and removal of excessive cytoplasm. Although these transformations are well defined at the morphological level, the mechanisms underlying these intricate processes are largely unknown. Here, we report that Iqcg, which was previously characterized to be involved in a chromosome translocation of human leukemia, is highly expressed in the spermatogenesis of mice and localized to the manchette in developing spermatids. Iqcg knockout causes male infertility, due to severe defects of spermiogenesis and resultant total immobility of spermatozoa. The axoneme in the Iqcg knockout sperm flagellum is disorganized and hardly any typical (“9+2”) pattern of microtubule arrangement could be found in Iqcg knockout spermatids. Iqcg interacts with calmodulin in a calcium dependent manner in the testis, suggesting that Iqcg may play a role through calcium signaling. Furthermore, cilia structures in the trachea and oviduct, as well as histological appearances of other major tissues, remain unchanged in the Iqcg knockout mice, suggesting that Iqcg is specifically required for spermiogenesis in mammals. These results might also provide new insights into the genetic causes of human infertility.

The lysine-specific demethylase 1 is a novel substrate of protein kinase CK2

Protein kinase CK2 is a pleiotropic serine/threonine kinase responsible for the generation of a substantial proportion of the human phosphoproteome. CK2 is generally found as a tetramer with two catalytic, α and α' and two non catalytic β subunits. CK2α C-terminal tail phosphorylation is regulated during the mitotic events and the absence of these phosphosites in α' suggests an isoform specialization. We used a proteomic approach to identify proteins specifically phosphorylated by a CK2α phosphomimetic mutant, CK2αT344ET360ES362ES370E (CK2α4E), in human neuroblastoma SKNBE cellular extract. One of these proteins is lysine-specific demethylase 1 (LSD1 or KDM1A), an important player of the epigenetic machinery. LSD1 is a FAD-dependent amine oxidase and promotes demethylation of lysine 4 and lysine 9 of mono- and di-methylated histone H3. We found that LSD1 is a new substrate and an interacting partner of protein kinase CK2. Three CK2 phosphosites, (Ser131, Ser137 and Ser166) in the N-terminal region of LSD1 have been identified. This domain is found in all chordates but not in more ancient organisms and it is not essential for LSD1 catalytic event while it could modulate the interaction with CK2 and with other partners in gene repressing and activating complexes. Our data support the view that the phosphorylation of the N-terminal domain by CK2 may represent a mechanism for regulating histone methylation, disclosing a new role for protein kinase CK2 in epigenetics.

Heat shock protein 90 functions to stabilize and activate the testis-specific serine/threonine kinases, a family of kinases essential for male fertility

Spermiogenesis is characterized by a profound morphological differentiation of the haploid spermatid into spermatozoa. The testis-specific serine/threonine kinases (TSSKs) comprise a family of post-meiotic kinases expressed in spermatids, are critical to spermiogenesis, and are required for male fertility in mammals. To explore the role of heat shock protein 90 (HSP90) in regulation of TSSKs, the stability and catalytic activity of epitope-tagged murine TSSKs were assessed in 293T and COS-7 cells. TSSK1, -2, -4, and -6 (small serine/threonine kinase) were all found to associate with HSP90, and pharmacological inhibition of HSP90 function using the highly specific drugs 17-AAG, SNX-5422, or NVP-AUY922 reduced TSSK protein levels in cells. The attenuation of HSP90 function abolished the catalytic activities of TSSK4 and -6 but did not significantly alter the specific activities of TSSK1 and -2. Inhibition of HSP90 resulted in increased TSSK ubiquitination and proteasomal degradation, indicating that HSP90 acts to control ubiquitin-mediated catabolism of the TSSKs. To study HSP90 and TSSKs in germ cells, a mouse primary spermatid culture model was developed and characterized. Using specific antibodies against murine TSSK2 and -6, it was demonstrated that HSP90 inhibition resulted in a marked decrease of the endogenous kinases in spermatids. Together, our findings demonstrate that HSP90 plays a broad and critical role in stabilization and activation of the TSSK family of protein kinases.

