Expression pattern of Boule in dairy goat testis and its function in promoting the meiosis in male germline stem cells (mGSCs)

Expressional Profiling of TEX11, ESRα and BOLL Genes in Yak under Different Feeding Conditions

Simple Summary

The yak (Bos grunniens) is regarded as one of the most magnificent domestic animals in the mountains of Asia, and it is well-adapted to the harsh environment of the Qinghai–Tibetan Plateau. Slow growth rate and low production and reproductive potential are the main limitations of yaks. It has been suggested that enhanced nutrition can improve reproductive efficiency in animals; however, this is still unclear for yaks. Hence, this study was designed to observe the effect of supplementary feeding on transcription and expression profiles of different genes related to reproduction. Such characterization under different feeding conditions can provide potential guidance for enhancement of the reproductive efficacy of yaks.

Abstract

Previous studies have demonstrated that nutrition plays a crucial part in improving the reproductive potential of farm animals; however, there is currently no research on the transcription and expression profiling of genes in yaks under different feeding conditions. Therefore, this research was planned to compare the transcription and expression profiles of TEX11, ESRα, and BOLL in yaks under natural grazing with concentrate supplementation (NG + CS) and NG without concentrate supplementation. The transcription and expressional levels of TEX11, ESRα, and BOLL mRNA were explored from the testes of yaks using qPCR, Western blotting, immunofluorescence, and immunochemistry. The results of the qPCR illustrated that the transcription levels of TEX11, ESRα, and BOLL were upregulated in the NG + CS group compared to those in the NG group. Moreover, the results of the immunochemistry and immunofluorescence showed that the expression of TEX11, ESRα, and BOLL proteins increased after concentrate supplementation. Meanwhile, ESRα protein levels were lower in the testes and epididymides of yaks in the NG group than in those in the NG + CS group. Similarly, BOLL protein expression was higher in the testes and epididymides of the NG + CS group, but its expression was lower in the epididymides of the NG group. Furthermore, Western blotting showed that the molecular weights of ESRα and BOLL proteins were 64 kDa and 31 kDa, respectively. Finally, in the conclusion we summarize how a proper level of dietary energy supplementation can improve the reproductive potential of yaks by upregulating genes related to reproduction.

Overexpression of DAZL, STRA8, and BOULE Genes and Treatment With BMP4 or Retinoic Acid Modulate the Expression of MSC Overexpressing Germ Cell Genes

In vitro gamete derivation from stem cells has potential applications in animal reproduction as an alternative method for the dissemination of elite animal genetics, production of transgenic animals, and conservation of endangered species. Mesenchymal stem cells (MSCs) may be suitable candidates for in vitro gamete derivation considering their differentiative capacity and their potential for cell therapy. Due to its relevance in gametogenesis, it has been reported that retinoic acid (RA) and bone morphogenetic protein (BMP) 4 are able to upregulate the expression of specific markers associated to the early stages of germ cell (GCs) differentiation in bovine fetal MSCs (bfMSCs). In the present study, we used polycistronic vectors containing combinations of GC genes DAZL, STRA8, and BOULE followed by exposure to BMP4 or RA to induce GC differentiation of bovine fetal adipose tissue-derived MSC (AT-MSCs). Cells samples at Day 14 were analyzed according to the expression of pluripotent genes NANOG and OCT4 and GC genes DAZL, STRA8, BOULE, PIWI, c-KIT, and FRAGILIS using Q-PCR. Fetal and adult testis and AT-MSCs samples were also analyzed for the expression of DAZL, STRA8, and NANOG using immunofluorescence. Increased gene expression levels in the adult testis and cell-specific distribution of DAZL, STRA8, and NANOG in the fetal testis suggest that these markers are important components of the regulatory network that control the in vivo differentiation of bovine GCs. Overexpression of DAZL and STRA8 in bi-cistronic and DAZL, STRA8, and BOULE in tri-cistronic vectors resulted in the upregulation of OCT4, NANOG, and PIWIL2 in bovine fetal AT-MSCs. While BMP4 repressed NANOG expression, this treatment increased DAZL and c-KIT and activated FRAGILIS expression in bovine fetal AT-MSCs. Treatment with RA for 14 days increased the expression of DAZL and FRAGILIS and maintained the mRNA levels of STRA8 in bovine fetal AT-MSCs transfected with bi-cistronic and tri-cistronic vectors. Moreover, RA treatment repressed the expression of OCT4 and NANOG in these cells. Thus, overexpression of DAZL, STRA8, and BOULE induced the upregulation of the pluripotent markers and PIWIL2 in transfected bovine fetal AT-MSCs. The partial activation of GC gene expression by BMP4 and RA suggests that both factors possess common targets but induce different gene expression effects during GC differentiation in overexpressing bovine fetal AT-MSCs.

