Gene Regulation in Spermatogenesis

The Role of Plzf in Spermatogonial Stem Cell Maintenance and Differentiation: Mapping the Transcriptional Dynamics and Key Interactions

Spermatogonial stem cells (SSCs) sustain and modulate spermatogenesis through intricate signaling pathways and transcription factors. Promyelocytic leukemia zinc-finger (Plzf, also known as Zbtb16) has been identified as a critical transcription factor influencing various signaling and differentiation pathways. Plzf plays a pivotal role in regulating the differentiation properties of SSCs and is essential for the proper maintenance of spermatogenesis. However, the transcription patterns of Plzf along the seminiferous tubules and its interaction network with adjacent partners still need to be fully elucidated. This study employed immunostaining techniques coupled with Fluidigm quantitative real-time polymerase chain reaction (Fluidigm qPCR) to quantify Plzf expression in undifferentiated and differentiated spermatogonia. Furthermore, we utilized bioinformatics analyses to identify Plzf partners and their associations with other regulatory factors. Immunohistostaining (IMH) revealed a high expression of Plzf in cells near the basal membrane of seminiferous tubules and a lower expression in the middle regions in vivo. Immunocytochemistry (ICC) demonstrated that undifferentiated spermatogonia exhibited significant Plzf positivity, whereas differentiated spermatogonia showed reduced Plzf expression in vitro. Fluidigm qPCR confirmed a significant differential expression of Plzf between undifferentiated and differentiated spermatogonia. In silico differential expression analysis between undifferentiated spermatogonia and spermatids indicated that Plzf is closely associated with Mycn, Lin28a, Kras, Ccnd1, and Jak1, highlighting the importance of these partnerships during spermatogenesis. Our findings suggest that the network of Plzf-related partners and their associated proteins involves differentiation, localization, apoptosis, and signal transduction. This comprehensive approach advances our understanding of Plzf transcription patterns and sheds light on its interactions with other cellular factors, revealing previously obscure pathways and interactions. These insights could lead to more effective diagnostic strategies for reproductive system-related diseases and inform the development of improved therapeutic and clinical applications.

Screening of Reference Genes for Quantitative Real-Time PCR Analysis in Tissues and during Testis Development, and Application to Analyze the Expression of kifc1 in Hemibarbus labeo (Teleostei, Cypriniformes, Cyprinidae)

The selection of proper reference genes is vital for ensuring precise quantitative real-time PCR (qPCR) assays. This study evaluates the stability of the expression of nine candidate reference genes in different tissues and during testicular development in H. labeo. The results show that eef1a is recommended as a reference gene for qPCR analysis in tissues and during testicular development. Furthermore, we evaluated the optimal number of reference genes needed when calculating gene expression levels using the geomean method, revealing that two reference genes are sufficient. Specifically, eef1a and rps27 are recommended for analysis of gene expression in tissues, whereas eef1a and actb are advised for evaluating gene expression during testicular development. In addition, we examined the expression pattern of kifc1, a kinesin involved in the reshaping of spermatids. We detected peak expression levels of kifc1 in testes, with its expression initially increasing before decreasing throughout testicular development. The highest expression of kifc1 was observed in stage IV testes, the active period of spermiogenesis, suggesting a possible role for kifc1 in the regulation of the reshaping of spermatids and hence testicular development. This study represents the first investigation of reference genes for H. labeo, providing a foundation for studying gene expression patterns and investigating gene expression regulation during testicular development.

Single-Cell Transcriptome Sequencing Reveals Molecular Expression Differences and Marker Genes in Testes during the Sexual Maturation of Mongolian Horses

This study aimed to investigate differences in testicular tissue morphology, gene expression, and marker genes between sexually immature (1-year-old) and sexually mature (10-year-old) Mongolian horses. The purposes of our research were to provide insights into the reproductive physiology of male Mongolian horses and to identify potential markers for sexual maturity. The methods we applied included the transcriptomic profiling of testicular cells using single-cell sequencing techniques. Our results revealed significant differences in tissue morphology and gene expression patterns between the two age groups. Specifically, 25 cell clusters and 10 cell types were identified, including spermatogonial and somatic cells. Differential gene expression analysis highlighted distinct patterns related to cellular infrastructure in sexually immature horses and spermatogenesis in sexually mature horses. Marker genes specific to each stage were also identified, including APOA1, AMH, TAC3, INHA, SPARC, and SOX9 for the sexually immature stage, and PRM1, PRM2, LOC100051500, PRSS37, HMGB4, and H1-9 for the sexually mature stage. These findings contribute to a deeper understanding of testicular development and spermatogenesis in Mongolian horses and have potential applications in equine reproductive biology and breeding programs. In conclusion, this study provides valuable insights into the molecular mechanisms underlying sexual maturity in Mongolian horses.

Rhox8 homeobox gene ablation leads to rete testis abnormality and male subfertility in mice†

The reproductive homeobox X-linked (Rhox) genes encode transcription factors that are expressed selectively in reproductive tissues including the testis, epididymis, ovary, and placenta. While many Rhox genes are expressed in germ cells in the mouse testis, only Rhox8 is expressed exclusively in the Sertoli cells during embryonic and postnatal development, suggesting a possible role of Rhox8 in embryonic gonad development. Previously, Sertoli cell-specific knockdown of RHOX8 resulted in male subfertility due to germ cell defects. However, this knockdown model was limited in examining the functions of Rhox8 as RHOX8 knockdown occurred only postnatally, and there was still residual RHOX8 in the testis. In this study, we generated new Rhox8 knockout (KO) mice using the CRISPR/Cas9 system. Sex determination and fetal testis development were apparently normal in mutant mice. Fertility analysis showed a low fecundity in Rhox8 KO adult males, with disrupted spermatogenic cycles, increased germ cell apoptosis, and reduced sperm count and motility. Interestingly, Rhox8 KO testes showed an increase in testis size with dilated seminiferous tubules and rete testis, which might be affected by efferent duct (ED) Rhox8 ablation dysregulating the expression of metabolism and transport genes in the EDs. Taken together, the data presented in this study suggest that Rhox8 in the Sertoli cells is not essential for sex determination and embryonic testis differentiation but has an important role in complete spermatogenesis and optimal male fertility.

Circadian desynchrony disturbs the function of rat spermatozoa

Decreased male fertility is a growing health problem that requires a better understanding of molecular events regulating reproductive competence. Here the effects of circadian desynchrony on the rat spermatozoa functionality were studied. Circadian desynchrony was induced in rats that lived for 2 months under disturbed light conditions designed to mimic shiftwork in humans (two days of constant light, two days of continual dark, and three days of 14:10 h light:dark schedule). Such a condition abolished circadian oscillations in the rats' voluntary activity, followed by a flattened transcriptional pattern of the pituitary gene encoding follicle stimulating hormone subunit (Fshb), and genes important for germ cell maturation (Tnp1 and Prm2) as well as the clock in seminiferous tubules. However, the number of spermatozoa isolated from the epididymis of the rats suffering from circadian desynchrony did not deviate from the controls. Nevertheless, spermatozoa functionality, estimated by motility and progesterone-induced acrosome reaction, was reduced compared to the control. These changes were associated with the altered level of main markers of mitochondrial biogenesis (Pprgc1a/PGC1A, Nrf1/NRF1, Tfam, Cytc), decreased mitochondrial DNA copy number, ATP content, and clock genes (Bmal1/BMAL1, Clock, Cry1/2, and Reverba). The principal-component-analysis (PCA) points to a positive association of the clock and mitochondrial biogenesis-related genes in spermatozoa from rats suffering circadian desynchrony. Altogether, the results show the harmful effect of circadian desynchrony on spermatozoa functionality, targeting energetic homeostasis.

