Dynamics of histone H2A, H4 and HS1ph during spermatogenesis with a focus on chromatin condensation and maturity of spermatozoa

H3T11 phosphorylation by CKII is required for heterochromatin formation in Neurospora

Heterochromatin is a key feature of eukaryotic genomes and is crucial for maintaining genomic stability. In fission yeast, heterochromatin nucleation is mainly mediated by DNA-binding proteins or the RNA interference (RNAi) pathway. In the filamentous fungus Neurospora crassa, however, the mechanism that causes the initiation of heterochromatin at the relics of repeat-induced point mutation is unknown and independent of the classical RNAi pathway. Here, we show that casein kinase II (CKII) and its kinase activity are required for heterochromatin formation at the well-defined 5-kb heterochromatin of the 5H-cat-3 region and transcriptional repression of its adjacent cat-3 gene. Similarly, mutation of the histone H3 phosphorylation site T11 also impairs heterochromatin formation at the same locus. The catalytic subunit CKA colocalizes with H3T11 phosphorylation (H3pT11) within the 5H-cat-3 domain and the deletion of cka results in a significant decrease in H3T11 phosphorylation. Furthermore, the loss of kinase activity of CKII results in a significant reduction of H3pT11, H3K9me3 (histone H3 lysine 9 trimethylation) and DNA methylation levels, suggesting that CKII regulates heterochromatin formation by promoting H3T11 phosphorylation. Together, our results establish that histone H3 phosphorylation by CKII is a critical event required for heterochromatin formation.

Sperm acrosomal released proteome reveals MDH and VDAC3 from mitochondria are involved in acrosome formation during spermatogenesis in Eriocheir sinensis

Acrosome is inextricably related to membranous organelles. The origin of acrosome is still controversial, one reason is that limited articles were reported about the proteomic analysis of the acrosome. Mitochondrial proteins were found exist in the acrosome, nevertheless, only limited attention has been paid to the function of mitochondrial proteins in the acrosome formation. Eriocheir sinensis sperm has a large acrosome, which makes it an ideal model to study acrosome formation. Here, we firstly compared the rate of acrosome reaction induced by the calcium ionophore A23187 and ionomycin. The rate of acrosome reaction induced by ionomycin is higher (95.8%) than A23187 (58.7%). Morphological changes were observed using light, confocal and transmission electron microscopy. Further more, proteins released during the acrosome reaction as induced by ionomycin were collected for LC-MS/MS analysis. A total of 945 proteins, including malate dehydrogenase (MDH) and voltage-dependent anion channel 3 (VDAC3), were identified in the acrosomal released proteome. The number of proteins from mitochondria (17.57%) was higher compared with endoplasmic reituculum (1.59%) and lysosomes (1.8%). To investigate the functions of target mitochondrial proteins during spermatogenesis, poly-antibodies of MDH in E. sinensis were prepared. The characteristics, further analyzed using immunofluorescence, of two mitochondrial proteins during acrosome formation showed that MDH and VDAC3 were independently involved in the formation of acrosomal membrane. These findings illustrate the acrosomal released proteome and provide important data resource for understanding the relationship between mitochondria and the acrosome in Decapoda crustacean.

Epigenetic Modulations for Prevention of Infectious Diseases in Shrimp Aquaculture

Aquaculture assumes a pivotal role in meeting the escalating global food demand, and shrimp farming, in particular, holds a significant role in the global economy and food security, providing a rich source of nutrients for human consumption. Nonetheless, the industry faces formidable challenges, primarily attributed to disease outbreaks and the diminishing efficacy of conventional disease management approaches, such as antibiotic usage. Consequently, there is an urgent imperative to explore alternative strategies to ensure the sustainability of the industry. In this context, the field of epigenetics emerges as a promising avenue for combating infectious diseases in shrimp aquaculture. Epigenetic modulations entail chemical alterations in DNA and proteins, orchestrating gene expression patterns without modifying the underlying DNA sequence through DNA methylation, histone modifications, and non-coding RNA molecules. Utilizing epigenetic mechanisms presents an opportunity to enhance immune gene expression and bolster disease resistance in shrimp, thereby contributing to disease management strategies and optimizing shrimp health and productivity. Additionally, the concept of epigenetic inheritability in marine animals holds immense potential for the future of the shrimp farming industry. To this end, this comprehensive review thoroughly explores the dynamics of epigenetic modulations in shrimp aquaculture, with a particular emphasis on its pivotal role in disease management. It conveys the significance of harnessing advantageous epigenetic changes to ensure the long-term viability of shrimp farming while deliberating on the potential consequences of these interventions. Overall, this appraisal highlights the promising trajectory of epigenetic applications, propelling the field toward strengthening sustainability in shrimp aquaculture.