Eif2s3y Promotes the Proliferation of Spermatogonial Stem Cells by Activating ERK Signaling

The future fertility of males with cancer may be irreversibly compromised by chemotherapy and/or radiotherapy. Spermatogonial stem cell transplantation is believed to be a way to restore fertility in men. However, the survival efficiency of transplanted cells is still low. Eukaryotic translation initiation factor 2 subunit 3 and structural gene Y-linked (Eif2s3y) located on the Y chromosome of male animals is a coding gene of eIF2γ which mainly functions in translation initiation. Recently, the emerging role of Eif2s3y in spermatogenesis has been emphasized in several studies. However, the underlying mechanism is still unclear. In addition, how Eif2s3y functions in large animals remains largely unknown. In this study, we obtained the CDS sequence of the Eif2s3y gene from the testis of dairy goats and found that this gene was highly expressed in the testis and was evolutionarily conserved among different species. Interestingly, overexpression of Eif2s3y promoted the proliferation of spermatogonial stem cells of dairy goats by activating the ERK signaling pathway. In animal experiments, overexpressing Eif2s3y promoted transplanted goat spermatogonial stem cells and produced more colonies after microinjection into the seminiferous tubules of infertile mice. In conclusion, our study highlights an undiscovered role of Eif2s3y in dairy goat reproduction. This finding may provide an important basis for future works regarding male spermatogenic cell restoration and represent a major advance toward surrogate sires becoming a tool for disseminating and regenerating germplasm in all mammals.

Histomorphological Comparisons and Expression Patterns of BOLL Gene in Sheep Testes at Different Development Stages

BOLL is implicated in mammalian testicular function maintenance and spermatogenesis. To understand the expression patterns and biological functions of sheep BOLL, we examined the expression and immunolocalization of BOLL in the developing testes of Small-Tail Han sheep aged 0 days (D0), 2 months (2M), 5 months (5M), 1 year (1Y), and 2 years (2Y), by qPCR, Western blot, and immunohistochemistry methods. Firstly, morphological studies revealed that, in addition to spermatogonia, ordered and clear spermatocytes, as well as round and elongated spermatids and sperm, were found in the 1Y and 2Y testicular seminiferous tubules of the sheep testes, compared with the D0, 2M, and 5M testes, as analyzed by hematoxylin and eosin (H&E) staining. The diameter and area of the seminiferous tubules, epithelial thickness, and the area and perimeter of the tubule lumens gradually increased with age. BOLL was specifically expressed in testes and upregulation of BOLL transcript expression was higher in the testes of the 1Y and 2Y groups than in those of the D0, 2M, and 5M groups. Similarly, BOLL protein was expressed mainly in the 1Y and 2Y testes, ranging from primary spermatocytes to round spermatids, as well as in the spermatozoa. This study is the first demonstration that sheep BOLL might serve as a key regulator of the spermiogenesis involved in sperm maturity, in addition to its role as a crucial meiotic regulator.

Reconstitution of male germline cell specification from mouse embryonic stem cells using defined factors in vitro

In vitro induction of functional haploid cells from embryonic stem cells (ESCs) has been reported by several groups. However, these reports either involve complex induction process with undefined induction factors or show low-induction efficiency. Here, we report complete meiosis in vitro from ESCs with defined induction factors. ESCs were first induced into primordial germ cell-like cells, which were further induced into male germline cells, including spermatogonial stem cell-like cells (SSCLCs) and spermatid-like cells. Importantly, the obtained SSCLCs were functional as infertile male mice sired healthy offspring via SSCLC transplantation. Further, we found that eukaryotic translation initiation factor 2 subunit 3 and structural gene Y-linked (Eif2s3y) was essential for spermatogenesis. Eif2s3y-overexpressing ESCs showed enhanced spermatogenesis in vitro, as demonstrated by higher expression levels of SSC-specific markers during SSCLC induction process, improved reproductive ability recovery of infertile male mice, and increased efficiency of haploid cell induction. Our work provides a convenient and efficient approach to obtain functional male germline cells.

