Cellular nucleic acid-binding protein is vital to testis development and spermatogenesis in mice

Cellular nucleic acid binding protein facilitates cardiac repair after myocardial infarction by activating β-catenin signaling

The regenerative capacity of the adult mammalian heart is limited, while the neonatal heart is an organ with regenerative and proliferative ability. Activating adult cardiomyocytes (CMs) to re-enter the cell cycle is an effective therapeutic method for ischemic heart disease such as myocardial infarction (MI) and heart failure. Here, we aimed to reveal the role and potential mechanisms of cellular nucleic acid binding protein (CNBP) in cardiac regeneration and repair after heart injury. CNBP is highly expressed within 7 days post-birth while decreases significantly with the loss of regenerative ability. In vitro, overexpression of CNBP promoted CM proliferation and survival, whereas knockdown of CNBP inhibited these processes. In vivo, knockdown of CNBP in CMs robustly hindered myocardial regeneration after apical resection in neonatal mice. In adult MI mice, CM-specific CNBP overexpression in the infarct border zone ameliorated myocardial injury in acute stage and facilitated CM proliferation and functional recovery in the long term. Quantitative proteomic analysis with TMT labeling showed that CNBP overexpression promoted the DNA replication, cell cycle progression, and cell division. Mechanically, CNBP overexpression increased the expression of β-catenin and its downstream target genes CCND1 and c-myc; Furthermore, Luciferase reporter and Chromatin immunoprecipitation (ChIP) assays showed that CNBP could directly bind to the β-catenin promoter and promote its transcription. CNBP also upregulated the expression of G1/S-related cell cycle genes CCNE1, CDK2, and CDK4. Collectively, our study reveals the positive role of CNBP in promoting cardiac repair after injury, providing a new therapeutic option for the treatment of MI.

Esketamine inhibits the c-Jun N-terminal kinase pathway in the spinal dorsal horn to relieve bone cancer pain in rats

Cancer-induced bone pain (CIBP) is one of the most common and feared symptoms in patients with advanced tumors. The X-C motif chemokine ligand 12 (CXCL12) and the CXCR4 receptor have been associated with glial cell activation in bone cancer pain. Moreover, mitogen-activated protein kinases (MAPKs), as downstream CXCL12/CXCR4 signals, and c-Jun, as activator protein AP-1 components, contribute to the development of various types of pain. However, the specific CIBP mechanisms remain unknown. Esketamine is a non-selective N-methyl-d-aspartic acid receptor (NMDA) inhibitor commonly used as an analgesic in the clinic, but its analgesic mechanism in bone cancer pain remains unclear. We used a tumor cell implantation (TCI) model and explored that CXCL12/CXCR4, p-MAPKs, and p-c-Jun were stably up-regulated in the spinal cord. Immunofluorescence images showed activated microglia in the spinal cord on day 14 after TCI and co-expression of CXCL12/CXCR4, p-MAPKs (p-JNK, p-ERK, p-p38 MAPK), and p-c-Jun in microglia. Intrathecal injection of the CXCR4 inhibitor AMD3100 reduced JNK and c-Jun phosphorylations, and intrathecal injection of the JNK inhibitor SP600125 and esketamine also alleviated TCI-induced pain and reduced the expression of p-JNK and p-c-Jun in microglia. Overall, our data suggest that the CXCL12/CXCR4-JNK-c-Jun signaling pathway of microglia in the spinal cord mediates neuronal sensitization and pain hypersensitivity in cancer-induced bone pain and that esketamine exerts its analgesic effect by inhibiting the JNK-c-Jun pathway.

Long non-coding RNA PRR7-AS1 promotes osteosarcoma progression via binding RNF2 to transcriptionally suppress MTUS1

Introduction

Osteosarcoma is a common bone malignant tumor in adolescents with high mortality and poor prognosis. At present, the progress of osteosarcoma and effective treatment strategies are not clear. This study provides a new potential target for the progression and treatment of osteosarcoma.