The solute carrier family 7 member 11 (SLC7A11) is regulated by LH/androgen and required for cystine/glutathione homeostasis in mouse Sertoli cells

Luteinizing hormone (LH) stimulates testosterone production from Leydig cells. Both LH and testosterone play important roles in spermatogenesis and male fertility. To identify LH - and testosterone - responsive transporter genes that play key roles in spermatogenesis, we performed large-scale gene expression analyses on testes obtained from adult control and Lhb knockout mice. We found a significant reduction in cystine/glutamate transporter encoding Slc7a11 mRNA in testes of Lhb null mice. We observed that Slc7a11/SLC7A11 expression was initiated pre-pubertally and developmentally regulated in mouse testis. Immunolocalization studies confirmed that SLC7A11 was mostly expressed in Sertoli cells in testes of control and germ cell-deficient mice. Western blot analyses indicated that SLC7A11 was significantly reduced in testes of mutant mice lacking either LH or androgen receptor selectively in Sertoli cells. Genetic and pharmacological rescue of Lhb knockout mice restored the testicular expression of Slc7a11 comparable to that observed in controls. Additionally, Slc7a11 mRNA was significantly suppressed upon Sertoli cell/testicular damage induced in mice by cadmium treatment. Knockdown of Slc7a11 in vitro in TM4 Sertoli cells or treatment of mice with sulfasalazine, a SLC7A11 inhibitor caused a significant reduction in intracellular cysteine and glutathione levels but glutamate content remained unchanged as determined by metabolomic analysis. Knockdown of Slc7a11 resulted in compensatory upregulation of other glutamate transporters belonging to the Slc1a family presumably to maintain intracellular glutamate levels. Collectively, our studies identified that SLC7A11 is an LH/testosterone-regulated transporter that is required for cysteine/glutathione but not glutamate homeostasis in mouse Sertoli cells.

Association of methyltetrahydrofolate reductase gene mutation, homocysteine level with semen quality of Iraqi infertile males

Background

Infertility is very common condition and almost 50% of cases are due to male factors. Several genetic and environmental factors are responsible for the poor quality and reduced number of sperms in several cases of infertility. The present study was designed to investigate the association between semen parameters, homocysteine, and the risk of C677T polymorphism of MTHFR gene in infertile males of Iraqi population.

Methods

This Case–control study has been conducted from February 2019 to July 2021 at a molecular laboratory in the Anatomy and Histology Department/college of Medicine/University of Kufa/Najaf/Iraq. It was composed of 353 infertile male patients. They were divided into five groups: 90 azoospermic, 84 oligospermia, 64 asthenospermic, 50 oligoasthenospermic, and 65 teratospermic with an age range 20–46 years compared with 100 fertile males as control with age range 21–49 years. In order to detect homocysteine levels, we used Hcy ELISA Kit. C677T mutation of MTHFR gene was employed by PCR–RFLP technique.

Results

Our data revealed three genotypes of MTHFR C677T, 167 (47.3%) subjects had CC genotype, 116 (32.9%) subjects had CT genotype and 70 (21.1%) subjects had TT genotype. Furthermore, T allele was associated with higher risk of infertility in all patients groups for any genetic model. In total infertile subjects (codominant model: CT vs. CC, OR = 2.0, 95% C.I = 1.2–3.3, P = 0.011; TT vs. CC, OR = 4.8, 95% C.I = 3.3–8.2, P = 0.0003; dominant model: CT + TT vs. CC, OR = 2.8, 95% C.I = 1.7–4.5, P = 0.0001). Oligoasthenospermic patients associated with higher risk in CT heterozygous genotype (OR = 2.8, 95% C.I = 1.0–4.9, P = 0.03) and TT homozygous of mutant allele (OR = 6.3, 95% C.I = 1.9–9.2, P = 0.002). Homocystein level was elevated in all infertile groups when compared with control group (P < 0.01), but the elevation was marked in oligoasthenospermia group. As well as, the level of Serum Hcy exhibited the highest value in TT mutant genotype (39.7 µmol/ml) followed by CT genotype (28.5 µmol/ml) while the lowest level of Hcy recorded in CC genotype (14.6 µmol/ml) for oligoasthenospermia group.

Conclusions

By relating the MTHFR C677T gene mutation with a higher homocystein level, the results showed that Iraqi males with this mutation are more likely to suffer from infertility.

Chromatoid Bodies in the Regulation of Spermatogenesis: Novel Role of GRTH

Post-transcriptional and translational control of specialized genes play a critical role in the progression of spermatogenesis. During the early stages, mRNAs are actively transcribed and stored, temporarily bound to RNA binding proteins in chromatoid bodies (CBs). CBs are membrane-less dynamic organelles which serve as storehouses and processing centers of mRNAs awaiting translation during later stages of spermatogenesis. These CBs can also regulate the stability of mRNAs to secure the correct timing of protein expression at different stages of sperm formation. Gonadotropin-regulated testicular RNA helicase (GRTH/DDX25) is an essential regulator of spermatogenesis. GRTH transports mRNAs from the nucleus to the cytoplasm and phospho-GRTH transports mRNAs from the cytoplasm to the CBs. During spermiogenesis, there is precise control of mRNAs transported by GRTH from and to the CBs, directing the timing of translation of critical proteins which are involved in spermatid elongation and acrosomal development, resulting in functional sperm formation. This chapter presents our current knowledge on the role of GRTH, phospho-GRTH and CBs in the control of spermiogenesis. In addition, it covers the components of CBs compared to those of stress granules and P-bodies.

Vapor cannabis exposure generationally affects male reproductive functions in mice

This study was performed to examine whether vapor exposure to cannabis plant matter negatively impacts male reproductive functions and testis development in mice. Adult CD-1 male mice (F0) were exposed to air (control) or 200 mg of vaporized cannabis plant matter 3x/day over a 10 day period. Subsequently, F0 males were bred with drug naïve CD-1 females to generate F1 males, and F1 offspring were used to generate F2 males. Cannabis vapor exposure decreased sperm count and/or motility in F0 and F1 males and disrupted the progression of germ cell development, as morphometric analyses exhibited an abnormal distribution of the stages of spermatogenesis in F0 males. Although plasma levels of testosterone were not affected by cannabis exposure in any ages or generations of males, dysregulated steroidogenic enzymes, Cyp11a1 and Cyp19a1, were observed in F0 testis. In the neonatal testis from F1 males, while apoptosis was not altered, DNA damage and DNMT1, but not DNMT3A and DNMT3B, were increased in germ cells following cannabis exposure. In contrast, the alterations of DNA damage and DNMT1 expression were not observed in F2 neonatal males. These results suggest that cannabis vapor exposure generationally affects male reproductive functions, probably due to disruption of spermatogenesis in the developing testis.

Network Analyses Predict Small RNAs That Might Modulate Gene Expression in the Testis and Epididymis of Bos indicus Bulls

Spermatogenesis relies on complex molecular mechanisms, essential for the genesis and differentiation of the male gamete. Germ cell differentiation starts at the testicular parenchyma and finishes in the epididymis, which has three main regions: head, body, and tail. RNA-sequencing data of the testicular parenchyma (TP), head epididymis (HE), and tail epididymis (TE) from four bulls (three biopsies per bull: 12 samples) were subjected to differential expression analyses, functional enrichment analyses, and co-expression analyses. The aim was to investigate the co-expression and infer possible regulatory roles for transcripts involved in the spermatogenesis of Bos indicus bulls. Across the three pairwise comparisons, 3,826 differentially expressed (DE) transcripts were identified, of which 384 are small RNAs. Functional enrichment analysis pointed to gene ontology (GO) terms related to ion channel activity, detoxification of copper, neuroactive receptors, and spermatogenesis. Using the regulatory impact factor (RIF) algorithm, we detected 70 DE small RNAs likely to regulate the DE transcripts considering all pairwise comparisons among tissues. The pattern of small RNA co-expression suggested that these elements are involved in spermatogenesis regulation. The 3,826 DE transcripts (mRNAs and small RNAs) were further subjected to co-expression analyses using the partial correlation and information theory (PCIT) algorithm for network prediction. Significant correlations underpinned the co-expression network, which had 2,216 transcripts connected by 158,807 predicted interactions. The larger network cluster was enriched for male gamete generation and had 15 miRNAs with significant RIF. The miRNA bta-mir-2886 showed the highest number of connections (601) and was predicted to down-regulate ELOVL3, FEZF2, and HOXA13 (negative co-expression correlations and confirmed with TargetScan). In short, we suggest that bta-mir-2886 and other small RNAs might modulate gene expression in the testis and epididymis, in Bos indicus cattle.