Goat Boule: Isoforms identification, mRNA expression in testis and functional study and promoter methylation profiles

A conserved gene in meiosis, the Boule gene is involved in meiosis and spermatogenesis. The deletion of this gene in males blocks meiosis and results in infertility. Alternative splicing variants of the Boule gene have been identified in humans, bovines, and bats, but in dairy goats remains unknown. This study was therefore to detect splicing variants of the goat Boule gene and explore their potential roles in meiosis. Three isoforms, denoted as Boule-a, Boule-b, and Boule-c, were identified in the testes of goats using real-time PCR (RT-PCR) and cloning sequencing. Compared to the normal Boule gene, Boule-a was found to lack exons 7 and 8, which corresponds to a predicted variant, X4, on the NCBI database. Boule-b lacked exon 8, and Boule-c only retained exons 1 and 2. Of these three variants, two were novel isoforms of the Boule gene. Quantitative RT-PCR (qRT-PCR) showed that the Boule-a and Boule-b expression patterns were significantly different between the adult goat testes and the postnatal testes of 42 and 56 days. Overexpression of Boule-a and Boule-c in GC-1 spg cells of model mice significantly repressed CDC2 expression. Bisulfite sequencing PCR (BSP) results showed that the promoter region of the Boule gene was hypermethylated in goat testes. A negative correlation between the methylation levels of the Boule gene promoter and total mRNA expression of its transcripts was found. Our data showed alternative splicing and promoter methylation in the goat Boule gene, suggesting that this gene may play an important role in the regulation of Boule expression and in meiosis processing.

EIF2S3Y suppresses the pluripotency state and promotes the proliferation of mouse embryonic stem cells

Eukaryotic translation initiation factor 2, subunit 3, and structural gene Y-linked (EIF2S3Y) is essential for spermatogenesis in mouse models. However, its effect on embryonic stem (ES) cells remains unknown. In our observation, differentiated ES cells showed higher levels of EIF2S3Y. To further elucidate its role in ES cells, we utilized ES-derived EIF2S3Y-overexpressing cells and found that EIF2S3Y down-regulated the pluripotency state of ES cells, which might be explained by decreased histone methylation levels because of reduced levels of ten-eleven translocation 1 (TET1). Moreover, EIF2S3Y-overexpressing cells showed an enhanced proliferation rate, which might be due to increased Cyclin A and Cyclin E levels. This study highlighted novel roles of EIF2S3Y in the pluripotency maintenance and proliferation control of ES cells, which would provide an efficient model to study germ cell generation as well as cancer development using ES cells, thus providing valuable target for clinical applications of ES cells.

Lin28a promotes self-renewal and proliferation of dairy goat spermatogonial stem cells (SSCs) through regulation of mTOR and PI3K/AKT

Lin28a is a conserved RNA-binding protein that plays an important role in development, pluripotency, stemness maintenance, proliferation and self-renewal. Early studies showed that Lin28a serves as a marker of spermatogonial stem cells (SSCs) and promotes the proliferation capacity of mouse SSCs. However, there is little information about Lin28a in livestock SSCs. In this study, we cloned Capra hircus Lin28a CDS and found that it is evolutionarily conserved. Lin28a is widely expressed in different tissues of Capra hircus, but is expressed at a high level in the testis. Lin28a is specifically located in the cytoplasm of Capra hircus spermatogonial stem cells and may also be a marker of dairy goat spermatogonial stem cells. Lin28a promoted proliferation and maintained the self-renewal of GmGSCs-I-SB in vivo and in vitro. Lin28a-overexpressing GmGSCs-I-SB showed an enhanced proliferation rate, which might be due to increased PCNA expression. Moreover, Lin28a maintained the self-renewal of GmGSCs-I-SB by up-regulating the expression of OCT4, SOX2, GFRA1, PLZF and ETV5. Furthermore, we found that Lin28a may activate the AKT, ERK, and mTOR signaling pathways to promote the proliferation and maintain the self-renewal of GmGSCs-I-SB.

The Modification of Tet1 in Male Germline Stem Cells and Interact with PCNA, HDAC1 to promote their Self-renewal and Proliferation

Epigenetic modification plays key roles in spermatogenesis, especially DNA methylation dynamic is important in sustaining normal spermatogenesis. Ten-eleven translocation 1 (Tet1) is not only a key demethylase, which works in specific gene regions, but also crosstalks with partners to regulate epigenetic progress as protein complexes. Dairy goat is an important livestock in China, while the unstable culture system in vitro inhibits optimization of new dairy goat species. The study of epigenetic modification in male germline stem cells (mGSCs) is beneficial to the optimization of adult stem cell culture system in vitro, and the improvement of sperm quality and breeding of selected livestock. In our study, we not only analyzed the morphology, gene expression, DNA methylation and histone methylation dynamic in mouse Tet1 (mTet1) modified mGSCs, we also analyzed the stemness ability by in vivo transplantation and explored the functional mechanism of Tet1 in dairy goat mGSCs. The results showed mTet1 modified mGSCs had better self-renewal and proliferation ability than wild-type mGSCs, mTet1 could also up-regulate JMJD3 to decrease H3K27me3, which also showed to suppress the MEK-ERK pathway. Furthermore, Co-IP analysis demonstrated that TET1 interact with PCNA and HDAC1 by forming protein complexes to comprehensively regulate dairy goat mGSCs and spermatogenesis.