Methods

The relationship between lncRNA PRR7-AS1 and osteosarcoma was analyzed using the osteosarcoma databases and clinical sample testing. Cell function assays and tumor lung metastasis were employed to study the effects of PRR7-AS1 on tumorigenesis in vivo and in vitro. Potential downstream RNF2 of PRR7-AS1 was identified and explored using RNA pulldown and RIP. The GTRD and KnockTF database were used to predict the downstream target gene, MTUS1, and ChIP-qPCR experiments were used to verify the working mechanismy. Rescue experiments were utilized to confirm the role of MTUS1 in the pathway.

Results

Deep mining of osteosarcoma databases combined with clinical sample testing revealed a positive correlation between lncRNA PRR7-AS1 and osteosarcoma progression. Knockdown of PRR7-AS1 inhibited osteosarcoma cell proliferation and metastasis in vitro and in vivo. Mechanistically, RNA pulldown and RIP revealed that PRR7-AS1 may bind RNF2 to play a cancer-promoting role. ChIP-qPCR experiments were utilized to validate the working mechanism of the downstream target gene MTUS1. RNF2 inhibited the transcription of MTUS1 through histone H2A lysine 119 monoubiquitin. Rescue experiments confirmed MTUS1 as a downstream direct target of PRR7-AS1 and RNF2.

Discussion

We identified lncRNA PRR7-AS1 as an important oncogene in osteosarcoma progression, indicating that it may be a potential target for diagnosis and prognosis of osteosarcoma.

BMI-1 promotes breast cancer proliferation and metastasis through different mechanisms in different subtypes

Breast cancer is among the most common malignant cancers in women. B-cell-specific Moloney murine leukemia virus integration site 1 (BMI-1) is a transcriptional repressor that has been shown to be involved in tumorigenesis, the cell cycle, and stem cell maintenance. In our study, increased expression of BMI-1 was found in both human triple negative breast cancer and luminal A-type breast cancer tissues compared with adjacent tissues. We also found that knockdown of BMI-1 significantly suppressed cell proliferation and migration in vitro and in vivo. Further mechanistic research demonstrated that BMI-1 directly bound to the promoter region of CDKN2D/BRCA1 and inhibited its transcription in MCF-7/MDA-MB-231. More importantly, we discovered that knockdown of CDKN2D/BRCA1 could promote cell proliferation and migration after repression by PTC-209. Our results reveal that BMI-1 transcriptionally suppressed BRCA1 in TNBC cell lines whereas, in luminal A cell lines, CDKN2D was the target gene. This provides a reference for the precise treatment of different types of breast cancer in clinical practice.

LINC01526 Promotes Proliferation and Metastasis of Gastric Cancer by Interacting with TARBP2 to Induce GNG7 mRNA Decay

Simple Summary

Many long noncoding RNAs play an important role in gastric cancer progression. In this study, we focused on LINC01526. Through expression and functional analyses, we obtained a preliminary understanding of the pro-cancer role of LINC01526 in gastric cancer. Furthermore, RNA pull-down and RNA immunoprecipitation chip assays demonstrated that LINC01526 interacts with TARBP2, an RNA-binding protein controlling mRNA stability. Moreover, TARBP2 could bind and destabilize GNG7 transcripts. Finally, the rescue assay disclosed that LINC01526 promoted gastric cancer progression by interacting with TARBP2, leading to the degradation of GNG7 mRNA.

Abstract

Gastric cancer is the most common malignancy of the human digestive system. Long noncoding RNAs (lncRNAs) influence the occurrence and development of gastric cancer in multiple ways. However, the function and mechanism of LINC01526 in gastric cancer remain unknown. Herein, we investigated the function of LINC01526 with respect to the malignant progression of gastric cancer. We found that LINC01526 was upregulated in gastric cancer cells and tissues. The function experiments in vitro and the Xenograft mouse model in vivo proved that LINC01526 could promote gastric cancer cell proliferation and migration. Furthermore, LINC01526 interacted with TAR (HIV-1) RNA-binding protein 2 (TARBP2) and decreased the mRNA stability of G protein gamma 7 (GNG7) through TARBP2. Finally, the rescue assay showed that downregulating GNG7 partially rescued the cell proliferation inhibited by LINC01526 or TARBP2 silencing. In summary, LINC01526 promoted gastric cancer progression by interacting with TARBP2, which subsequently degraded GNG7 mRNA. This study not only explores the role of LINC01526 in gastric cancer, but also provides a laboratory basis for its use as a new biomarker for diagnosis and therapeutic targets.