Galnt3 deficiency disrupts acrosome formation and leads to oligoasthenoteratozoospermia

Galnt3 belongs to the GalNAc transferase gene family involved in the initiation of mucin-type O-glycosylation. Male Galnt3-deficient (Galnt3(-/-)) mice were infertile, as previously reported by Ichikawa et al. (2009). To investigate the involvement of Galnt3 in spermatogenesis, we examined the differentiation of germ cells in Galnt3(-/-) mice. Galnt3 mRNA was most highly expressed in testis, and Galnt3 protein was localized in the cis-medial parts of the Golgi stacks of spermatocytes and spermatids in the seminiferous tubules. Spermatozoa in Galnt3(-/-) mice were rare and immotile, and most of them had deformed round heads. They exhibited abnormal acrosome and disturbed mitochondria arrangement in the flagella. At the cap phase, proacrosomal vesicles of various sizes, which had not coalesced to form a single acrosomal vesicle, were attached to the nucleus in Galnt3(-/-) mice. TUNEL-positive cells were increased in the seminiferous tubules. The binding of VVA lectin, which recognizes the Tn antigen (GalNAc-O-Ser/Thr), in the acrosomal regions of spermatids and spermatozoa in Galnt3(-/-) mice was drastically reduced. Equatorin is a N, O-sialoglycoprotein localized in the acrosomal membrane and is suggested to be involved in sperm-egg interaction. Immunohistochemical and Western blot analyses showed a drastic reduction in the reactivity with MN9 antibody, which recognizes the O-glycosylated moiety of equatorin and inhibits sperm-egg interaction. These findings indicate that deficiency of Galnt3 results in a severe reduction of mucin-type O-glycans in spermatids and causes impaired acrosome formation, leading to oligoasthenoteratozoospermia, and suggest that Galnt3 may also be involved in the process of fertilization through the O-glycosylation of equatorin.

Absence of Dpy19l2, a new inner nuclear membrane protein, causes globozoospermia in mice by preventing the anchoring of the acrosome to the nucleus

Sperm-head elongation and acrosome formation, which take place during the last stages of spermatogenesis, are essential to produce competent spermatozoa that are able to cross the oocyte zona pellucida and to achieve fertilization. During acrosome biogenesis, acrosome attachment and spreading over the nucleus are still poorly understood and to date no proteins have been described to link the acrosome to the nucleus. We recently demonstrated that a deletion of DPY19L2, a gene coding for an uncharacterized protein, was responsible for a majority of cases of type I globozoospermia, a rare cause of male infertility that is characterized by the exclusive production of round-headed acrosomeless spermatozoa. Here, using Dpy19l2 knockout mice, we describe the cellular function of the Dpy19l2 protein. We demonstrate that the protein is expressed predominantly in spermatids with a very specific localization restricted to the inner nuclear membrane facing the acrosomal vesicle. We show that the absence of Dpy19l2 leads to the destabilization of both the nuclear dense lamina (NDL) and the junction between the acroplaxome and the nuclear envelope. Consequently, the acrosome and the manchette fail to be linked to the nucleus leading to the disruption of vesicular trafficking, failure of sperm nuclear shaping and eventually to the elimination of the unbound acrosomal vesicle. Finally, we show for the first time that Dpy19l3 proteins are also located in the inner nuclear envelope, therefore implying that the Dpy19 proteins constitute a new family of structural transmembrane proteins of the nuclear envelope.