Modification of Tet1 and histone methylation dynamics in dairy goat male germline stem cells

OBJECTIVES

Tet (ten-eleven translocation) protein 1 is a key enzyme for DNA demethylation, which modulates DNA methylation and gene transcription. DNA methylation and histone methylation are critical elements in self-renewal of male germline stem cells (mGSCs) and spermatogenesis. mGSCs are the only type of adult stem cells able to achieve intergenerational transfer of genetic information, which is accomplished through differentiated sperm cells. However, numerous epigenetic obstacles including incomplete DNA methylation and histone methylation dynamics make establishment of stable livestock mGSC cell lines difficult. The present study was conducted to detect effects of DNA methylation and histone methylation dynamics in dairy goat mGSCs self-renewal and proliferation, through overexpression of Tet1.

MATERIALS AND METHODS

An immortalized dairy goat mGSC cell line bearing mouse Tet1 (mTet1) gene was screened and characteristics of the cells were assayed by quantitative real-time PCR (qRT-PCR), immunofluorescence assay, western blotting, fluorescence activated cell sorting (FACS) and use of the cell counting kit (CCK8) assay.

RESULTS

The screened immortalized dairy goat mGSC cell line bearing mTet1, called mGSC-mTet1 cells was treated with optimal doxycycline (Dox) concentration to maintain Tet1 gene expression. mGSC-mTet1 cells proliferated at a significantly greater rate than wild-type mGSCs, and mGSCs-specific markers such as proliferating cell nuclear antigen (PCNA), cyclinD1 (CCND1), GDNF family receptor alpha 1 (Gfra1) and endogenic Tet1, Tet2 were upregulated. The cells exhibited not only reduction in level of histone methylation but also changes in nuclear location of that methylation marker. While H3K9me3 was uniformly distributed throughout the nucleus of mGSC-mTet1 cells, it was present in only particular locations in mGSCs. H3K27me3 was distributed surrounding the edges of nuclei of mGSC-mTet1 cells, while it was uniformly distributed throughout nuclei of mGSCs. Our results conclusively demonstrate that modification of mGSCs with mTet1 affected mGSC maintenance and seemed to promote establishment of stable goat mGSC cell lines.

CONCLUSIONS

Taken together, our data suggest that Tet1 had novel and dynamic roles for regulating maintenance of pluripotency and proliferation of mGSCs by forming complexes with PCNA and histone methylation dynamics. This may provide new solutions for mGSCs stability and livestock mGSC cell line establishment.

VEGF/VEGFR2 Signaling Regulates Germ Cell Proliferation in vitro and Promotes Mouse Testicular Regeneration in vivo

Vascular endothelial growth factor (VEGF) plays fundamental roles in testicular development; however, its function on testicular regeneration remains unknown. The objective of this study was to explore the roles VEGF/VEGFR2 signaling plays in mouse germ cells and in mouse testicular regeneration. VEGF and the VEGFR2 antagonist SU5416 were added to culture medium to evaluate their effects on spermatogonial stem cell line (C18-4 cells) proliferation. Testicular cells obtained from newborn male ICR mice were grafted into the dorsal region of male BALB/c nude mice. VEGF and SU5416 were injected into the graft sites to assess the effects of the VEGF and VEGFR2 signaling pathways on testicular reconstitution. The grafts were analyzed after 8 weeks. We found that VEGF promoted C18-4 proliferation in vitro, indicating its role in germ cell survival. HE staining revealed that seminiferous tubules were reconstituted and male germ cells from spermatogonia to spermatids could be observed in testis-like tissues 8 weeks after grafting. A few advantaged male germ cells, including spermatocytes and spermatids, were found in SU5416-treated grafts. Moreover, VEGF enhanced the expression of genes specific for male germ cells and vascularization in 8-week grafts, whereas SU5416 decreased the expression of these genes. SU5416-treated grafts had a lower expression of MVH and CD31, indicating that blockade of VEGF/VEGFR2 signaling reduces the efficiency of seminiferous tubule reconstitution. Collectively, these data suggest that VEGF/VEGFR2 signaling regulates germ cell proliferation and promotes testicular regeneration via direct action on germ cells and the enhancement of vascularization.