Identification of proline-rich protein 11 as a major regulator in mouse spermatogonia maintenance via an increase in BMI1 protein stability

BACKGROUND

Spermatogenesis accompanied by self-renewal and differentiation of spermatogonia under complicated regulation is crucial for male fertility. Our previous study demonstrated that the loss of the B-lymphoma Mo-MLV insertion region 1 (BMI1) could cause male infertility and found a potential interaction between BMI1 and proline-rich protein 11 (PRR11); however, the specific co-regulatory effects of BMI1/PRR11 on spermatogonia maintenance remain unclear.

METHODS AND RESULTS

The expression of PRR11 was downregulated in a mouse spermatogonia cell line (GC-1) via transfection with PRR11-siRNAs, and PRR11 knockdown was verified by real-time reverse transcriptase polymerase chain reaction (RT-qPCR). The proliferative activity of GC-1 cells was determined using the cell counting kit (CCK-8), colony formation, and 5-ethynyl-2-deoxyuridine (EdU) incorporation assay. A Transwell assay was performed to evaluate the effects of PRR11 on GC-1 cell migration. A terminal deoxynucleotidyl transferase dUTP nick end labeling assay was used to measure GC-1 cell apoptosis. Furthermore, co-immunoprecipitation, RT-qPCR, and western blot analyses were used for investigating the regulatory mechanisms involved in this regulation. It was found that downregulation of PRR11 could cause a marked inhibition of proliferation and migration and induced apoptosis in GC-1 cells. Moreover, silencing of PRR11 obviously led to a reduction in the BMI1 protein level. PRR11 was found to interact with BMII at the endogenous protein level. PRR11 knockdown produced a decrease in BMI1 protein stability via an increase in BMI1 ubiquitination after which derepression in the transcription of protein tyrosine phosphatase receptor type M (Ptprm) occurred. Importantly, knockdown of Ptprm in PRR11-deficient GC-1 cells led to a reversal of proliferation and migration of GC-1 cells.

CONCLUSIONS

This study uncovered a novel mechanism by which PRR11 cooperated with BMI1 to facilitate GC-1 maintenance through targeting Ptprm. Our findings may provide a better understanding of the regulatory network in spermatogonia maintenance.

Hypogonadism in Males With Genetic Neurodevelopmental Syndromes

Genetic syndromes that affect the nervous system may also disrupt testicular function, and the mechanisms for these effects may be interrelated. Most often neurological signs and symptoms predominate and hypogonadism remains undetected and untreated, while in other cases, a thorough evaluation of a hypogonadal male reveals previously unrecognized ataxia, movement disorder, muscle weakness, tremor, or seizures, leading to a syndromic diagnosis. Androgen deficiency in patients with neurological diseases may aggravate muscle weakness and fatigue and predispose patients to osteoporosis and obesity. The purpose of this mini review is to provide a current understanding of the clinical, biochemical, histologic, and genetic features of syndromes in which male hypogonadism and neurological dysfunction may coexist and may be encountered by the clinical endocrinologist.

Role of p38 MAPK Signalling in Testis Development and Male Fertility

The testis is an important male reproductive organ, which ensures reproductive function via the secretion of testosterone and the generation of spermatozoa. Testis development begins in the embryonic period, continues after birth, and generally reaches functional maturation at puberty. The stress-activated kinase, p38 mitogen-activated protein kinase (MAPK), regulates multiple cell processes including proliferation, differentiation, apoptosis, and cellular stress responses. p38 MAPK signalling plays a crucial role in testis development by regulating spermatogenesis, the fate determination of pre-Sertoli, and primordial germ cells during embryogenesis, the proliferation of testicular cells in the postnatal period, and the functions of mature Sertoli and Leydig cells. In addition, p38 MAPK signalling is involved in decreased male fertility when exposed to various harmful stimuli. This review will describe in detail the biological functions of p38 MAPK signalling in testis development and male reproduction, together with its pathological role in male infertility.