Human adenylate kinase 6 regulates WNK1 (with no lysine kinase-1) phosphorylation states and affects ion homeostasis in NT2 cells

Adenylate kinase 6 (AK6), a nucleus localized phosphotransferase in mammalians, shows ubiquitously expression and broad substrate activity in different tissues and cell types. Although the function of AK6 has been extensively studied in different cancer cell lines, its role in mammalian germline is still unknown. Here we showed that knockdown of AK6 inhibits cell proliferation and promotes cell apoptosis in human testicular carcinoma (NT2 cells). Co-immunoprecipitation experiment and in vitro pull down assay identified WNK1 (with no lysine kinase-1) as one of the AK6 interacting proteins in NT2 cells. Moreover, we found that AK6 regulates the phosphorylation states of WNK1 (Thr60) and affects phosphorylation level of Akt (Ser473) upon hypotonic condition, probably affecting chloride channel and regulating ion transport and homeostasis in NT2 cells and consequently contributing to the decreased cell proliferation rate. In conclusion, AK6 regulates WNK1 phosphorylation states and affects ion homeostasis in NT2 cells. These findings provide new insights into the function of AK6 and WNK1 in human testicular carcinoma. This work also provides foundation for further mechanism study of AK6 in spermatogenesis.

Role of Phosphorylated Gonadotropin-Regulated Testicular RNA Helicase (GRTH/DDX25) in the Regulation of Germ Cell Specific mRNAs in Chromatoid Bodies During Spermatogenesis

GRTH/DDX25 is a member of the DEAD-box family of RNA helicases that play an essential role in spermatogenesis. GRTH knock-in (KI) mice with the human mutant GRTH gene (R242H) show loss of the phospho-species from cytoplasm with preservation of the non-phospho form in the cytoplasm and nucleus. GRTH KI mice are sterile and lack elongated spermatids and spermatozoa, with spermatogenic arrest at step 8 of round spermatids which contain chromatoid body (CB) markedly reduced in size. We observed an absence of phospho-GRTH in CB of GRTH KI mice. RNA-Seq analysis of mRNA isolated from CB revealed that 1,421 genes show differential abundance, of which 947 genes showed a decrease in abundance and 474 genes showed an increase in abundance in GRTH KI mice. The transcripts related to spermatid development, differentiation, and chromatin remodeling (Tnp1/2, Prm1/2/3, Spem1/2, Tssk 2/3/6, Grth, tAce, and Upf2) were reduced, and the transcripts encoding for factors involved in RNA transport, regulation, and surveillance and transcriptional and translational regulation (Eef1a1, Ppp1cc, Pabpc1, Ybx3, Tent5b, H2al1m, Dctn2, and Dync1h1) were increased in the CB of KI mice and were further validated by qPCR. In the round spermatids of wild-type mice, mRNAs of Tnp2, Prm2, and Grth were abundantly co-localized with MVH protein in the CB, while in GRTH KI mice these were minimally present. In addition, GRTH binding to Tnp1/2, Prm1/2, Grth, and Tssk6 mRNAs was found to be markedly decreased in KI. These results demonstrate the importance of phospho-GRTH in the maintenance of the structure of CB and its role in the storage and stability of germ cell-specific mRNAs during spermiogenesis.

The anatomy, movement, and functions of human sperm tail: an evolving mystery

Sperms have attracted attention of many researchers since it was discovered by Antonie van Leeuwenhoek in 1677. Though a small cell, its every part has complex structure and different function to play in carrying life. Sperm tail is most complicated structure with more than 1000 proteins involved in its functioning. With the advent of three-dimensional microscopes, many studies are undergoing to understand exact mechanism of sperm tail movement. Most recent studies have shown that sperms move by spinning rather than swimming. Each subunit of tail, including axonemal, peri-axonemal structures, plays essential roles in sperm motility, capacitation, hyperactivation, fertilization. Furthermore, over 2300 genes are involved in spermatogenesis. A number of genetic mutations have been linked with abnormal sperm flagellar development leading to motility defects and male infertility. It was found that 6% of male infertility cases are related to genetic causes, and 4% of couples undergoing intracytoplasmic sperm injection for male subfertility have chromosomal abnormalities. Hence, an understanding of sperm tail development and genes associated with its normal functioning can help in better diagnosis of male infertility and its management. There is still a lot that needs to be discovered about genes, proteins contributing to normal human sperm tail development, movement, and role in male fertility. Sperm tail has complex anatomy, with surrounding axoneme having 9 + 2 microtubules arrangement along its entire length and peri-axonemal structures that contribute in sperm motility and fertilization. In future sperm tail-associated genes, proteins and subunits can be used as markers of male fertility.

Characterization of sheep spermatogenesis through single-cell RNA sequencing

Spermatogenesis is an important biological process in male reproduction. The interaction between male germ cells and somatic cells during spermatogenesis, is necessary for male reproductive activities. This cellular heterogeneity has made it difficult to profile distinct cell types at different stages of development. Here, we present the first comprehensive, unbiased single-cell transcriptomic study of sheep spermatogenesis using 10× genomics single cell sequencing (scRNA-seq). We collected scRNA-seq data from 11 772 cells from the adult sheep testis and identified all known germ cells (including early primary spermatocytes, late primary spermatocytes, round spermatids, elongated spermatids, and sperm), and somatic cells (Sertoli cells and Leydig cells), as well as one somatic cell that unexpectedly contained leukocytes. The functional enrichment analysis indicated that several pathways of cell cycle, gamete generation, protein processing, and mRNA surveillance pathways were significantly enriched in testicular germ cell types, and ribosome pathway was significantly enriched in testicular somatic cell types. Further analysis identified several stage-specific marker genes of sheep germ cells, such as EZH2, SOX18, SCP2, PCNA, and PRKCD. Our research explored for the first time of the changes in the transcription level of various cell types during the process of sheep spermatogenesis, providing new insights for sheep spermatogenesis and spermatogenic cell development.

m6A-dependent biogenesis of circular RNAs in male germ cells

The majority of circular RNAs (circRNAs) spliced from coding genes contain open reading frames (ORFs) and thus, have protein coding potential. However, it remains unknown what regulates the biogenesis of these ORF-containing circRNAs, whether they are actually translated into proteins and what functions they play in specific physiological contexts. Here, we report that a large number of circRNAs are synthesized with increasing abundance when late pachytene spermatocytes develop into round and then elongating spermatids during murine spermatogenesis. For a subset of circRNAs, the back splicing appears to occur mostly at m6A-enriched sites, which are usually located around the start and stop codons in linear mRNAs. Consequently, approximately a half of these male germ cell circRNAs contain large ORFs with m6A-modified start codons in their junctions, features that have been recently shown to be associated with protein-coding potential. Hundreds of peptides encoded by the junction sequences of these circRNAs were detected using liquid chromatography coupled with mass spectrometry, suggesting that these circRNAs can indeed be translated into proteins in both developing (spermatocytes and spermatids) and mature (spermatozoa) male germ cells. The present study discovered not only a novel role of m6A in the biogenesis of coding circRNAs, but also a potential mechanism to ensure stable and long-lasting protein production in the absence of linear mRNAs, i.e., through production of circRNAs containing large ORFs and m6A-modified start codons in junction sequences.

Epigenetic Regulation and Risk Factors During the Development of Human Gametes and Early Embryos

Drastic epigenetic reprogramming occurs during human gametogenesis and early embryo development. Advances in low-input and single-cell epigenetic techniques have provided powerful tools to dissect the genome-wide dynamics of different epigenetic molecular layers in these processes. In this review, we focus mainly on the most recent progress in understanding the dynamics of DNA methylation, chromatin accessibility, and histone modifications in human gametogenesis and early embryo development. Deficiencies in remodeling of the epigenomes can cause severe developmental defects, infertility, and long-term health issues in offspring. Aspects of the external environment, including assisted reproductive technology procedures, parental diets, and unhealthy parental habits, may disturb the epigenetic reprogramming processes and lead to an aberrant epigenome in the offspring. Here, we review the current knowledge of the potential risk factors of aberrant epigenomes in humans.