PLZF-Induced Upregulation of CXCR4 Promotes Dairy Goat Male Germline Stem Cell Proliferation by Targeting Mir146a

Previous studies have shown that promyelocytic leukemia zinc finger (PLZF), chemokine (C-X-C motif) receptor 4 (CXCR4) and mir146a were associated with the self-renewal of mouse spermatogonial stem cells (SSCs); however, there is little information on their effects on the fate of livestock SSCs. Here, we have identified a regulatory pathway in dairy goat mGSCs, involving PLZF, mir146a and the SDF-1 receptor CXCR4. PLZF overexpression downregulated mir146a and simultaneously upregulated the expression of CXCR4 protein, whereas PLZF knockdown (siPLZF) induced the specifically opposite effects. The in vitro assays demonstrated that PLZF specifically interacts with and suppresses the mir146a promoter, and mir146a targets CXCR4 to impede its translation. The levels of ERK1/2 phosphorylation in the mGSCs overexpressed CXCR4 and PLZF were upregulated, respectively, whereas mir146a expression was decreased and CXCR4 protein was increased. Mir146a overexpression and siPLZF impaired mGSC proliferation and differentiation, however, Mir146a knockdown induced the opposite effects. The effects of PLZF and mir146a were mediated regulation by mir146a and CXCR4, respectively. Overexpression of CXCR4 or addition of CXCL12 in cultures of dairy goat mGSCs resulted in the upregulation of their signaling, and the phosphorylation of ERK1/2 was increased. Collectively, these findings indicate that PLZF is an important transcription factor in the regulation of the expression of CXCR4 to promote dairy goat mGSC proliferation by targeting mir146a.

Characterization of immortalized dairy goat male germline stem cells (mGSCs)

Male germline stem cells (mGSCs), in charge for the fertility in male testis, are the only kind of adult stem cells that transmit genetic information to next generation, with promising prospects in germplasm resources preservation and optimization, and production of transgenic animals. Mouse male germline stem cell lines have been established and are valuable for studying the mechanisms of spermatogenesis. However, there is a lack of stable mGSC cell lines in livestock, which restricts the progress of transgenic research and related biotechnology. Here, we firstly established an immortalized dairy goat mGSC cell line to study the biological properties and the signaling pathways associated with mGSCs self-renewal and differentiation. The ectopic factors SV40 large T antigen and Bmi1 genes were transduced into dairy goat mGSCs, and the results showed that the proliferation of these cells that were named mGSCs-I-SB was improved significantly. They maintained the typical characteristics including the expression of mGSC markers, and the potential to differentiate into all three germ layers, sperm-like cells in vitro. Additionally, mGSCs-I-SB survived and differentiated into three germ layer cell types when they were transplanted into chicken embryos. Importantly, the cells also survived in mouse spermatogenesis deficiency model testis which seemed to be the golden standard to examine mGSCs. Conclusively, our results demonstrate that mGSCs-I-SB present the characteristics of mGSCs and may promote the future study on goat mGSCs.

Genome-Wide DNA Methylation Analysis Identifies Novel Hypomethylated Non-Pericentromeric Genes with Potential Clinical Implications in ICF Syndrome

INTRODUCTION AND RESULTS

Immunodeficiency, centromeric instability and facial anomalies syndrome (ICF) is a rare autosomal recessive disease, characterized by severe hypomethylation in pericentromeric regions of chromosomes (1, 16 and 9), marked immunodeficiency and facial anomalies. The majority of ICF patients present mutations in the DNMT3B gene, affecting the DNA methyltransferase activity of the protein. In the present study, we have used the Infinium 450K DNA methylation array to evaluate the methylation level of 450,000 CpGs in lymphoblastoid cell lines and untrasformed fibroblasts derived from ICF patients and healthy donors. Our results demonstrate that ICF-specific DNMT3B variants A603T/STP807ins and V699G/R54X cause global DNA hypomethylation compared to wild-type protein. We identified 181 novel differentially methylated positions (DMPs) including subtelomeric and intrachromosomic regions, outside the classical ICF-related pericentromeric hypomethylated positions. Interestingly, these sites were mainly located in intergenic regions and inside the CpG islands. Among the identified hypomethylated CpG-island associated genes, we confirmed the overexpression of three selected genes, BOLL, SYCP2 and NCRNA00221, in ICF compared to healthy controls, which are supposed to be expressed in germ line and silenced in somatic tissues.

