HnRNPL as a key factor in spermatogenesis: Lesson from functional proteomic studies of azoospermia patients with sertoli cell only syndrome

The lncRNA Gm8097 is associated with hypospermatogenesis

OBJECTIVE

To investigate whether long non-coding RNA (lncRNA) Gm8097 (LncGm8097) is associated with male infertility.

METHODS

The expression and bilogical role of LncGm8097 were investigated.

RESULTS

LncGm8097 expression was down-regulated in the testis tissues with moderate and severe hypospermatogenesis compared with those with normal spermatogenesis and mild hypospermatogenesis (p<0.05). LncGm8097 down-regulation significantly promoted apoptosis and inhibited proliferation in GC1 and GC2 cells. In addition, LncGm8097 was significantly down-regulated in mouse model of hypospermatogenesis and correlated with cell apoptosis and proliferation. LncGm8097 was located immediately upstream of PRPS2, and correlated with Bcl-2/P53/caspase 6/caspase 9 signal pathway.

CONCLUSION

LncGm8097 down-regulation correlates with hypospermatogenesis, which may offer new insights into the pathogenesis of male infertility.

The expression spectrum of yak epididymal epithelial cells reveals the functional diversity of caput, corpus and cauda regions

Sperm undergo a series of changes in the epididymis region before acquiring the ability to move and fertilize, and the identification of genes expressed in a region-specific manner in the epididymis provides a valuable insight into functional differences between regions. We collected epididymal tissue from three yaks and cultured epithelial cells from the caput, corpus and cauda regions of the yak epididymis using the tissue block method. RNA sequencing analysis (RNA-seq) technology was used to detect gene expression in yak epididymal caput, corpus and cauda epithelial cells. The results showed that the DEGs were highest in the caput vs. corpus comparison, and lowest in the corpus vs. cauda comparison. Six DEGs were verified by real-time fluorescence quantitative PCR (qRT-PCR), consistent with transcriptome sequencing results. The significantly enriched DNA replication pathway in the caput vs. corpus was coordinated with cell proliferation, while upregulated DEGs such as POLD1 and MCM4 were found in the DNA replication pathway. The AMPK signaling pathway was found significantly enriched in the caput vs cauda, suggesting its involvement in sperm maturation and capacitation. The TGF beta signaling pathway was screened in the corpus vs cauda and is crucial for mammalian reproductive regulation. Upregulated DEGs (TGFB3, INHBA, INHBB) are involved in the TGF beta signaling pathway. This study provides a reference for culturing yak epididymal epithelial cells in vitro, and elucidates the transcriptional profiles of epithelial cells in different segments of the epididymis, revealing the regulatory and functional differences between different segments, providing basic data for exploring the molecular mechanism of yak sperm maturation and improving the reproductive capacity of high-altitude mammals.

Sertoli cells require hnRNPC to support normal spermatogenesis and male fertility in mice†

Sertoli cells act as highly polarized testicular cells that nutritionally support multiple stages of germ cell development. However, the gene regulation network in Sertoli cells for modulating germ cell development has yet to be fully understood. In this study, we report that heterogeneous nuclear ribonucleoproteins C in Sertoli cells are essential for germ cell development and male fertility. Conditional knockout of heterogeneous nuclear ribonucleoprotein C in mouse Sertoli cells leads to aberrant Sertoli cells proliferation, disrupted cytoskeleton of Sertoli cells, and compromised blood-testis barrier function, resulting in loss of supportive cell function and, ultimately, defective spermiogenesis in mice. Further ribonucleic acid-sequencing analyses revealed these phenotypes are likely caused by the dysregulated genes in heterogeneous nuclear ribonucleoprotein C-deficient Sertoli cells related to cell adhesion, cell proliferation, and apoptotic process. In conclusion, this study demonstrates that heterogeneous nuclear ribonucleoprotein C plays a critical role in Sertoli cells for maintaining the function of Sertoli cells and sustaining steady-state spermatogenesis in mice.

HNRNPU's multi-tasking is essential for proper cortical development

Heterogeneous nuclear ribonucleoprotein U (HNRNPU) is a nuclear protein that plays a crucial role in various biological functions, such as RNA splicing and chromatin organization. HNRNPU/scaffold attachment factor A (SAF-A) activities are essential for regulating gene expression, DNA replication, genome integrity, and mitotic fidelity. These functions are critical to ensure the robustness of developmental processes, particularly those involved in shaping the human brain. As a result, HNRNPU is associated with various neurodevelopmental disorders (HNRNPU-related neurodevelopmental disorder, HNRNPU-NDD) characterized by developmental delay and intellectual disability. Our research demonstrates that the loss of HNRNPU function results in the death of both neural progenitor cells and post-mitotic neurons, with a higher sensitivity observed in the former. We reported that HNRNPU truncation leads to the dysregulation of gene expression and alternative splicing of genes that converge on several signaling pathways, some of which are likely to be involved in the pathology of HNRNPU-related NDD.

Sertoli cell-only syndrome: advances, challenges, and perspectives in genetics and mechanisms

Male infertility can be caused by quantitative and/or qualitative abnormalities in spermatogenesis, which affects men's physical and mental health. Sertoli cell-only syndrome (SCOS) is the most severe histological phenotype of male infertility characterized by the depletion of germ cells with only Sertoli cells remaining in the seminiferous tubules. Most SCOS cases cannot be explained by the already known genetic causes including karyotype abnormalities and microdeletions of the Y chromosome. With the development of sequencing technology, studies on screening new genetic causes for SCOS are growing in recent years. Directly sequencing of target genes in sporadic cases and whole-exome sequencing applied in familial cases have identified several genes associated with SCOS. Analyses of the testicular transcriptome, proteome, and epigenetics in SCOS patients provide explanations regarding the molecular mechanisms of SCOS. In this review, we discuss the possible relationship between defective germline development and SCOS based on mouse models with SCO phenotype. We also summarize the advances and challenges in the exploration of genetic causes and mechanisms of SCOS. Knowing the genetic factors of SCOS offers a better understanding of SCO and human spermatogenesis, and it also has practical significance for improving diagnosis, making appropriate medical decisions, and genetic counseling. For therapeutic implications, SCOS research, along with the achievements in stem cell technologies and gene therapy, build the foundation to develop novel therapies for SCOS patients to produce functional spermatozoa, giving them hope to father children.