Structural disorder and local order of hNopp140

Human nucleolar phosphoprotein p140 (hNopp 140) is a highly phosphorylated protein inhibitor of casein kinase 2 (CK2). As in the case of many kinase-inhibitor systems, the inhibitor has been described to belong to the family of intrinsically disordered proteins (IDPs), which often utilize transient structural elements to bind their cognate enzyme. Here we investigated the structural status of this protein both to provide distinct lines of evidence for its disorder and to point out its transient structure potentially involved in interactions and also its tendency to aggregate. Structural disorder of hNopp140 is apparent by its anomalous electrophoretic mobility, protease sensitivity, heat stability, hydrodynamic behavior on size-exclusion chromatography, (1)H NMR spectrum and differential scanning calorimetry scan. hNopp140 has a significant tendency to aggregate and the change of its circular dichroism spectrum in the presence of 0-80% TFE suggests a tendency to form local helical structures. Wide-line NMR measurements suggest the overall disordered character of the protein. In all, our data suggest that this protein falls into the pre-molten globule state of IDPs, with a significant tendency to become ordered in the presence of its partner as demonstrated in the presence of transcription factor IIB (TFIIB).

CK2α is essential for embryonic morphogenesis

CK2 is a highly conserved serine-threonine kinase involved in biological processes such as embryonic development, circadian rhythms, inflammation, and cancer. Biochemical experiments have implicated CK2 in the control of several cellular processes and in the regulation of signal transduction pathways. Our laboratory is interested in characterizing the cellular, signaling, and molecular mechanisms regulated by CK2 during early embryonic development. For this purpose, animal models, including mice deficient in CK2 genes, are indispensable tools. Using CK2α gene-deficient mice, we have recently shown that CK2α is a critical regulator of mid-gestational morphogenetic processes, as CK2α deficiency results in defects in heart, brain, pharyngeal arch, tail bud, limb bud, and somite formation. Morphogenetic processes depend upon the precise coordination of essential cellular processes in which CK2 has been implicated, such as proliferation and survival. Here, we summarize the overall phenotype found in CK2α (-/- ) mice and describe our initial analysis aimed to identify the cellular processes affected in CK2α mutants.

Toxicological effect of emodin in mouse testicular gene expression profile

Emodin (1,3,8-trihydroxy-6-methyl-anthraquinone) is a herbal medicine extracted from the rhizomes of Rheum palmatum, and is known as an inhibitor of casein kinase II (CK2). The CK2α' knockout mice are known to be male-infertile; however, there have been no reports on the toxicity of emodin in male reproductive organs/tissues. To evaluate the toxicological effects of emodin on differential gene expression profiles of the testis as compared with acrylamide, mice were orally administered emodin and acrylamide for 5 days at a dose of 1000 and 50 mg kg(-1) per day, respectively, and euthanized 24 h after the final administration. Both chemicals induced hypospermatogenesis, eosinophilic change and apoptosis of germ cell. A DNA microarray analysis showed that the IGF-1 receptor signaling was most closely related to the above testicular toxicity induced by emodin, and the RhoA regulation, TGF/WNT and cytoskeletal remodeling, TNFR1 signaling and adenosine A2A receptor signaling were commonly associated with the two chemicals. We selected 36 genes associated with CK2, apoptosis and spermatogenesis and determined their expression by quantitative reverse transcription-polymerase chain reaction (qPCR). Both chemicals perturbed the expression of genes associated with CK2. Genes related to spermatogenesis were also affected, as evidenced by hypospermatogenesis, and eosinophilic change and apoptosis of germ cell. The results suggest that emodin causes testicular toxicity, including apoptosis with related the IGF-1 receptor signaling pathway, and the two chemicals commonly affect CK2, spermatogenesis and sperm motility via four pathways, such as TNFR1 signaling.

Dynamics of the mammalian sperm membrane modification leading to fertilization: a cytological study

Fertilization occurs when the sperm penetrates the egg, resulting in the combination of paternal and maternal genomes for the propagation of generations. To perform the task, the mammalian sperm membrane system, constructed during spermatogenesis, undergoes biochemical and cytological modifications. In this review, the following three points are discussed: (i) the nature of the acrosomal membrane disclosed by various types of microscopy, including transmission electron microscopy and the recently developed high-resolution fluorescence microscopy, (ii) the nascent acrosomal membrane dysfunction during acrosome biogenesis and (iii) the modification of the sperm membrane during sperm-egg interaction.