SAT2 regulates Sertoli cell-germline interactions via STIM1-mediated ROS/WNT/β-catenin signaling pathway

As the main component of seminiferous tubules, Sertoli cells are in close contact with germ cells and generate niche signals, which exhibit pivotal functions in spermatogenesis and male fertility. However, the regulatory mechanisms of Sertoli cell-germline interactions (SGIs) in the testes of neonatal mice (NM) remain largely unclear. Previously, we identified spermidine/spermine N1-acetyl transferase 2 (SAT2) and stromal interaction molecule 1 (STIM1) to be potential regulators of testicular cord formation via comparative proteomics analysis. Here, we demonstrated a novel role of SAT2 for SGIs during testicular development in NM. Testicular explants lacking SAT2 affected the mislocation, but not the quantity, of Sertoli cells, which led to maintenance defects in spermatogonial stem cells (SSCs). Interestingly, SAT2 was essential for the migration of TM4 cells, a Sertoli cell line. Mechanistically, SAT2 was able to bind STIM1, repress its expression, and regulate homeostasis of a reactive oxygen species/wingless type (WNT)/β-catenin pathway in NM testes. Collectively, our study identified that SAT2 was able to regulate SGIs via a STIM1-mediated WNT signaling pathway.

E3 ubiquitin ligase ASB17 is required for spermiation in mice

Background

A major goal of spermiation is to degrade the apical ectoplasmic specialization (ES) junction between Sertoli cells and elongating spermatids in preparation for the eventual disengagement of spermatids into the lumen. E3 ubiquitin ligases mediate the process of ubiquitination and the subsequent proteasomal degradation, but their specific role during spermiation remains largely unexplored.

Methods

Ankyrin repeat and SOCS box protein 17 (Asb17)-knockout mice were generated via a CRISPR/Cas9 approach. Epididymal sperm parameters were assessed by a computer-assisted sperm analysis (CASA) system, and morphological analysis of testicular tissues were performed based on histological and immunostaining staining, and transmission electron microscopy (TEM). The interactions between ASB17 and Espin (ESPN) were predicted by HawkDock server and validated through protein pull-down and immunoprecipitation assays.

Results

We report that ASB17, an E3 ligase, is required for the completion of spermiation and that mice lacking Asb17 are oligozoospermic owing to spermiation failure. ASB17-deficient mice are fertile; however, spermatids exhibit a disorganized ES junction, resulting in retention within the seminiferous epithelium. Mechanistically, ASB17 deficiency leads to excess accumulation of ESPN, an actin-binding essential structural component of the ES. We determined that ASB17 regulates the removal of the ES through ubiquitin mediated protein degradation of ESPN.

Conclusions

In summary, our study describes a role for ASB17 in the regulation of cell-cell junctions between germ cells and somatic cells in the testis. These findings establish a novel mechanism for the regulatory role of E3 ligases during spermatogenesis.

ZDHHC19 localizes to the cell membrane of spermatids and is involved in spermatogenesis

Sperm is the ultimate executor of male reproductive function. Normal morphology, quantity, and motility of sperm ensure the normal reproductive process. Palmitoylation is a posttranslational modification mediated by palmitoyltransferases whereby palmitoyl is added to proteins. Seven palmitoyltransferases have been identified in Saccharomyces cerevisiae and 23 in humans (including ZDHHC1-9 and ZDHHC11-24), with corresponding homologs in mice. We identified two testis-specific palmitoyltransferases ZDHHC11 and ZDHHC19 in mice. The Zdhhc11 and Zdhhc19-knockout mouse models were constructed, and it was found that the Zdhhc11 knockout males were fertile, while Zdhhc19 knockout males were sterile. ZDHHC19 is located in the cell membrane of step 4-9 spermatids in the mouse testis, and phenotypic analysis showed that the testicular weight ratio in the Zdhhc19-/- mice decreased along with the number and motility of the sperm decreased, while sperm abnormalities increased, mainly due to the "folded" abnormal sperm caused by sperm membrane fusion, suggesting the involvement of ZDHHC19 in maintaining membrane stability in the male reproductive system. In addition, Zdhhc19-/- mice showed abnormal sperm morphologies and apoptosis during spermatogenesis, suggesting that spermatogenesis in the Zdhhc19-/- mice was abnormal. These results indicate that ZDHHC19 promotes membrane stability in male germ cells. Summary sentence: ZDHHC19 is located in the cell membrane of Step4-9 spermatids in mouse testis; Zdhhc19 knockout mice showed male infertility, abnormal spermatogenesis, sperm morphology and motility.