hnRNPH1 establishes Sertoli-germ cell crosstalk through cooperation with PTBP1 and AR, and is essential for male fertility in mice

Spermatogenesis depends on the crosstalk of Sertoli cells (SCs) and germ cells. However, the gene regulatory network establishing the communications between SCs and germ cells remains unclear. Here, we report that heterogeneous nuclear ribonucleoprotein H1 (hnRNPH1) in SCs is essential for the establishment of crosstalk between SCs and germ cells. Conditional knockout of hnRNPH1 in mouse SCs leads to compromised blood-testis barrier function, delayed meiotic progression, increased germ cell apoptosis, sloughing of germ cells and, eventually, infertility of mice. Mechanistically, we discovered that hnRNPH1 could interact with the splicing regulator PTBP1 in SCs to regulate the pre-mRNA alternative splicing of the target genes functionally related to cell adhesion. Interestingly, we also found hnRNPH1 could cooperate with the androgen receptor, one of the SC-specific transcription factors, to modulate the transcription level of a group of genes associated with the cell-cell junction and EGFR pathway by directly binding to the gene promoters. Collectively, our findings reveal a crucial role for hnRNPH1 in SCs during spermatogenesis and uncover a potential molecular regulatory network involving hnRNPH1 in establishing Sertoli-germ cell crosstalk.

Proteomics of azoospermia: Towards the discovery of reliable markers for non-invasive diagnosis

PURPOSE

Azoospermia, as the most severe form of male infertility, no longer indicates sterility due to modern medical advancements. The current diagnostic procedure based on testicular biopsy has several drawbacks which urges the development of novel, non-invasive diagnostic procedures based on biomarkers. In the last two decades, there have been many proteomics studies investigating potential azoospermia biomarkers. In this review, we aimed to provide a critical evaluation of these studies.

EXPERIMENTAL DESIGN

Published articles were gathered by systematic literature search using Pubmed, Science Direct, and Google Scholar databases until March 2022 and were further preselected to include only studies on human samples.

RESULTS

A detailed review of these studies encompassed the proteomics platforms, sources of material, proposed candidate biomarkers, and their potential diagnostic specificity and sensitivity. In addition, emphasis was put on the top, most identified and validated biomarker candidates and their potential for discriminating azoospermia types and subtypes as well as predicting sperm retrieval success rate.

CONCLUSIONS

Proteomics research of azoospermia has laid the groundwork for the development of a more streamlined biomarker testing. The future research should be focused on well-designed studies including samples from all types/subtypes as well as further testing of the most promising biomarkers identified so far.

Applications of MALDI-MS/MS-Based Proteomics in Biomedical Research

Matrix-assisted laser desorption/ionization (MALDI) mass spectrometry (MS) is one of the most widely used techniques in proteomics to achieve structural identification and characterization of proteins and peptides, including their variety of proteoforms due to post-translational modifications (PTMs) or protein-protein interactions (PPIs). MALDI-MS and MALDI tandem mass spectrometry (MS/MS) have been developed as analytical techniques to study small and large molecules, offering picomole to femtomole sensitivity and enabling the direct analysis of biological samples, such as biofluids, solid tissues, tissue/cell homogenates, and cell culture lysates, with a minimized procedure of sample preparation. In the last decades, structural identification of peptides and proteins achieved by MALDI-MS/MS helped researchers and clinicians to decipher molecular function, biological process, cellular component, and related pathways of the gene products as well as their involvement in pathogenesis of diseases. In this review, we highlight the applications of MALDI ionization source and tandem approaches for MS for analyzing biomedical relevant peptides and proteins. Furthermore, one of the most relevant applications of MALDI-MS/MS is to provide "molecular pictures", which offer in situ information about molecular weight proteins without labeling of potential targets. Histology-directed MALDI-mass spectrometry imaging (MSI) uses MALDI-ToF/ToF or other MALDI tandem mass spectrometers for accurate sequence analysis of peptide biomarkers and biological active compounds directly in tissues, to assure complementary and essential spatial data compared with those obtained by LC-ESI-MS/MS technique.

Comparative proteomics analysis of human FFPE testicular tissues reveals new candidate biomarkers for distinction among azoospermia types and subtypes

Understanding molecular mechanisms that underpin azoospermia and discovery of biomarkers that could enable reliable, non-invasive diagnosis is highly needed. Using label-free data-independent LC-MS/MS acquisition coupled with ion mobility, we compared the FFPE testicular proteome of patients with obstructive (OA) and non-obstructive azoospermia (NOA) subtypes hypospermatogenesis (Hyp) and Sertoli cell-only syndrome (SCO). Out of 2044 proteins identified based on ≥2 peptides, 61 proteins had the power to quantitatively discriminate OA from NOA and 30 to quantitatively discriminate SCO from Hyp and OA. Among these, H1-6, RANBP1 and TKTL2 showed superior potential for quantitative discrimination among OA, Hyp and SCO. Integrin signaling pathway, adherens junction, planar cell polarity/convergent extension pathway and Dectin-1 mediated noncanonical NF-kB signaling were significantly associated with the proteins that could discriminate OA from NOA. Comparison with 2 transcriptome datasets revealed 278 and 55 co-differentially expressed proteins/genes with statistically significant positive correlation. Gene expression analysis by qPCR of 6 genes (H1-6, RANBP1, TKTL2, TKTL1, H2BC1, and ACTL7B) with the highest discriminatory power on protein level and the same regulation trend with transcriptomic datasets, confirmed proteomics results. In summary, our results suggest some underlying pathways in azoospermia and broaden the range of potential novel candidates for diagnosis. SIGNIFICANCE: Using a comparative proteomics approach on testicular tissue we have identified several pathways associated with azoospermia and a number of testis-specific and germ cell-specific proteins that have the potential to pinpoint the type of spermatogenesis failure. Furthermore, comparison with transcriptomics datasets based on genome-wide gene expression analyses of human testis specimens from azoospermia patients identified proteins that could discriminate between obstructive and non-obstructive azoospermia subtypes on both protein and mRNA levels. Up to our knowledge, this is the first integrated comparative analysis of proteomics and transcriptomics data from testicular tissues. We believe that the data from our study contributes significantly to increase the knowledge of molecular mechanisms of azoospermia and pave the way for new investigations in regards to non-invasive diagnosis.