Investigation of the association of idiopathic male infertility with polymorphisms in the methionine synthase (MTR) gene

OBJECTIVE

Spermatogenesis is a complex process that is regulated by a number of genes, some of which are involved in folate-dependent 1-carbon metabolism. Methionine synthase (encoded by MTR) is a key enzyme participating in this pathway. This study aimed to investigate the relationship of the MTR 2756A > G polymorphism with idiopathic male fertility in the Iranian population.

METHODS

The participants of this study included 100 men with idiopathic infertility and 100 healthy men as the control group. Genotyping of MTR 2756A > G was performed using the polymerase chain reaction and restriction fragment length polymorphism technique. The obtained data were analyzed using SPSS ver. 20.0 with a level of confidence of p< 0.05.

RESULTS

The frequencies of the A and G alleles at this locus were 77% and 23% in infertile patients and 84% and 16% in the control group, respectively. The frequencies of the GG, GA, and AA genotypes were 5%, 36%, and 59% in the infertile patients versus 3%, 27%, and 70% in the control group, respectively. No significant difference was observed in any genetic models.

CONCLUSION

In general, the findings of this study suggest that the MTR 2756A > G single-nucleotide polymorphism is not a predisposing factor for idiopathic infertility in men.

Temporal Dynamics of DNA Methylation Patterns in Response to Rearing Juvenile Steelhead (Oncorhynchus mykiss) in a Hatchery versus Simulated Stream Environment

Genetic selection is often implicated as the underlying cause of heritable phenotypic differences between hatchery and wild populations of steelhead trout (Oncorhynchus mykiss) that also differ in lifetime fitness. Developmental plasticity, which can also affect fitness, may be mediated by epigenetic mechanisms such as DNA methylation. Our previous study identified significant differences in DNA methylation between adult hatchery- and natural-origin steelhead from the same population that could not be distinguished by DNA sequence variation. In the current study, we tested whether hatchery-rearing conditions can influence patterns of DNA methylation in steelhead with known genetic backgrounds, and assessed the stability of these changes over time. Eyed-embryos from 22 families of Methow River steelhead were split across traditional hatchery tanks or a simulated stream-rearing environment for 8 months, followed by a second year in a common hatchery tank environment. Family assignments were made using a genetic parentage analysis to account for relatedness among individuals. DNA methylation patterns were examined in the liver, a relatively homogeneous organ that regulates metabolic processes and somatic growth, of juveniles at two time points: after eight months of rearing in either a tank or stream environment and after a subsequent year of rearing in a common tank environment. Further, we analyzed DNA methylation in the sperm of mature 2-year-old males from the earlier described treatments to assess the potential of environmentally-induced changes to be passed to offspring. Hepatic DNA methylation changes in response to hatchery versus stream-rearing in yearling fish were substantial, but few persisted after a second year in the tank environment. However, the early rearing environment appeared to affect how fish responded to developmental and environmental signals during the second year since novel DNA methylation differences were identified in the livers of hatchery versus stream-reared fish after a year of common tank rearing. Furthermore, we found profound differences in DNA methylation due to age, irrespective of rearing treatment. This could be due to smoltification associated changes in liver physiology after the second year of rearing. Although few rearing-treatment effects were observed in the sperm methylome, strong family effects were observed. These data suggest limited potential for intergenerational changes, but highlight the importance of understanding the effects of kinship among studied individuals in order to properly analyze and interpret DNA methylation data in natural populations. Our work is the first to study family effects and temporal dynamics of DNA methylation patterns in response to hatchery-rearing.

Associations of C677T polymorphism in methylenetetrahydrofolate reductase (MTHFR) gene with male infertility risk: A meta-analysis

PURPOSE

Methylenetetrahydrofolate reductase is one of the key enzymes in folate metabolism. But the association between polymorphism and the risk of male infertility is still controversial. Therefore, this study used a meta-analysis on the collection of data to analyze MTHFR gene C677T polymorphism (known as c.665 C>T, rs1801133, p.Ala222Val).

METHODS

PubMed, EMBASE, China National Knowledge Infrastructure (CNKI), and Wan fang. Data were searched to identify eligible studies. We sifted the data collection by Hardy-Weinberg equilibrium calculator and used odds ratios (ORs) and 95% confidence intervals (95% CIs) to conduct data through RevMan5.0 and StataSE12.0 software.

RESULTS

A total of 15 studies have 3853 patients with infertility and 3613 healthy controls in this meta-analysis. Our results showed that T variant of MTHFR C677T gene polymorphism was significantly associated with an increased risk of male infertility (forT vs. C: OR=1.38, 95% CI=1.18-1.63; for TT vs. CC: OR=1.86, 95% CI=1.36-2.54; for CT vs. CC: OR=1.34, 95% CI=1.03-1.74; for TT vs. CT: OR=1.52, 95% CI=1.26-1.84; for TT vs. CT+CC: OR=1.42, 95% CI=1.19-1.70; for TT+CT versus CC: OR=1.46, 95%CI=1.05-2.04). In addition, the results indicated that T allele had the positive association which was driven by East-asian populations (random: OR=1.44, 95% CI=1.2-1.74; fixed: OR=1.39, 95% CI=1.20-1.61), Middle-eastern populations (random: OR=1.30, 95% CI=1.05-1.63; fixed: OR=1.30, 95% CI=1.05-1.63) and Mixed-race (random: OR=1.96, 95% CI=1.35-2.85; fixed: OR=1.31, 95% CI=1.20-1.43).

CONCLUSION

This meta-analysis suggests that MTHFR C677T polymorphism is associated with male infertility.

Sperm proteome and reproductive technologies in mammals

Sperm is highly differentiated cell that can be easily obtained and purified. Mature sperm is considered to be transcriptionally and translationally silent and incapable of protein synthesis. Recently, a large number of proteins have been identified in sperm from different species by using the proteomic approaches. Clinically, sperm proteins can be used as markers for male infertility due to different protein profiles identified in sperm from fertile and infertile male animals. Recent evidences have shown that the conditions of sperm preservation in vitro can also change the sperm protein profiles. This paper reviews the recent scientific publications available to address sperm proteome and their relationship with sperm cryopreservation, capacitation, fertilization, and separation of X and Y sperm. Future directions in the application of sperm proteomics to develop or optimize reproductive technologies in mammals are also discussed.

Highly conserved epigenetic regulation of BOULE and DAZL is associated with human fertility

Separation of germ cells from somatic cells is a widespread feature of animal sexual reproduction, with a core set of germ cell factors conserved among diverse animals. It is not known what controls their conserved gonad-specific expression. Core components of epigenetic machinery are ancient, but its role in conserved tissue expression regulation remains unexplored. We found that promoters of the reproductive genes BOULE and DAZL exhibit differential DNA methylation, consistent with their gonad-specific expression in humans and mice. Low or little promoter methylation from the testicular tissue is attributed to spermatogenic cells of various stages in the testis. Such differential DNA methylation is present in the orthologous promoters not only of other mammalian species, but also of chickens and fish, supporting a highly conserved epigenetic mechanism. Furthermore, hypermethylation of DAZL and BOULE promoters in human sperm is associated with human infertility. Our data strongly suggest that epigenetic regulation may underlie conserved germ-cell-specific expression, and such a mechanism may play an important role in human fertility.-Zhang, C., Xue, P., Gao, L., Chen, X., Lin, K., Yang, X., Dai, Y., Xu, E. Y. Highly conserved epigenetic regulation of BOULE and DAZL is associated with human fertility.

Autophagy regulates spermatid differentiation via degradation of PDLIM1

Spermiogenesis is a complex and highly ordered spermatid differentiation process that requires reorganization of cellular structures. We have previously found that Atg7 is required for acrosome biogenesis. Here, we show that autophagy regulates the round and elongating spermatids. Specifically, we found that Atg7 is required for spermatozoa flagella biogenesis and cytoplasm removal during spermiogenesis. Spermatozoa motility of atg7-null mice dropped significantly with some extra-cytoplasm retained on the mature sperm head. These defects are associated with an impairment of the cytoskeleton organization. Functional screening revealed that the negative cytoskeleton organization regulator, PDLIM1 (PDZ and LIM domain 1 [elfin]), needs to be degraded by the autophagy-lysosome-dependent pathway to facilitate the proper organization of the cytoskeleton. Our results thus provide a novel mechanism showing that autophagy regulates cytoskeleton organization mainly via degradation of PDLIM1 to facilitate the differentiation of spermatids.