BMI1 promotes spermatogonia proliferation through epigenetic repression of Ptprm

Spermatogonia are accountable for spermatogenesis and male fertility, but the underlying mechanisms involved in spermatogonia maintenance are not clear. B lymphoma Mo-MLV insertion region 1 (BMI1) is a key component of epigenetic silencers. BMI1 is essential for stem-cell maintenance. Here, we attempted to uncover the role of BMI1 in spermatogonia maintenance using a mouse spermatogonia cell line (GC-1) and Bmi1-knockout (KO) mouse model. We showed that BMI1 promoted the proliferation and inhibited apoptosis of GC-1 cells. Mechanistically, we present in vitro and in vivo evidence to show that BMI1 binds to the promoter region of the Protein tyrosine phosphatase receptor type M (PTPRM) gene, thereby driving chromatin remodeling and gene silencing. Knockdown of Ptprm expression significantly improved spermatogonia proliferation in BMI1-deficient GC-1 cells. Collectively, our data show, for the first time, an epigenetic mechanism involving in BMI1-mediated gene silencing in spermatogonia maintenance, and provide potential targets for the treatment of male infertility.

BMI1 Drives Steroidogenesis Through Epigenetically Repressing the p38 MAPK Pathway

Testosterone biosynthesis progressively decreases in aging males primarily as a result of functional changes to Leydig cells. Despite this, the mechanisms underlying steroidogenesis remain largely unclear. Using gene knock-out approaches, we and others have recently identified Bmi1 as an anti-aging gene. Herein, we investigate the role of BMI1 in steroidogenesis using mouse MLTC-1 and primary Leydig cells. We show that BMI1 can positively regulate testosterone production. Mechanistically, in addition to its known role in antioxidant activity, we also report that p38 mitogen-activated protein kinase (MAPK) signaling is activated, and testosterone levels reduced, in BMI1-deficient cells; however, the silencing of the p38 MAPK pathway restores testosterone production. Furthermore, we reveal that BMI1 directly binds to the promoter region of Map3k3, an upstream activator of p38, thereby modulating its chromatin status and repressing its expression. Consequently, this results in the inhibition of the p38 MAPK pathway and the promotion of steroidogenesis. Our study uncovered a novel epigenetic mechanism in steroidogenesis involving BMI1-mediated gene silencing and provides potential therapeutic targets for the treatment of hypogonadism.

Vitamin K-Dependent γ-Glutamyl Carboxylase in Sertoli Cells Is Essential for Male Fertility in Mice

γ-Glutamyl carboxylase (GGCX) is a vitamin K (VK)-dependent enzyme that catalyzes the γ-carboxylation of glutamic acid residues in VK-dependent proteins. The anticoagulant warfarin is known to reduce GGCX activity by inhibiting the VK cycle and was recently shown to disrupt spermatogenesis. To explore GGCX function in the testis, here, we generated Sertoli cell-specific Ggcx conditional knockout (Ggcx scKO) mice and investigated their testicular phenotype. Ggcx scKO mice exhibited late-onset male infertility. They possessed morphologically abnormal seminiferous tubules containing multinucleated and apoptotic germ cells, and their sperm concentration and motility were substantially reduced. The localization of connexin 43 (Cx43), a gap junction protein abundantly expressed in Sertoli cells and required for spermatogenesis, was distorted in Ggcx scKO testes, and Cx43 overexpression in Sertoli cells rescued the infertility of Ggcx scKO mice. These results highlight GGCX activity within Sertoli cells, which promotes spermatogenesis by regulating the intercellular connection between Sertoli cells and germ cells.