hnRNPH1 recruits PTBP2 and SRSF3 to modulate alternative splicing in germ cells

Coordinated regulation of alternative pre-mRNA splicing is essential for germ cell development. However, the underlying molecular mechanism that controls alternative mRNA expression during germ cell development remains elusive. Herein, we show that hnRNPH1 is highly expressed in the reproductive system and recruits the PTBP2 and SRSF3 to modulate the alternative splicing in germ cells. Conditional knockout Hnrnph1 in spermatogenic cells causes many abnormal splicing events, thus affecting the genes related to meiosis and communication between germ cells and Sertoli cells. This is characterized by asynapsis of chromosomes and impairment of germ-Sertoli communications, which ultimately leads to male sterility. Markedly, Hnrnph1 germline-specific mutant female mice are also infertile, and Hnrnph1-deficient oocytes exhibit a similar defective synapsis and cell-cell junction as seen in Hnrnph1-deficient male germ cells. Collectively, our data support a molecular model wherein hnRNPH1 governs a network of alternative splicing events in germ cells via recruitment of PTBP2 and SRSF3.

Coordinated regulation of alternative splicing is essential for germ cell development. Here, the authors report that hnRNPH1 interacts with alternative splicing factors PTBP2 and SRSF3 in the germline to regulate pre-mRNA alternative splicing.

Implementing a preimplantation proteomic approach to advance assisted reproduction technologies in the framework of predictive, preventive, and personalized medicine

The evolution of the field of assisted reproduction technology (ART) in the last 40 years has significantly contributed to the management of global infertility. Despite the great numbers of live births that have been achieved through ART, there is still potential for increasing the success rates. As a result, there is a need to create optimum conditions in order to increase ART efficacy. The selection of the best sperm, oocyte, and embryo, as well as the achievement of optimal endometrial receptivity, through the contribution of new diagnostic and treatment methods, based on a personalized proteomic approach, may assist in the attainment of this goal. Proteomics represent a powerful new technological development, which seeks for protein biomarkers in human tissues. These biomarkers may aid to predict the outcome, prevent failure, and monitor in a personalized manner in vitro fertilization (IVF) cycles. In this review, we will present data from studies that have been conducted in the search for such biomarkers in order to identify proteins related to good sperm, oocyte, and embryo quality, as well as optimal endometrial receptivity, which may later lead to greater results and the desirable ART outcome.

Deletion of Hnrnpk Gene Causes Infertility in Male Mice by Disrupting Spermatogenesis

HnRNPK is a heterogeneous nuclear ribonucleoprotein (hnRNP) that has been firmly implicated in transcriptional and post-transcriptional regulation. However, the molecular mechanisms by which hnRNPK orchestrates transcriptional or post-transcriptional regulation are not well understood due to early embryonic lethality in homozygous knockout mice, especially in a tissue-specific context. Strikingly, in this study, we demonstrated that hnRNPK is strongly expressed in the mouse testis and mainly localizes to the nucleus in spermatogonia, spermatocytes, and round spermatids, suggesting an important role for hnRNPK in spermatogenesis. Using a male germ cell-specific hnRNPK-depleted mouse model, we found that it is critical for testicular development and male fertility. The initiation of meiosis of following spermatogenesis was not affected in Hnrnpk cKO mice, while most germ cells were arrested at the pachytene stage of the meiosis and no mature sperm were detected in epididymides. The further RNA-seq analysis of Hnrnpk cKO mice testis revealed that the deletion of hnRNPK disturbed the expression of genes involved in male reproductive development, among which the meiosis genes were significantly affected, and Hnrnpk cKO spermatocytes failed to complete the meiotic prophase. Together, these results identify hnRNPK as an essential regulator of spermatogenesis and male fertility.

A de novo paradigm for male infertility

De novo mutations are known to play a prominent role in sporadic disorders with reduced fitness. We hypothesize that de novo mutations play an important role in severe male infertility and explain a portion of the genetic causes of this understudied disorder. To test this hypothesis, we utilize trio-based exome sequencing in a cohort of 185 infertile males and their unaffected parents. Following a systematic analysis, 29 of 145 rare (MAF < 0.1%) protein-altering de novo mutations are classified as possibly causative of the male infertility phenotype. We observed a significant enrichment of loss-of-function de novo mutations in loss-of-function-intolerant genes (p-value = 1.00 × 10^-5) in infertile men compared to controls. Additionally, we detected a significant increase in predicted pathogenic de novo missense mutations affecting missense-intolerant genes (p-value = 5.01 × 10^-4) in contrast to predicted benign de novo mutations. One gene we identify, RBM5, is an essential regulator of male germ cell pre-mRNA splicing and has been previously implicated in male infertility in mice. In a follow-up study, 6 rare pathogenic missense mutations affecting this gene are observed in a cohort of 2,506 infertile patients, whilst we find no such mutations in a cohort of 5,784 fertile men (p-value = 0.03). Our results provide evidence for the role of de novo mutations in severe male infertility and point to new candidate genes affecting fertility.