Chromatoid Body Protein TDRD6 Supports Long 3' UTR Triggered Nonsense Mediated mRNA Decay

Chromatoid bodies (CBs) are spermiogenesis-specific organelles of largely unknown function. CBs harbor various RNA species, RNA-associated proteins and proteins of the tudor domain family like TDRD6, which is required for a proper CB architecture. Proteome analysis of purified CBs revealed components of the nonsense-mediated mRNA decay (NMD) machinery including UPF1. TDRD6 is essential for UPF1 localization to CBs, for UPF1-UPF2 and UPF1-MVH interactions. Upon removal of TDRD6, the association of several mRNAs with UPF1 and UPF2 is disturbed, and the long 3’ UTR-stimulated but not the downstream exon-exon junction triggered pathway of NMD is impaired. Reduced association of the long 3’ UTR mRNAs with UPF1 and UPF2 correlates with increased stability and enhanced translational activity. Thus, we identified TDRD6 within CBs as required for mRNA degradation, specifically the extended 3’ UTR-triggered NMD pathway, and provide evidence for the requirement of NMD in spermiogenesis. This function depends on TDRD6-promoted assembly of mRNA and decay enzymes in CBs.

Tudor-domain containing protein 6 (TDRD6) is a central component of the chromatoid body (CB) in male germ cells. Chromatoid bodies, which are present in spermatids, contain RNA and protein, are not enclosed by membranes, and typically reside close to the nucleus. Without TDRD6, a much distorted CB structure is observed, and this work asked for the functional contribution of TDRD6 to spermatids. We found that TDRD6 is required for localization of an RNA degradation machinery to the CB. This so-called nonsense mediated decay (NMD) machinery, known from somatic cells, destroys mRNAs that feature premature stop codons. Absence of TDRD6 significantly impairs one specific mechanism of NMD, which depends on long 3’ untranslated regions of the transcripts. Thus, the CB component TDRD6 acts in the assembly of the NMD machinery in the CB.

Decreased spermatogenesis led to alterations of testis-specific gene expression in male mice following nano-TiO2 exposure

Although TiO2 nanoparticles (NPs) exposure has been demonstrated to cross blood-testis barrier and accumulate in the testis resulting in the reduction of sperm numbers, limited data with respect to the molecular mechanism of decreased spermatogenesis caused by TiO2 NP exposure. In this research, testicular damage, sperm number and alterations in testis-specific gene expressions in male mice induced by intragastric administration with TiO2 NPs for six months were investigated. It was found out that TiO2 NPs could migrate to cells, deposit in the testis and epididymis and thus cause damages to relevant organs, which are, to be more specific, the reductions of total sperm concentrations and sperm motility and an enhancement in the number of abnormal sperms in the cauda epididymis. Furthermore, the individual expression regarding to the mRNAs and proteins of testis-specific genes, including Cdc2, Cyclin B1, Dmcl, TERT, Tesmin, TESP-1, XPD and XRCCI, were significantly declined, whereas Gsk3-β and PGAM4 expressions were greatly elevated in mouse testis due to the exposures, which in fact implied that the reduced spermatogenesis may be involved in the alternated testis-specific gene expressions in those exposed male mice.

Comparison of Protamine 1 to Protamine 2 mRNA Ratio and YBX2 gene mRNA Content in Testicular Tissue of Fertile and Azoospermic Men

Background

Although aberrant protamine (PRM) ratios have been observed in infertile men, the mechanisms that implicit the uncoupling of PRM1 and PRM2 expression remain unclear. To uncover these mechanisms, in this observational study we have compared the PRM1/PRM2 mRNA ratio and mRNA contents of two regulatory factors of these genes.

Materials and Methods

In this experimental study, sampling was performed by a multi-step method from 50 non-obstructive azoospermic and 12 normal men. After RNA extraction and cDNA synthesis, real-time quantitative polymerase chain reaction (RT- QPCR) was used to analyze the PRM1, PRM2, Y box binding protein 2 (YBX2) and JmjC-containing histone demethylase 2a (JHDM2A) genes in testicular biopsies of the studied samples.

Results

The PRM1/PRM2 mRNA ratio differed significantly among studied groups, namely 0.21 ± 0.13 in azoospermic samples and -0.8 ± 0.22 in fertile samples. The amount of PRM2 mRNA, significantly reduced in azoospermic patients. Azoospermic men exhibited significant under expression of YBX2 gene compared to controls (P<0.001). mRNA content of this gene showed a positive correlation with PRM mRNA ratio (R=0.6, P=0.007). JHDM2A gene expression ratio did not show any significant difference between the studied groups (P=0.3). We also observed no correlation between JHDM2A mRNA content and the PRM mRNA ratio (R=0.2, P=0.3).

Conclusion

We found significant correlation between the aberrant PRM ratio (PRM2 under expression) and lower YBX2 mRNA content in testicular biopsies of azoospermic men compared to controls, which suggested that downregulation of the YBX2 gene might be involved in PRM2 under expression. These molecules could be useful biomarkers for predicting male infertility.

The spatiotemporal expression and localization implicates a potential role for SerpinB11 in the process of mouse spermatogenesis and apoptosis

In this study, the spatiotemporal expression of SerpinB11 in the mouse testis from postnatal 1-60 d was checked, the SerpinB11 protein strongly localized in the intermediate spermatogonia, B-type spermatogonium, preleptotene spermatocyte, leptonema spermatocyte, zygotene spermatocyte, but weakly localized in the pachytene spermatocyte, diplotene spermatocyte, sphere sperm, and the apoptotic sperm was positive stained of SerpinB11 protein, the localization of cell cycle marker CDK4 and meiosis marker SCP3 were investigated, and the SCP3 and SerpinB11 colocalized in the intermediate spermatogonia, B-type spermatogonium, preleptotene spermatocyte. Taken together, these results suggested that SerpinB11 might involved in spermatogenesis and apoptosis.

TMEM203 Is a Novel Regulator of Intracellular Calcium Homeostasis and Is Required for Spermatogenesis

Intracellular calcium signaling is critical for initiating and sustaining diverse cellular functions including transcription, synaptic signaling, muscle contraction, apoptosis and fertilization. Trans-membrane 203 (TMEM203) was identified here in cDNA overexpression screens for proteins capable of modulating intracellular calcium levels using activation of a calcium/calcineurin regulated transcription factor as an indicator. Overexpression of TMEM203 resulted in a reduction of Endoplasmic Reticulum (ER) calcium stores and elevation in basal cytoplasmic calcium levels. TMEM203 protein was localized to the ER and found associated with a number of ER proteins which regulate ER calcium entry and efflux. Mouse Embryonic Fibroblasts (MEFs) derived from Tmem203 deficient mice had reduced ER calcium stores and altered calcium homeostasis. Tmem203 deficient mice were viable though male knockout mice were infertile and exhibited a severe block in spermiogenesis and spermiation. Expression profiling studies showed significant alternations in expression of calcium channels and pumps in testes and concurrently Tmem203 deficient spermatocytes demonstrated significantly altered calcium handling. Thus Tmem203 is an evolutionarily conserved regulator of cellular calcium homeostasis, is required for spermatogenesis and provides a causal link between intracellular calcium regulation and spermiogenesis.