MRNIP is essential for meiotic progression and spermatogenesis in mice

Meiotic homologous recombination (HR) initiates with the programmed generation of DNA double-strand breaks (DSBs), which result in the exchange of genetic information and genome diversity. This process requires the tight cooperation of the MRE11-RAD50-NBS1 (MRN) complex to promote DSB formation and DNA end resection. However, the mechanism regulating MRN complex remains to be explored. In the present study, we report that MRN-interacting protein, MRNIP, is a novel factor for HR and is crucial for the expression of the MRN complex and loading of recombinases DMC1/RAD51. Knockout of Mrnip in mice led to aberrant synapsis, impaired HR, and male subfertility. In conclusion, MRNIP is a novel HR factor that probably promotes meiotic progression through the MRN complex.

Retinoic Acid Induced Protein 14 (Rai14) is dispensable for mouse spermatogenesis

BACKGROUND

Retinoic Acid Induced Protein 14 (Rai14) is an evolutionarily conserved gene that is highly expressed in the testis. Previous experiments have reported that small interfering RNA (siRNA)-mediated gene knockdown (KD) of Rai14 in rat testis disrupted spermatid polarity and transport. Of note, a gene knockout (KO) model is considered the "gold standard" for in vivo assessment of crucial gene functions. Herein, we used CRISPR/Cas9-based gene editing to investigate the in vivo role of Rai14 in mouse testis.

METHODS

Sperm concentration and motility were assayed using a computer-assisted sperm analysis (CASA) system. Histological and immunofluorescence (IF) staining and transmission electron microscopy (TEM) were used to visualize the effects of Rai14 KO in the testes and epididymides. Terminal deoxynucleotidyl transferase-dUTP nick-end labeling (TUNEL) was used to determine apoptotic cells. Gene transcript levels were calculated by real-time quantitative PCR.

RESULTS

Rai14 KO in mice depicted normal fertility and complete spermatogenesis, which is in sharp contrast with the results reported previously in a Rai14 KD rat model. Sperm parameters and cellular apoptosis did not appear to differ between wild-type (WT) and KO group. Mechanistically, in contrast to the well-known role of Rai14 in modulating the dynamics of F-actin at the ectoplasmic specialization (ES) junction in the testis, morphological changes of ES junction exhibited no differences between Rai14 KO and WT testes. Moreover, the F-actin surrounded at the ES junction was also comparable between the two groups.

CONCLUSION

In summary, our study demonstrates that Rai14 is dispensable for mouse spermatogenesis and fertility. Although the results of this study were negative, the phenotypic information obtained herein provide an enhanced understanding of the role of Rai14 in the testis, and researchers may refer to these results to avoid conducting redundant experiments.

Transferrin receptor (TFRC) is essential for meiotic progression during mouse spermatogenesis

Meiosis is a highly conserved process, and is responsible for the production of haploid gametes and generation of genetic diversity. We previously identified the transferrin receptor (TFRC) in the proteome profile of mice neonatal testes, indicating the involvement of the TFRC in meiosis. However, the exact molecular role of the TFRC in meiosis remains unclear. In this study, we aimed to determine the function of the TFRC in neonatal testicular development by TFRC knockdown using the testis culture platform. Our results showed high TFRC expression in 2-week testes, corresponding to the first meiotic division. Targeting TFRC using morpholino oligonucleotides resulted in clear spermatocyte apoptosis. In addition, we used the chromosomal spread technique to show that a deficiency of TFRC caused the accumulation of leptotene and zygotene spermatocytes, and a decrease of pachytene spermatocytes, indicating early meiotic arrest. Moreover, the chromosomes of TFRC-deficient pachytene spermatocytes displayed sustained γH2AX association, as well as SYCP1/SYCP3 dissociation beyond the sex body. Therefore, our results demonstrated that the TFRC is essential for the progression of spermatocyte meiosis, particularly for DNA double-stranded break repair and chromosomal synapsis.