Proteomic and phosphoproteomic profiles of Sertoli cells in buffalo

Sertoli cells provide nutrients and support for germ cell differentiation and maintain a stable microenvironment for spermatogenesis. Comprehensive identification of Sertoli cellular proteins is important in understanding spermatogenesis. In this study, we performed an integrative analysis of the proteome and phosphoproteome to explore the role of Sertoli cells in spermatogenesis. A total of 2912 and 753 proteins were identified from the proteome and phosphoproteome in Sertoli cells, respectively; 438 proteins were common to the proteome and phosphoproteome. Data are available via ProteomeXchange with identifier PXD024984. In the proteome, ACTG1, ACTB, ACTA2, MYH9 were the most abundant proteins. Gene Ontology (GO) analysis indicated that most of the proteins were involved in the processes of localization, biosynthesis, gene expression, and transport. In addition, some of the proteins related to Sertoli cell functions were also enriched. In the phosphoproteome, most of the proteins were involved in gene expression and the RNA metabolic process; the pathways mainly involved the spliceosome, mitogen-activated protein kinase signaling pathway, focal adhesion, and tight junctions. The pleckstrin homology-like domain is the most highly enriched protein domain in phosphoproteins. Cyclin-dependent kinases and protein kinases C were found to be highly active kinases in the kinase-substrate network analysis. Ten proteins most closely related to network stability were found in the analysis of the network interactions of proteins identified jointly in the phosphoproteome and proteome. Through immunohistochemistry and immunofluorescence verification of vimentin, it was found that there were localization differences between phosphorylated and non-phosphorylated vimentin in testicular tissue. This study is the first in-depth proteomic and phosphoproteomic analysis of buffalo testicular Sertoli cells. The results provide insight into the role of Sertoli cells in spermatogenesis and provide clues for further study of male reproduction.

Somatic CG6015 mediates cyst stem cell maintenance and germline stem cell differentiation via EGFR signaling in Drosophila testes

Stem cell niche is regulated by intrinsic and extrinsic factors. In the Drosophila testis, cyst stem cells (CySCs) support the differentiation of germline stem cells (GSCs). However, the underlying mechanisms remain unclear. In this study, we found that somatic CG6015 is required for CySC maintenance and GSC differentiation in a Drosophila model. Knockdown of CG6015 in CySCs caused aberrant activation of dpERK in undifferentiated germ cells in the Drosophila testis, and disruption of key downstream targets of EGFR signaling (Dsor1 and rl) in CySCs results in a phenotype resembling that of CG6015 knockdown. CG6015, Dsor1, and rl are essential for the survival of Drosophila cell line Schneider 2 (S2) cells. Our data showed that somatic CG6015 regulates CySC maintenance and GSC differentiation via EGFR signaling, and inhibits aberrant activation of germline dpERK signals. These findings indicate regulatory mechanisms of stem cell niche homeostasis in the Drosophila testis.

Novel Gene Regulation in Normal and Abnormal Spermatogenesis

Spermatogenesis is a complex and dynamic process which is precisely controlledby genetic and epigenetic factors. With the development of new technologies (e.g., single-cell RNA sequencing), increasingly more regulatory genes related to spermatogenesis have been identified. In this review, we address the roles and mechanisms of novel genes in regulating the normal and abnormal spermatogenesis. Specifically, we discussed the functions and signaling pathways of key new genes in mediating the proliferation, differentiation, and apoptosis of rodent and human spermatogonial stem cells (SSCs), as well as in controlling the meiosis of spermatocytes and other germ cells. Additionally, we summarized the gene regulation in the abnormal testicular microenvironment or the niche by Sertoli cells, peritubular myoid cells, and Leydig cells. Finally, we pointed out the future directions for investigating the molecular mechanisms underlying human spermatogenesis. This review could offer novel insights into genetic regulation in the normal and abnormal spermatogenesis, and it provides new molecular targets for gene therapy of male infertility.

Insights and clinical potential of proteomics in understanding spermatogenesis

Introduction: With the worldwide decline on male fertility potential, the importance of the insight of the spermatogenic process has been increasing. In recent years, proteomic methodologies have been applied to seminal fluid of infertile men to search for infertility potential biomarkers. However, to understand the spermatogenic event and to search for treatment to spermatogenic impairment, comparative analysis of testicular proteomics is considered a powerful methodology.Areas covered: Herein, we present a critical overview of the studies addressing proteomic alterations in the development of spermatogenesis during puberty, as well as during the different phases of the spermatogenic event. The comparative studies of the proteomic testicular profile of men with and without spermatogenic impairment are also discussed and key proteins and pathways involved highlighted.Expert opinion: The usage of whole human testicular tissue with its heterogeneous cellular composition makes proteome data interpretation particularly challenging. This may be minimized by controlled experiments involving the collection of testicular tissue and sperm from the same individuals, integrated in a clinically characterized cohort of healthy and infertile men. The analysis of specific subcellular proteomes can add more information to the proteomic puzzle, opening new treatment possibilities for infertile/subfertile men.

Sertoli cell-only syndrome: etiology and clinical management

Almost 50% of infertility cases are due to male factors, and spermatogenesis failure is one of the most severe forms of male infertility. Sertoli cell-only syndrome (SCOS) also known as germ cell aplasia is characterized by azoospermia in which the seminiferous tubules of testicular biopsy are lined only with Sertoli cells. The definitive diagnosis of SCOS is by diagnostic testicular biopsy. Although SCOS may be a result of Klinefelter syndrome, most of the SCOS men have a normal karyotype. Along with genetic aberrations, signaling pathways and endocrine processes might be major factors in the development of SCOS. Sperm retrieval and intracytoplasmic sperm injection (ICSI) are available treatments for SCOS. However, some SCOS patients do not have therapeutic options to help them having a biological child. This review aims to summarize our present knowledge about SCOS and to highlight the importance of future researches in the diagnosis and treatment of this disorder.