Rhox8 Ablation in the Sertoli Cells Using a Tissue-Specific RNAi Approach Results in Impaired Male Fertility in Mice

The reproductive homeobox X-linked, Rhox, genes encode transcription factors that are selectively expressed in reproductive tissues. While there are 33 Rhox genes in mice, only Rhox and Rhox8 are expressed in Sertoli cells, suggesting that they may regulate the expression of somatic-cell gene products crucial for germ cell development. We previously characterized Rhox5-null mice, which are subfertile, exhibiting excessive germ cell apoptosis and compromised sperm motility. To assess the role of Rhox8 in Sertoli cells, we used a tissue-specific RNAi approach to knockdown RHOX8 in vivo, in which the Rhox5 promoter was used to drive Rhox8-siRNA transgene expression in the postnatal Sertoli cells. Western and immunohistochemical analysis confirmed Sertoli-specific knockdown of RHOX8. However, other Sertoli markers, Gata1 and Rhox5, maintained normal expression patterns, suggesting that the knockdown was specific. Interestingly, male RHOX8-knockdown animals showed significantly reduced spermatogenic output, increased germ cell apoptosis, and compromised sperm motility, leading to impaired fertility. Importantly, our results revealed that while some RHOX5-dependent factors were also misregulated in Sertoli cells of RHOX8-knockdown animals, the majority were not, and novel putative RHOX8-regulated genes were identified. This suggests that while reduction in levels of RHOX5 and RHOX8 in Sertoli cells elicits similar phenotypes, these genes are not entirely redundant. Taken together, our study underscores the importance of Rhox genes in male fertility and suggests that Sertoli cell-specific expression of Rhox5 and Rhox8 is critical for complete male fertility.

MTHFR 677C>T polymorphism increases the male infertility risk: a meta-analysis involving 26 studies

Background and Objectives

Methylenetetrahydrofolate reductase (MTHFR) polymorphism may be a risk factor for male infertility. However, the epidemiologic studies showed inconsistent results regarding MTHFR polymorphism and the risk of male infertility. Therefore, we performed a meta-analysis of published case-control studies to re-examine the controversy.

Methods

Electronic searches of PubMed, EMBASE, Google Scholar and China National Knowledge Infrastructure (CNKI) were conducted to select eligible literatures for this meta-analysis (updated to June 19, 2014). According to our inclusion criteria and the Newcastle-Ottawa Scale (NOS), only high quality studies that observed the association between MTHFR polymorphism and male infertility risk were included. Crude odds ratio (OR) with 95% confidence interval (CI) was used to assess the strength of association between the MTHFR polymorphism and male infertility risk.

Results

Twenty-six studies involving 5,575 cases and 5,447 controls were recruited. Overall, MTHFR 677C>T polymorphism showed significant associations with male infertility risk in both fixed effects (CT+TT vs. CC: OR = 1.34, 95% CI: 1.23–1.46) and random effects models (CT+TT vs. CC: OR = 1.39, 95% CI: 1.19–1.62). Further, when stratified by ethnicity, sperm concentration and control sources, the similar results were observed in Asians, Caucasians, Azoo or OAT subgroup and both in population-based and hospital-based controls. Nevertheless, no significant association was only observed in oligo subgroup.

Conclusions

Our results indicated that the MTHFR polymorphism is associated with an increased risk of male infertility. Further well-designed analytical studies are necessary to confirm our conclusions and evaluate gene-environment interactions with male infertility risk.

Imidacloprid induces morphological and molecular damages on testis of lizard (Podarcis sicula)

The insecticide imidacloprid was evaluated under laboratory conditions in the adult male Italian wall lizards (Podarcis sicula) to assess its potential toxicity. By an acute oral test, LD50 was 503.76 mg/kg. Changes in spermatogenesis, plasma sex hormone levels and androgen and oestrogen receptor mRNAs were analysed by subchronic test and simulated environmental exposure. 15-days subchronic test, in which lizards were orally dosed on alternate days at 0, 10, 50, 100 mg/kg bw, showed a dose-dependent changes of testicular architecture and an increase of apoptotic processes. In a 30-days simulated environmental exposure spermatogenesis was arrested at secondary spermatocyte level and only few primary spermatocytes were TUNEL-positive. In all experimental groups imidacloprid was able to decrease both the level of sex hormones and the steroid receptor mRNAs. The results demonstrate that imidacloprid affects reproduction function of male lizards therefore precautions must be taken to minimize the harmful effects of this compound.

Fsh and Lh direct conserved and specific pathways during flatfish semicystic spermatogenesis

The current view of the control of spermatogenesis by Fsh and Lh in non-mammalian vertebrates is largely based on studies carried out in teleosts with cystic and cyclic spermatogenesis. Much less is known concerning the specific actions of gonadotropins during semicystic germ cell development, a type of spermatogenesis in which germ cells are released into the tubular lumen where they transform into spermatozoa. In this study, using homologous gonadotropins and a candidate gene approach, for which the genes' testicular cell-type-specific expression was established, we investigated the regulatory effects of Fsh and Lh on gene expression during spermatogenesis in Senegalese sole (Solea senegalensis), a flatfish with asynchronous and semicystic germ cell development. During early spermatogenesis, Fsh and Lh upregulated steroidogenesis-related genes and nuclear steroid receptors, expressed in both somatic and germ cells, through steroid-dependent pathways, although Lh preferentially stimulated the expression of downstream genes involved in androgen and progestin syntheses. In addition, Lh specifically promoted the expression of spermatid-specific genes encoding spermatozoan flagellar proteins through direct interaction with the Lh receptor in these cells. Interestingly, at this spermatogenic stage, Fsh primarily regulated genes encoding Sertoli cell growth factors with potentially antagonistic effects on germ cell proliferation and differentiation through steroid mediation. During late spermatogenesis, fewer genes were regulated by Fsh or Lh, which was associated with a translational and posttranslational downregulation of the Fsh receptor in different testicular compartments. These results reveal that conserved and specialized gonadotropic pathways regulate semicystic spermatogenesis in flatfish, which may spatially adjust cell germ development to maintain a continuous reservoir of spermatids in the testis.

Transcriptomic profiling in Silurana tropicalis testes exposed to finasteride

Investigations of endocrine disrupting chemicals found in aquatic ecosystems with estrogenic and androgenic modes of action have increased over the past two decades due to a surge of evidence of adverse effects in wildlife. Chemicals that disrupt androgen signalling and steroidogenesis can result in an imbalanced conversion of testosterone (T) into 17β-estradiol (E2) and other androgens such as 5α-dihydrotestosterone (5α-DHT). Therefore, a better understanding of how chemicals perturb these pathways is warranted. In this study, the brain, liver, and testes of Silurana tropicalis were exposed ex vivo to the human drug finasteride, a potent steroid 5α-reductase inhibitor and a model compound to study the inhibition of the conversion of T into 5α-DHT. These experiments were conducted (1) to determine organ specific changes in sex steroid production after treatment, and (2) to elucidate the transcriptomic response to finasteride in testicular tissue. Enzyme-linked immunosorbent assays were used to measure hormone levels in media following finasteride incubation for 6 h. Finasteride significantly increased T levels in the media of liver and testis tissue, but did not induce any changes in E2 and 5α-DHT production. Gene expression analysis was performed in frog testes and data revealed that finasteride treatment significantly altered 1,434 gene probes. Gene networks associated with male reproduction such as meiosis, hormone biosynthesis, sperm entry, gonadotropin releasing hormone were affected by finasteride exposure as well as other pathways such as oxysterol synthesis, apoptosis, and epigenetic regulation. For example, this study suggests that the mode of action by which finasteride induces cellular damage in testicular tissue as reported by others, is via oxidative stress in testes. This data also suggests that 5-reductase inhibition disrupts the expression of genes related to reproduction. It is proposed that androgen-disrupting chemicals may mediate their action via 5-reductases and that the effects of environmental pollutants are not limited to the androgen receptor signalling.

Mouse BAZ1A (ACF1) is dispensable for double-strand break repair but is essential for averting improper gene expression during spermatogenesis

ATP-dependent chromatin remodelers control DNA access for transcription, recombination, and other processes. Acf1 (also known as BAZ1A in mammals) is a defining subunit of the conserved ISWI-family chromatin remodelers ACF and CHRAC, first purified over 15 years ago from Drosophila melanogaster embryos. Much is known about biochemical properties of ACF and CHRAC, which move nucleosomes in vitro and in vivo to establish ordered chromatin arrays. Genetic studies in yeast, flies and cultured human cells clearly implicate these complexes in transcriptional repression via control of chromatin structures. RNAi experiments in transformed mammalian cells in culture also implicate ACF and CHRAC in DNA damage checkpoints and double-strand break repair. However, their essential in vivo roles in mammals are unknown. Here, we show that Baz1a-knockout mice are viable and able to repair developmentally programmed DNA double-strand breaks in the immune system and germ line, I-SceI endonuclease-induced breaks in primary fibroblasts via homologous recombination, and DNA damage from mitomycin C exposure in vivo. However, Baz1a deficiency causes male-specific sterility in accord with its high expression in male germ cells, where it displays dynamic, stage-specific patterns of chromosomal localization. Sterility is caused by pronounced defects in sperm development, most likely a consequence of massively perturbed gene expression in spermatocytes and round spermatids in the absence of BAZ1A: the normal spermiogenic transcription program is largely intact but more than 900 other genes are mis-regulated, primarily reflecting inappropriate up-regulation. We propose that large-scale changes in chromatin composition that occur during spermatogenesis create a window of vulnerability to promiscuous transcription changes, with an essential function of ACF and/or CHRAC chromatin remodeling activities being to safeguard against these alterations.