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

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

BMI1 promotes steroidogenesis through maintaining redox homeostasis in mouse MLTC-1 and primary Leydig cells

In males, aging is accompanied by decline in serum testosterone levels due to impairment of testicular Leydig cells. The polycomb protein BMI1 has recently been identified as an anti-aging factor. In our previous study, BMI1 null mice showed decreased serum testosterone and Leydig cell population, excessive oxidative stress and p16/p19 signaling activation. However, a cause-and-effect relationship between phenotypes and pathways was not investigated. Here, we used the rescue approach to study the role of oxidative stress or p16/p19 in BMI1-mediated steroidogenesis. Our results revealed that treatment with antioxidant NAC, but not down-regulation of p16/p19, largely rescued cell senescence, DNA damage and steroidogenesis in BMI1-deficient mouse MLTC-1 and primary Leydig cells. Collectively, our study demonstrates that BMI1 orchestrates steroidogenesis mainly through maintaining redox homeostasis, and thus, BMI1 may be a novel and potential therapeutic target for treatment of hypogonadism.

Myotubularin related protein 7 is essential for the spermatogonial stem cell homeostasis via PI3K/AKT signaling

Myotubularin related protein 7 (MTMR7), a key member of the MTMR family, depicts phosphatase activity and is involved in myogenesis and tumor growth. We have previously identified MTMR7 in the proteomic profile of mouse spermatogonial stem cell (SSC) maturation and differentiation, implying that MTMR7 is associated with neonatal testicular development. In this study, to further explore the distribution and function of MTMR7 in mouse testis, we studied the effect of Mtmr7 knockdown on neonatal testicular development by testicular and SSC culture methods. Our results revealed that MTMR7 is exclusively located in early germ cells. Deficiency of MTMR7 by morpholino in neonatal testis caused excessive SSC proliferation, which was attributable to the aberrant PI3K/AKT signaling activation. Altogether, our study demonstrates that MTMR7 maintains SSC homeostasis by inhibiting PI3K/AKT signaling activation.

Multiple signaling pathways in Sertoli cells: recent findings in spermatogenesis

The functions of Sertoli cells in spermatogenesis have attracted much more attention recently. Normal spermatogenesis depends on Sertoli cells, mainly due to their influence on nutrient supply, maintenance of cell junctions, and support for germ cells' mitosis and meiosis. Accumulating evidence in the past decade has highlighted the dominant functions of the MAPK, AMPK, and TGF-β/Smad signaling pathways during spermatogenesis. Among these pathways, the MAPK signaling pathway regulates dynamics of tight junctions and adherens junctions, proliferation and meiosis of germ cells, proliferation and lactate production of Sertoli cells; the AMPK and the TGF-β/Smad signaling pathways both affect dynamics of tight junctions and adherens junctions, as well as the proliferation of Sertoli cells. The AMPK signaling pathway also regulates lactate supply. These signaling pathways combine to form a complex regulatory network for spermatogenesis. In testicular tumors or infertile patients, the activities of these signaling pathways in Sertoli cells are abnormal. Clarifying the mechanisms of signaling pathways in Sertoli cells on spermatogenesis provides new insights into the physiological functions of Sertoli cells in male reproduction, and also serves as a pre-requisite to identify potential therapeutic targets in abnormal spermatogenesis including testicular tumor and male infertility.

Stromal interaction molecule 1 is required for neonatal testicular development in mice

Stromal interaction molecule 1 (STIM1) is a transmembrane endoplasmic reticulum protein, and it serves as a Ca²⁺ sensor and activator of store-operated Ca²⁺ entry (SOCE). We have previously identified STIM1 in the proteome profile of mice neonatal testes, revealing STIM1 to be associated with neonatal testicular development. Here, to further explore the location and function of STIM1 in mice testes, we studied the effect of Stim1 gene knockdown on neonatal testicular development by testicular culture. Our results revealed that STIM1 was primarily located in Sertoli cells. Knockdown of Stim1 gene using morpholino in neonatal testis caused the mislocation of Sertoli cells and loss of germ cells, which were associated with the aberrant reactive oxygen species (ROS) activation, while inhibition of ROS could partly rescue the phenotypes caused by Stim1 gene knockdown. In conclusion, our study suggests that STIM1 can maintain neonatal testicular development by inhibiting ROS activation.