Dynamics of hyperacetylated histone H4 (H4Kac) during spermatogenesis in four decapod crustaceans

During spermatogenesis, the transition from histone to protamine is highly conserved in most invertebrates and vertebrates. Thus far, a large and growing body of literature has demonstrated that histones and histone modifications still exist in the sperm nucleus of decapod crustaceans. H4Kac is believed to play an important role in the process of sperm chromatin condensation. However, the dynamics of hyperacetylated histone H4 (H4Kac) during spermatogenesis in decapoda are still unknown. In this paper, the distribution of H4Kac in four decapod crustaceans (Eriocheir sinensis, Charybdis japonica, Procambarus clarkii, and Macrobrachium nipponense) were investigated via immunofluorescence. Our results indicated that H4Kac was visible in the mature sperm nucleus of E. sinensis, C. japonica, and M. nipponense. Unlike the other three species, H4Kac was translocated from the nuclei to cytoplasm in mid-spermatids of P. clarkii. Eventually, H4Kac were not present in mature spermatozoa of P. clarkii. Importantly, we observed for the first time that H4Kac was distributed outside the nucleus, which reminds us that H4Kac may participate in the formation of acrosome structure in decapod crustaceans and may be a prerequisite for proper chromatin decondensation.

De novo transcriptome assembly from the gonads of a scleractinian coral, Euphyllia ancora: molecular mechanisms underlying scleractinian gametogenesis

BACKGROUND

Sexual reproduction of scleractinians has captured the attention of researchers and the general public for decades. Although extensive ecological data has been acquired, underlying molecular and cellular mechanisms remain largely unknown. In this study, to better understand mechanisms underlying gametogenesis, we isolated ovaries and testes at different developmental phases from a gonochoric coral, Euphyllia ancora, and adopted a transcriptomic approach to reveal sex- and phase-specific gene expression profiles. In particular, we explored genes associated with oocyte development and maturation, spermiogenesis, sperm motility / capacitation, and fertilization.

RESULTS

1.6 billion raw reads were obtained from 24 gonadal samples. De novo assembly of trimmed reads, and elimination of contigs derived from symbiotic dinoflagellates (Symbiodiniaceae) and other organisms yielded a reference E. ancora gonadal transcriptome of 35,802 contigs. Analysis of 4 developmental phases identified 2023 genes that were differentially expressed during oogenesis and 678 during spermatogenesis. In premature/mature ovaries, 631 genes were specifically upregulated, with 538 in mature testes. Upregulated genes included those involved in gametogenesis, gamete maturation, sperm motility / capacitation, and fertilization in other metazoans, including humans. Meanwhile, a large number of genes without homology to sequences in the SWISS-PROT database were also observed among upregulated genes in premature / mature ovaries and mature testes.

CONCLUSIONS

Our findings show that scleractinian gametogenesis shares many molecular characteristics with that of other metazoans, but it also possesses unique characteristics developed during cnidarian and/or scleractinian evolution. To the best of our knowledge, this study is the first to create a gonadal transcriptome assembly from any scleractinian. This study and associated datasets provide a foundation for future studies regarding gametogenesis and differences between male and female colonies from molecular and cellular perspectives. Furthermore, our transcriptome assembly will be a useful reference for future development of sex-specific and/or stage-specific germ cell markers that can be used in coral aquaculture and ecological studies.

Spermiogenic histone transitions and chromatin decondensation in Decapoda

Decapoda are among of the most diverse groups of Crustacea with an important economic value, and have thus been the focus of various reproductive biology studies. Although spermatozoa are morphologically diverse, decapod spermatozoa possess common features, such as being non-motile and having uncondensed nuclear chromatin. Many scholars have studied uncondensed chromatin in decapod spermatozoa; however, the role of biologically regulated decondensation in spermatozoa remains unclear. In this study, histone changes in the spermatozoa of five commercially relevant aquatic crustacean species (Eriocheir sinensis, Scylla paramamosain, Procambarus clarkii, Fenneropenaeus chinensis, and Macrobrachium nipponense) were studied via liquid chromatography-tandem mass spectrometry (LC-MS/MS) and immunofluorescence. The LC-MS/MS results confirmed that all four core histones were present in the sperm nuclei of the five Decapoda species. Positive fluorescent signals from histones H2A, H2B, H3, and H4 were detected in the spermatozoa nuclei of E. sinensis, S. paramamosain and M. nipponense via immunofluorescence. Histone H2A was first identified in the membrane sheets or cytoplasm of mature sperm in P. clarkii and F. chinensis, whereas H3 and H4 were generally distributed in the nucleus of the spermatozoa. Histone H2B gradually disappeared during spermiogenesis and was not found in the sperm of P. clarkii and F. chinensis eventually. Our data suggest that core histones are instructive and necessary for chromatin decondensation in decapods spermatozoa. Thus, our results may help resolve the complex sperm histone code and provide a reference for the study of spermatozoa evolution in Decapoda.