The eukaryotic genome is packaged into a periodic nucleoprotein complex known as chromatin. Wrapping of DNA around nucleosomes, the basic repeat unit of chromatin, enables packing of long stretches of DNA into a compact nucleus but also impedes access by protein factors involved in essential cellular processes such as transcription, replication, recombination and repair. Chromatin remodeling factors are multi-protein complexes that utilize the energy released during ATP-hydrolysis to assemble, reposition, restructure and disassemble nucleosomes. These complexes disrupt histone-DNA contacts to ‘remodel’ the chromatin and grant access to the genome. Alternatively, access can also be denied to repress transcription, for example. Spermatogenesis, the developmental program that produces sperm, comprises a dramatic chromatin makeover and the induction of a transcriptional program that engages nearly one-third of the genome. Here we provide evidence suggesting that these large-scale alterations leave the genomic material vulnerable to spurious transcriptional changes which are normally repressed by ACF1 (BAZ1A in mammals), the defining member of the well-studied ACF/CHRAC chromatin remodeling complex. These findings indicate that Baz1a plays a previously unrealized role in male fertility and may represent a novel target for male contraceptive development.

Regulated expression of Rhox8 in the mouse ovary: evidence for the role of progesterone and RHOX5 in granulosa cells

The gonadotropin surge is the essential trigger to stimulate ovulation and luteinization of ovarian follicles. While the hormone signals from the brain that initiate ovulation are known, the specific targets which regulate this process are not well known. In this study, we assessed the suitability of the Rhox homeobox gene cluster to serve as the master regulators of folliculogenesis. In superovulated (equine chorionic gonadotropin [eCG]/human chorionic gonadotropin [hCG]) mice, the Rhox genes exhibited four distinct windows of peak expression, suggesting that these genes may regulate specific events during the ovulatory cycle. Like many members of the cluster, Rhox8 mRNA and protein were induced by follicle stimulating hormone [FSH]/eCG in granulosa cells. However, Rhox8 displayed unique peak expression at 8 h post-hCG administration, implying it might be the lone member of the cluster regulated by progesterone. Subsequent promoter analysis in granulosa cells revealed relevant homeobox binding and progesterone response elements within Rhox8's 5'-flanking region. In superovulated mice, progesterone receptor (PGR) is recruited to the Rhox8 promoter, as assessed by chromatin immunoprecipitation. In Rhox5-null mice, Rhox8 mRNA was reduced at 2 h and 4 h post-hCG administration but recovered once the follicles passed the antral stage of development. Conversely, in progesterone receptor knockout mice, Rhox8 exhibited normal stimulation by eCG but failed to reach its peak mRNA level at 8 h post-hCG found in wild-type mice. This suggests a model in which Rhox8 transcription is dependent upon RHOX5 during early folliculogenesis and upon progesterone during the periovulatory window when RHOX5 normally wanes. In support of this model, transfection of RHOX5 and PGR expression plasmids stimulated, whereas dominant negative and mutant constructs inhibited, Rhox8 promoter activity.

Tzfp represses the androgen receptor in mouse testis

The testis zinc finger protein (Tzfp), also known as Repressor of GATA, belongs to the BTB/POZ zinc finger family of transcription factors and is thought to play a role in spermatogenesis due to its remarkably high expression in testis. Despite many attempts to find the in vivo role of the protein, the molecular function is still largely unknown. Here, we address this issue using a novel mouse model with a disrupted Tzfp gene. Homozygous Tzfp null mice are born at reduced frequency but appear viable and fertile. Sertoli cells in testes lacking Tzfp display an increase in Androgen Receptor (AR) signaling, and several genes in the testis, including Gata1, Aie1 and Fanc, show increased expression. Our results indicate that Tzfp function as a transcriptional regulator and that loss of the protein leads to alterations in AR signaling and reduced number of apoptotic cells in the testicular tubules.

Digital gene expression tag profiling analysis of the gene expression patterns regulating the early stage of mouse spermatogenesis

Detailed characterization of the gene expression patterns in spermatogonia and primary spermatocytes is critical to understand the processes which occur prior to meiosis during normal spermatogenesis. The genome-wide expression profiles of mouse type B spermatogonia and primary spermatocytes were investigated using the Solexa/Illumina digital gene expression (DGE) system, a tag based high-throughput transcriptome sequencing method, and the developmental processes which occur during early spermatogenesis were systematically analyzed. Gene expression patterns vary significantly between mouse type B spermatogonia and primary spermatocytes. The functional analysis revealed that genes related to junction assembly, regulation of the actin cytoskeleton and pluripotency were most significantly differently expressed. Pathway analysis indicated that the Wnt non-canonical signaling pathway played a central role and interacted with the actin filament organization pathway during the development of spermatogonia. This study provides a foundation for further analysis of the gene expression patterns and signaling pathways which regulate the molecular mechanisms of early spermatogenesis.

Genome-wide identification of Sox8-, and Sox9-dependent genes during early post-natal testis development in the mouse

The SOX8 and SOX9 transcription factors are involved in, among others, sex differentiation, male gonad development and adult maintenance of spermatogenesis. Sox8(-/-) mice lacking Sox9 in Sertoli cells fail to form testis cords and cannot establish spermatogenesis. Although genetic and histological data show an important role for these transcription factors in regulating spermatogenesis, it is not clear which genes depend upon them at a genome-wide level. To identify transcripts that respond to the absence of Sox8 in all cells and Sox9 in Sertoli cells we measured mRNA concentrations in testicular samples from mice at 0, 6 and 18 days post-partum. In total, 621 and 629 transcripts were found at decreased or increased levels, respectively, at different time points in the mutant as compared to the control samples. These mRNAs were categorized as preferentially expressed in Sertoli cells or germ cells using data obtained with male and female gonad samples and enriched testicular cell populations. Five candidate genes were validated at the protein level. Furthermore, we identified putative direct SOX8 and SOX9 target genes by integrating predicted SOX-binding sites present in potential regulatory regions upstream of the transcription start site. Finally, we used protein network data to gain insight into the effects on regulatory interactions that occur when Sox8 and Sox9 are absent in developing Sertoli cells. The integration of testicular samples with enriched Sertoli cells, germ cells and female gonads enabled us to broadly distinguish transcripts directly affected in Sertoli cells from others that respond to secondary events in testicular cell types. Thus, combined RNA profiling signals, motif predictions and network data identified putative SOX8/SOX9 target genes in Sertoli cells and yielded insight into regulatory interactions that depend upon these transcription factors. In addition, our results will facilitate the interpretation of genome-wide in vivo SOX8 and SOX9 DNA binding data.

Proteome analysis of the fathead minnow (Pimephales promelas) reproductive testes

Proteomics is becoming more widely used as a tool in fish physiology and toxicology and can offer mechanistic insight into organism responses to environmental signals and stressors. Using a LTQ Orbitrap Velos MS/MS, we detected 1075 proteins in the reproductive testis of fathead minnow. Proteins localized to the testis included those with a role in spermatogenesis, DNA repair, gamete meiosis, and proteins that have methylation and phosporylation activity, which are important regulatory mechanisms required for sperm maturation. Enrichment analysis revealed that proteins involved in translation, excision DNA repair, and chromatin remodeling were significantly enriched in the testis (>25% protein coverage of the cellular pathways). Proteins involved in RNA metabolism, spliceosome assembly, metabolism, and DNA unwinding were localized to the testis, and the DEAD (Asp-Glu-Ala-Asp) box RNA-dependent helicase family was well represented in this reproductive tissue. Based upon common detected proteins and functional processes between FHMs and the more ancient sharks, other ray-finned fishes, and mammals, we hypothesize that biological processes involved in the testis (DNA unwinding, RNA processing, spliceosome assembly) have been conserved throughout vertebrate evolution. This study provides the foundation for more in depth proteomics studies investigating the effects of hormones and endocrine disruptors in the teleostean testes.