CONCLUSIONS

In conclusion, this study contributes in clarifying the direct relationship between DNA methylation defect and gene expression impairment in ICF syndrome, identifying novel direct target genes of DNMT3B. A high percentage of the DMPs are located in the subtelomeric regions, indicating a specific role of DNMT3B in methylating these chromosomal sites. Therefore, we provide further evidence that hypomethylation in specific non-pericentromeric regions of chromosomes might be involved in the molecular pathogenesis of ICF syndrome. The detection of DNA hypomethylation at BOLL, SYCP2 and NCRNA00221 may pave the way for the development of specific clinical biomarkers with the aim to facilitate the identification of ICF patients.

Epigenetic regulation of bovine spermatogenic cell-specific gene boule

Non-primate mammals have two deleted azoospermia (DAZ) family genes, DAZL and Boule; genes in this family encode RNA-binding proteins essential for male fertility in diverse animals. Testicular DAZL transcription is regulated by epigenetic factors such as DNA methylation. However, nothing is known about the epigenetic regulation of Boule. Here, we explored the role of DNA methylation in the regulation of the bovine Boule (bBoule) gene. We found that a long CpG island (CGI) in the bBoule promoter was hypermethylated in the testes of cattle-yak hybrids with low bBoule expression, whereas cattle had relatively low methylation levels (P < 0.01), and there was no difference in the methylation level in the short CGI of the gene body between cattle and cattle-yak hybrids (P > 0.05). We identified a 107 bp proximal core promoter region of bBoule. Intriguingly, the differences in the methylation level between cattle and cattle-yak hybrids were larger in the core promoter than outside the core promoter. An in vitro methylation assay showed that the core promoter activity of bBoule decreased significantly after M.SssI methylase treatment (P < 0.01). We also observed dramatically increased bBoule transcription in bovine mammary epithelial cells (BMECs) after treatment with the methyltransferase inhibitor 5-Aza-dC. Taken together, our results establish that methylation status of the core promoter might be involved in testicular bBoule transcription, and may provide new insight into the epigenetic regulation of DAZ family genes and clinical insights regarding male infertility.

The Tet1 and histone methylation expression pattern in dairy goat testis

DNA methylation and histone methylation are critical for mammalian development. Ten-eleven translocation (Tet1), a key regulator of DNA methylation, has been identified as a key enzyme for the activation of DNA demethylation; histone H3 lysine 9 (H3K9) and 27 (H3K27) methylation repress gene expression. Significant progress on the biological functions of Tet proteins has been made in mice and humans. However, their expression pattern and function in the male germ cells in the dairy goat testis are still unclear. The present study described the expression pattern of Tet1, H3K9, and H3K27 in the dairy goat testis and cultured goat spermatogonia stem cells (gSSCs). The results showed that Tet1 was weakly expressed in the dairy goat's testis compared to other organ tissues. Tet1, 5-hydroxymethylcytosine, H3K9, and H3K27 expressions were positive and dynamically changing during spermatogenesis; however, they showed weak expression in neonate stage in vivo. Tet1 and 5-hydroxymethylcytosine showed low expression in gSSCs in vitro in differentiated cultures. These will provide new perspectives for DNA methylation/demethylation and better regulation of epigenetic modifications in gSSCs.

Expression profile of Nanos2 gene in dairy goat and its inhibitory effect on Stra8 during meiosis

OBJECTIVES

Nanos2, an RNA-binding protein, belongs to the Nanos gene-coding family and contains two CCHC zinc-finger motifs. In mouse, it plays a pivotal role in male germ cell development, and self-renewal of spermatogonial stem cells. However, little is known of its expression pattern and functions in dairy goat testis.

MATERIALS AND METHODS

Immunohistochemistry and quantitative reverse transcription-polymerase chain reaction (qRT-PCR) were used to generate the expression profile of Nanos2 in dairy goat testis. Furthermore, its overexpression effects on male germline stem cells (mGSCs) were studied using qRT-PCR, immunofluorescence, dual-luciferase reporter assay and western blotting.

RESULTS

Nanos2 is a conservative gene expressed widely in various tissues, especially in pancreas, and it displays higher expression in adult testes than in other age groups. Overexpression of Nanos2 significantly downregulated meiosis-related genes, including Stra8 and Scp3, which induced inhibition of meiosis. Results from dual-luciferase reporter assay and western blotting indicated that Nanos2 directly downregulated Stra8 in goat GmGSCs.