Histone Post-Translational Modifications and CircRNAs in Mouse and Human Spermatozoa: Potential Epigenetic Marks to Assess Human Sperm Quality

Spermatozoa (SPZ) are motile cells, characterized by a cargo of epigenetic information including histone post-translational modifications (histone PTMs) and non-coding RNAs. Specific histone PTMs are present in developing germ cells, with a key role in spermatogenic events such as self-renewal and commitment of spermatogonia (SPG), meiotic recombination, nuclear condensation in spermatids (SPT). Nuclear condensation is related to chromatin remodeling events and requires a massive histone-to-protamine exchange. After this event a small percentage of chromatin is condensed by histones and SPZ contain nucleoprotamines and a small fraction of nucleohistone chromatin carrying a landascape of histone PTMs. Circular RNAs (circRNAs), a new class of non-coding RNAs, characterized by a nonlinear back-spliced junction, able to play as microRNA (miRNA) sponges, protein scaffolds and translation templates, have been recently characterized in both human and mouse SPZ. Since their abundance in eukaryote tissues, it is challenging to deepen their biological function, especially in the field of reproduction. Here we review the critical role of histone PTMs in male germ cells and the profile of circRNAs in mouse and human SPZ. Furthermore, we discuss their suggested role as novel epigenetic biomarkers to assess sperm quality and improve artificial insemination procedure.

Essential Role of Histone Replacement and Modifications in Male Fertility

Spermiogenesis is a complex cellular differentiation process that the germ cells undergo a distinct morphological change, and the protamines replace the core histones to facilitate chromatin compaction in the sperm head. Recent studies show the essential roles of epigenetic events during the histone-to-protamine transition. Defects in either the replacement or the modification of histones might cause male infertility with azoospermia, oligospermia or teratozoospermia. Here, we summarize recent advances in our knowledge of how epigenetic regulators, such as histone variants, histone modification and their related chromatin remodelers, facilitate the histone-to-protamine transition during spermiogenesis. Understanding the molecular mechanism underlying the modification and replacement of histones during spermiogenesis will enable the identification of epigenetic biomarkers of male infertility, and shed light on potential therapies for these patients in the future.

Missense mutation in DNAJB13 gene correlated with male fertility in asthenozoospermia

BACKGROUND

The most common type of male infertility is asthenospermia. We cloned DnaJ heat shock protein family member B13 (Dnajb13/DNAJB13), a type II HSP40 family member that is highly expressed in the testis. DNAJB13 plays a crucial role in sperm flagellar function.

OBJECTIVES

The aim of this study was to investigate whether a correlation exists between DNAJB13 and low sperm motility in infertile men.

MATERIALS AND METHODS

In the present study, we performed a mutation screening of the DNAJB13 gene in 92 idiopathic asthenozoospermia patients and 200 men with normal fertility. Additionally, we used immunoelectron microscopy, co-immunoprecipitation, mass spectrometric detection, indirect immunofluorescence assay, transmission electron microscopy studies, isobaric tags for relative and absolute quantitation, and multiple reaction monitoring studies to analyze changes in DNAJB13 protein.

RESULTS

A novel c.106T>C mutation of DNAJB13 was present in nearly 10% (9/92) of idiopathic asthenozoospermia patients and was absent in 200 fertile men. A computer-assisted sperm analyzer and transmission electron microscopy analysis using samples from 9 patients with DNAJB13 mutations demonstrated that most spermatozoa were immotile due to sperm tail defects. Multiple reaction monitoring results indicated that DNAJB13 protein levels were reduced after gene mutation. We achieved a pregnancy rate of 100% in 8 patients with DNAJB13 mutations using ICSI.

DISCUSSION AND CONCLUSION

The DNAJB13 heterozygous variant may affect fertility. ICSI can help these patients with low fertility to father children.