Protein kinase CK2 and new binding partners during spermatogenesis

Protein kinase CK2 is an ubiquitously expressed enzyme that is absolutely necessary for the survival of cells. Besides the holoenzyme consisting of the regulatory β-subunit and the catalytic α- or α'-subunit, the subunits exist in separate forms. The subunits bind to a number of other cellular proteins. We show the expression of individual subunits as well as interaction with the transitional nuclear protein TNP1 and with the motor neuron protein KIF5C during spermatogenesis. TNP1 is a newly identified binding partner of the α-subunit of CK2. CK2α and KIF5C were found in late spermatogenesis, whereas CK2β and TNP1 were found in early spermatogenesis. CK2α, CK2α', TNP1, and KIF5C were detected in the acrosome of spermatozoa, while CK2β was detectable in the mid-piece. Combinations of CK2 subunits might determine interactions with other proteins during spermatogenesis. KIF5C as a kinesin motor neuron protein is probably involved in the redistribution of proteins during spermatogenesis.

Identification of a novel HSP70-binding cochaperone critical to HSP90-mediated activation of small serine/threonine kinase

We previously reported the identification of small serine/threonine kinase (SSTK) that is expressed in postmeiotic germ cells, associates with HSP90, and is indispensable for male fertility. Sperm from SSTK-null mice cannot fertilize eggs in vitro and are incapable of fusing with eggs that lack zona pellucida. Here, using the yeast two-hybrid screen, we have discovered a novel SSTK-interacting protein (SIP) that is expressed exclusively in testis. The gene encoding SIP is restricted to mammals and encodes a 125-amino acid polypeptide with a predicted tetratricopeptide repeat domain. SIP is co-localized with SSTK in the cytoplasm of spermatids as they undergo restructuring and chromatin condensation, but unlike SSTK, is not retained in the mature sperm. SIP binds to SSTK with high affinity (K(d) ∼10 nM), and the proteins associate with each other when co-expressed in cells. In vitro, SIP inhibited SSTK kinase activity, whereas the presence of SIP in cells resulted in enzymatic activation of SSTK without affecting Akt or MAPK activity. SIP was found to be associated with cellular HSP70, and analyses with purified proteins revealed that SIP directly bound HSP70. Importantly, SSTK recruited SIP onto HSP90, and treatment of cells with the specific HSP90 inhibitor, 17-allylamino-17-demethoxygeldanamycin, completely abolished SSTK catalytic activity. Hence, these findings demonstrate that HSP90 is essential for functional maturation of the kinase and identify SIP as a cochaperone that is critical to the HSP90-mediated activation of SSTK.

A newly discovered mutation in PICK1 in a human with globozoospermia

Globozoospermia is a human infertility syndrome caused by spermatogenesis defects (OMIM 102530). Acrosome plays an important role at the site of sperm-zonapellucida binding during the fertilization process. Thus, malformation of the acrosome is the most prominent feature seen in globozoospermia. Disruption of several mouse genes, including Gopc (Golgi-associated PDZ and coiled-coil motif containing protein), Hrb (HIV-1 Rev binding protein), Csnk2a2 (casein kinase 2, alpha prime polypeptide) and Pick1 (protein interacting with C kinase 1), results in a phenotype similar to globozoospermia in humans, which suggests their potential role in the disease. However, no mutations with a clear link to globozoospermia have been identified in these genes in humans. In this study, we screened the candidate genes mentioned above in three globozoospermia type I patients and discovered a homozygous missense mutation (G198A) in exon 13 of the PICK1 gene in a Chinese family. The family member affected by this homozygous missense mutation showed a complete lack of acrosome. Using the candidate gene screening strategy, our study is the first to identify an autosomal recessive genetic mutation in PICK1 that was responsible for globozoospermia in humans.