CONCLUSIONS

Taken together, these results suggest that Nanos2 plays an important role in spermatogonia and that its overexpression restrained meiosis in the dairy goat.

Identification and characterization of yak (Bos grunniens) b-Boule gene and its alternative splice variants

Boule is responsible for meiotic arrest of sperms and male sterility during mammalian spermatogenesis. In the present study, we first identified yak b-Boule gene and its two alternative splice variants. The full length coding region of yak b-Boule is 888bp and encodes a 295-amino acid protein with a typical RNA-recognition motif (RRM) and a Deleted in Azoospermia (DAZ) repetitive sequence motif. Two alternative splice variants of yak b-Boule were generated following the consensus "GT-AG" rule and named b-Boule1 (36bp deletion in exon 3) and b-Boule2 (deletion of integral exon 7), respectively. In male yak, b-Boule, b-Boule1 and b-Boule2 were found to be exclusively expressed in the testes at a ratio of 81:0.1:1. Intriguingly, the mRNA expression levels of b-Boule and b-Boule1 in yak testis were significantly higher than those in cattle-yak, although no significant difference was observed for b-Boule2 expression between the yak and cattle-yak. These results suggest that b-Boule gene, which is partially regulated by alternative splicing, may be involved in the process of yak spermatogenesis.

Promyelocytic leukaemia zinc finger maintains self-renewal of male germline stem cells (mGSCs) and its expression pattern in dairy goat testis

OBJECTIVES

Previous studies have shown that promyelocytic leukaemia zinc finger (PLZF) is a spermatogonia-specific transcription factor in the testis, required to regulate self-renewal and maintenance of the spermatogonia stem cell. Up to now, expression and function of PLZF in the goat testis has not been known. The objectives of this study were to investigate PLZF expression pattern in the dairy goat and its effect on male goat germline stem cell (mGSC) self-renewal and differentiation.

MATERIALS AND METHODS

Testis development and expression patterns of PLZF in the dairy goat were analysed by haematoxylin and eosin staining, immunohistochemistry and reverse transcription-polymerase chain reaction (RT-PCR). Furthermore, effects of PLZF overexpression on mGSC self-renewal and differentiation were evaluated by quantitative RT-PCR (QRT-PCR), immunofluorescence and BrdU incorporation assay.

RESULTS

Promyelocytic leukaemia zinc finger was essential for dairy goat testis development and expression of several proliferation and pluripotency-associated proteins including OCT4, C-MYC were upregulated by PLZF overexpression. The study demonstrated that PLZF played a key role in maintaining self-renewal of mGSCs and its overexpression enhanced expression of proliferation-associated genes.

CONCLUSIONS

Promyelocytic leukaemia zinc finger could function in the dairy goat as well as in other species in maintaining self-renewal of germline stem cells and this study provides a model to study the mechanism on self-renewal and differentiation of mGSCs in livestock.

Conservation and function of Dazl in promoting the meiosis of goat male germline stem cells

Dazl (deleted in azoospermia-like) is a conserved gene in mammalian meiosis, which encodes RNA binding protein required for spermatocyte meiosis. Up to date, the expression and function of Dazl in the goat testis are unknown. The objectives of this study were to investigate the expression pattern of Dazl in dairy goat testis and their function in male germline stem cells (mGSCs). The results first revealed that the expression level of Dazl in adult testes was significantly higher than younger and immature goats, and azoospermia and male intersex testis. The dairy goat Dazl is highly conserved analysed by several online and bioinformatics software, respectively. Over-expression of Dazl promoted the expression of meiosis-related genes in dairy goat mGSCs. The expression of Stra8 was up-regulated by over-expression of Dazl analysed by Luciferase reporter assay. Taken together, results suggest the Dazl plays an important role in dairy goat spermatogenesis and that over-expression of Dazl may promote Stra8 expression in dairy goat mGSCs.

Expression pattern of Ngn3 in dairy goat testis and its function in promoting meiosis by upregulating Stra8

OBJECTIVES

Ngn3 is a typical transcription factor and marker of differentiating spermatogonial stem cells (SSCs) in mouse, belonging to the basic helix-loop-helix (bHLH) family. Its gene is specifically expressed in A type spermatogonia in mouse testis, thus plays a critical role in controlling differentiation of SSCs. However, roles of Ngn3 and its protein in dairy goat testis remain unknown.

MATERIALS AND METHODS

Testis development and expression patterns of Ngn3 were analysed by immunofluorescence and quantitative reverse transcription-polymerase chain reaction (QRT-PCR) in the dairy goat. Furthermore, effects of its overexpression on male germline stem cells (mGSCs) were evaluated by QRT-PCR, immunofluorescence, luciferase reporter assay and western blotting.