Ultrastructure of spermiogenesis and the distribution of spermatozoal nuclear histones in the Japanese mantis shrimp, Oratosquilla oratoria (Crustacea: Stomatopoda)

The Japanese mantis shrimp Oratosquilla oratoria (Stomatopoda; Crustacea) is one of the most economically important aquatic species of Pacific shrimp and it is distributed from Japan to the coast of China, the Philippines, the Malay Peninsula, and the Hawaiian Islands. Early studies described certain characteristics of spermatogenesis and the sperm ultrastructure in Stomatopoda, but the composition of sperm basic nuclear proteins (SBNPs) remains completely unknown. We studied the sperm ultrastructure of O. oratoria using transmission electron microscopy and the histone composition using immunofluorescence and immunoelectron microscopy. We found that the spherical nucleus is adjacent to the electron translucent external coat, which occurs in early spermatids. The acrosomal structure begins to form at the junction of the nucleus and the external coat. At the mid-spermatid stage, part of the chromatin appears to be more electron-dense than the external coat side. The aflagellate sperm of O. oratoria, are rounded or slightly ovoid in shape and have a consistent granular nucleus, an acrosome structure of pushpin shape and a spherical vesicular body in which faintly granular material is scattered. The acrosome consists of an acrosomal vesicle, perforatorium, and subacrosomal material. The sperm contains histones H2A, H2B, H3, H4, H3.3, H2AX, and H2AZ as well as some histone modifications, that is, H3K9me3, H3K4me2, H3S10ph, H4Kac, and H2A + H4S1ph. Histones are localized not only in the nucleus of the sperm but also in other structures outside the nucleus. The results may provide new perspectives for systematic studies of crustaceans and their sperm chromatin components. These findings extend the study of the sperm structure of Stomatopoda and provide basic data to elucidate the epigenetic mechanism of fertilization.

H2AFZ, RNF4 and NR4A1 loci are associated with boar semen quality by population association studies

Spermatogenesis is a complex process regulated by many genes. In this study, H2AFZ, RNF4 and NR4A1 genes were selected as candidate genes for boar semen quality traits based on their functions during spermatogenesis, and the associations of three loci (H2AFZ c.192 + 210-192 + 213delCGAT, RNF4 c.374 + 358 T > C and NR4A1 c.956 + 796 A > G) with sperm quality traits were analyzed in Duroc (n = 185), Large White (n = 87) and Landrace (n = 49) pig populations. The results showed H2AFZ c.192 + 210-192 + 213delCGAT AA boars produced 1.52% lower abnormal sperm rate (ASR) than AB boars in Landrace pigs (p < 0.05); RNF4 c.374 + 358 TC boars produced 0.31 × 10⁸/ml higher sperm concentration (SCON) than CC boars (p < 0.05) in Large White pigs; NR4A1 c.956 + 796 A > G was associated with ASR in Duroc and Large White pigs and was associated with sperm motility (MOT) in Large White and Landrace pigs. This study indicated the H2AFZ, RNF4 and NR4A1 loci were the potential molecular markers for improving the semen quality traits in boars.

Transcriptome using Illumina sequencing reveals the traits of spermatogenesis and developing testes in Eriocheir sinensis

Chinese mitten crab (Eriocheir sinensis) has the spermatozoa with typical aflagellate, decondensed chromatin, cup-shaped nuclei, and radial arms. However, the mechanism of spermatogenesis during which the specific spermatozoa are generated in this species is yet unclear. Here, the transcriptome of developing testis in E. sinensis was analyzed using the ways of RNA-seq and bioinformatics analysis to identify candidate genes potentially involved in development of testis and spermatogenesis. The Illumina HiSeq2500 sequencing of three replicons of samples produced a total of 145.19 M clean reads representing with a total of 21.34 Gb bases and 45.48% GC content. 56.30% clean reads were mapped to the draft genome of E. sinensis. The assembly of the transcriptome yielded contigs of 5691802 sequences and unigenes of 406527 sequences. Total 24246 and 40793 transcripts were annotated using Swissprot and Nr database, respectively. There were 48213 (70.31%) and 7858 (46.25%) transcripts with identity of more than 99 matching to mature testis unigenes in the databases of Nr and EST, respectively. The analytic results of KOG, GO and KEGG showed wide potential molecular functions of transcripts in the developing testes. KEGG analysis of unigenes yielded total 9422 predicted genes. Those predicted genes were involved in total 216 KEGG pathways related to the physiological activities of developing testis. 1975 predicted genes were involved in cellular and subcellular structural alteration of male germ cells. There were important roles of some pathways in the processes of morphological and structural biogenesis pertaining to testis development and spermatogenesis. Other 583 unigenes encoding the genetic and epigenetic factors also be found, which might contribute to the decondensation and stability of decondensed nuclei in the spermatozoa. These predicted events provide a view of the potential molecular mechanisms of development of testis and spermatogenesis in E. sinensis.