Comparison of proteomic profiles from the testicular tissue of males with impaired and normal spermatogenesis

In this study, we aimed to explore the potential differences in proteomic profiles from the testicular tissue of azoospermatic men with impaired spermatogenesis and normal spermatogenesis. Isobaric tags for relative and absolute quantitation (iTRAQ) labeled technology and LC-MS/MS technology were used to identify differentially expressed proteins. Potential functions of differentially expressed proteins were predicted using gene ontology (GO) and the Kyoto encyclopedia of genes and genomes (KEGG). Immunohistochemistry (IHC) and western blot (WB) were used to verify the differentially expressed proteins. A protein-protein interaction (PPI) network was built to outline the regulatory network of differentially expressed proteins. A total of 3,945 proteins were identified in men with normal and impaired spermatogenesis. Of these, 116 proteins were differentially expressed in men with impaired spermatogenesis: 39 were upregulated and 77 were downregulated. Furthermore, we found that these differentially expressed proteins were mainly involved in the cellular component, which may be mainly associated with the spliceosome, ribosome, and thyroid hormone synthesis signaling pathways. The spliceosome- and ribosome-associated proteins YBX1, FBL, and HNRNPU were downregulated. And the proteomic profile of testicular tissue in men with impaired spermatogenesis is different from that of men with normal spermatogenesis. For this reason, differentially expressed proteins such as YBX1, FBL and HNRNPU might be involved in the pathology of spermatogenesis dysfunction.Abbreviations: iTRAQ: Isobaric tags for relative and absolute quantitation;GO: Gene ontology; KEGG: Kyoto encyclopedia of genes and genomes; IHC: Immunohistochemistry; WB: Western blot; PPI: Protein-protein interaction; ICSI: Intracytoplasmic sperm injection; BP: Biological process; CC: Cellular components; MF: Molecular function; snoRNA: Small nucleolar RNA; snRNA: Small nuclear RNA; LC-MS/MS: Liquid chromatography and MS/MS analysis; BSA: Bovine serum albumin; SD: Spermatogenic dysfunction; micro-TESE: Testicular microscopic sperm extraction.

Roles of heterogeneous nuclear ribonucleoprotein L in enamel organ development and the differentiation of ameloblasts

OBJECTIVE

We aimed to explore the role of Heterogeneous Nuclear Ribonucleoprotein L(hnRNP L) in enamel organ development through hnRNP L conditional knockout mice and knockdown of hnRNP L expression in mouse ameloblast-lineage cells (mALCs) METHODS: We created K14cre-mediated hnRNP L conditional knockout mice (hnRNP L^K14/fl) and silenced the expression of hnRNP L in mALCs to investigate the role of hnRNP L in enamel organ development.

RESULTS

We found that hnRNP L^K14/fl mice presented enamel organ development defects with reduced number of inner enamel epithelium (IEE) cells. The proliferation and differentiation of the IEE cells/ameloblasts were suppressed. The cell proliferation and mineralization ability were also decreased after hnRNP L knockdown. Further studies showed that Bone Morphogenetic Protein (BMP) signaling pathway was attenuated after the knockdown of hnRNP L expression both in vivo and in vitro.

CONCLUSIONS

These findings suggest that hnRNP L plays a critical role in enamel organ development by promoting the IEE cell/ameloblast proliferation and differentiation. BMP signaling pathway may be involved in the process.

Phosphoribosyl-pyrophosphate synthetase 2 (PRPS2) depletion regulates spermatogenic cell apoptosis and is correlated with hypospermatogenesis

Phosphoribosyl-pyrophosphate synthetase 2 (PRPS2) is a rate-limiting enzyme and plays an important role in purine and pyrimidine nucleotide synthesis. Recent studies report that PRPS2 is involved in male infertility. However, the role of PRPS2 in hypospermatogenesis is unknown. In this study, the relationship of PRPS2 with hypospermatogenesis and spermatogenic cell apoptosis was investigated. The results showed that PRPS2 depletion increased the number of apoptotic spermatogenic cells in vitro. PRPS2 was downregulated in a mouse model of hypospermatogenesis. When PRPS2 expression was knocked down in mouse testes, hypospermatogenesis and accelerated apoptosis of spermatogenic cells were noted. E2F transcription factor 1 (E2F1) was confirmed as the target gene of PRPS2 and played a key role in cell apoptosis by regulating the P53/Bcl-xl/Bcl-2/Caspase 6/Caspase 9 apoptosis pathway. Therefore, these data indicate that PRPS2 depletion contributes to the apoptosis of spermatogenic cells and is associated with hypospermatogenesis, which may be helpful for the diagnosis of male infertility.

HnRNP-F regulates EMT in bladder cancer by mediating the stabilization of Snail1 mRNA by binding to its 3' UTR

Background

Heterogeneous nuclear ribonucleoprotein F (hnRNP-F) has been implicated in multiple cancers, suggesting its role in tumourigenesis, but the potential oncogenic role and mechanism of hnRNP-F in bladder cancer (BC) remain incompletely understood.

Methods

HnRNP-F was identified by proteomic methods. A correlation of hnRNP-F expression with prognosis was analysed in 103 BC patients. Then, we applied in vitro and in vivo methods to reveal the behaviours of hnRNP-F in BC tumourigenesis. Furthermore, the interaction between hnRNP-F and Snail1 mRNA was examined by RNA immunoprecipitation (RIP), and Snail1 mRNA stability was measured after treatment with actinomycin D. Finally, the binding domain between hnRNP-F and Snail1 mRNA was verified by constructing Snail1 mRNA truncations and mutants.