RESULTS

Revealed that Ngn3 was expressed more highly during puberty and in the adult than in testis of other ages. Overexpression of Ngn3 promoted expression of meiosis-related gene Stra8 and stem-cell differentiation marker CD117, but suppressed expression of Plzf, a classical marker of SSCs. Furthermore, Ngn3 did not promote expression of Stra8 directly as shown in transcription and translation levels detected by luciferase reporter assay and western blotting.

CONCLUSIONS

Taken together, these results suggest that Ngn3 plays an important role in spermatogenesis and that overexpression of Ngn3 can promote meiosis in testis of the dairy goat.

The function of Msx1 gene in promoting meiosis of dairy goat male germline stem cells (mGSCs)

During sequential stages of meiosis, numerous cytoplasmic and nuclear events take place in which many germline and non-germline genes involved. It is demonstrated that the germline gene Stra8 and synaptonemal complex protein 3 (Scp3) play an important role in the meiosis. Recently, studies showed Msx1, a DNA-binding protein taking part in the skeletal development, also having a functional attractive factor to Stra8 and Scp3 in the meiosis. In this study, we cloned the gene Msx1 then transfected the Msx1 constructed recombination plasmid, pMsx1-Ires2-AcGFP, into the dairy goat germline stem cells (male germline stem cells) and analysed the effects of Msx1 on the expression of Stra8 and Scp3. The results showed that Msx1 could enhance the expression of Stra8 and Scp3 and promote the meiosis in goat testicular cells. Bmp4 activated the expression of Msx1 and Stra8. This study suggests that Msx1 plays an important role in spermatogenesis and meiosis.

The effects of Nanos2 on Boule and Stra8 in male germline stem cells (mGSCs)

The mitosis-meiosis switch is a key event in the differentiation of germ cells. Meiosis is important in development biology, however, it has not been clear what is the regulation mechanism in mammals. Our previous study showed that Boule could activate Stra8 directly and result in the meiosis initiation of dairy goat male germline stem cells (mGSCs). Nanos2, a RNA-binding protein, plays critical roles in the suppression of meiosis by preventing Stra8 expression and maintain the male germ cell development. The main purpose of this study was to explore whether Nanos2 represses Stra8 transcription through Boule or not. We found ectopic over-expression of Nanos2 in GC-1 and mGSCs down-regulated Stra8 transcription and translation, and Boule expression was not affected. It was in consistent with our expectation that RA could up-regulate Boule and Stra8 expression, but down-regulate Nanos2 expression in mGSCs. In dairy goat, the expression levels of Boule and Stra8 would rise with the increase of age, but the expression level of Nanos2 in 90 dpp and adult testis had not shown a clear change. In conclusion, Nanos2 represses Stra8 expression but not through Boule in dairy goat mGSCs.

miR-34c works downstream of p53 leading to dairy goat male germline stem-cell (mGSCs) apoptosis

OBJECTIVES

Recent lines of evidence have indicated that miR-34c can play important roles in regulation of the cell cycle, cell senescence and apoptosis of mouse and human tumour cells, spermatogenesis, and male germ-cell apoptosis. However, there is little information on the effects of miR-34c on proliferation and apoptosis of livestock male germ cells. The dairy goat is a convenient domestic species for biological investigation and application. The purpose of this study was to investigate the effects of miR-34c on apoptosis and proliferation of dairy goat male germline stem cells (mGSCs), as well as to determine the relationship between p53 and miR-34c in this species.

MATERIALS AND METHODS

Morphological observation, miRNA in situ hybridisation (ISH), bromodeoxyuridine staining, flow cytometry, quantitative-RT-PCR (Q-RT-PCR) and western blotting were utilized to ascertain apoptosis and proliferation of mGSCs, through transfection of miR-34c mimics (miR-34c), miR-34c inhibitor (anti-miR-34c), miR-34c mimics and inhibitors co-transfected (mixture) compared to control groups.

RESULTS

Results manifested that miR-34c over-expression promoted mGSCs apoptosis and suppressed their proliferation. Simultaneously, a variety of apoptosis-related gene expression was increased while some proliferation-related genes were downregulated. Accordingly, miR-34c promoted apoptosis in mGSCs and reduced their proliferation; moreover, expression of miR-34c was p53-dependent.

CONCLUSIONS

This study is the first to provide a model for study of miRNAs and mechanisms of proliferation and apoptosis in male dairy goat germ cells.