Identification and characterization of promoter and regulatory regions for mouse Adam2 gene expression

ADAM2, a member of the 'a disintegrin and metalloprotease' (ADAM) family, is a key protein in mammalian fertilization that is specifically expressed in testicular germ cells. Here, we investigated the transcriptional regulation of the mouse Adam2 gene. An in silico analysis identified two conserved non-coding sequences located upstream of the mouse and human ADAM2 genes. The upstream region of the mouse Adam2 gene was found to lack typical TATA and CAAT boxes, and to have a high GC content. Our in vitro transient transfection-reporter analysis identified a promoter in this region of the mouse Adam2 gene, along with regulatory regions that inhibit the activity of this promoter in somatic cells. Site-directed mutagenesis revealed that the caudal-type homeobox 1 and CCTC-binding factor motifs are responsible for the inhibitory activities of the repressor regions. Finally, electrophoretic mobility shift assays showed putative transcription factor-promoter DNA complexes, and DNA-affinity chromatography and proteomic analyses identified myelin gene regulatory factor as a binding partner of the Adam2 promoter. This provides the first identification and characterization of promoter and repressor regions that regulate the transcription of the mouse Adam2 gene, and offers insights into the regulation of this germ-cell-specific gene.

Androgen-responsive microRNAs in mouse Sertoli cells

Although decades of research have established that androgen is essential for spermatogenesis, androgen's mechanism of action remains elusive. This is in part because only a few androgen-responsive genes have been definitively identified in the testis. Here, we propose that microRNAs – small, non-coding RNAs – are one class of androgen-regulated trans-acting factors in the testis. Specifically, by using androgen suppression and androgen replacement in mice, we show that androgen regulates the expression of several microRNAs in Sertoli cells. Our results reveal that several of these microRNAs are preferentially expressed in the testis and regulate genes that are highly expressed in Sertoli cells. Because androgen receptor-mediated signaling is essential for the pre- and post-meiotic germ cell development, we propose that androgen controls these events by regulating Sertoli/germ cell-specific gene expression in a microRNA-dependent manner.

Dynamic expression pattern and subcellular localization of the Rhox10 homeobox transcription factor during early germ cell development

Homeobox genes encode transcription factors that regulate diverse developmental events. The largest known homeobox gene cluster - the X-linked mouse reproductive homeobox (Rhox) cluster - harbors genes whose expression patterns and functions are largely unknown. Here, we report that a member of this cluster, Rhox10, is expressed in male germ cells. Rhox10 is highly transcribed in spermatogonia in vivo and is upregulated in response to the differentiation-inducing agent retinoic acid in vitro. Using a specific RHOX10 antiserum that we generated, we found that RHOX10 protein is selectively expressed in fetal gonocytes, germline stem cells, spermatogonia, and early spermatocytes. RHOX10 protein undergoes a dramatic shift in subcellular localization as germ cells progress from mitotically arrested gonocytes to mitotic spermatogonia and from mitotic spermatogonia to early meiotic spermatocytes, consistent with RHOX10 performing different functions in these stages.

A-MYB (MYBL1) stimulates murine testis-specific Ldhc expression via the cAMP-responsive element (CRE) site

Generally, knowledge of the mechanism regulating gene expression in primary spermatocytes is incomplete. We have used the lactate dehydrogenase gene (Ldhc) as a model to explore these mechanisms during spermatogenesis. Its 100-bp core promoter contained two essential elements common to many genes, a GC box and a CRE site. Here we report results that support a model in which transcription factor MYBL1 acts as a coactivator directing tissue-specific expression via the CRE cis element. We hypothesize that this is a common mechanism involving activation of multiple genes in the primary spermatocyte. MYBL1 is expressed predominantly as a tissue-specific transcription factor in spermatocytes and breast epithelial cells. Our finding that LDHC expression is lost in 21-day testes of MYBL1 mutant mice supports our hypothesis. In the GC1-spg germ cell line exogenous MYBL1 induces activity 4- to 8-fold, although extracts from these cells do not show MYBL1 binding activity for the Myb consensus sequences in the Ldhc promoter by EMSA. Rather, MYBL1 stimulates expression from a synthetic promoter containing only CRE elements, suggesting MYBL1 activates the promoter by interacting with protein that binds to a CRE element. Mutation of three Myb sites does not affect Ldhc promoter activity significantly (P > 0.05). CREB-binding protein (CBP) is a coactivator that interacts with CRE-binding protein CREB. We show that the transactivation domain (TAD) in MYBL1 interacts with the KIX domain in CBP, and the TAD domain and DNA binding domain in MYBL1 each interact with the CREB N-terminal domain. MYBL1 also stimulated expression from testis-specific genes Pgk2 (phosphoglycerate kinase 2) and Pdha2 (pyruvate dehydrogenase alpha 2) promoters, each of which contains CRE promoter elements and is expressed in primary spermatocytes. We propose that MYBL1 directs germ cell-specific activation via the CRE site of certain genes that are activated specifically in the primary spermatocyte, although other, more indirect effects of MYBL1 remain a possible explanation for our results.

DNA demethylation-dependent AR recruitment and GATA factors drive Rhox5 homeobox gene transcription in the epididymis

Mammalian male fertility depends on the epididymis, a highly segmented organ that promotes sperm maturation and protects sperm from oxidative damage. Remarkably little is known about how gene expression is controlled in the epididymis. A candidate to regulate genes crucial for epididymal function is reproductive homeobox gene on X chromosome (RHOX)5, a homeobox transcription factor essential for optimal sperm motility that is expressed in the caput region of the epididymis. Here, we report the identification of factors that control Rhox5 gene expression in epididymal cells in a developmentally regulated and region-specific fashion. First, we identify GATA transcription factor-binding sites in the Rhox5 proximal promoter (Pp) necessary for Rhox5 expression in epididymal cells in vitro and in vivo. Adjacent to the GATA sites are androgen-response elements, which bind to the nuclear hormone receptor androgen receptor (AR), and are responsible for the AR-dependent expression of Rhox5 in epididymal cells. We provide evidence that AR is recruited to the Pp in a region-specific and developmentally regulated manner in the epididymis that is dictated not only by differential AR availability but differential methylation of the Pp. Site-specific methylation of the Pp cytosine and guanine separated by one phosphate, most of which overlap with androgen-response elements, inhibited both AR occupancy at the Pp and Pp-dependent transcription in caput epididymal cells. Together, our data support a model in which DNA methylation, AR, and GATA factors collaborate to dictate the unique developmental and region-specific expression pattern of the RHOX5 homeobox transcription factor in the caput epididymis, which in turn controls the expression of genes critical for promoting sperm motility and function.

Regulation of an RNA granule during spermatogenesis: acetylation of MVH in the chromatoid body of germ cells

During mammalian spermatogenesis, the mouse VASA homolog (MVH; also known as DDX4), a germ-cell-specific DEAD-box type RNA-binding protein, localizes in a germline-specific RNA granule termed the chromatoid body (CB). Genetic analyses have revealed that MVH is essential for progression through spermatogenesis, although the molecular mechanisms of its function remain elusive. We found that the acetyltransferase Hat1, and its cofactor, p46, are specifically colocalized with MVH in the CB and acetylate MVH at Lys405, leading to inactivation of its RNA-binding activity. Notably, the acetylation is developmentally regulated, paralleling the temporally regulated colocalization of Hat1 and p46 in the CB. We have identified 858 mRNAs as MVH targets, a large proportion of which correspond to previously known translationally arrested genes. Importantly, eIF4B mRNA, a target of MVH, is selectively released from the MVH-ribonucleoprotein (RNP) complex when MVH is acetylated, paralleling an increase in eIF4B protein. These findings reveal a previously unknown signaling pathway that links acetylation to RNA processing in the control of spermatogenesis.