Finding

HnRNP-F is significantly upregulated in BC tissue, and its increased expression is associated with a poor prognosis in BC patients. HnRNP-F is necessary for tumour growth, inducing epithelial-mesenchymal transition (EMT) and metastasis in BC. The changes in Snail1 expression were positively correlated with hnRNP-F at both the mRNA and protein levels when hnRNP-F was silenced or enhanced, suggesting that Snail1 is likely a downstream target of hnRNP-F that mediates its effects on enhancing invasion, metastasis and EMT in BC. The overexpression of hnRNP-F caused an increase in the stability of Snail1 mRNA. Our RNA chip analysis revealed that hnRNP-F could combine with Snail1 mRNA, and we further demonstrated that hnRNP-F could directly bind to the 3′ untranslated region (3′ UTR) of Snail1 mRNA to enhance its stability.

Interpretation

Our findings suggest that hnRNP-F mediates the stabilization of Snail1 mRNA by binding to its 3′ UTR, subsequently regulating EMT.

14-3-3 epsilon plays an important role in testicular germ cell apoptosis: A functional proteomic study of experimental varicocele

The latest perspective indicates that apoptotic dysregulation is an important mechanism in male infertility induced by varicocele. To elucidate the molecular mechanism of apoptosis caused by varicocele, we used proteomics (2D-MALDI-TOF MS) to identify the altered proteins in the testes of experimental varicocele rats compared with the control. Here, 21 significantly different protein spots were detected by proteomics technology. 14-3-3 epsilon (14-3-3ε) was our subsequent research target because of its function in apoptosis. The expression of 14-3-3ε in rat testes was confirmed by Western blot and immunohistochemistry, and the terminal deoxynucleotidyl transferase dUTP nick end labelling (TUNEL) method was used to analyse the apoptosis of germ cells. GC-1 spg cells transfected with small interfering RNA were used to confirm the function of 14-3-3ε in vitro. 14-3-3ε protein expression decreased, accompanied by a higher apoptosis index in rat testes of the varicocele group. Furthermore, 14-3-3ε siRNA-treated GC-1 spg cells caused the upregulation of the apoptotic rate detected by flow cytometry. The expression of Bax and Bcl-2 was found to be regulated by 14-3-3ε in vitro. Our investigation demonstrated the pro-apoptotic function of the downregulation of 14-3-3ε, which may play an important role in germ cell apoptosis induced by varicocele.

Interference with lactate metabolism by mmu-miR-320-3p via negatively regulating GLUT3 signaling in mouse Sertoli cells

Disruption of the nursery function in Sertoli cells (SCs) by reducing lactate production, a preferred energy substrate for developed germ cells (spermatocytes and spermatids), is tightly associated with spermatogenic failure such as SC-only syndrome (SCOS). However, whether this complicated pathogenesis is regulated by certain miRNAs at the post-transcriptional level remain fascinating but largely unknown. Here we show for the first time that mmu-miR-320-3p was exclusively expressed in murine SCs and this expression was significantly induced in busulphan-treated murine testis. The most efficient stimulatory germ cell types for the induction of apoptosis-elicited mmu-miR-320-3p expression were meiotic spermatocytes and haploid spermatids. Functionally, forced expression of the exogenous mmu-miR-320-3p in SCs compromises male fertility by causing oligozoospermia and defection of sperm mobility. Mechanistically, mmu-miR-320-3p negatively regulates lactate production of SCs by directly inhibiting glucose transporter 3 (GLUT3) expression. Thus, dysregulation of mmu-miR-320-3p/GLUT3 cascade and consequently of lactate deficiency may be a key molecular event contributing the germ cell loss by SC dysfunction. Future endeavor in the continuous investigation of this important circulating miRNA may shed novel insights into epigenetic regulation of SCs nursery function and the etiology of azoospermia, and offers novel therapeutic and prognostic targets for SCOS.

Single-cell RNA-seq uncovers dynamic processes and critical regulators in mouse spermatogenesis

A systematic interrogation of male germ cells is key to complete understanding of molecular mechanisms governing spermatogenesis and the development of new strategies for infertility therapies and male contraception. Here we develop an approach to purify all types of homogeneous spermatogenic cells by combining transgenic labeling and synchronization of the cycle of the seminiferous epithelium, and subsequent single-cell RNA-sequencing. We reveal extensive and previously uncharacterized dynamic processes and molecular signatures in gene expression, as well as specific patterns of alternative splicing, and novel regulators for specific stages of male germ cell development. Our transcriptomics analyses led us to discover discriminative markers for isolating round spermatids at specific stages, and different embryo developmental potentials between early and late stage spermatids, providing evidence that maturation of round spermatids impacts on embryo development. This work provides valuable insights into mammalian spermatogenesis, and a comprehensive resource for future studies towards the complete elucidation of gametogenesis.

Interferon regulatory factor 1 and a variant of heterogeneous nuclear ribonucleoprotein L coordinately silence the gene for adhesion protein CEACAM1

The adhesion protein carcinoembryonic antigen-related cell adhesion molecule 1 (CEACAM1) is widely expressed in epithelial cells as a short cytoplasmic isoform (S-iso) and in leukocytes as a long cytoplasmic isoform (L-iso) and is frequently silenced in cancer by unknown mechanisms. Previously, we reported that interferon response factor 1 (IRF1) biases alternative splicing (AS) to include the variable exon 7 (E7) in CEACAM1, generating long cytoplasmic isoforms. We now show that IRF1 and a variant of heterogeneous nuclear ribonucleoprotein L (Lv1) coordinately silence the CEACAM1 gene. RNAi-mediated Lv1 depletion in IRF1-treated HeLa and melanoma cells induced significant CEACAM1 protein expression, reversed by ectopic Lv1 expression. The Lv1-mediated CEACAM1 repression resided in residues Gly⁷¹-Gly⁸⁹ and Ala³⁸-Gly⁸⁹ in Lv1's N-terminal extension. ChIP analysis of IRF1- and FLAG-tagged Lv1-treated HeLa cells and global treatment with the global epigenetic modifiers 5-aza-2'-deoxycytidine and trichostatin A indicated that IRF1 and Lv1 together induce chromatin remodeling, restricting IRF1 access to the CEACAM1 promoter. In interferon γ-treated HeLa cells, the transcription factor SP1 did not associate with the CEACAM1 promoter, but binding by upstream transcription factor 1 (USF1), a known CEACAM1 regulator, was greatly enhanced. ChIP-sequencing revealed that Lv1 overexpression in IRF1-treated cells induces transcriptional silencing across many genes, including DCC (deleted in colorectal carcinoma), associated with CEACAM5 in colon cancer. Notably, IRF1, but not IRF3 and IRF7, affected CEACAM1 expression via translational repression. We conclude that IRF1 and Lv1 coordinately regulate CEACAM1 transcription, alternative splicing, and translation and may significantly contribute to CEACAM1 silencing in cancer.