Casein Kinase II: an attractive target for anti-cancer drug design

Casein Kinase II (CK2) is a ubiquitous serine/threonine kinase that is highly conserved in eukaryotic cells. CK2 has been shown to impact cell growth and proliferation, as numerous growth-related proteins are substrates of CK2. More importantly, experimental evidence linking increased expression and activity of CK2 to human cancers underscores the relevance of CK2 biology to cellular transformation and carcinogenesis. Due to the critical regulatory role CK2 plays in cell fate determination in cancer cells, there is a tremendous interest in the development of CK2-specific therapies. Supporting this, recent reports have demonstrated that genetic manipulation of CK2 expression as well as pharmacological inhibition of its enzymatic activity sensitizes cancers to apoptotic stimuli. Here we provide a succinct account of the biology of CK2, its cellular substrates, its pro-survival and pro-proliferation activity, and highlight evidence for its involvement in human cancer.

Surfing the wave, cycle, life history, and genes/proteins expressed by testicular germ cells. Part 4: intercellular bridges, mitochondria, nuclear envelope, apoptosis, ubiquitination, membrane/voltage-gated channels, methylation/acetylation, and transcription factors

As germ cells divide and differentiate from spermatogonia to spermatozoa, they share a number of structural and functional features that are common to all generations of germ cells and these features are discussed herein. Germ cells are linked to one another by large intercellular bridges which serve to move molecules and even large organelles from the cytoplasm of one cell to another. Mitochondria take on different shapes and features and topographical arrangements to accommodate their specific needs during spermatogenesis. The nuclear envelope and pore complex also undergo extensive modifications concomitant with the development of germ cell generations. Apoptosis is an event that is normally triggered by germ cells and involves many proteins. It occurs to limit the germ cell pool and acts as a quality control mechanism. The ubiquitin pathway comprises enzymes that ubiquitinate as well as deubiquitinate target proteins and this pathway is present and functional in germ cells. Germ cells express many proteins involved in water balance and pH control as well as voltage-gated ion channel movement. In the nucleus, proteins undergo epigenetic modifications which include methylation, acetylation, and phosphorylation, with each of these modifications signaling changes in chromatin structure. Germ cells contain specialized transcription complexes that coordinate the differentiation program of spermatogenesis, and there are many male germ cell-specific differences in the components of this machinery. All of the above features of germ cells will be discussed along with the specific proteins/genes and abnormalities to fertility related to each topic.

Surfing the wave, cycle, life history, and genes/proteins expressed by testicular germ cells. Part 3: developmental changes in spermatid flagellum and cytoplasmic droplet and interaction of sperm with the zona pellucida and egg plasma membrane

Spermiogenesis constitutes the steps involved in the metamorphosis of spermatids into spermatozoa. It involves modification of several organelles in addition to the formation of several structures including the flagellum and cytoplasmic droplet. The flagellum is composed of a neck region and middle, principal, and end pieces. The axoneme composed of nine outer microtubular doublets circularly arranged to form a cylinder around a central pair of microtubules is present throughout the flagellum. The middle and principal pieces each contain specific components such as the mitochondrial sheath and fibrous sheath, respectively, while outer dense fibers are common to both. A plethora of proteins are constituents of each of these structures, with each playing key roles in functions related to the fertility of spermatozoa. At the end of spermiogenesis, a portion of spermatid cytoplasm remains associated with the released spermatozoa, referred to as the cytoplasmic droplet. The latter has as its main feature Golgi saccules, which appear to modify the plasma membrane of spermatozoa as they move down the epididymal duct and hence may be partly involved in male gamete maturation. The end product of spermatogenesis is highly streamlined and motile spermatozoa having a condensed nucleus equipped with an acrosome. Spermatozoa move through the female reproductive tract and eventually penetrate the zona pellucida and bind to the egg plasma membrane. Many proteins have been implicated in the process of fertilization as well as a plethora of proteins involved in the development of spermatids and sperm, and these are high lighted in this review.