Increased Sat2 expression is associated with busulfan-induced testicular Sertoli cell injury

Busulfan is a chemotherapeutic agent used to treat chronic myelogenous leukemia and other myeloproliferative disorders. Increasing evidence has demonstrated that busulfan may induce testicular dysfunction by targeting genes that are expressed in the testis. Here, we showed that spermidine/spermine N1-acetyltransferase 2 (Sat2) was present in testicular Sertoli cells, and its expression was significantly increased by busulfan treatment. To investigate the implications of Sat2 upregulation for cell growth and function, a Sat2-overexpressing TM4 Sertoli cell model was established. Increased Sat2 expression led to inhibited cell proliferation and arrested cell cycle. Based on iTRAQ proteomics analysis, we revealed that Sat2 overexpression is detrimental to cell cycle progression and cell communication, and notably, Sat2 may disturb protein metabolic processes by altering translation regulation and protein complex subunit organization. In summary, the present study provides evidence that Sat2 upregulation induces alterations in the growth and function of Sertoli cells. In testis tissue subjected to busulfan, increased expression of Sat2 can cause cellular injury and subsequent organ damage, which could lead to male infertility. Therefore, Sat2 may be a novel molecular target for treating busulfan-induced testicular toxicity.

The Use of Proteomics in Assisted Reproduction

Despite the explosive increase in the use of Assisted Reproductive Technologies (ART) over the last 30 years, their success rates remain suboptimal. Proteomics is a rapidly-evolving technology-driven science that has already been widely applied in the exploration of human reproduction and fertility, providing useful insights into its physiology and leading to the identification of numerous proteins that may be potential biomarkers and/or treatment targets of a successful ART pregnancy. Here we present a brief overview of the techniques used in proteomic analyses and attempt a comprehensive presentation of recent data from mass spectrometry-based proteomic studies in humans, regarding all components of ARTs, including the male and female gamete, the derived zygote and embryo, the endometrium and, finally, the ART offspring both pre- and postnatally.

Sperm mRNAs and microRNAs as candidate markers for the impact of toxicants on human spermatogenesis: an application to tobacco smoking

Spermatozoa contain a complex population of RNAs including messenger RNAs (mRNAs) and small RNAs such as microRNAs (miRNA). It has been reported that these RNAs can be used to understand the mechanisms by which toxicological exposure affects spermatogenesis. The aim of our study was to compare mRNA and miRNA profiles in spermatozoa from eight smokers and eight non-smokers, and search for potential relationships between mRNA and miRNA variation. All men were selected based on their answers to a standard toxic exposure questionnaire, and sperm parameters. Using mRNA and miRNA microarrays, we showed that mRNAs from 15 genes were differentially represented between smokers and non-smokers (p<0.01): five had higher levels and 10 lower levels in the smokers. For the microRNAs, 23 were differentially represented: 16 were higher and seven lower in the smokers (0.004≤p<0.01). Quantitative RT-PCR confirmed the lower levels in smokers compared to non-smokers for hsa-miR-296-5p, hsa-miR-3940, and hsa-miR-520d-3p. Moreover, we observed an inverse relationship between the levels of microRNAs and six potential target mRNAs (B3GAT3, HNRNPL, OASL, ODZ3, CNGB1, and PKD2). Our results indicate that alterations in the level of a small number of microRNAs in response to smoking may contribute to changes in mRNA expression in smokers. We conclude that large-scale analysis of spermatozoa RNAs can be used to help understand the mechanisms by which human spermatogenesis responds to toxic substances including those in tobacco smoke.

PRPS2 Expression Correlates with Sertoli-Cell Only Syndrome and Inhibits the Apoptosis of TM4 Sertoli Cells

PURPOSE

Sertoli-cell only syndrome is one of the reasons for male infertility but its pathogenesis remains unclear. PRPS2, a subset of PRS, is reported to be a potential protein associated with Sertoli-cell only syndrome. In this study we further investigated the correlation between PRPS2 and Sertoli-cell only syndrome, and evaluated the effect of PRPS2 expression on apoptosis of TM4 Sertoli cells.

MATERIALS AND METHODS

PRPS2 expression was detected in patients with Sertoli-cell only syndrome and normal spermatogenesis, and in Sertoli-cell only syndrome mouse models by immunohistochemistry, quantitative reverse transcription-polymerase chain reaction and Western blot. PRPS2 expression in TM4 Sertoli cells was then down-regulated and up-regulated by lentivirus vectors. The effect of PRPS2 expression on cell apoptosis and cell cycle transition was evaluated by flow cytometry.

RESULTS

PRPS2 expression in patients with Sertoli-cell only syndrome was significantly greater than in those with normal spermatogenesis. A significant increase in PRPS2 expression was observed in Sertoli-cell only syndrome mouse models. PRPS2 over expression significantly inhibited cell apoptosis and promoted cell cycle transition in TM4 Sertoli cells. However, PRPS2 down-regulation showed a reverse effect. Moreover, results revealed that PRPS2 over expression inhibited cell apoptosis via the p53/Bcl-2/caspase-9/caspase-3/caspase-6/caspase-7 signaling pathway.

CONCLUSIONS

PRPS2 expression correlates with Sertoli-cell only syndrome and inhibits the apoptosis of TM4 Sertoli cells via the p53/Bcl-2/caspases signaling pathway.

PGAM1 is Involved in Spermatogenic Dysfunction and Affects Cell Proliferation, Apoptosis, and Migration

OBJECTIVE

To investigate the correlation between PGAM1 and spermatogenic dysfunction and to evaluate the effect of expression of PGAM1 on the function of germ cells.

METHODS

Expression of PGAM1 was detected in 40 cases of infertile males with definite pathological diagnosis and 12 cases of mouse models with spermatogenic dysfunction by immunohistochemistry. Then, cell proliferation, apoptosis, and migration were evaluated when expression of PGAM1 was knocked down by a specific small interfering RNA in GC1 and TM4 cells.

RESULTS

The positive rates of PGAM1 in patients with normal spermatogenesis, mild hypospermatogenesis, severe hypospermatogenesis, and Sertoli cell-only syndrome were 90%, 80%, 10%, 100%, respectively, and the difference was significant (P < .001). Meanwhile, expression of PGAM1 was found to be significantly decreased in mouse models with spermatogenic dysfunction. Moreover, when expression of PGAM1 was knocked down in GC1 cells, the proliferation and migration were significantly inhibited, but the rate of apoptosis was significantly increased. Furthermore, PGAM1 downregulation in TM4 cells significantly inhibited proliferation and promoted apoptosis but didn't affect migration.

CONCLUSION

PGAM1 correlates with spermatogenic distinction and affects the function of cell proliferation, apoptosis and migration.

Excretion of urinary orosomucoid 1 protein is elevated in patients with chronic heart failure

Easily screening markers for early detection of chronic heart failure (CHF) are lacking. We identified twenty differently expressed proteins including orosomucoid 1(ORM1) in urine between patients with CHF and normal controls by proteomic methods. Bioinformatics analyses suggested ORM1 could be used for further analysis. After verification by western blotting, the urinary levels of ORM1 were quantified with enzyme-linked immunosorbent assay (ELISA) by correcting for creatinine expression. The ORM1-Cr was significantly elevated in CHF patients than normal controls (6498.83±4300.21 versus 2102.26±1069.24 ng/mg). Furthermore, a Spearman analysis indicated that the urinary ORM1 levels had a high positive correlation with the classification of CHF, and the multivariate analysis suggested that the urinary ORM1 content was associated with the plasma amino-terminal pro- brain natriuretic peptide (NT-proBNP) (OR: 2.106, 95% CI: 1.213–3.524, P = 0.002) and the New York Heart Association (NYHA) classification (OR: 3.019, 95% CI: 1.329–4.721, P<0.001). In addition, receiving operating curve (ROC) analyses suggested that an optimum cut-off value of 2484.98 ng/mg with 90.91% sensitivity and 85.48% specificity, respectively, could be used for the diagnosis of CHF. To sum up, our findings indicate that ORM1 could be a potential novel urinary biomarker for the early detection of CHF.

Proteomic analysis of testicular ischemia-reperfusion injury in rats

Testicular torsion is a urological emergency that leads to serious testicular damage and male infertility. We performed this study to identify specific proteins that are differentially expressed in response to testicular torsion and detorsion-induced ischemia-reperfusion (I-R) injury. Adult male rats were divided into two groups: a sham-operated group and a testicular I-R group. Testicular torsion was induced by rotating the left testis 720° in a clockwise direction for 1 hr, and then, detorsion was performed for 24 hr. After this testicular tissues were collected, protein analysis was performed using two-dimensional gel electrophoresis and Western blot analyses. Testicular I-R injury resulted in serious histopathologic damage to the germinal cells in the seminiferous tubules and increased the number of TUNEL-positive cells in testicular tissue. Specific protein spots with a greater than 2.5-fold change in intensity between the sham-operated and testicular I-R groups were identified by mass spectrometry. Among these proteins, levels of peroxiredoxin 6, thioredoxin, heterogeneous nuclear ribonucleoproteins, ubiquitin carboxyl terminal hydrolase isozyme L5 and zinc finger AN1-type domain 3 were decreased in the testicular I-R group compared to the sham-operated group. Moreover, Western blot analysis clearly showed the decrease of these proteins in the testicular I-R group. These proteins have spermatogenesis and anti-oxidative functions. These findings suggest that testicular I-R results in cell death due to altered expression of several proteins with spermatogenesis and anti-oxidation functions.

Identification of urinary Gc-globulin as a novel biomarker for bladder cancer by two-dimensional fluorescent differential gel electrophoresis (2D-DIGE)

Improving the early detection rate and surveillance of bladder cancer remains a great challenge in medicine. Here, we identified sixteen proteins including Gc-globulin (GC) in urine from bladder cancer patients and normal controls by two-dimensional fluorescent differential gel electrophoresis (2D-DIGE) and matrix-assisted laser desorption time-of-flight mass spectrometry (MALDI-TOF/TOF MS). Bioinformatics analyses indicated GC played important roles in the regulation of growth, apoptosis, death and epidermal growth factor receptor activity. The GC expression patterns in urine or tissue from cases and controls were further quantified by western blotting, immunohistochemical staining and enzyme-linked immunosorbent assay (ELISA). ELISA quantification by correcting for creatinine expression showed GC-Cr was significantly increased in bladder cancer patients than in benign bladder damages cases and normal controls (1013.70±851.25 versus 99.34±55.87, 105.32±47.81 ng/mg, respectively). Receiver operating characteristic (ROC) analysis suggested that at 161.086 ng/mg urinary GC, bladder cancer could be detected with 92.31% sensitivity and 83.02% specificity, and 1407.481 ng/mg with 82.61% sensitivity and 88.24% specificity could be used for the detection of infiltrating urothelial carcinoma of bladder cancer. Taken together, we identified GC as a potential novel urinary biomarker for the early detection and surveillance of bladder cancer.